PART 36--NOISE STANDARDS: AIRCRAFT TYPE AND AIRWORTHINESS CERTIFICATION
Special Federal Aviation Regulation No. 41 [Note]
Subpart A--General
Sec.
36.1 Applicability and definitions.
36.2 Special retroactive requirements.
36.3 Compatibility with airworthiness requirements.
36.5 Limitation of part.
36.6 Incorporations by reference.
36.7 Acoustical change: Transport category large airplanes and turbojet
powered airplanes.
36.9 Acoustical change: Propeller-driven small airplanes and propeller-
driven commuter category airplanes.
36.11 Acoustical change: Helicopters.
Subpart B--Noise Measurement and Evaluation for Transport Category Large
Airplanes and Turbojet Powered Airplanes
36.101 Noise measurement.
36.103 Noise evaluation.
Subpart C--Noise Limits for Subsonic Transport Category Large Airplanes and
Subsonic Turbojet Powered Airplanes
36.201 Noise limits.
Subpart D--Noise Limits for Supersonic Transport Category Airplanes
36.301 Noise limits: Concorde.
Subpart E--[Reserved]
Subpart F--Propeller Driven Small Airplanes and Propeller-Driven, Commuter
Category Airplanes
36.501 Noise limits.
Subpart G--[Reserved]
Subpart H--Helicopters
36.801 Noise Measurement.
36.803 Noise evaluation and calculation.
36.805 Noise limits.
Subparts I--N [Reserved]
Subpart O--Operating Limitations and Information
36.1501 Procedures, noise levels and other information.
36.1581 Manuals, markings, and placards.
36.1583 Noncomplying agricultural and fire fighting airplanes.
Appendix A--Aircraft Noise Measurement under Sec. 36.101
Appendix B--Aircraft Noise Evaluation under Sec. 36.103
Appendix C--Noise Levels for Transport Category and Turbojet Powered
Airplanes under Sec. 36.201
Appendix D--E [Reserved]
Appendix F--Flyover Noise Requirements for Propeller-Driven Small Airplane
and Propeller-Driven, Commuter Category Airplane Certification Tests
Prior to December 22, 1988
Appendix G--Takeoff Noise Requirements for Propeller-Driven Small Airplane
and Propeller-Driven, Commuter Category Airplane Certification Tests on
or After December 22, 1988
Appendix H--Noise Requirements for Helicopters Under Subpart H
Appendix I--[Reserved]
Appendix J--Alternative Noise Certification Procedure for Helicopters Under
Subpart H Having A Maximum Certificated Takeoff Weight Of Not More Than
6,000 Pounds
Authority: 49 U.S.C. App. 1344, 1348, 1354(a), 1355, 1421, 1423, 1424,
1425, 1428, 1429, 1430, 1431(b), 1651(b)(2), 2101, 2121 through 2125; 42
U.S.C. 4321 et. seq.; E.O. 11514, 35 FR 4247, 3 CFR, 1966-1970 Comp., p. 902;
49 U.S.C. 106(g).
Source: Docket No. 9337, 34 FR 18364, Nov. 18, 1969, unless otherwise
noted.
Special Federal Aviation Regulation No. 41
Editorial Note: For the text of SFAR No. 41 see Part 21 of this chapter.
Subpart A--General
Sec. 36.1 Applicability and definitions.
(a) This part prescribes noise standards for the issue of the following
certificates:
(1) Type certificates, and changes to those certificates, and standard
airworthiness certificates, for subsonic transport category large airplanes,
and for subsonic turbojet powered airplanes regardless of category.
(2) Type certificates and changes to those certificates, standard
airworthiness certificates, and restricted category airworthiness
certificates, for propeller-driven, small airplanes, and for propeller-
driven, commuter category airplanes except those airplanes that are designed
for "agricultural aircraft operations" (as defined in Sec. 137.3 of this
chapter, as effective on January 1, 1966) or for dispersing fire fighting
materials to which Sec. 36.1583 of this part does not apply.
(3) A type certificate and changes to that certificate, and standard
airworthiness certificates, for Concorde airplanes.
(4) Type certificates, and changes to those certificates, for helicopters
except those helicopters that are designated exclusively for "argicultural
aircraft operations" (as defined in Sec. 137.3 of this chapter, as effective
on January 1, 1966), for dispensing fire fighting materials, or for carrying
external loads (as defined in Sec. 133.1(b) of this chapter, as effective on
December 20, 1976).
(b) Each person who applies under Part 21 of this chapter for a type of
airworthiness certificate specified in this part must show compliance with
the applicable requirements of this part, in addition to the applicable
airworthiness requirements of this chapter.
(c) Each person who applies under Part 21 of this chapter for approval of
an acoustical change described in Sec. 21.93(b) of this chapter must show
that the aircraft complies with the applicable provisions of Secs. 36.7,
36.9, or 36.11 of this part in addition to the applicable airworthiness
requirements of this chapter.
(d) Each person who applies for the original issue of a standard
airworthiness certificate for a transport category large airplane or for a
turbojet powered airplane under Sec. 21.183 must, regardless of date of
application, show compliance with the following provisions of this part
(including Appendix C):
(1) The provisions of this part in effect on December 1, 1969, for subsonic
airplanes that have not had any flight time before--
(i) December 1, 1973, for airplanes with maximum weights greater than
75,000 pounds, except for airplanes that are powered by Pratt & Whitney Turbo
Wasp JT3D series engines;
(ii) December 31, 1974, for airplanes with maximum weights greater than
75,000 pounds and that are powered by Pratt & Whitney Turbo Wasp JT3D series
engines; and
(iii) December 31, 1974, for airplanes with maximum weights of 75,000
pounds and less.
(2) The provisions of this part in effect on October 13, 1977, including
the stage 2 noise limits, for Concorde airplanes that have not had flight
time before January 1, 1980.
(3) December 31, 1974, for airplanes with maximum weights of 75,000 lbs.
and less.
(e) Each person who applies for the original issue of a standard
airworthiness certificate under Sec. 21.183, or for the original issue of a
restricted category airworthiness certificate under Sec. 21.185, for
propeller-driven, commuter category airplanes for a propeller driven small
airplane that has not had any flight time before January 1, 1980, must show
compliance with the applicable provisions of this part.
(f) For the purpose of showing compliance with this part for transport
category large airplanes and turbojet powered airplanes regardless of
category, the following terms have the following meanings:
(1) A "Stage 1 noise level" means a takeoff, sideline or approach noise
level greater than the Stage 2 noise limits prescribed in section C36.5(a)(2)
of Appendix C of this part.
(2) A "Stage 1 airplane" means an airplane that has not been shown under
this part to comply with the takeoff, sideline, and approach noise levels
required for Stage 2 or Stage 3 airplanes.
(3) A "Stage 2 noise level" means a noise level at or below the Stage 2
noise limits prescribed in section C36.5(a)(2) of Appendix C of this part but
higher than the Stage 3 noise limits prescribed in section C36.5(a)(3) of
Appendix C of this part.
(4) A "Stage 2 airplane" means an airplane that has been shown under this
part to comply with Stage 2 noise levels prescribed in section C36.5 of
Appendix C of this part (including use of the applicable tradeoff provisions)
and that does not comply with the requirements for a Stage 3 airplane.
(5) A "Stage 3 noise level" means a noise level at or below the Stage 3
noise limits prescribed in section C36.5(a)(3) of Appendix C of this part.
(6) A "Stage 3 airplane" means an airplane that has been shown under this
part to comply with Stage 3 noise levels prescribed in section C36.5 of
Appendix C of this part (including use of the applicable tradeoff
provisions).
(7) A "subsonic airplane" means an airplane for which the maximum operating
limit speed, Mmo, does not exceed a Mach number of 1.
(8) A "supersonic airplane" means an airplane for which the maximum
operating limit speed, Mmo, exceeds a Mach number of 1.
(g) For the purpose of showing compliance with this part for transport
category large airplanes and turbojet airplanes regardless of category, each
airplane may not be identified as complying with more than one stage or
configuration simultaneously.
(h) For the purpose of showing compliance with this part, for helicopters
in the primary, normal, transport, and restricted categories, the following
terms have the specified meanings:
(1) Stage 1 noise level means a takeoff, flyover, or approach noise level
greater than the Stage 2 noise limits prescribed in section H36.305 of
Appendix H of this part, or a flyover noise level greater than the Stage 2
noise limits prescribed in section J36.305 of appendix J of this part.
(2) Stage 1 helicopter means a helicopter that has not been shown under
this part to comply with the takeoff, flyover, and approach noise levels
required for Stage 2 helicopters as prescribed in section H36.305 of Appendix
H of this part, or a helicopter that has not been shown under this part to
comply with the flyover noise level required for Stage 2 helicopters as
prescribed in section J36.305 of Appendix J of this part.
(3) Stage 2 noise level means a takeoff, flyover, or approach noise level
at or below the Stage 2 noise limits prescribed in section H36.305 of
Appendix H of this part, or a flyover noise level at or below the Stage 2
limit prescribed in section J36.305 of Appendix J of this part.
(4) Stage 2 helicopter means a helicopter that has been shown under this
part to comply with Stage 2 noise limits (including applicable tradeoffs)
prescribed in section H36.305 of Appendix H of this part, or a helicopter
that has been shown under this part to comply with the Stage 2 noise limit
prescribed in section J36.305 of Appendix J of this part.
[Doc. No. 13243, Amdt. 36-4, 40 FR 1034, Jan. 6, 1975 as amended by Amdt. 36-
7, 42 FR 12370, Mar. 3, 1977; Amdt. 36-10, 43 FR 28419, June 29, 1978; Amdt.
36-11, 45 FR 67066, Oct. 9, 1980; Amdt. 36-13, 52 FR 1836, Jan. 15, 1987;
Amdt. 36-14, 53 FR 3540, Feb. 5, 1988; 53 FR 7728, Mar. 10, 1988; Amdt. 36-
15, 53 FR 16366, May 6, 1988; Amdt. 36-19, 57 FR 41369, Sept. 9, 1992; Amdt.
36-20, 57 FR 42854, Sept. 16, 1992]
Sec. 36.2 Special retroactive requirements.
(a) Notwithstanding Sec. 21.17 of this chapter, each person who applies for
a type certificate:
(1) For an airplane covered by this part, irrespective of the date of
application for the type certificate, or
(2) For a helicopter covered by this part, on or after March 6, 1986,
must show compliance with the applicable provisions of this part.
(b) Notwithstanding Sec. 21.101(a) of this chapter, each person who applies
for an acoustical change to a type design specified in Sec. 21.93(b) of this
chapter must show compliance with the applicable provisions of this part.
[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as amended by Amdt. 36-14, 53 FR
3540, Feb. 5, 1988]
Sec. 36.3 Compatibility with airworthiness requirements.
It must be shown that the aircraft meets the airworthiness regulations
constituting the type certification basis of the aircraft under all
conditions in which compliance with this part is shown, and that all
procedures used in complying with this part, and all procedures and
information for the flight crew developed under this part, are consistent
with the airworthiness regulations constituting the type certification basis
of the aircraft.
[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as amended by Amdt. 36-14, 53 FR
3540, Feb. 5, 1988]
Sec. 36.5 Limitation of part.
Pursuant to 49 U.S.C. 1431(b)(4), the noise levels in this part have been
determined to be as low as is economically reasonable, technologically
practicable, and appropriate to the type of aircraft to which they apply. No
determination is made, under this part, that these noise levels are or should
be acceptable or unacceptable for operation at, into, or out of, any airport.
Sec. 36.6 Incorporations by reference.
(a) General. This part prescribes certain standards and procedures which
are not set forth in full text in the rule. Those standards and procedures
are contained in published material which is reasonably available to the
class of persons affected and has been approved for incorporation by
reference by the Director of the Federal Register under 5 U.S.C. 552 (a) and
1 CFR Part 51.
(b) Incorporated matter. (1) Each publication, or part of a publication,
which is referenced but not set forth in full-text in this part and which is
identified in paragraph (c) of this section is hereby incorporated by
reference and made a part of Part 36 of this chapter with the approval of the
Director of the Federal Register.
(2) Incorporated matter which is subject to subsequent change is
incorporated by reference according to the specific reference and to the
identification statement. Adoption of any subsequent change in incorporated
matter is made under Part 11 of this chapter and 1 CFR Part 51.
(c) Identification statement. The complete title or description which
identifies each published matter incorporated by reference in this part is as
follows:
(1) International Electrotechnical Commission (IEC) Publications. (i) IEC
Publication No. 179, entitled "Precision Sound Level Meters," dated 1973.
(ii) IEC Publication No. 225, entitled "Octave, Half-Octave, Third Octave
Band Filters Intended for the Analysis of Sounds and Vibrations," dated 1966.
(iii) IEC Publication No. 651, entitled "Sound Level Meters," first
edition, dated 1979.
(iv) IEC Publication No. 561, entitled "Electro-acoustical Measuring
Equipment for Aircraft Noise Certification," first edition, dated 1976.
(v) IEC Publication No. 804, entitled "Integrating-averaging Sound Level
Meters," first edition, dated 1985.
(2) Society of Automotive Engineers (SAE) Publications. (i) SAE ARP 866A,
entitled "Standard Values at Atmospheric Absorption as a Function of
Temperature and Humidity for Use in Evaluating Aircraft Flyover Noise," dated
March 15, 1975.
(d) Availability for purchase. Published material incorporated by reference
in this part may be purchased at the price established by the publisher or
distributor at the following mailing addresses:
(1) IEC publications. (i) The Bureau Central de la Commission
Electrotechnique, Internationale, 1, rue de Varembe, Geneva, Switzerland.
(ii) American National Standard Institute, 1430 Broadway, New York City,
New York 10018.
(2) SAE publications. Society of Automotive Engineers, Inc., 400
Commonwealth Drive, Warrentown, Pennsylvania 15096.
(e) Availability for inspection. A copy of each publication incorporated by
reference in this part is available for public inspection at the following
locations:
(1) FAA Office of the Chief Counsel, Rules Docket, Room 916, Federal
Aviation Administration Headquarters Building, 800 Independence Avenue, SW.,
Washington, D.C.
(2) Department of Transportation, Branch Library, Room 930, Federal
Aviation Administration Headquarters Building, 800 Independence Avenue, SW.,
Washington, D.C.
(3) The respective Region Headquarters of the Federal Aviation
Administration as follows:
(i) New England Region Headquarters, 12 New England Executive Park,
Burlington, Massachusetts 01803.
(ii) Eastern Region Headquarters, Federal Building, John F. Kennedy (JFK)
International Airport, Jamaica, New York 11430.
(iii) Southern Region Headquarters, 3400 Norman Berry Drive, East Point,
Georgia 30344.
(iv) Great Lakes Region Headquarters, O'Hare Lake Office Center, 2300 East
Devon Avenue, Des Plaines, Illinois 60018.
(v) Central Region Headquarters, Federal Building, 601 East 12th Street,
Kanasa City Missouri 64106.
(vi) Southwest Region Headquarters, 4400 Blue Mound Road, Fort Worth, Texas
76193-0000.
(vii) Northwest Mountain Region Headquarters, 17900 Pacific Highway South,
Seattle, Washington 98168.
(viii) Western-Pacific Region Headquarters, 15000 Aviation Boulevard,
Hawthorne, California 92007.
(ix) Alaskan Region Headquarters, 701 C Street, Anchorage, Alaska 99513.
(x) European Office Headquarters, 15, Rue de la Loi (3rd Floor), B-1040
Brussels, Belgium.
[Amdt. 36-9, 43 FR 8739, Mar. 3, 1978, as amended by Amdt. 36-16, 53 FR
47400, Nov. 22, 1988; Amdt. 36-20, 57 FR 42854, Sept. 16, 1992]
Sec. 36.7 Acoustical change: Transport category large airplanes and turbojet
powered airplanes.
(a) Applicability. This section applies to all transport category large
airplanes and turbojet powered airplanes for which an acoustical change
approval is applied for under Sec. 21.93(b) of this chapter.
(b) General requirements. Except as otherwise specifically provided, for
each airplane covered by this section, the acoustical change approval
requirements are as follows:
(1) In showing compliance, noise levels must be measured and evaluated in
accordance with the applicable procedures and conditions prescribed in
Appendices A and B of this part.
(2) Compliance with the noise limits prescribed in section C36.5 of
Appendix C must be shown in accordance with the applicable provisions of
sections C36.7 and C36.9 of Appendix C of this part.
(c) Stage 1 airplanes. For each Stage 1 airplane prior to the change in
type design, in addition to the provisions of paragraph (b) of this section,
the following apply:
(1) If an airplane is a Stage 1 airplane prior to the change in type
design, it may not, after the change in type design, exceed the noise levels
created prior to the change in type design. The tradeoff provisions of
section C36.5(b) of Appendix C of this part may not be used to increase the
Stage 1 noise levels, unless the aircraft qualifies as a Stage 2 airplane.
(2) In addition, for an airplane for which application is made after
September 17, 1971--
(i) There may be no reduction in power or thrust below the highest
airworthiness approved power or thrust, during the tests conducted before and
after the change in type design; and
(ii) During the takeoff and sideline noise tests conducted before the
change in type design, the quietest airworthiness approved configuration
available for the highest approved takeoff weight must be used.
(d) Stage 2 airplanes. If an airplane is a Stage 2 airplane prior to the
change in type design, the following apply, in addition to the provisions of
paragraph (b) of this section:
(1) Airplanes with high bypass ratio turbojet engines. For an airplane that
has turbojet engines with a bypass ratio of 2 or more before a change in type
design--
(i) The airplane, after the change in type design, may not exceed either
(A) each Stage 3 noise limit by more than 3 EPNdB, or (B) each Stage 2 noise
limit, whichever is lower:
(ii) The tradeoff provisions of section C36.5(b) of Appendix C of this part
may be used in determining compliance under this paragraph with respect to
the Stage 2 noise limit or to the Stage 3 plus 3 EPNdB noise limits, as
applicable; and
(iii) During the takeoff and sideline noise test conducted before the
change in type design, the quietest airworthiness approved configuration
available for the highest approved takeoff weight must be used.
(2) Airplanes that do not have high bypass ratio turbojet engines. For an
airplane that does not have turbojet engines with a bypass ratio of 2 or more
before a change in type design--
(i) The airplane may not be a Stage 1 airplane after the change in type
design; and
(ii) During the takeoff and sideline noise tests conducted before the
change in type design, the quietest airworthiness approved configuration
available for the highest approved takeoff weight must be used.
(e) Stage 3 airplanes. If an airplane is a Stage 3 airplane prior to the
change in type design, the following apply, in addition to the provisions of
paragraph (b) of this section:
(1) If compliance with Stage 3 noise levels is not required before the
change in type design, the airplane must--
(i) Be a Stage 2 airplane after the change in type design and compliance
must be shown under the provisions of paragraph (d)(1) or (d)(2) of this
section, as appropriate; or
(ii) Remain a Stage 3 airplane after the change in type design. Compliance
must be shown under the provisions of paragraph (e)(2) of this section.
(2) If compliance with Stage 3 noise levels is required before the change
in type design, the airplane must be a Stage 3 airplane after the change in
type design.
(3) Applications on or after [August 14, 1989.] The airplane must remain a
Stage 3 airplane after the change in type design.
[Amdt. 36-7, 42 FR 12371, Mar. 3, 1977; Amdt. 36-8, 43 FR 8730, Mar. 2, 1978;
Amdt. 36-10, 43 FR 28420, June 29, 1978; Amdt. 36-12, 46 FR 33464, June 29,
1981; Amdt. 36-15, 53 FR 16366, May 6, 1988; 53 FR 18950, May 25, 1988; Amdt.
36-17, 54 FR 21040, May 15, 1989]
Sec. 36.9 Acoustical change: Propeller-driven small airplanes and propeller-
driven commuter category airplanes.
For propeller-driven small airplanes in the primary, normal, utility,
acrobatic, transport, and restricted categories and for propeller-driven,
commuter category airplanes for which an acoustical change approval is
applied for under Sec. 21.93(b) of this chapter after January 1, 1975, the
following apply:
(a) If the airplane was type certificated under this part prior to a change
in type design, it may not subsequently exceed the noise limits specified in
Sec. 36.501 of this part.
(b) If the airplane was not type certificated under this part prior to a
change in type design, it may not exceed the higher of the two following
values:
(1) The noise limit specified in Sec. 36.501 of this part, or
(2) The noise level created prior to the change in type design, measured
and corrected as prescribed in Sec. 36.501 of this part.
[Amdt. 36-16, 53 FR 47400, Nov. 22, 1988; 53 FR 50157, Dec. 13, 1988; Amdt.
36-19, 57 FR 41369, Sept. 9, 1992]
Sec. 36.11 Acoustical change: Helicopters.
This section applies to all helicopters in the primary, normal, transport,
and restricted categories for which an acoustical change approval is applied
for under Sec. 21.93(b) of this chapter on or after March 6, 1986. Compliance
with the requirements of this section must be demonstrated under appendix H
of this part, or, for helicopters having a maximum certificated takeoff
weight of not more than 6,000 pounds, compliance with this section may be
demonstrated under Appendix J of this part.
(a) General requirements. Except as otherwise provided, for helicopters
covered by this section, the acoustical change approval requirements are as
follows:
(1) In showing compliance with the requirements of appendix H of this part,
noise levels must be measured, evaluated, and calculated in accordance with
the applicable procedures and conditions prescribed in parts B and C of
appendix H of this part. For helicopters having a maximum certificated
takeoff weight of not more than 6,000 pounds that alternatively demonstrate
compliance under appendix J of this part, the flyover noise level prescribed
in appendix J of this part must be measured, evaluated, and calculated in
accordance with the applicable procedures and conditions prescribed in parts
B and C of appendix J of this part.
(2) Compliance with the noise limits prescribed in section H36.305 of
appendix H of this part must be shown in accordance with the applicable
provisions of part D of appendix H of this part. For those helicopters that
demonstrate compliance with the requirements of appendix J of this part,
compliance with the noise levels prescribed in section J36.305 of appendix J
of this part must be shown in accordance with the applicable provisions of
part D of appendix J of this part.
(b) Stage 1 helicopters. Except as provided in Sec. 36.805(c), for each
Stage 1 helicopter prior to a change in type design, the helicopter noise
levels may not, after a change in type design, exceed the noise levels
specified in section H36.305(a)(1) of appendix H of this part where the
demonstration of compliance is under appendix H of this part. The tradeoff
provisions under section H36.305(b) of appendix H of this part may not be
used to increase any Stage 1 noise level beyond these limits. If an applicant
chooses to demonstrate compliance under appendix J of this part, for each
Stage 1 helicopter prior to a change in type design, the helicopter noise
levels may not, after a change in type design, exceed the Stage 2 noise
levels specified in section J36.305(a) of Appendix J of this part.
(c) Stage 2 helicopters. For each helicopter that is Stage 2 prior to a
change in type design, the helicopter must be a Stage 2 helicopter after a
change in type design.
[Amdt. 36-20, 57 FR 42854, Sept. 16, 1992]
Subpart B--Noise Measurement and Evaluation for Transport Category Large
Airplanes and Turbojet Powered Airplanes
Sec. 36.101 Noise measurement.
For transport category large airplanes and turbojet powered airplanes the
noise generated by the airplane must be measured under Appendix A of this
part or under an approved equivalent procedure.
[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as amended by Amdt. 36-10, 43 FR
28420, June 29, 1968]
Sec. 36.103 Noise evaluation.
For transport category large airplanes and turbojet powered airplanes noise
measurement information obtained under Sec. 36.101 must be evaluated under
Appendix B of this part or under an approved equivalent procedure.
[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as amended by Amdt. 36-10, 43 FR
28420, June 29, 1978]
Subpart C--Noise Limits for Subsonic Transport Category Large Airplanes and
Subsonic Turbojet Powered Airplanes
Sec. 36.201 Noise limits.
(a) For subsonic transport category large airplanes and subsonic turbojet
powered airplanes compliance with this section must be shown with noise
levels measured and evaluated as prescribed in Subpart B of this part, and
demonstrated at the measuring points, and in accordance with the flight test
conditions under sections C36.7 and C36.9 (or an approved equivalent
procedure), prescribed under Appendix C of this part.
(b) Type certification applications for subsonic transport category large
airplanes and all subsonic turbojet powered airplanes must show that the
noise levels of the airplane are no greater than the Stage 3 noise limits
prescribed in section C36.5(a)(3) of Appendix C of this part.
[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as amended by Amdt. 36-7, 42 FR
12371, Mar. 3, 1977; Amdt. 36-8, 43 FR 8730, Mar. 2, 1978; Amdt. 36-10, 43 FR
28420, June 29, 1978; Amdt. 36-12, 46 FR 33464, June 29, 1981; Amdt. 36-15,
53 FR 16366, May 6, 1988]
Subpart D--Noise Limits for Supersonic Transport Category Airplanes
Sec. 36.301 Noise limits: Concorde.
(a) General. For the Concorde airplane, compliance with this subpart must
be shown with noise levels measured and evaluated as prescribed in Subpart B
of this part, and demonstrated at the measuring points prescribed in Appendix
C of this part.
(b) Noise limits. It must be shown, in accordance with the provisions of
this part in effect on October 13, 1977, that the noise levels of the
airplane are reduced to the lowest levels that are economically reasonable,
technologically practicable, and appropriate for the Concorde type design.
[Amdt. 36-10, 43 FR 28420, June 29, 1978]
Subpart E--[Reserved]
Subpart F--Propeller Driven Small Airplanes And Propeller-Driven, Commuter
Category Airplanes
Sec. 36.501 Noise limits.
(a) Compliance with this subpart must be shown for--
(1) Propeller driven small airplanes for which application for the issuance
of a new, amended, or supplemental type certificate in the normal, utility,
acrobatic, transport, or restricted category is made on or after October 10,
1973; and propeller-driven, commuter category airplanes for which application
for the issuance of a type certificate in the commuter category is made on or
after January 15, 1987.
(2) Propeller driven small airplanes and propeller-driven, commuter
category airplanes for which application is made for the original issuance of
a standard airworthiness certificate or restricted category airworthiness
certificate, and that have not had any flight time before January 1, 1980
(regardless of date of application).
(3) Airplanes in the primary category:
(i) Except as provided in paragraph (a)(3)(ii) of this section, for an
airplane for which application for a type certificate in the primary category
is made, and that was not previously certificated under appendix F of this
part, compliance with appendix G of this part must be shown.
(ii) For an airplane in the normal, utility or acrobatic category that (A)
has a type certificate issued under this chapter, (B) has a standard
airworthiness certificate issued under this chapter, (C) has not undergone an
acoustical change from its type design, (D) has not previously been
certificated under appendix F or G of this part, and (E) for which
application for conversion to the primary category is made, no further
showing of compliance with this part is required.
(b) For aircraft covered by this subpart for which certification tests are
completed before December 22, 1988, compliance must be shown with noise
levels as measured and prescribed in Parts B and C of Appendix F, or under
approved equivalent procedures. It must be shown that the noise level of the
airplane is no greater than the applicable limit set in Part D of Appendix F.
(c) For aircraft covered by this subpart for which certification tests are
not completed before December 22, 1988, compliance must be shown with noise
levels as measured and prescribed in Parts B and C of Appendix G, or under
approved equivalent procedures. It must be shown that the noise level of the
airplane is no greater than the applicable limits set in Part D of Appendix
G.
[Doc. No. 13243, 40 FR 1034, Jan. 6, 1975, as amended by Amdt. 36-13, 52 FR
1836, Jan. 15, 1987; Amdt. 36-16, 53 FR 47400, Nov. 22, 1988; Amdt. 36-19,
57 FR 41369, Sept. 9, 1992]
Subpart G--[Reserved]
Subpart H--Helicopters
Source: Amdt. 36-14, 53 FR 3540, Feb. 5, 1988; 53 FR 7728, Mar. 10, 1988,
unless otherwise noted.
Sec. 36.801 Noise measurement.
For primary, normal, transport, or restricted category helicopters for
which certification is sought under appendix H of this part, the noise
generated by the helicopter must be measured at the noise measuring points
and under the test conditions prescribed in part B of appendix H of this
part, or under an FAA-approved equivalent procedure. For those primary,
normal, transport, and restricted category helicopters having a maximum
certificated takeoff weight of not more than 6,000 pounds for which
compliance with appendix J of this part is demonstrated, the noise generated
by the helicopter must be measured at the noise measuring point and under the
test conditions prescribed in part B of appendix J of this part, or an FAA-
approved equivalent procedure.
[Amdt. 36-20, 57 FR 42854, Sept. 16, 1992]
Sec. 36.803 Noise evaluation and calculation.
The noise measurement data required under Sec. 36.801 and obtained under
appendix H of this part must be corrected to the reference conditions
contained in part A of appendix H of this part, and evaluated under the
procedures of part C of appendix H of this part, or an FAA-approved
equivalent procedure. The noise measurement data required under Sec. 36.801
and obtained under appendix J of this part must be corrected to the reference
conditions contained in part A of appendix J of this part, and evaluated
under the procedures of part C of appendix J of this part, or an FAA-approved
equivalent procedure.
[Amdt. 36-20, 57 FR 42854, Sept. 16, 1992]
Sec. 36.805 Noise limits.
(a) Compliance with the noise levels prescribed under part D of appendix H
of this part, or under part D of appendix J of this part, must be shown for
helicopters for which application for issuance of a type certificate in the
primary, normal, transport, or restricted category is made on or after March
6, 1986.
(b) For helicopters covered by this section, except as provided in
paragraph (c) or (d)(2) of this section, it must be shown either:
(1) For those helicopters demonstrating compliance under Appendix H of this
part, the noise levels of the helicopter are no greater than the applicable
limits prescribed under section H36.305 of Appendix H of this part, or
(2) For helicopters demonstrating compliance under Appendix J of this part,
the noise level of the helicopter is no greater than the limit prescribed
under section J36.305 of appendix J of this part.
(c) For helicopters for which application for issuance of an original type
certificate in the primary, normal, transport, or restricted category is made
on or after March 6, 1986, and which the FAA finds to be the first civil
version of a helicopter that was designed and constructed for, and accepted
for operational use by, an Armed Force of the United States or the U.S. Coast
Guard on or before March 6, 1986, it must be shown that the noise levels of
the helicopter are no greater than the noise limits for a change in type
design as specified in section H36.305(a)(1)(ii) of Appendix H of this part
for compliance demonstrated under appendix H of this part, or as specified in
section J36.305 of appendix J of this part for compliance demonstrated under
appendix J of this part. Subsequent civil versions of any such helicopter
must meet the Stage 2 requirements.
(d) Helicopters in the primary category:
(1) Except as provided in paragraph (d)(2) of this section, for a
helicopter for which application for a type certificate in the primary
category is made, and that was not previously certificated under Appendix H
of this part, compliance with Appendix H of this part must be shown.
(2) For a helicopter that:
(i) Has a normal or transport type certificate issued under this chapter,
(ii) Has a standard airworthiness certificate issued under this chapter,
(iii) Has not undergone an acoustical change from its type design,
(iv) Has not previously been certificated under Appendix H of this part,
and
(v) For which application for conversion to the primary category is made,
no further showing of compliance with this part is required.
[Amdt. 36-20, 57 FR 42855, Sept. 16, 1992]
Subparts I--N [Reserved]
Subpart O--Operating Limitations and Information
Sec. 36.1501 Procedures, noise levels and other information.
(a) All procedures, weights, configurations, and other information or data
employed for obtaining the certified noise levels prescribed by this part,
including equivalent procedures used for flight, testing, and analysis, must
be developed and approved. Noise levels achieved during type certification
must be included in the approved airplane (rotorcraft) flight manual.
(b) Where supplemental test data are approved for modification or extension
of an existing flight data base, such as acoustic data from engine static
tests used in the certification of acoustical changes, the test procedures,
physical configuration, and other information and procedures that are
employed for obtaining the supplemental data must be developed and approved.
[Amdt. 36-15, 53 FR 16366, May 6, 1988]
Sec. 36.1581 Manuals, markings, and placards.
(a) If an Airplane Flight Manual or Rotorcraft Flight Manual is approved,
the approved portion of the Airplane Flight Manual or Rotorcraft Flight
Manual must contain the following information, in addition to that specified
under Sec. 36.1583 of this part. If an Airplane Flight Manual or Rotorcraft
Flight Manual is not approved, the procedures and information must be
furnished in any combination of approved manual material, markings, and
placards.
(1) For transport category large airplanes and turbojet powered airplanes,
the noise level information must be one value for each takeoff, sideline, and
approach as defined and required by Appendix C of this part, along with the
maximum takeoff weight, maximum landing weight, and configuration.
(2) For propeller driven small airplanes the noise level information must
be one value for flyover as defined and required by Appendix F of this part,
along with the maximum takeoff weight and configuration.
(b) If supplemental operational noise level information is included in the
approved portion of the Airplane Flight Manual, it must be segregated,
identified as information in addition to the certificated noise levels, and
clearly distinguished from the information required under Sec. 36.1581(a).
(c) The following statement must be furnished near the listed noise levels:
No determination has been made by the Federal Aviation Administration that
the noise levels of this aircraft are or should be acceptable or unacceptable
for operation at, into, or out of, any airport.
(d) For transport category large airplanes and turbojet powered airplanes,
for which the weight used in meeting the takeoff or landing noise
requirements of this part is less than the maximum weight established under
the applicable airworthiness requirements, those lesser weights must be
furnished, as operating limitations in the operating limitations section of
the Airplane Flight Manual. Further, the maximum takeoff weight must not
exceed the takeoff weight that is most critical from a takeoff noise
standpoint.
(e) For propeller driven small airplanes and for propeller-driven, commuter
category airplanes for which the weight used in meeting the flyover noise
requirements of this part is less than the maximum weight by an amount
exceeding the amount of fuel needed to conduct the test, that lesser weight
must be furnished, as an operating limitation, in the operating limitations
section of an approved Airplane Flight Manual, in approved manual material,
or on an approved placard.
(f) For primary, normal, transport, and restricted category helicopters, if
the weight used in meeting the takeoff, flyover, or approach noise
requirements of appendix H of this part, or the weight used in meeting the
flyover noise requirement of appendix J of this part, is less than the
certificated maximum takeoff weight established under either Sec. 27.25(a) or
Sec. 29.25(a) of this chapter, that lesser weight must be furnished as an
operating limitation in the operating limitations section of the Rotorcraft
Flight Manual, in FAA-approved manual material, or on an FAA-approved
placard.
(g) Except as provided in paragraphs (d), (e), and (f) of this section, no
operating limitations are furnished under this part.
[Doc. 13243, 40 FR 1035, Jan. 6, 1975 as amended by Amdt. 36-10, 43 FR 28420,
June 29, 1978; Amdt. 36-11, 45 FR 67066, Oct. 9, 1980; Amdt. 36-13, 52 FR
1836, Jan. 15, 1987. Redesignated and amended by Amdt. 36-14, 53 FR 3540,
Feb. 5, 1988; 53 FR 7728, Mar. 10, 1988; Amdt. 36-15, 53 FR 16366, May 6,
1988; 53 FR 18950, May 25, 1988; Amdt. 36-20, 57 FR 42855, Sept. 16, 1992]
Sec. 36.1583 Noncomplying agricultural and fire fighting airplanes.
(a) This section applies to propeller-driven, small airplanes that--
(1) Are designed for "agricultural aircraft operations" (as defined in Sec.
137.3 of this chapter, effective on January 1, 1966) or for dispensing fire
fighting materials; and
(2) Have not been shown to comply with the noise levels prescribed under
Appendix F of this part--
(i) For which application is made for the original issue of a standard
airworthiness certificate and that do not have any flight time before January
1, 1980; or
(ii) For which application is made for an acoustical change approval, for
airplanes which have a standard airworthiness certificate after the change in
the type design, and that do not have any flight time in the changed
configuration before January 1, 1980.
(b) For airplanes covered by this section an operating limitation reading
as follows must be furnished in the manner prescribed in Sec. 36.1581:
Noise abatement: This airplane has not been shown to comply with the noise
limits in FAR Part 36 and must be operated in accordance with the noise
operating limitation prescribed under FAR Sec. 91.815.
[Amdt. 36-11, 45 FR 67066, Oct. 9, 1980. Redesignated by Amdt. 36-14, 53 FR
3540, Feb. 5, 1988; Amdt. 36-18, 54 FR 34330, Aug. 18, 1989]
Effective Date Note: At 54 FR 34330, Aug. 18, 1989, Sec. 36.1583(b) was
amended by changing the cross reference "Sec. 91.56" to "Sec. 91.815",
effective August 18, 1990.
Appendix A--Aircraft Noise Measurement Under Sec. 36.101
Sec.
A36.1 Noise certification test and measurement conditions.
A36.3 Measurement of aircraft noise received on the ground.
A36.5 Reporting and correcting measured data.
A36.7 Symbols and units.
A36.9 Atmospheric attenuation of sound.
A36.11 Detailed correction procedures.
Section A36.1 Noise certification test and measurement conditions.
(a) General. This section prescribes the conditions under which aircraft
noise certification tests must be conducted and the measurement procedures
that must be used to measure aircraft noise during each test conducted on or
after April 3, 1978.
(b) Test site requirements. (1) Tests to show compliance with established
aircraft noise certification levels must consist of a series of takeoffs and
approaches (or stabilized flight path segments thereof) during which
measurements must be taken at noise measuring stations located at the
measuring points prescribed in section C36.3 of Appendix C of this part. Each
recorded segment must include measurements throughout the entire time period
in which the recorded signal is within 10 dB of PNLTM.
(2) During each test takeoff, simultaneous measurements should be made at
the sideline noise measuring stations on each side of the runway and also at
the takeoff noise measuring station. However, if test site conditions make it
impractical to simultaneously measure takeoff and sideline noise, and if each
of the other sideline measurement requirements is met, independent
measurements may be made of the sideline noise under simulated flight path
techniques. If the reference flight path includes a power cutback before the
maximum possible sideline noise level is developed, the reduced sideline
noise level which is the maximum value developed by the simulated flight path
technique must be the certificated sideline noise value.
(3) If the height of the ground at a noise measuring station differs from
that of the nearest point on the runway by more than 20 feet, corrections
must be made as prescribed in section A36.5(d) of this appendix.
(4) The location of each noise measuring station must be surrounded by
relatively flat terrain having no excessive sound absorption characteristics,
such as might be caused by thick, matted, or tall grass, shrubs, or wooded
areas.
(5) An airport tower, or other facility, used to obtain required
measurements of meteorological conditions at the test site must be approved
in accordance with section A36.9(b)(1) of this appendix.
(6) During the period when the flyover noise/time record indicates the
noise measurement is within 10 dB of PNLTM, no obstruction that significantly
influences the sound field from the aircraft may exist--
(i) For a takeoff, approach, or sideline measuring station, within a
conical space above the measuring position (the point on the ground
vertically below the microphone), the cone being defined by an axis normal to
the ground and by a half-angle 80 degrees from this axis; and
(ii) For a sideline noise measuring station, above the line of sight
between the microphone and the aircraft.
(7) A minimum of two noise measuring stations, symmetrically positioned
about the test flight track, must be used to define the maximum sideline
noise with respect to location and level as required by section C36.3 of
Appendix C of this part. For turbojet powered aircraft, when approved by the
FAA, the maximum sideline noise at takeoff thrust may be assumed to occur at
the point (or its approved equivalent) along the extended centerline of the
runway where the aircraft reaches 1000 feet (305 meters) altitude above
ground level. A height of 1440 feet (439 meters) may be assumed for Stage 1
or Stage 2 four engine airplanes. The altitude of the aircraft as it passes
the microphone stations must be within +500 to -0 feet (+150 to -0 meters) of
the target altitude. For aircraft powered by other than turbojet engines, the
altitude for maximum sideline noise must be determined experimentally.
(c) Weather restrictions. The tests must be conducted under the following
atmospheric conditions:
(1) No rain or other precipitation.
(2) Ambient air temperature between 36 degrees F and 95 degrees F (2.2
degrees C and 35 degrees C), inclusively, over that portion of the sound
propagation path between the aircraft and a point 10 meters above the ground
at the noise measuring station.
(3) Relative humidity and ambient temperature over that portion of the
sound propagation path between the aircraft and a point 10 meters above the
ground at the noise measuring station is such that the sound attenuation in
the one-third octave band centered a 8 kHz is not greater than 12 dB/100
meters and the relative humidity is between 20 and 95 percent, inclusively.
However, if the dew point and dry bulb temperature used for obtaining
relative humidity are measured with a device which is accurate to within +/-
0.5 deg.C, the sound attenuation rate shall not exceed 14 dB/100 meters in
the one-third octave band centered at 8kHz.
(4) Average wind velocity 10 meters above ground is not to exceed 12 knots
and the crosswind velocity for the airplane is not to exceed 7 knots. The
average wind velocity shall be determined using a thirty-second averaging
period spanning the 10 dB down time interval. Maximum wind velocity 10 meters
above ground is not to exceed 15 knots and the crosswind velocity is not to
exceed 10 knots during the 10 dB down time interval.
(5) No anomalous wind conditions (including turbulence) which will
significantly affect the noise level of the aircraft when the noise is
recorded at each noise measuring station.
(d) Aircraft testing procedures.--(1) The aircraft testing procedures and
noise measurements must be conducted and processed in an approved manner
which yields the noise evaluation measure designated as Effective Perceived
Noise Level (EPNL) in units of EPNdB, as prescribed in Appendix B of this
part.
(2) The aircraft height and lateral position relative to the extended
centerline of the runway must be determined by an FAA approved method which
is independent of normal flight instrumentation, such as radar tracking,
theodolite triangulation, laser trajectography, or photographic scaling
techniques.
(3) The aircraft position along the flight path must be related to the
noise recorded at the noise measuring stations by means of synchronizing
signals at an approved sampling rate. The position of the aircraft must be
recorded relative to the runway during the entire time period in which the
recorded signal is within 10 dB of PNLTM. Measuring and sampling equipment
must be approved by the FAA.
(4) Each takeoff test must meet the conditions of section C36.7 of Appendix
C of this part.
(5) If a takeoff test series is conducted at weights other than the maximum
takeoff weight for which noise certification is requested, the following
additional requirements apply:
(i) At least one takeoff test must be conducted at a weight at, or above,
the maximum certification weight.
(ii) Each test weight must be within +5 percent or -10 percent of the
maximum certification weight.
(6) Each approach test must be conducted with the aircraft stabilized and
following a 3.0 degree +/-0.5 degree approach angle and must meet the
requirements of section C36.9 of Appendix C of this part.
(7) If an approach test series is conducted at weights other than the
maximum landing weight for which certification is requested, the following
additional requirements apply:
(i) At least one approach test must be conducted at a weight at, or above,
the maximum landing weight.
(ii) Each test weight must exceed 90 percent of the maximum landing weight.
(8) Aircraft performance data sufficient to make the correction required
under section A36.5 of this appendix must be recorded at an approved sampling
rate using FAA approved equipment.
Section A36.3 Measurement of aircraft noise received on the ground.
(a) General. (1) The measurements prescribed in this section provide the
data for determining the one-third octave band noise produced by aircraft
during testing at specific noise measuring stations, as a function of time.
(2) Sound pressure level data for aircraft noise certification purposes
must be obtained with approved acoustical equipment and measurement
practices.
(3) Paragraphs (b), (c), and (d) of this section prescribe the required
equipment specifications. Paragraphs (e) and (f) prescribe the calibration
and measurement procedures required for each certification test series.
(b) Measurement system. The acoustical measurement system must consist of
approved equipment equivalent to the following:
(1) A microphone system with frequency response and directivity which are
compatible with the measurement and analysis system accuracy prescribed in
paragraph (c) of this section.
(2) Tripods or similar microphone mountings that minimize interference with
the sound energy being measured.
(3) Recording and reproducing equipment whose characteristics, frequency
response, and dynamic range are compatible with the response and accuracy
requirements of paragraph (c) of this section.
(4) Calibrators using sine wave, or pink noise, of known levels. When pink
noise (defined in paragraph (e)(1) of this section) is used, the signal must
be described in terms of its root-mean-square (rms) value.
(5) Analysis equipment with the response and accuracy which meets or
exceeds the requirements of paragraph (d) of this section.
(6) Attenuators used for range changing in sensing, recording, reproducing,
or analyzing aircraft sound must be capable of being operated in equal-
interval decibel steps with no error between any two settings which exceeds
0.2 dB.
(c) Sensing, recording, and reproducing equipment. (1) The sound produced
by the aircraft must be recorded in such a way that the complete information,
including time history, is retained. A magnetic tape recorder is acceptable.
(2) The microphone must be a pressure sensitive capacitive type, or its
approved equivalent, such as free field type with incidence corrector.
(i) After an adequate "warm-up" period, at least as long as that specified
by the equipment manufacturer, the system output for constant acoustical
input shall change by not more than 0.3 dB within any one hour nor by more
than 0.4 dB within 5 hours.
(ii) The variation of microphone and preamplifier system sensitivity within
an angle of +/-30 degrees of grazing (60-120 degrees from the normal to the
diaphragm) must not exceed the following values:
Change in
sensitivity
Frequency (HZ) (dB)
45 to 1,120 1.0
1,120 to 2,240 1.5
2,240 to 4,500 2.5
4,500 to 7,100 4.0
7,100 to 11,200 5.0
With the wind screen in place, the variation in sensitivity in the plane of
the diaphragm of the microphone system shall not exceed 1.0 dB over the
frequency range 45 to 11,200 Hz.
(iii) The free-field frequency response of the microphone system at the
reference incidence direction shall lie within an envelope having the
following values:
Change in
Tolerance
Frequency (HZ) (dB)
45 to 4,500 +/-1.0
4,500 to 5,600 +/-1.5
5,600 to 7,100 +1.5 to -2.0
7,100 to 9,000 +1.5 to -3.0
9,000 to 11,200 +2.0 to -4.0
Note: The requirements of this paragraph may be determined by a pressure
response calibration (which may be obtained from an electrostatic calibrator
in combination with manufacturer provided corrections) or an anechoic free-
field facility.
(iv) Specifications concerning sensitivity to environmental factors such as
temperature, relative humidity, and vibration must in conformity with the
recommendations of International Electrotechnical Commission (IEC)
Publication No. 179, entitled "Precision Sound Level Meters" (as incorporated
by reference under Sec. 36.6 of this part).
(v) If the wind speed exceeds 6 knots, a windscreen must be employed with
the microphone during each measurement of aircraft noise. Correction for any
insertion loss produced by the windscreen as a function of frequency, must be
applied to the measured data and any correction applied must be reported.
(3) If a magnetic tape recorder is used to store data for subsequent
analysis, the record/replay system (including tape) must conform to the
following:
(i) The electric background noise produced by the system in each one-third
octave must be at least 35 dB below the standand recording level, which is
defined as that level which is either 10 dB below the 3 pecent harmonic
distortion level for direct recording or +/-40 percent deviation for
frequency modulation (FM) recording.
(ii) At the standard recording level, the corrected frequency response in
each selected one-third octave band between 44 Hz and 180 Hz must be flat
within +/-0.75 dB, and in each band between 180 Hz and 11,200 Hz must be flat
within +/-0.25 dB.
(iii) If the overall system satisfies the requirements of paragraph
(c)(2)(ii) of this section, and if the limitations of the dynamic range of
the equipment are insufficient to obtain adequate spectral information, high
frequency pre-emphasis may be added to the recording channel with the
converse de-emphasis on playback. If pre-emphasis is added, the
instantaneously recorded sound pressure level between 800 Hz and 11,200 Hz of
the maximum measured noise signal must not vary more than 20 dB between the
levels of the maximum and minimum one-third octave bands.
(d) Analysis equipment. (1) A frequency analysis of the acoustic signal
must be performed using one-third octave filters which conform to the
recommendations of International Electrotechnical Commission (IEC)
Publication No. 225, entitled "Octave, Half-Octave, and Third-Octave Band
Filters Intended for Analysis of Sounds and Vibrations" (as incorporated by
reference under Sec. 36.6 of this part).
(2) A set of 24 consecutive one-third octave filters must be used. The
first filter of the set must be centered at a geometric mean frequency of 50
Hz and the last filter at 10,000 Hz.
(i) The output of each filter must contain less than 0.5 dB ripple.
(ii) The correction for effective bandwidth relative to the response at the
center frequency response for each one-third octave band filter must be
determined by measuring the filter response to sinusoidal signals at a
minimum of 20 frequencies equally spaced between the two adjacent preferred
one-third octave frequencies or by using an approved equivalent procedure.
(3) The analyzer indicating device may be either analog or digital, or a
combination of both. The preferred sequence of signal processing is:
(i) Squaring the one-third octave filter outputs;
(ii) Averaging or intergrating; and
(iii) Coverting linear formulation to logarithmic.
(4) Each detector must operate over a minimum dynamic range of 60 dB and
perform as a true-mean-square device for sinusoidal tone bursts having crest
factors of at least 3 over the following dynamic range:
(i) Up to 30 dB below full-scale reading must be accurate within +0.5 dB;
(ii) Between 30 dB and 40 dB below full-scale reading must be accurate
within +1.0 dB; and
(iii) In excess of 40 dB below full-scale reading must be accurate within
+2.5 dB.
(5) The averaging properties of the integrator must be tested as follows:
(i) White noise must be passed through the 200 Hz one-third octave band
filter and the output fed in turn to each detector/integrator. The standard
deviation of the measured levels must then be determined from a large number
of samples of the filtered white noise taken at intervals of not less than 5
seconds. The value of the standard deviation must be within the interval
0.48+/-0.06 dB for a probability limit of 95 percent. (An approved equivalent
method may be substituted for this test on those analyzers where the test
signal cannot readily be fed directly to each detector/integrator.)
(ii) For each detector/integrator, the response to a sudden onset or
interruption of a constant amplitude sinusoidal signal at the respective one-
third octave band center, frequency must be measured at sampling times 0.5,
1.0, 1.5, and 2.0 seconds after the onset or interruption. The rising
responses must be the following amounts before the steady-state level:
0.5 seconds......................................................4.0+/-1.0 dB
1.0 seconds....................................................1.75+/-0.75 dB
1.5 seconds......................................................1.0+/-0.5 dB
2.0 seconds......................................................0.6+/-0.5 dB
(iii) The falling response must be such that the sum of the decibel
readings (below the initial steady-state level) and the corresponding rising
response reading are 6.5+/-1.0 dB, at each sampling time.
(iv) Analyzers using true integration cannot meet the requirements of
paragraphs (d)(5) (i), (ii), and (iii) of this section directly, because
their overall average time is greater than the sampling interval. For these
analyzers, compliance must be demonstrated in terms of the equivalent output
of the data processor. Further, in cases where readout and resetting require
a dead-time during acquisition, the percentage loss of the total data must
not exceed one percent.
(6) The sampling interval between successive readouts shall not exceed 500
milliseconds and its precise value must be known to within +/-one (1)
percent. The instant in time by which a readout is characterized, shall be
the midpoint of the average period. (The averaging period is defined as twice
the effective time constant of the analyzer.)
(7) The amplitude resolution of the analyzer must be at least 0.25 dB.
(8) After all systematic errors have been eliminated, each output level
from the analyzer must be accurate within +/-1.0 dB of the level of the input
signal. The total systematic errors for each of the output levels must not
exceed +/-3.0 dB. For contiguous filter systems, the systematic correction
between adjacent one-third octave channels must not exceed 4.0 dB.
(9) The dynamic range capability of the analyzer for display of a single
aircraft noise event (in terms of the difference between full-scale output
level and the maximum noise level of the analyzer equipment) must be at least
60 dB.
(e) Calibrations. (1) Within the five days before the beginning of each
test series, the complete electronic system (as installed in the field,
including cables) must be electronically calibrated for frequency and
amplitude by the use of a pink noise signal of known amplitudes covering the
range of signal levels furnished by the microphone. For purposes of this
section, a "pink noise" means a noise whose noise-power/unit-frequency is
inversely proportional to frequency at frequencies within the range of 44 Hz
to 11,200 Hz. The signal used must be described in terms of its average root-
mean-square (rms) values for a nonoverload signal level. This system
calibration must be repeated within five days of the end of each test series,
or as required by the FAA.
(2) Immediately before and after each day's testing, a recorded acoustic
calibration of the system must be made in the field with an acoustic
calibrator to check the system sensitivity and provide an acoustic reference
level for the analysis of the sound level data. The performance of equipment
in the system will be considered satisfactory if, during each day's testing,
the variation does not exceed 0.5 dB.
(3) A normal incidence pressure calibration of the combined microphone/
preamplifier must be performed with pure tones at each preferred one-third
octave frequency from 50 Hz to 10,000 Hz. This calibration must be completed
within the 90 days before the beginning of each test series.
(4) Each reel of magnetic tape must:
(i) Be pistonphone calibrated; and
(ii) At its beginning and end, carry a calibration signal consisting of at
least a 15 second burst of pink noise, as defined in paragraph (e)(1) of this
section.
(5) Data obtained from tape recorded signals are not considered reliable if
the difference between the pink noise signal levels, before and after the
tests in each one-third octave band, exceeds 0.75 dB.
(6) The one-third octave filters must have been demonstrated to be in
conformity with the recommendations of IEC Publication 225 (as incorporated
by reference under Sec. 36.6 of this part) during the six calendar months
preceding the beginning of each test series. However, the correction for
effective bandwidth relative to the center frequency response may be
determined for each filter--
(i) By measuring the filter response to sinusoidal signals at a minimum of
twenty frequencies equally spaced between the two adjacent preferred one-
third octave frequencies; or
(ii) By using an approved alternative technique.
(7) A performance calibration analysis of each piece of calibration
equipment, including piston phones, reference microphones, and voltage insert
devices, must have been made during the six calendar months preceding the
beginning of each day's test series. Each calibration must be traceable to
the National Bureau of Standards.
(f) Noise measurement procedures. (1) Each microphone must be oriented so
that the diaphragm is substantially in the plane defined by the flight path
of the aircraft and the measuring station. The microphone located at each
noise measuring station must be placed so that its sensing element is
approximately 4 feet above ground.
(2) Immediately before and immediately after each series of test runs and
each day's testing, a recorded acoustic calibration of the system prescribed
in section A36.3(e)(2) of this appendix must be made in the field to check
the acoustic reference level for the analysis of the sound level data.
Ambient noise must be recorded for at least 10 seconds and be representative
of the acoustical background, including systemic noise, that exists during
the flyover test run. During that recorded period, each component of the
system must be set at the gain-levels used for aircraft noise measurement.
(3) The mean background noise spectrum must contain the sound pressure
levels, which, in each preferred third octave band in the range of 50 Hz to
10,000 Hz, are the averages of the energy of the sound pressure levels in
every preferred third octave. When analyzed in PNL, the resulting mean
background noise level must be at least 20 PNdB below the maximum PNL of the
aircraft.
(4) Corrections for recorded levels of background noise are allowed, within
the limits prescribed in Sec. A36.5(d)(3) of this appendix.
Section A36.5 Reporting and correcting measured data.
(a) General. Data representing physical measurements, or corrections to
measured data, including corrections to measurements for equipment response
deviations, must be recorded in permanent form and appended to the record.
Each correction must be reported and is subject to FAA approval. An estimate
must be made of each individual error inherent in each of the operations
employed in obtaining the final data.
(b) Data reporting. (1) Measured and corrected sound pressure levels must
be presented in one-third octave band levels obtained with equipment
conforming to the standards prescribed in section A36.3 of this appendix.
(2) The type of equipment used for measurement and analysis of all
acoustics, aircraft performance, and meteorological data must be reported.
(3) The atmospheric environmental data required to demonstrate compliance
with section A36.1(c) of this appendix, measured throughout the test period
under section A36.9(b)(3) of this appendix, must be reported.
(4) Conditions of local topography, ground cover, or events which may
interfere with sound recording must be reported.
(5) The following aircraft information must be reported:
(i) Type, model, and serial numbers (if any) of aircraft engines.
(ii) Gross dimensions of aircraft and location of engines.
(iii) Aircraft gross weight for each test run.
(iv) Aircraft configuration, including flap and landing gear positions.
(v) Airspeed in knots.
(vi) Engine performance parameters relevant to noise generation, such as
net thrust, engine pressure ratio, exhaust temperatures, and fan or
compressor rotational speeds.
(vii) Aircraft flight path (above ground level in feet) determined by an
FAA approved method which is independent of normal flight instrumentation,
such as radar tracking, theodolite triangulation, laser trajectography, or
photographic scaling techniques.
(6) Aircraft speed and position, and engine performance parameters must be
recorded at an approved sampling rate sufficient to correct to the noise
certification reference conditions prescribed in paragraph (c) of this
section. Lateral position relative to the extended centerline of the runway,
configuration, and gross weight must be reported.
(c) Noise certification reference conditions. (1) Meteorological
conditions. Aircraft position and performance data and the noise measurements
must be corrected to the following homogeneous noise certification reference
atmospheric conditions:
(i) Sea level pressure of 2116 psf (76 cm mercury).
(ii) Ambient temperature of 77 degrees F (25 degrees C).
(iii) Relative humidity of 70 percent.
(iv) Zero wind.
(2) Aircraft conditions. The reference condition for takeoff is the maximum
weight, except as provided in Sec. 36.1581(b) of this part. The reference
conditions for approach tests consist of--
(i) Maximum landing weight, except as provided in Sec. 36.1581(d) of this
part;
(ii) Approach angle of 3 degrees; and
(iii) Aircraft height of 394 feet above the ground at the noise measuring
station.
(d) Data corrections. (1) Aircraft position and performance data and the
noise measurement must be corrected to the noise certification reference
conditions as prescribed in paragraph (c) of this section. The measured
atmospheric conditions must be those obtained in accordance with section
A36.1(c) of this appendix and paragraph (b)(3) of this section. Atmospheric
attenuation sound corrections must be made under section A36.9 of this
appendix.
(2) The measured flight path must be corrected by an amount equal to the
difference between the applicants predicted flight path for the certification
reference conditions and the measured flight path at the test conditions.
Necessary corrections relating to aircraft flight path or performance may be
derived from approved data other than certification test data. The source
noise must be corrected from approved data for the difference between
measured and reference engine conditions, together with appropriate
allowances for sound attenuation with distance. The Effective Perceived Noise
Level (EPNL) correction must be less than 2.0 EPNdB for any combination of
the following:
(i) The aircraft's not passing vertically above the measuring station.
(ii) Any difference between 394 feet and the actual minimum distance of the
aircraft's ILS antenna from the approach measuring station.
(iii) Any difference between the actual approach angle and the noise
certification reference approach flight path.
(iv) Any correction of the measured noise levels which accounts for any
difference between the test engine thrust or power and the reference engine
thrust or power.
Detailed correction requirements are prescribed in section A36.11 of this
appendix.
(3) Aircraft sound pressure levels within the 10 dB-down points (described
in section B36.9 of Appendix B) must exceed the mean background sound
pressure levels determined under section A36.3(f)(3) by at least 3 dB in each
one-third octave band (or be corrected under an FAA approved method) to be
included in the computation of the overall noise level of the aircraft. An
EPNL may not be computed or reported from data from which more than four one-
third octave bands in any spectrum within the 10 dB-down points have been
excluded under this paragraph.
(4) Where more than seven one-third octaves are within 3 dB of the ambient
noise levels, a time/frequency interpolation of the noise data shall be
performed using an approved procedure.
(5) If equivalent test procedures, different from the reference procedures,
are used, the test procedures and all methods for adjusting the results to
the reference procedures must be approved by the FAA. The amounts of
adjustments must not exceed 16 EPNdB on takeoff and 8 EPNdB on approach, and
if the adjustments are more than 8 EPNdB and 4 EPNdB respectively, the
resulting numbers must not be within 2 EPNdB of the appropriate Appendix C
noise levels including tradeoffs.
(e) Validity of results. (1) The test results must produce three mean EPNL
values within the 90 percent confidence limits, each value consisting of the
arithmetic mean of the corrected noise measurements for all valid test runs
at the takeoff, approach, and sideline measuring stations, respectively. If
more than one noise measurement system is used at any single measuring
station, the resulting data for each test run (after correction) must be
averaged as a single measurement. If more than one test site or noise
measuring station location is used, each valid test run must be included in
the computation of the mean EPNL values and their confidence limits.
(2) The minimum sample size acceptable for each of the three certification
measurements (takeoff, approaches, and sideline) is six. The number of
samples must be large enough to establish statistically for each of the three
mean noise certification levels a 90 percent confidence limit which does not
exceed +/-1.5 EPNdB. No test result may be omitted from the averaging
process, unless otherwise specified by the FAA.
(3) The mean EPNL values and their 90 percent confidence limits obtained by
the procedure described in this paragraph must be those by which the noise
emission of the aircraft is assessed against the noise certification
criteria, and must be reported.
(4) If equivalent procedures are to be used to certificate several airplane
configurations of the same type from noise tests of a single airplane, the
test procedures and analysis methods must be approved by the FAA. The request
for approval must identify the noise measurement test procedures and data
base, the airplane configurations, procedures and analysis methods, the
method for establishing the 90 percent confidence limit for each noise
certification level, and the proposed equivalent procedures.
Section A36.7 Symbols and units.
(a) General. The symbols used in Appendixes A and B of this part have the
following meanings.
Symbol Unit Meaning
ant Antilogarithm to the
Base 10.
C(k) dB Tone Correction. The
factor to be added to
PLN(k) to account for
the presence of
spectral irregularities
such as tones at the k-
th increment of time.
d Sec Duration Time. The
length of the
significant noise time
history being the time
interval between the
limits of t(1) and t(2)
to the nearest second.
D dB Duration Correction. The
factor to be added to
PNLM to account for the
duration of the noise.
EPNL EPNdB Effective Perceived
Noise Level. The value
of PNL adjusted for
both the presence or
discrete frequencies
and the time history.
(The unit EPNdB is used
instead of the unit
dB.)
f(i) or fi Hz Frequency. The
geometrical mean
frequency for the i-th
one-third octave band.
F(i,k) dB Delta-dB. The difference
between the original
and background sound
pressure levels in the
i-th one-third octave
band at the k-th
interval of time.
h dB dB-Down. The level to be
subtracted from PNLTM
that defines the
duration of the noise.
H % Relative Humidity. The
ambient atmospheric
relative humidity.
(i) or i Frequency Band Index.
The numerical indicator
that denotes any one of
the 24 one-third octave
bands with geometrical
mean frequencies from
50 to 10,000 Hz.
(k) Time Increment Index.
The numerical indicator
that denotes the number
of equal time
increments that have
elapsed from a
reference zero.
log Logarithm to the Base
10.
log n (a) Noy discontinuity
Coordinate. The log n
value of the
intersection point of
the straight lines
representing the
variation of SPL with
log n.
M(b), M(c) Noy Inverse Slope. The
reciprocals of the
slopes of the straight
lines representing the
variation of SPL with
log n.
n noy Perceived Noisiness. The
perceived noisiness at
any instant of time
that occurs in a
specified frequency
range.
n(i, k) noy Perceived Noisiness. The
perceived noisiness at
the k-th instant of
time that occurs in the
i-th one-third octave
band.
n(k) noy Maximum Perceived
Noisiness. The maximum
value of all of the 24
values of n(i) that
occurs at the k-th
instant of time.
N(k) noy Total Perceived
Noisiness. The total
perceived noisiness at
the k-th instant of
time calculated from
the 24-instantaneous
values of n(i, k).
p(b), p(c) Noy Slope. The slopes of
the straight lines
representing the
variation of SPL with
log n.
PNL PNdB Perceived Noise Level.
The perceived noise
level at any instant of
time (the unit PNdB is
used instead of the
unit dB).
PNL(k) PNdB Perceived Noise Level.
The perceived noise
level calculated from
the 24 values of SPL
(i, k) at the k-th
increment of time. (The
unit PNdB is used
instead of the unit
dB.)
PNLM PNdB Maximum Perceived Noise
Level. The maximum
value of PNL(k) that
occurs during the
aircraft flyover. (The
unit PNdB is used
instead of the unit
dB.)
PNLT PNdB Tone Corrected Perceived
Noise Level. The value
of PNL adjusted for the
presence of spectral
irregularities
(discrete frequencies)
at any instant of time.
(The unit PNdB is used
instead of the unit
dB.)
PNLT(k) PNdB Tone Corrected Perceived
Noise Level. The value
of PNL(k) adjusted for
the presence of
discrete frequencies
that occurs at the k-th
increment of time. (The
unit PNdB is used
instead of the unit
dB.)
PNLTM PNdB Maximum tone Corrected
Perceived Noise Level.
The maximum value of
PNLT(k) that occurs
during the aircraft
flyover. (The unit PNdB
is used instead of the
unit dB.)
s(i, k) dB Slope of Sound Pressure
Level. The change in
level between adjacent
one-third octave band
sound pressure levels
at the i-th band for
the k-th instant of
time.
<Delta>s(i, k) dB Change in Slope of Sound
Pressure Level.
s'(i, k) dB Adjusted Slope of Sound
Pressure Level. The
change in level between
adjacent adjusted one-
third octave band sound
pressure levels at the
i-th band for the k-th
instant of time.
s(i, k) dB Average Slope of Sound
Pressure Level.
SPL dB re 0.0002 microbar Sound Pressure Level.
The sound pressure
level at any instant of
time that occurs in a
specified frequency
range.
SPL(a) dB re 0.002 microbar Noy Discontinuity
Coordinate. The SPL
value of the
intersection point of
the straight lines
representing the
variation of SPL with
log n.
SPL(b) dB re 0.002 microbar Noy Intercept. The
SPL(c) intercepts on the SPL-
axis of the straight
lines representing the
variation of SPL with
log n.
SPL(l, k) dB re 0.002 microbar Sound Pressure Level.
The sound pressure
level at the k-th
instant of time that
occurs in the i-th one-
third octave band.
SPL'(l, k) dB re 0.002 microbar Adjusted Sound Pressure
Level. The first
approximation to
background level in the
i-th one-third octave
band for the k-th
instant of time.
SPL''(l, k) dB re 0.002 microbar Background Sound
Pressure Level. The
final approximation to
background level in the
i-th one-third octave
band for the k-th
instant of time.
SPLi dB re 0.002 microbar Maximum Sound Pressure
Level. The sound
pressure level that
occurs in the i-th one-
third octave band of
the spectrum for PNL-
TM.
SPLic dB re 0.002 microbar Corrected Maximum Sound
Pressure Level. The
sound pressure level
that occurs in the i-th
one-third octave band
of the spectrum for
PNLTM corrected for
atmospheric sound
absorption.
t Sec Elapsed Time. The length
of time measured from a
reference zero.
t(1), t(2) Sec Time Limit. The
beginning and end of
the significant noise
time history defined by
h.
<Delta>t Sec Time Increment. The
equal increments of
time for which PNL(k)
and PNLT (k) are
calculated.
T Sec Normalizing Time
Constant. The length of
time used as a
reference in the
integration method for
computing duration
corrections.
T deg.F Temperature. The ambient
atmospheric temperature
<alpha>i dB/ft Test Atmospheric
<alpha>i' dB/1000 ft Absorption. The
atmospheric attenuation
of sound that occurs in
the i-th one-third
octave band for the
measured atmospheric
temperature and
relative humidity.
<alpha>io dB/ft Reference Atmospheric
<alpha>io' dB/1000 ft Absorption. The
atmospheric attenuation
of sound that occurs in
the i-th one-third
octave band for the
reference atmospheric
temperature and
relative humidity.
<beta> Degrees First Constant Climb
Angle.
<psi> Degrees Second Constant Climb
Angle.
<delta> Degrees Thrust Cutback Angles.
<epsilon> Degrees The angles defining the
points on the takeoff
flight path at which
thrust reduction is
started and ended
respectively.
<eta> Degrees Approach Angle.
<theta> Degrees Takeoff Noise Angle. The
angle between the
flight path and noise
path for takeoff
operation. It is
identical for both
measured and corrected
flight paths.
<mu> Degrees Approach Noise Angle.
The angle between the
flight path and the
noise path for approach
operation. It is
identical for both
measured and corrected
flight paths.
<Delta>l EPNdB PNLT Correction. The
correction to be added
to the EPNL calculated
from measured data to
account for noise level
changes due to
differences in
atmospheric absorption
and noise path length
between reference and
test conditions.
<Delta>2 EPNdB Noise Path Duration
Correction. The
correction to be added
to the EPNL calculated
from measured data to
account for noise level
changes due to the
noise duration because
of differences in
flyover altitude
between reference and
test condition.
<Delta>3 EPNdB Weight Correction. The
correction to be added
to the EPNL calculated
from measured data to
account for noise level
changes due to
differences between
maximum and test
aircraft weights.
<Delta>4 EPNdB Approach Angle
Correction. The
correction to be added
to the EPNL calculated
from measured data to
account for noise level
changes due to
differences between 3
deg. and the test
approach angle.
<Delta>AB Feet (/1/ )
<Delta><beta> Degrees (/1/ )
<Delta><gamma> Degrees (/1/ )
<Delta><delta> Degrees (/1/ )
<Delta><epsilon> Degrees (/1/ )
<Delta>e Degrees (/1/ )
/1/ Takeoff Profile Changes. The changes in the basic parameters defining
the takeoff profile due to differences between reference and test
conditions.
Flight Profile Identification Positions
Position Description
A Start of takeoff roll.
B Liftoff.
C Start of first constant climb.
D Start of thrust reduction.
E Start of second constant climb.
Ec Start of second constant climb on corrected flight path.
F End of noise certification takeoff flight path.
Fc End of second constant climb on corrected flight path.
G Start of noise certification approach flight path.
Gr Start of noise certification approach on reference flight path.
H Position on approach path directly above noise measuring station.
I Start of level off.
Ir Start of level off on reference approach flight path.
J Touchdown.
K Takeoff noise measuring station.
L Sideline noise measuring station (not on flight track).
M End of noise type certification takeoff flight track.
N Approach noise measuring station.
O Threshold of approach end of runway.
P Start of noise type certification approach flight track.
Q Position on measured takeoff flight path corresponding to PNLTM at
station K.
Qc Position on corrected takeoff flight path corresponding to PNLTM at
station K.
R Position on measured takeoff flight path nearest to station K.
Rc Position on corrected takeoff flight path nearest to station K.
S Position on measured approach flight path corresponding to PNLTM at
station N.
Sr Position on reference approach flight path corresponding to PNLTM
at station N.
T Position on measured approach flight path nearest to station N.
Tr Position on reference approach flight path nearest to station N.
X Position on measured takeoff flight path corresponding to PNLTM at
station L.
Xc Position on corrected takeoff flight path corresponding to PNLTM at
station L.
Flight Profile Distances
Distance Unit Meaning
AB feet Length of Takeoff Roll. The distance along the runway between
the start of takeoff roll and lift off.
AK feet Takeoff Measurement Distance. The distance from the start of
roll to the takeoff noise measurement station along the
extended centerline of the runway.
AM feet Takeoff Flight Track Distance. The distance from the start of
roll to the takeoff flight track position along the extended
centerline of the runway for which the position of the
aircraft need no longer be recorded.
KQ feet Measured Takeoff Noise Path. The distance from station K to
the measured aircraft position Q.
KQc feet Corrected Takeoff Noise Path. The distance from station K to
the corrected aircraft position Qc.
KR feet Measured Takeoff Minimum Distance. The distance from station
K to point R on the measured flight path.
KRc feet Corrected Takeoff Minimum Distance. The distance from station
K to point Rc on the corrected flight path.
LX feet Measured Sideline Noise Path. The distance from station L to
the measured aircraft position X.
LXc feet Corrected Sideline Noise Path. The distance from station L to
the corrected aircraft position Xc.
NH feet Aircraft Approach Height. The vertical distance between the
aircraft and the approach measuring station.
NS feet Measured Approach Noise Path. The distance from station N to
the measured aircraft position S.
NSr feet Reference Approach Noise Path. The distance from station N to
the reference aircraft position Sr.
NT feet Measured Approach Minimum Distance. The distance from station
N to point T on the measured flight path.
NTr feet Reference Approach Minimum Distance. The distance from
station N to point Tr on the corrected flight path; it
equals 393 feet.
ON feet Approach Measurement Distance. The distance from the runway
threshold to the approach measurement station along the
extended centerline of the runway.
OP feet Approach Flight Track Distance. The distance from the runway
threshold to the approach flight track position along the
extended centerline of the runway for which the position of
the aircraft need no longer be recorded.
Section A36.9 Atmospheric attenuation of sound.
(a) General. The measured values of the one-third octave band spectra must
conform, or be corrected, to the reference-day conditions listed in section
A36.5(c) of this appendix. Each correction must account for any differences
in the atmospheric attenuation of sound between the test-day conditions and
the reference-day conditions along the sound propagation path between the
aircraft and the microphone. Unless the meteorological conditions conform to
those prescribed in section A36.1(c) of this appendix, the test data are not
acceptable.
(b) Meteorological measurements. (1) The wind velocity, temperature and
relative humidity measurements required under this part must be measured in
the vicinity of the noise measuring stations. The location of the
meteorological measurements must be approved by the FAA as representative of
those atmospheric conditions existing near the surface over the geographical
area in which aircraft noise measurements are made. In some cases, a fixed
meteorological station (such as those found at airports or other facilities)
may meet this requirement.
(2) The temperature and relative humidity must be measured from a point 10
meters above the surface at the measuring stations to the altitude of the
aircraft, using previously approved equipment and methods.
(3) Meteorological measurements must be obtained within 25 minutes of each
noise test measurement. Meteorological data must be interpolated to actual
times of each noise measurement.
(c) Attenuation rates. The atmospheric attenuation rates of sound with
distance for each one-third octave band from 50Hz to 10,000 Hz must be
determined in accordance with the formulations and tabulations of SAE ARP
866A, entitled "Standard Values of Atmospheric Absorption as a Function of
Temperatures and Humidity for Use in Evaluating Aircraft Flyover Noise" (as
incorporated by reference under Sec. 36.6 of this part).
(d) Correction for atmospheric attenuation. (1) EPNL values calculated for
measured data must be corrected by the methods prescribed in section
A36.11(d) of this appendix whenever--
(i) The ambient atmospheric conditions of temperature and relative humidity
do not conform to the reference conditions (77 degrees F. and 70 percent,
respectively), or
(ii) The measured takeoff and approach flight paths do not conform to the
reference flight paths.
(2) If the atmospheric absorption coefficients do not vary over the PNLTM
sound propagation path by more than +/- 1.6 dB/1000 ft (+/- 0.5 dB/100
meters) in the 3150 Hz one-third octave band from the value of the absorption
coefficient derived from the meteorological measurement obtained at 10 meters
above the surface, the mean of the values of the atmospheric absorption
coefficients at 10 meters above the surface and at the altitude of the
aircraft at PNLTM may be used to determine the atmospheric attenuation rates
for each one-third octave band. The resulting atmospheric attenuation rate
may be used to compute the PNLTM correction under section A36.11(d) of this
appendix.
(3) If the conditions do not conform to those prescribed in paragraph
(d)(2) of this section, the corrections for atmospheric attenuation must be
determined by the following layered-atmosphere procedure:
(i) The sound propagation path must be divided into increments no greater
than 100 feet in altitude, and the average temperature and relative humidity
that exists within each increment at the time of the test must be calculated
from the meteorological data required under paragraph (b) of this section.
(ii) Atmospheric attenuation rates must be determined under paragraph (c)
of this section for each one-third octave band in each altitude increment.
(iii) The mean attenuation rate over the complete sound propagation path
from the aircraft to the microphone must be computed for each one-third
octave band from 50 Hz to 10,000 Hz. These rates must be used in computing
the corrections required in section A36.11(d) of this appendix.
Section A36.11 Detailed correction procedures.
(a) General. If the test conditions do not conform to those prescribed as
noise certification reference conditions under section A36.5 of this
appendix, the following correction procedure and requirements apply:
(1) If a positive value results from any difference between reference and
test conditions, and appropriate positive correction must be made to the EPNL
calculated from the measured data. Conditions which can result in a positive
value include:
(i) Atmospheric absorption of sound under test conditions which is greater
than the reference;
(ii) Test flight path at an altitude which is higher than the reference; or
(iii) Test weight which is less than maximum certification weight.
(2) If a negative value results from any difference between reference and
test conditions, no correction may be made to the EPNL calculated from the
measured data, unless the difference results from:
(i) An atmospheric absorption of sound under test conditions which is less
than the reference; or
(ii) A test flight path at an altitude which is lower than the reference.
(3) The following correction procedures may produce one or more possible
correction values which must be added algebraically to the EPNL calculated as
if the tests were conducted completely under the noise certification
reference conditions:
(i) The flight profiles must be determined for both takeoff and approach,
and for both reference and test conditions. The procedures require noise and
flight path recording with a synchronized time signal from which the test
profile can be delineated, including the aircraft position for which PNLTM is
observed at the noise measuring station. For takeoff, the flight profile
corrected to reference conditions may be derived from FAA approved
manufacturer's data; however, for approach, the reference profile is
prescribed under paragraph (c)(2) of this section.
(ii) The sound propagation paths to the microphone from the aircraft
position corresponding to PNLTM are determined for both the test and
reference profiles. The SPL values in the spectrum of PNLTM must then be
corrected for the effects of--
(A) Change in atmospheric sound absorption;
(B) Atmospheric sound absorption on the change in sound propagation path
length; and
(C) Inverse square law on the change in sound propagation path length. The
corrected values of SPL are then converted to PNLT from which must be
subtracted PNLTM. The resulting difference represents the correction which
must be added algebraically to the EPNL calculated from the measured data.
(iii) The minimum distances from both the test and reference profiles to
the noise measuring station must be calculated and used to determine a noise
duration correction due to any change in the altitude of aircraft flyover.
The duration correction must be added algebraically to the EPNL calculated
from the measured data.
(iv) From approved data in the form of curves or tables giving the
variation of EPNL with engine thrust or test speed, corrections are
determined and must be added to the EPNL (which is calculated from the
measured data) to account for noise level changes due to differences between
test conditions and reference conditions.
(v) From approved data corrections are determined and must be added
algebraically to the EPNL (which is calculated from measured data) to account
for noise level changes due to differences between 3 degrees and the test
approach angle.
(b) Takeoff profiles. (1) Figure A1 illustrates a typical takeoff profile.
(i) The aircraft begins the takeoff roll at point A, lifts off at point B,
and initiates the first constant climb at point C at an angle <beta>. The
noise abatement thrust cutback is started at point D and completed at point E
where the second constant climb is defined by the angle <gamma> (usually
expressed in terms of the gradient in percent). The end of the noise
certification takeoff flight path is represented by aircraft position F whose
vertical projection on the flight track (extended centerline of the runway)
is point M. The position of the aircraft must be recorded for the entire
interval during which the measured aircraft noise level is within 10 dB of
PNLTM. Position K is the takeoff noise measuring station whose distance AK is
specified as 21,325 feet (6,500 meters). However, if it is necessary to
reduce AK to less than 21,325 feet, the procedures prescribed in paragraph
(f) of this section must be followed. Position L is the sideline noise
measuring station located on a line parallel to, and the prescribed distance
from, the runway centerline where the noise level during takeoff is greatest.
(ii) The takeoff profile is defined by five parameters--(A) AB, the length
of takeoff roll; (B) <beta> the first constant climb angle; (C) <gamma>, the
second constant climb angle; and (D) >>, and e, the thrust cutback angles.
These five parameters are functions of the aircraft performance and weight,
and the atmospheric conditions of temperature, pressure, and wind velocity
and direction.
(2) If the test conditions do not conform to those prescribed as reference
conditions under section A36.5 of this appendix, the corresponding test and
reference profile parameters will be different, as shown in Figure A2. The
profile parameter changes, identifies as <Delta>AB, <Delta><beta>,
<Delta><gamma>, <Delta>>>, and <Delta><epsilon> may be derived from the
manufacturer's data (if approved by the FAA) and may be used to define the
fight profile corrected to the reference conditions. The relationships
between the measured and corrected takeoff flight profiles may then be used
to determine the corrections, which, if positive, must be applied to the EPNL
calculated from the measured data.
Figure A1 -- Measured Takeoff Profile
Figure A2 -- Comparison of Measured and Corrected
Takeoff Profiles
[ ...Illustrations appear here... ]
Note: Under reference atmospheric conditions and with maximum takeoff
weight, the gradient of the second constant climb angle (<gamma>) may not be
less than 4 percent. However, the actual gradient will depend upon the test
atmospheric conditions, assuming maximum takeoff weight and the parameters
characterizing engine performance are constant (rpm, epr, or any other
parameter used by the pilot).
(3) Figure A3 illustrates portions of the measured and corrected takeoff
flight paths including the significant geometrical relationships influencing
sound propagation. EF represents the measured second constant flight path
with climb angle <gamma>, and EcFc represents the corrected second constant
flight path at reduced climb angle <gamma>-<Delta><gamma>. Position Q
represents the aircraft location on the measured takeoff flight path for
which PNLTM is observed at the noise measuring station K, and Qc is the
corresponding position on the corrected flight path. The measured and
corrected sound propagation paths are KQ and KQc, respectively, which form
the same angle <theta> with their flight paths. Position R represents the
point on the measured takeoff flight path nearest the noise measuring station
K, and Rc is the corresponding position on the corrected flight path. The
minimum distance to the measured and corrected flight paths are indicated by
the lines KR and KRc, respectively, which are normal to their flight paths.
Figure A3 -- Takeoff Profile Characteristics Influencing
Sound Propagation
Figure A4 -- Measured Approach Profile
[ ...Illustrations appear here... ]
(c) Approach profiles. (1) Figure A4 illustrates a typical approach
profile.
(i) The beginning of the noise certification approach profile is
represented by aircraft position G whose vertical projection on the flight
track (extended centerline of the runway) is point P. The position of the
aircraft should be recorded for a distance OP from the runway threshold O to
ensure recording of the entire interval during which the measured aircraft
noise is within 10 dB of PNLTM.
(ii) The aircraft approaches at an angle passes vertically over the noise
measuring station N at a height of NH, begins the level off at position I,
and touches down at position J. The distance ON is prescribed as 6,562 feet
(2,000 meters).
(iii) The approach profile is defined by the approach angle and the
height NH which are functions of the aircraft operating conditions controlled
by the pilot. If the measured approach profile parameters do not conform to
the corresponding reference approach parameters (3 degrees and 394 feet,
respectively, as shown in Figure A5), corrections, if positive, must be
applied to the EPNL calculated from the measured data.
Figure A5 -- Comparison of Measured and Corrected
Approach Profiles
Figure A6 -- Approach Profile Characteristics Influencing
Sound Propagation
[ ...Illustrations appear here... ]
(2) Figure A6 illustrates portions of the measured and reference approach
flight paths, including the significant geometrical relationships influencing
sound propagation. GI represents the measured approach path with approach
angle --, and GrIr represents the reference approach flight path at lower
altitude and approach angle of 3 degrees. Position S represents the aircraft
location on the measured approach flight path for which PNLTM is observed at
the noise measuring station N, and Sr is the corresponding position on the
reference approach flight path. The measured and corrected sound propagation
paths are NS and NSr, respectively, which form the same angle l with their
flight paths. Position T represents the point on the measured approach flight
path nearest the noise measuring station N, and Tr is the corresponding point
on the reference approach flight path. The minimum distances to the measured
and reference flight paths are indicated by the lines NT and NTr,
respectively, which are normal to their flight paths. NOTE: The reference
approach flight path is defined by --=3 degrees and NH=394 feet. Consequently
NTr can also be defined; NTr=393 feet to the nearest foot and is, therefore,
considered to be one of the reference parameters.
(d) PNLT corrections. If the ambient atmospheric conditions of temperature
and relative humidity are not those prescribed as reference conditions under
Sec. A36.5(c) of this appendix (77 degrees F and 70 percent, respectively),
corrections to the EPNL values must be calculated from the measured data
under paragraph (a) of this section as follows:
(1) Takeoff flight path. For the takeoff flight path shown in Figure A3,
the spectrum of PNLTM observed at station K for the aircraft at position Q is
decomposed into its individual SPLi values.
(i) Step 1. A set of corrected values are then computed as follows:
SPLic=SPLi +]]io (KQ-KQc)
+(]]i-]]io) KQ +20 log (KQ/KQc)
where SPLi and SPLic are the measured and corrected sound pressure levels,
respectively, in the i-th one-third octave band. The first correction term
accounts for the effects of change in atmospheric sound absorption where
<alpha>i and ]]io are the sound absorption coefficients for the test
(determined under section A36.9(d)) and reference atmospheric conditions,
respectively, for the i-th one-third octave band and KQ is the measured
takeoff sound propagation path. The second correction term accounts for the
effects of atmospheric sound absorption on the change in the sound
propagation path length where KQc is the corrected takeoff sound propagation
path. The third correction term accounts for the effects of the inverse
square law on the change in the sound propagation path length.
(ii) Step 2. The corrected values of SPLic are then converted to PNLT and a
correction term calculated as follows:
<Delta>1=PNLT-PNLTM
which represents the correction to be added algebraically to the EPNL
calculated from the measured data.
(2) Approach flight path.
(i) The procedure prescribed in paragraph (d)(1) of this section for
takeoff flight paths is also used for the approach flight path, except that
the value for SPLic relate to the approach sound propagation paths shown in
Figure A6 as follows:
SPLic=SPLi +(<alpha>i-<alpha>io) NS
+<alpha>io (NS-NSr)
+20 log (NS/NSr)
where NS and NSr are the measured and reference approach sound propagation
paths, respectively.
(ii) The remainder of the procedure is the same as that prescribed in
paragraph (d)(1)(ii) of this section, regarding takeoff flight path.
(3) Sideline flight path. The procedure prescribed in paragraph (d)(1) of
this section for takeoff flight paths is also used for the sideline flight
path, except that the values of SPLic relate only to the measured sideline
sound propagation path as follows:
SPLic=SPLi +(<alpha>i-<alpha>io) LX
+<alpha>io (LX-LXc)
+20 log (LX/LXc)
where LX is the measured sideline sound propagation path from station L
(Figure A1) to position X of the aircraft for which PNLTM is observed at
station L and LXc is the corrected sideline sound propagation path.
(e) Duration corrections. If the measured takeoff and approach flight paths
do not conform to those prescribed as the corrected and reference flight
paths, under section A36.11 (b) and (c) respectively, it will be necessary to
apply duration corrections to the EPNL values calculated from the measured
data. Such corrections must be calculated as follows:
(1) Takeoff flight path. For the takeoff flight path shown in Figure A3,
the correction term is calculated using the formula--
D2 = -7.5 log (KR/KRc)
which represents the correction which must be added algebraically to the EPNL
calculated from the measured data. The lengths KR and KRc are the measured
and corrected takeoff minimum distances from the noise measuring station K to
the measured and the corrected flight paths respectively. A negative sign
indicates that, for the particular case of a duration correction, the EPNL
calculated from the measured data must be reduced if the measured flight path
is at a greater altitude than the corrected flight path.
(2) Approach flight path. For the approach flight path shown in Figure A6,
the correction term is calculated using the formula--
D 2 = -7.5 log (NT/393)
where NT is the measured approach minimum distance from the noise measuring
station N to the measured flight path and 393 feet is the minimum distance
from station N to the reference flight path.
(3) Sideline flight path. For the sideline flight path, the correction term
is calculated using the formula--
D 2 = -7.5 log (LX/LXc)
where LX and LXc are the measured and corrected sideline noise measuring
distances, respectively, from the noise measuring station L to the aircraft
position X or Xc, respectively on the takeoff flight path.
(f) Nonstandard location correction. When takeoff and approach noise
measurements are conducted at points other than those prescribed in section
C36.1 of Appendix C, the EPNL value computed from these measurements must be
corrected to the value that would have occurred at the prescribed measuring
points under one of the following procedures:
(1) Simplified procedure. Unless the amount of adjustment exceeds 8 dB on
takeoff or 4 dB on approach, or the correction results in a final EPNL value
which is within 1.0 dB of the noise levels prescribed in Appendix C of this
part, the correction procedures prescribed in paragraphs (d) and (e) of this
section may be used. Since this procedure accounts for extrapolation of PNLTM
from the close-in measurement station to the prescribed measuring point, the
remaining corrections for differences between test and reference conditions,
including thrust and airspeed, must be made afterward.
(2) Integrated procedure. If the correction factor exceeds 8 dB on takeoff
or 4 dB on approach, or the correction results in a final EPNL value which is
within 1.0 dB of the noise levels prescribed in Appendix C of this part, the
following correction procedure must be used:
(i) Each 1/2 second spectrum measured during a flyover at a noise
measuring station which is closer to the flight path than the prescribed
reference distance must be adjusted under a procedure similar to that
prescribed under paragraph (d)(1) of this section, regarding PNLT
corrections. However, the distances which must be used are those values of KQ
and KQc for the sound propagation path (and hence value of <theta>) for PNLTM
which represents the actual, measured sound propagation path (and path
angle), and the corresponding sound propagation path (and path angle) as if
the measurements had been made at the 21,325 foot measuring point under
reference acoustic-day conditions.
(ii) After the measured one half (1/2) second spectra have been corrected
to the measuring points prescribed in section C36.1 of Appendix C, the
remaining noise evaluation must be conducted under the procedures prescribed
in Appendix B of this part, including the appropriate reference thrust and
air speed corrections.
[Amdt. 36-9, 43 FR 8739, Mar. 2, 1978, as amended at 44 FR 3031, Jan. 15,
1979; Amdt. 36-15, 53 FR 16367, May 6, 1988; 53 FR 18835, May 25, 1988; 53 FR
51087, Dec. 19, 1988]
Appendix B--Aircraft Noise Evaluation Under Sec. 36.103
Sec.
B36.1 General.
B36.3 Perceived noise level.
B36.5 Correction for spectral irregularities.
B36.7 Maximum tone corrected perceived noise level.
B36.9 Duration correction.
B36.11 Effective perceived noise level.
B36.13 Mathematical formulation of noy tables.
Section B36.1 General. The procedures in this appendix must be used to
determine the noise evaluation quantity designated as effective perceived
noise level, EPNL, under Secs. 36.103 and 36.803. These procedures, which use
the physical properties of noise measured as prescribed by Appendix A of this
part, consist of the following:
(a) The 24 one-third octave bands of sound pressure level are converted to
perceived noisiness by means of a noy table. The noy values are combined and
then converted to instantaneous perceived noise levels, PNL(k).
(b) A tone correction factor, C(k), is calculated for each spectrum to
account for the subjective response to the presence of the maximum tone.
(c) The tone correction factor is added to the perceived noise level to
obtain tone corrected perceived noise levels, PNLT(k), at each one-half
second increment of time. The instantaneous values of tone corrected
perceived noise level are noted with respect to time and the maximum value,
PNLTM, is determined.
PNLT(k)=PNL(k)+C(k)
(d) A duration correction factor, D, is computed by integration under the
curve of tone corrected perceived noise level versus time.
(e) Effective perceived noise level, EPNL, is determined by the algebraic
sum of the maximum tone corrected perceived noise level and the duration
correction factor.
EPNL=PNLTM+D
Section B36.3 Perceived noise level. Instantaneous perceived noise levels,
PNL(k), must be calculated from instantaneous one-third octave band sound
pressure levels, SPL(i,k), as follows:
(a) Step 1. Convert each one-third octave band SPL(i,k), from 50 to 10,000
Hz, to perceived noisiness, n(i,k), by reference to Table B1, or to the
mathematical formulation of the noy table given in Sec. B36.13 of this
appendix.
(b) Step 2. Combine the perceived noisiness values, n(i,k), found in step 1
by the following formula:
N(k)=n(k)+0.15 [[SUM 2 4 i-1
n(i,k)]-n (k)]=0.85
n(K)+0.15SUM 24 i-1n(i,k)
where n(k) is the largest of the 24 values of n(i,k) and N(k) is the total
perceived noisiness.
(c) Step 3. Convert the total perceived noisiness, N(k), into perceived
noise level, PNL(k), by the following formula:
PNL(k)=40.0+33.22 log N(k)
which is plotted in Figure B1. PNL(k) may also be obtained by choosing N(k)
in the 1,000 Hz column of Table B1 and then reading the corresponding value
of SPL(i,k) which, at 1,000 Hz, equals PNL(k).
Figure B1 -- Perceived Noise Level As A Function of Noys
[ ...Illustration appears here... ]
Table B1 Perceived Noisiness (NOYs) as a Function of Sound
Pressure Level
1/3 Octave
Band Center
Frequencies
in Hz (c/s)
**
SPL 50 63 80 100 125 160 200 250 315 400 500
4
5
6
7
8
9
10
11
12
12
14
15
16 0.10 0.10
17 0.11 0.11
18 0.10 0.13 0.13
19 0.11 0.14 0.14
20 0.13 0.16 0.16
21 0.10 0.14 0.18 0.18
22 0.11 0.16 0.21 0.21
23 0.13 0.18 0.24 0.24
24 0.10 0.14 0.21 0.27 0.27
25 0.11 0.16 0.24 0.30 0.30
26 0.13 0.18 0.27 0.33 0.33
27 0.10 0.14 0.21 0.30 0.35 0.35
28 0.11 0.16 0.24 0.33 0.38 0.38
29 0.13 0.18 0.27 0.35 0.41 0.41
30 0.10 0.14 0.21 0.30 0.38 0.45 0.45
31 0.11 0.16 0.24 0.33 0.41 0.49 0.49
32 0.13 0.18 0.27 0.36 0.45 0.53 0.53
33 0.14 0.21 0.30 0.39 0.49 0.57 0.57
34 0.10 0.16 0.24 0.33 0.42 0.53 0.62 0.62
35 0.11 0.18 0.27 0.36 0.46 0.57 0.67 0.67
36 0.13 0.21 0.30 0.40 0.50 0.62 0.73 0.73
37 0.15 0.24 0.33 0.43 0.55 0.67 0.79 0.79
38 0.17 0.27 0.37 0.48 0.60 0.73 0.85 0.85
39 0.10 0.20 0.30 0.41 0.52 0.65 0.79 0.92 0.92
40 0.12 0.23 0.33 0.45 0.57 0.71 0.85 1.00 1.00
41 0.14 0.26 0.37 0.50 0.63 0.77 0.92 1.07 1.07
42 0.16 0.30 0.41 0.55 0.69 0.84 1.00 1.15 1.15
43 0.19 0.33 0.45 0.61 0.76 0.92 1.07 1.23 1.23
44 0.10 0.22 0.37 0.50 0.67 0.83 1.00 1.15 1.32 1.32
45 0.12 0.26 0.42 0.55 0.74 0.91 1.08 1.24 1.41 1.41
46 0.14 0.30 0.46 0.61 0.82 1.00 1.16 1.33 1.52 1.52
47 0.16 0.34 0.52 0.67 0.90 1.08 1.25 1.42 1.62 1.62
48 0.19 0.38 0.58 0.74 1.00 1.17 1.34 1.53 1.74 1.74
49 0.10 0.22 0.43 0.65 0.82 1.08 1.26 1.45 1.64 1.87 1.87
50 0.12 0.26 0.49 0.72 0.90 1.17 1.36 1.56 1.76 2.00 2.00
51 0.14 0.30 0.55 0.80 1.00 1.26 1.47 1.68 1.89 2.14 2.14
52 0.17 0.34 0.62 0.90 1.08 1.36 1.58 1.80 2.03 2.30 2.30
53 0.21 0.39 0.70 1.00 1.18 1.47 1.71 1.94 2.17 2.46 2.46
54 0.25 0.45 0.79 1.09 1.28 1.50 1.85 2.09 2.33 2.64 2.64
55 0.30 0.51 0.89 1.18 1.39 1.71 2.00 2.25 2.50 2.83 2.83
56 0.34 0.59 1.00 1.29 1.50 1.85 2.15 2.42 2.69 3.03 3.03
57 0.39 0.67 1.09 1.40 1.63 2.00 2.33 2.61 2.88 3.25 3.25
58 0.45 0.77 1.18 1.53 1.77 2.15 2.51 2.81 3.10 3.48 3.48
59 0.51 0.87 1.29 1.66 1.92 2.33 2.71 3.03 3.32 3.73 3.73
60 0.59 1.00 1.40 1.81 2.08 2.51 2.93 3.26 3.57 4.00 4.00
61 0.67 1.10 1.53 1.97 2.26 2.71 3.16 3.51 3.83 4.29 4.29
62 0.77 1.21 1.66 2.15 2.45 2.93 3.41 3.79 4.11 4.59 4.59
63 0.87 1.32 1.81 2.34 2.65 3.16 3.69 4.06 4.41 4.92 4.92
64 1.00 1.45 1.97 2.54 2.88 3.41 3.98 4.39 4.73 5.28 5.28
65 1.11 1.60 2.15 2.77 3.12 3.69 4.30 4.71 5.08 5.66 5.66
66 1.22 1.75 2.34 3.01 3.39 3.99 4.64 5.07 5.45 6.06 6.06
67 1.35 1.92 2.54 3.28 3.68 4.30 5.01 5.46 5.85 6.50 6.50
68 1.49 2.11 2.77 3.57 3.99 4.64 5.41 5.88 6.27 6.96 6.96
69 1.65 2.32 3.01 3.80 4.33 5.01 5.84 6.33 6.73 7.46 7.46
70 1.82 2.59 3.28 4.23 4.69 5.41 6.31 6.81 7.23 8.00 8.00
71 2.02 2.79 3.57 4.60 5.09 5.84 6.81 7.33 7.75 8.57 8.57
72 2.23 3.07 3.88 5.01 5.52 6.31 7.36 7.90 8.32 9.19 9.19
73 2.46 3.37 4.23 5.45 5.99 6.81 7.94 8.50 8.93 9.85 9.85
74 2.72 3.70 4.60 5.94 6.50 7.36 8.57 9.15 9.59 10.6 10.6
75 3.01 4.06 5.01 6.46 7.05 7.94 9.19 9.85 10.3 11.3 11.3
76 3.32 4.46 5.45 7.03 7.65 8.57 9.85 10.6 11.0 12.1 12.1
77 3.67 4.89 5.94 7.66 8.29 9.19 10.6 11.3 11.8 13.0 13.0
78 4.06 5.37 6.46 8.33 9.00 9.85 11.3 12.1 12.7 13.9 13.9
79 4.49 5.90 7.03 9.07 9.76 10.6 12.1 13.0 13.6 14.9 14.9
80 4.96 6.48 7.66 9.85 10.6 11.3 13.0 13.9 14.6 16.0 16.0
81 5.48 7.11 8.33 10.6 11.3 12.1 13.9 14.9 15.7 17.1 17.1
82 6.06 7.81 9.07 11.3 12.1 13.0 14.9 16.0 16.9 18.4 18.4
83 6.70 8.57 9.87 12.1 13.0 13.9 16.0 17.1 18.1 19.7 19.7
84 7.41 9.41 10.7 13.0 13.9 14.9 17.1 18.4 19.4 21.1 21.1
85 8.19 10.3 11.7 13.9 14.9 16.0 18.4 19.7 20.8 22.6 22.6
86 9.05 11.3 12.7 14.9 16.0 17.1 19.7 21.1 22.4 24.3 24.3
87 10.0 12.1 13.9 16.0 17.1 18.4 21.1 22.6 24.0 26.0 26.0
88 11.1 13.0 14.9 17.1 18.4 19.7 22.6 24.3 25.8 27.9 27.9
89 12.2 13.9 16 .0 18.4 19.7 21.1 24.3 26.0 27.7 29.9 29.9
90 13.5 14.9 17.1 19.7 21.1 22.6 26.0 27.9 29.7 32.0 32.0
91 14.9 16.0 18.4 21.1 22.6 24.3 27.9 29.9 31.8 34.3 34.3
92 16.0 17.1 19.7 22.6 24.3 26.0 29.9 32.0 34.2 36.8 36.8
93 17.1 18.4 21.1 24.3 26.0 27.9 32.0 34.3 36.7 39.4 39.4
94 18.4 19.7 22.6 26.0 27.9 29.9 34.3 36.8 39.4 42.2 42.2
95 19.7 21.1 24.3 27.9 29.9 32.0 36.8 39.4 42.2 45.3 45.3
96 21.1 22.6 26.0 29.9 32.0 34.3 39.4 42.2 45.3 48.5 48.5
97 22.6 24.3 27.9 32.0 34.3 36.8 42.2 45.3 48.5 52.0 52.0
98 24.3 26.0 29.9 34.3 36.8 39.4 45.3 48.5 52.0 55.7 55.7
99 26.0 27.9 32.0 36.8 39.4 42.2 48.5 52.0 55.7 59.7 59.7
100 27.9 29.9 34.3 39.4 42.2 45.3 52.0 55.7 59.7 64.0 64.0
101 29.9 32.0 36.8 42.2 45.3 48.5 55.7 59.7 64.0 68.6 68.6
102 32.0 34.3 39.4 45.3 48.5 52.0 59.7 64.0 68.6 73.5 73.5
103 34.3 36.8 42.2 48.5 52.0 55.7 64.0 68.6 73.5 78.8 78.8
104 36.8 39.4 45.3 52.0 55.7 59.7 68.6 73.5 78.8 84.4 84.4
105 39.4 42.2 48.5 55.7 59.7 64.0 73.5 78.8 84.4 90.5 90.5
106 42.2 45.3 52.0 59.7 64.0 68.6 78.8 84.4 90.5 97.0 97.0
107 45.3 48.5 55.7 64.0 68.6 73.5 84.4 90.5 97.0 104 104
108 48.5 52.0 59.7 68.6 73.5 78.8 90.5 97.0 104 111 111
109 52.0 55.7 64.0 73.5 78.8 84.4 97.0 104 111 119 119
110 55.7 59.7 68.6 78.8 84.4 90.5 104 111 119 128 128
111 59.7 64.0 73.5 84.4 90.5 97.0 111 119 128 137 137
112 64.0 68.6 78.8 90.4 97.0 104 119 128 137 147 147
113 64.6 73.5 84.4 97.0 104 111 128 137 147 158 158
114 73.5 78.8 50.5 104 111 119 137 147 158 169 169
115 78.8 84.4 97.0 111 119 128 147 158 169 181 181
116 84.4 90.5 104 119 128 137 158 169 181 194 194
117 90.5 97.6 111 128 137 147 169 181 194 208 208
118 97.0 104 119 137 147 158 181 194 208 223 223
119 104 111 128 147 158 169 194 208 223 239 239
120 111 119 137 158 169 181 208 223 239 256 256
121 119 128 147 169 181 194 223 239 256 274 274
122 128 137 158 181 194 208 239 256 274 294 294
123 137 147 169 194 208 223 256 274 294 315 315
124 147 158 181 208 223 239 274 294 315 338 338
125 158 169 194 223 239 256 294 315 338 362 362
126 169 181 208 239 256 274 315 338 362 388 388
127 181 194 223 256 274 294 338 362 388 416 416
128 194 208 239 274 294 315 362 388 416 446 446
129 208 223 256 294 315 338 388 416 446 478 478
130 223 239 274 315 338 362 416 446 478 512 512
131 239 256 294 338 362 388 446 478 512 549 549
132 256 274 315 362 388 416 478 512 549 588 588
133 274 294 338 388 416 446 512 549 588 630 630
134 294 315 362 416 446 478 549 588 630 676 676
135 315 338 388 446 478 512 588 630 676 724 724
136 338 362 416 478 512 549 630 676 724 776 776
137 362 388 446 512 549 588 676 724 776 832 832
138 398 416 478 549 588 630 724 776 832 891 891
139 416 446 512 588 630 676 776 832 891 955 955
140 446 478 549 630 676 724 832 891 955 1024 1024
141 478 512 588 676 724 776 891 955 1024 1098 1098
142 512 549 630 724 776 832 955 1024 1098 1176 1176
143 549 588 676 776 832 891 1024 1098 1176 1261 1261
144 588 630 724 832 891 955 1098 1176 1261 1351 1351
145 630 676 776 891 955 1024 1176 1261 1351 1448 1448
146 676 724 832 955 1024 1098 1261 1351 1448 1552 1552
147 724 776 891 1024 1098 1176 1351 1448 1552 1664 1664
148 776 832 955 1098 1176 1261 1448 1552 1664 1783 1783
149 832 891 1024 1176 1261 1351 1552 1664 1783 1911 1911
150 891 955 1098 1261 1351 1448 1664 1783 1911 2048 2048
[ ...Table continues... ]
SPL 630 800 1000 1250 1600 2000 2500
4
5 0.10
6 0.11
7 0.13
8 0.14
9 0.10 0.16
10 0.11 0.17
11 0.13 0.19
12 0.10 0.14 0.22
12 0.11 0.16 0.24
14 0.13 0.18 0.27
15 0.10 0.14 0.21 0.30
16 0.10 0.10 0.10 0.11 0.16 0.24 0.33
17 0.11 0.11 0.11 0.13 0.18 0.27 0.35
18 0.13 0.13 0.13 0.15 0.21 0.30 0.38
19 0.14 0.14 0.14 0.17 0.24 0.33 0.41
20 0.16 0.16 0.16 0.20 0.27 0.36 0.45
21 0.18 0.18 0.18 0.23 0.30 0.39 0.49
22 0.21 0.21 0.21 0.26 0.33 0.42 0.53
23 0.24 0.24 0.24 0.30 0.36 0.46 0.57
24 0.27 0.27 0.27 0.33 0.40 0.50 0.62
25 0.30 0.30 0.30 0.35 0.43 0.55 0.67
26 0.33 0.33 0.33 0.38 0.48 0.60 0.73
27 0.35 0.35 0.35 0.41 0.52 0.65 0.79
28 0.38 0.38 0.38 0.45 0.57 0.71 0.85
29 0.41 0.41 0.41 0.49 0.63 0.77 0.92
30 0.45 0.45 0.45 0.53 0.69 0.84 1.00
31 0.49 0.49 0.49 0.57 0.76 0.92 1.07
32 0.53 0.53 0.53 0.62 0.83 1.00 1.15
33 0.57 0.57 0.57 0.67 0.91 1.07 1.23
34 0.62 0.62 0.62 0.73 1.00 1.15 1.32
35 0.67 0.67 0.67 0.79 1.07 1.23 1.41
36 0.73 0.73 0.73 0.85 1.15 1.32 1.51
37 0.79 0.79 0.79 0.92 1.23 1.41 1.62
38 0.85 0.85 0.85 1.00 1.32 1.51 1.74
39 0.92 0.92 0.92 1.07 1.41 1.62 1.86
40 1.00 1.00 1.00 1.15 1.51 1.74 1.99
41 1.07 1.07 1.07 1.23 1.62 1.86 2.14
42 1.15 1.15 1.15 1.32 1.74 1.99 2.29
43 1.23 1.23 1.23 1.41 1.86 2.14 2.45
44 1.32 1.32 1.32 1.52 1.99 2.29 2.63
45 1.41 1.41 1.41 1.62 2.14 2.45 2.81
46 1.52 1.52 1.52 1.74 2.29 2.63 3.02
47 1.62 1.62 1.62 1.87 2.45 2.81 3.23
48 1.74 1.74 1.74 2.00 2.63 3.02 3.46
49 1.87 1.87 1.87 2.14 2.81 3.23 3.71
50 2.00 2.00 2.00 2.30 3.02 3.46 3.97
51 2.14 2.14 2.14 2.46 3.23 3.71 4.26
52 2.30 2.30 2.30 2.64 3.46 3.97 4.56
53 2.46 2.46 2.46 2.83 3.71 4.26 4.69
54 2.64 2.64 2.64 3.03 3.97 4.56 5.24
55 2.83 2.83 2.83 3.25 4.26 4.89 5.61
56 3.03 3.03 3.03 3.48 4.56 5.24 6.01
57 3.25 3.25 3.25 3.73 4.89 5.61 6.44
58 3.48 3.48 3.48 4.00 5.24 6.01 6.90
59 3.73 3.73 3.73 4.29 5.61 6.44 7.39
60 4.00 4.00 4.00 4.59 6.01 6.90 7.92
61 4.29 4.29 4.29 4.92 6.44 7.39 8.49
62 4.59 4.59 4.59 5.28 6.90 7.92 9.09
63 4.92 4.92 4.92 5.66 7.39 8.49 9.74
64 5.28 5.28 5.28 6.06 7.52 9.09 10.4
65 5.66 5.66 5.66 6.50 8.49 9.74 11.2
66 6.06 6.06 6.06 6.96 9.09 10.4 12.0
67 6.50 6.50 6.50 7.46 9.74 11.2 12.8
68 6.96 6.96 6.96 8.00 10.4 12.0 13.8
69 7.46 7.46 7.46 8.57 11.2 12.8 14.7
70 8.00 8.00 8.00 9.19 12.0 13.8 15.8
71 8.57 8.57 8.57 9.85 12.8 14.7 16.9
72 9.19 9.19 9.19 10.6 13.8 15.8 18.1
73 9.85 9.85 9.85 11.3 14.7 16.9 19.4
74 10.6 10.6 10.6 12.1 15.8 18.1 20.8
75 11.3 11.3 11.3 13.0 16.9 19.4 22.3
76 12.1 12.1 12.1 13.9 18.1 20.8 23.9
77 13.0 13.0 13.0 14.9 19.4 22.3 25.6
78 13.9 13.9 13.9 16.0 20.8 23.9 27.4
79 14.9 14.9 14.9 17.1 22.3 25.6 29L4
80 16.0 16.0 16.0 18.4 23.9 27.4 31.5
81 17.1 17.1 17.1 19.7 25.6 29.4 33.7
82 18.4 18.4 18.4 21.1 27.4 31.5 36.1
83 19.7 19.7 19.7 22.6 29.4 33.7 38.7
84 21.1 21.1 21.1 24.3 31.5 36.1 41.5
85 22.6 22.6 22.6 26.0 33.7 38.7 44.4
86 24.3 24.3 24.3 27.9 36.1 41.5 47.6
87 26.0 26.0 26.0 29.9 38.7 44.4 51.0
88 27.9 27.9 27.9 32.0 41.5 47.6 54.7
89 29.9 29.9 29.9 34.3 44.4 51.0 58.6
90 32.0 32.0 32.0 36.8 47.6 54.7 62.7
91 34.3 34.3 34.3 39.4 51.0 58.6 67.2
92 36.8 36.8 36.8 42.2 54.7 62.7 72.0
93 39.4 39.4 39.4 45.3 58.6 67.2 77.2
94 42.2 42.2 42.2 48.5 62.7 72.0 82.7
95 45.3 45.3 45.3 52.0 67.2 77.2 88.6
96 48.5 48.5 48.5 55.7 72.0 82.7 94.9
97 52.0 52.0 52.0 59.7 77.2 88.6 102
98 55.7 55.7 55.7 64.0 82.7 94.9 109
99 59.7 59.7 59.7 68.6 88.6 102 117
100 64.0 64.0 64.0 73.5 94.9 109 125
101 68.6 68.6 68.6 78.8 102 117 134
102 73.5 73.5 73.5 84.4 109 125 144
103 78.8 78.8 78.8 90.5 117 134 154
104 84.4 84.4 84.4 97.0 125 144 165
105 90.5 90.5 90.5 104 134 154 177
106 97.0 97.0 97.0 111 144 165 189
107 104 104 104 119 154 177 203
108 111 111 111 128 165 189 217
109 119 119 119 137 177 203 233
110 128 128 128 137 189 217 249
111 137 137 137 158 203 233 267
112 147 147 147 169 217 249 286
113 158 158 158 181 233 267 307
114 169 169 169 194 249 286 329
115 181 181 181 208 267 307 352
116 194 194 194 223 286 329 377
117 208 208 208 239 307 352 404
118 223 223 223 256 329 377 433
119 239 239 239 274 352 404 464
120 256 256 256 294 377 433 497
121 274 274 274 315 404 464 533
122 294 294 294 338 433 497 571
123 315 315 315 362 464 533 611
124 338 338 338 388 497 571 655
125 362 362 362 416 533 611 702
126 388 388 388 446 571 655 752
127 416 416 416 479 611 702 806
128 446 446 446 512 655 752 863
129 478 478 478 549 702 806 925
130 512 512 512 588 752 863 991
131 549 549 549 630 806 925 1062
132 588 588 588 676 863 991 1137
133 630 630 630 724 925 1062 1219
134 676 676 676 776 991 1137 1306
135 724 724 724 832 1062 1219 1399
136 776 776 776 891 1137 1306 1499
137 832 832 832 955 1219 1399 1606
138 891 891 891 1024 1306 1499 1721
139 955 955 955 1098 1399 1606 1844
140 1024 1024 1024 1176 1499 1721 1975
141 1098 1098 1098 1261 1606 1844
142 1176 1176 1176 1351 1721 1975
143 1261 1261 1261 1448 1844
144 1351 1351 1351 1552 1975
145 1448 1448 1448 1664
146 1552 1552 1552 1783
147 1664 1664 1664 1911
148 1783 1783 1783 2048
149 1911 1911 1911
150 2048 2048 2048
[ ...Table continues... ]
SPL 3150 4000 5000 6300 8000 10000
4 0.10 0.10
5 0.11 0.10
6 0.12 0.11
7 0.14 0.13 0.10
8 0.16 0.14 0.11
9 0.17 0.16 0.14
10 0.19 0.18 0.16 0.10
11 0.22 0.21 0.18 0.12
12 0.24 0.24 0.21 0.14
12 0.27 0.27 0.24 0.16
14 0.30 0.30 0.27 0.19
15 0.33 0.33 0.30 0.22
16 0.35 0.35 0.33 0.26
17 0.38 0.38 0.35 0.30 0.10
18 0.41 0.41 0.38 0.33 0.12
19 0.45 0.45 0.41 0.36 0.14
20 0.49 0.49 0.45 0.39 0.17
21 0.53 0.53 0.46 0.42 0.21 0.10
22 0.57 0.57 0.53 0.46 0.25 0.11
23 0.62 0.62 0.57 0.50 0.30 0.13
24 0.67 0.67 0.62 0.55 0.33 0.15
25 0.73 0.73 0.67 0.60 0.36 0.17
26 0.79 0.79 0.73 0.65 0.39 0.20
27 0.85 0.85 0.79 0.71 0.42 0.23
28 0.92 0.92 0.85 0.77 0.46 0.26
29 1.00 1.00 0.92 0.84 0.50 0.30
30 1.07 1.07 1.00 0.92 0.55 0.33
31 1.15 1.15 1.07 1.00 0.60 0.37
32 1.23 1.23 1.15 1.07 0.65 0.41
33 1.32 1.32 1.23 1.15 0.71 0.45
34 1.41 1.41 1.32 1.23 0.77 0.50
35 1.51 1.51 1.41 1.32 0.84 0.55
36 1.62 1.62 1.51 1.41 0.92 0.61
37 1.74 1.74 1.62 1.51 1.00 0.67
38 1.86 1.86 1.74 1.62 1.10 0.74
39 1.99 1.99 1.86 1.74 1.21 0.82
40 2.14 2.14 1.99 1.86 1.34 0.90
41 2.29 2.29 2.14 1.99 1.48 1.00
42 2.45 2.45 2.29 2.14 1.63 1.10
43 2.63 2.63 2.45 2.29 1.79 1.21
44 2.81 2.81 2.63 2.45 1.99 1.34
45 3.02 3.02 2.81 2.63 2.14 1.48
46 3.23 3.23 3.02 2.81 2.29 1.63
47 3.46 3.46 3.23 3.02 2.45 1.79
48 3.71 3.71 3.46 3.23 2.63 1.98
49 3.97 3.97 3.71 3.46 2.81 2.18
50 4.26 4.26 3.97 3.71 3.02 2.40
51 4.56 4.56 4.26 3.97 3.23 2.63
52 4.89 4.89 4.56 4.26 3.46 2.81
53 5.24 5.24 4.89 4.56 3.71 3.02
54 5.61 5.61 5.24 4.89 3.97 3.23
55 6.01 6.01 5.61 5.24 4.26 3.46
56 6.44 6.44 6.01 5.61 4.56 3.71
57 6.90 6.90 6.44 6.01 4.89 3.97
58 7.39 7.39 6.90 6.44 5.24 4.26
59 7.92 7.92 7.39 6.90 5.61 4.56
60 8.49 8.49 7.92 7.39 6.01 4.89
61 9.09 9.09 8.49 7.92 6.44 5.24
62 9.74 9.74 9.09 8.49 6.90 5.61
63 10.4 10.4 9.74 9.09 7.39 6.01
64 11.2 11.2 10.4 9.74 7.92 6.44
65 12.0 12.0 11.2 10.4 8.49 6.90
66 12.8 12.8 12.0 11.2 9.09 7.39
67 13.8 13.8 12.8 12.0 9.74 7.92
68 14.7 14.7 13.8 12.8 10.4 8.49
69 15.8 15.8 14.7 13.8 11.2 9.09
70 16.9 16.9 15.8 14.7 12.0 9.74
71 18.1 18.1 16.9 15.8 12.8 10.4
72 19.4 19.4 18.1 16.9 13.8 11.2
73 20.8 20.8 19.4 18.1 14.7 12.0
74 22.3 22.3 20.8 19.4 15.8 12.8
75 23.9 23.9 22.3 20.8 16.9 13.8
76 25.6 25.6 23.9 22.3 18.1 14.7
77 27.4 27.4 25.6 23.9 19.4 15.8
78 29.4 29.4 27.4 25.6 20.8 16.9
79 31.5 31.5 29.4 27.4 22.3 18.1
80 33.7 33.7 31.5 29.4 23.9 19.4
81 36.1 36.1 33.7 31.5 25.6 20.8
82 38.7 38.7 36.1 33.7 27.4 22.3
83 41.5 41.5 38.7 36.1 29.4 23.9
84 44.4 44.4 41.5 38.7 31.5 25.6
85 47.6 47.6 44.4 41.5 33.7 27.4
86 51.0 51.0 47.6 44.4 36.1 29.4
87 54.7 54.7 51.0 47.6 38.7 31.5
88 58.6 58.6 54.7 51.0 41.5 33.7
89 62.7 62.7 58.6 54.7 44.4 36.1
90 67.2 67.2 62.7 58.6 47.6 38.7
91 72.6 72.0 67.2 62.7 51.0 41.5
92 77.2 77.2 72.0 67.2 54.7 44.4
93 82.7 82.7 77.2 72.0 58.6 47.6
94 88.6 88.6 82.7 77.2 62.7 51.0
95 94.9 94.9 88.6 82.7 67.2 54.7
96 102 102 94.9 88.6 72.0 58.6
97 109 109 102 94.9 77.2 62.7
98 117 117 105 102 82.7 67.2
99 125 125 117 109 88.6 72.0
100 134 134 125 117 94.9 77.2
101 144 144 134 125 102 82.7
102 154 154 144 134 109 88.6
103 165 165 154 144 117 94.9
104 177 177 165 154 125 102
105 189 189 177 165 134 109
106 203 203 189 177 144 117
107 217 217 203 109 154 125
108 233 233 217 203 165 134
109 249 249 233 217 177 144
110 267 267 249 233 189 154
111 286 286 267 249 203 165
112 307 307 286 267 217 177
113 329 329 307 286 233 189
114 352 352 329 307 249 203
115 377 377 352 329 267 217
116 404 404 377 352 286 233
117 433 433 404 377 307 249
118 464 464 433 404 329 267
119 497 497 464 433 352 286
120 533 533 497 464 377 307
121 571 571 533 497 404 329
122 611 611 571 533 433 352
123 655 655 611 571 464 377
124 702 702 655 611 497 404
125 752 752 702 655 533 433
126 806 806 752 702 571 464
127 863 863 606 732 611 497
128 925 925 863 806 655 533
129 991 991 925 863 702 571
130 1062 1062 991 925 752 611
131 1137 1137 1062 991 606 655
132 1219 1219 1137 1062 863 702
133 1306 1306 1219 1137 925 752
134 1399 1399 1306 1219 991 606
135 1499 1499 1399 1306 1062 863
136 1606 1606 1499 1399 1197 925
137 1721 1721 1606 1499 1219 991
138 1844 1844 1721 1606 1306 1062
139 1975 1975 1844 1721 1399 1137
140 1975 1844 1499 1219
141 1975 1606 1306
142 1721 1399
143 1844 1499
144 1975 1606
145 1721
146 1844
147 1975
148
149
150
[** This header applies to all remaining
columns in this segment and extends to
the next segment.]
Section B36.5 Correction for spectral irregularities. Noise having
pronounced irregularities in the spectrum (for example, discrete frequency
components or tones), must be adjusted by the correction factor C(k)
calculated as follows:
(a) Step 1. Starting with the corrected sound pressure level in the 80 Hz
one-third octave band (band number 3), calculate the changes in sound
pressure level (or "slopes") in the remainder of the one-third octave bands
as follows:
s(3,k)=no value
s(4,k)=SPL(4,k)-SPL(3,k)
.
.
.
s(i,k)=SPL(i,k)-SPL[(i-l),k]
.
.
.
s(24,k)=SPL(24,k)-SPL(23,k)
(b) Step 2. Encircle the value of the slope, s(i,k), where the absolute
value of the change in slope is greater than 5; that is, where
+/- <Delta>s(i,k) +/- = +/- s(i,k)-s[(i-1),k] +/- >5
(c) Step 3. (1) If the encircled value of the slope s(i,k) is positive and
algebraically greater than the slope s[(i-1),k], encircle SPL(I,K).
(2) If the encircled value of the slope s(1,k) is zero or negative and the
slope s[i-1),k] is positive, encircle (SPL[(i-1),k])
(3) For all other cases, no sound pressure level value is to be encircled.
(d) Step 4. Omit all SPL(i,k) encircled in Step 3 and compute new sound
pressure levels SPL'(i,k) as follows:
(1) For nonencircled sound pressure levels, let the new sound pressure
levels equal the original sound pressure levels,
SPL'(i,k)=SPL(i,k)
(2) For encircled sound pressure levels in bands 1-23, let the new sound
pressure level equal the arithmetic average of the preceding and following
sound pressure levels.
SPL'(i,k)=(1/2)[SPL[(i-1),k]+SPL[(i+1),k]]
(3) If the sound pressure level in the highest frequency band (i=24) is
encircled, let the new sound pressure level in that band equal
SPL'(24,k)=SPL(23,k+s(23,k).
(e) Step 5. Recompute new slopes s' (i,k), including one for an imaginary
25-th band, as follows:
s'(3,k)=s'(4,k)
s'(4,k)=SPL'(4,k)-SPL'(3,k)
.
.
.
s'(i,k)=SPL'(i,k)-SPL'[(i-1),k]
s'(24,k)=SPL'(24,k)-SPL'(23,k)
s'(25,k)=s'(24,k)
(f) Step 6. For i from 3 to 23, compute the arithmetic average of the three
adjacent slopes as follows:
s(i,k)=(1/3)[s'(i,k)+s'[(i+1),k] +s'[(i+2),k]]
(g) Step 7. Compute final adjusted one-third octave-band sound pressure
levels, SPL'' (i,k), by beginning with band number 3 and proceeding to band
number 24 as follows:
SPL''(3,k)=SPL(3,k)
SPL''(4,k)=SPL''(3.k)+s(3.k)
.
.
.
SPL''(i,k)=SPL''[(i-1),k]+s[(i-1),k]
.
.
.
SPL''(24,k)=SPL''(23,k)+s(23,k)
(h) Step 8. Calculate the differences, F(i,k), between the original and the
adjusted sound pressure levels as follows:
F(i,k)=SPL(i,k)-SPL''(i,k)
and note only value greater than one and a half.
(i) Step 9. For each of the 24 one-third octave bands, determine tone
correction factors from the sound pressure level differences F(i,k) and Table
B2.
Table B2 -- Tone Correction Factors
[ ...Illustration appears here... ]
Level Tone
difference correction
Frequency f, Hz F, dB C, dB
50</=f<500 1 1/2*</=F<3 F/3-1/2
3</=F<20 F/6
20</=F 3 1/2
500</=f</=5,000 1 1/2*</=F<3 2 F/3-1
3</=F<20 F/3
20</=F 6 2/3
5,000<f</=10,000 1 1/2*</=F<3 F/3-1/2
3</=F<20 F/6
20</=F 3 1/3
* See Step 8.
(j) Step 10. Designate the largest of the tone correction factors,
determined in Step 9, as C(k). An example of the tone correction procedure is
given in Table B3.
(k) Tone corrected perceived noise levels PNLT(k) are determined by adding
the C(k) values to corresponding PNL(k) values, that is,
PNLT(k)=PNL(k)+C(k)
(l) For any i-th one-third octave band, at any k-th increment of time, for
which the tone correction factor is suspected to result from something other
than (or in addition to) an actual tone (or any special irregularity other
than aircraft noise), an additional analysis may be made using a filter with
a bandwidth narrower than one-third of an octave. If the narrow band analysis
corroborates that suspicion, then a revised value for the background sound
pressure level, SPL''(i,k) may be determined from the analysis and used to
compute a revised tone correction factor, F(i,k), for that particular one-
third octave band.
(m) Tones resulting from ground-plane reflections in the 800 Hz and lower
one-third octave bands may be excluded from the calculation of corrections
for spectral irregularities. To qualify for this exclusion, the pseudotones
must be clearly identified as not being related to the engine noise. This
identification may be made either by comparing measured data with data from a
flush mounted microphone, or by observing the Doppler shift characteristics
of the tone during the flyover-noise/time history. Since pseudotones are
related to ground reflections, a microphone mounted flush to the ground will
yield a spectral shape which can be distinguished from that produced by the
4-foot high microphone at those frequencies which can be related to ground
reflection's geometrical relationships. Identification through Doppler
shifting (the symmetric variation of frequency with time) can be made because
the Doppler frequency variation yields a frequency increase for an
approaching signal and a frequency decrease for a receding signal.
Pseudotones at frequencies above 800 Hz generally should not yield
significant tone corrections. However, for consistency, each tone correction
value must be included in the computation for spectral irregularities. While
the tone corrections below 800 Hz may be ignored for the spectral
irregularity correction, the SPL values must be included in the noy
calculation prescribed in section B36.13 of this appendix.
(n) After the value of PNLTM for each flyover-noise/time history, is
identified, the frequency for the largest tone correction factor (C(k)) must
be identified for the two preceding and the two succeeding, 500-milli-second
time intervals, to identify possible tone suppression at PNLTM as a result of
band sharing of the tone. If the value of C(k) for PNLTM is less than the
average value of C(k) for those five consecutive time intervals, that average
value of C(k) must be used to compute a new value for PNLTM.
Section B36.7 Maximum tone corrected perceived noise level. (a) The maximum
tone corrected perceived noise level, PNLTM, is the maximum calculated value
of the tone corrected perceived noise level, PNLT(k), calculated in
accordance with the procedure of section B36.5 of this appendix. Figure B2 is
an example of a flyover noise time history where the maximum value is clearly
indicated. Half-second time intervals, <Delta>t, are small enough to obtain a
satisfactory noise time history.
Table B3 -- Example of Tone Correction Calculation for a
Turbofan Engine
[ ...Illustration appears here... ]
(b) If there are no pronounced irregularities in the spectrum, then the
procedure of Sec. B36.5 of this Appendix would be redundant since PNLT(k)
would be identically equal to PNL(k). For this case, PNLTM would be the
maximum value of PNL(k) and would equal PNLM.
Section B36.9 Duration correction. The duration correction factor D is
determined by the integration technique defined by the expression:
t(2)
D = 10 log [(1/T) INTEGRAL ant [PNLT/10] dt ] - PNLTM
t(1)
Figure B2 -- Example of Perceived Noise Level Corrected
For Tones As A Function of Aircraft Flyover Time
[ ...Illustration appears here... ]
Where T is a normalizing time constant, PNLTM is the maximum value of PNLT,
and t(1) and t(2) are the limits of the significant noise time history.
(a) Since PNLT is calculated from measured values of SPL, there will, in
general, be no obvious equation for PNLT as a function of time. Consequently,
the equation can be rewritten with a summation sign instead of an integral
sign as follows:
d/ Dt
D = 10 log [(1/T) SUM Dt ant [PNLT(k)/10]] - PNLTM
k=0
where <Delta>t is the length of the equal increments of time for which
PNLT(k) is calculated and d is the time interval to the nearest 1.0 second
during which PNLT(k) is within a specified value, h, of PNLTM.
(b) Half-second time intervals for <Delta>t are small enough to obtain a
satisfactory history of the perceived noise level. A shorter time interval
may be selected by the applicant provided approved limits and constants are
used.
(c) The following values for T, <Delta>t,and h, must be used in calculating
D:
T=10 sec,
<Delta>t=0.5 sec. (or the approved sampling time interval), and
h=10 dB.
Using the above values, the equation for D becomes
2d
D = 10 log [ SUM ant [PNLT(k)/10]] - PNLTM - 13
k=0
Where the integer d is the duration time defined by the points that are 10 dB
less than PNLTM.
(d) If the 10 dB-down points fall between calculated PNLT(k) values (the
usual case), the applicable limits for the duration time must be chosen from
the PNLT(k) values closest to PNLTM-10. For those cases with more than one
peak value of PNLT(k), the applicable limits must be chosen to yield the
largest possible value for the duration time.
(e) If the value of PNLT(k) at the 10 dB-down points is 90 PNdB or less,
the value of d may be taken as the time interval between the initial and the
final times for which PNLT(k) equals 90 PNdB.
(f) The aircraft testing procedures must include the 10 dB-down points in
the flyover noise/time record.
Section B36.11 Effective perceived noise level. (a) The total subjective
effect of an aircraft flyover is designated "effective perceived noise
level," EPNL, and is equal to the algebraic sum of the maximum value of the
tone corrected perceived noise level, PNLTM, and the duration correction, D.
That is,
EPNL=PNLTM+D
where PNLTM and D are calculated under sections B36.7 and B36.9 of this
appendix.
(b) The above equation can be rewritten by substituting the equation for D
from Sec. B36.9 of this appendix, that is,
2d
EPNL = 10 log [ SUM ant [PNLT(k)/10]] - 13
k=0
(c) If, during a test flight, one or more peak values of PNLT are observed
which are within 2 dB of PNLTM, the value of EPNL shall be calculated for
each, as well as for PNLTM. If any EPNL value exceeds the value at the moment
of PNLTM, the maximum value of such exceedance must be added as a further
adjustment to the EPNL calculated from the measured data.
Section B36.13 Mathematical formulation of noy tables.
(a) The relationship between sound pressure level and perceived noisiness
given in Table B1 is illustrated in Figure B3. The variation of log (n) with
SPL for a given one-third octave band can be expressed by straight lines as
shown in Figure B3.
(1) The slopes of the straight lines M(b), M(c), and M(d) and M(e);
(2) The intercepts of the lines on the SPL axis, SPL (b) and SPL (c); and
(3) The coordinates of the discontinuities, SPL (a) and log n(a); SPL (d)
and log n = -1.0; and SPL (e) and log n = log (0.3).
(b) The important aspects of the mathematical formulation are:
(1) SPL " SPL (a)
n = antilog [M(c)*(SPL-SPL(c))]
(2) SPL (b) > SPL < SPL (a)
n = antilog [M(b)*(SPL-SPL(b))]
(3) SPL (e) > SPL < SPL (b)
n = antilog [M(e)*(SPL-SPL(b))]
(4) SPL (d) > SPL < SPL (e)
n = 0.1 antilog [M(d)*(SPL-SPL(d))]
(c) Table B4 lists the values of the important constants necessary to
calculate sound pressure level as a function of perceived noisiness.
Figure B3 -- Perceived Noisiness As A Function of Sound Pressure Level
Table B4 -- Constants for Mathematically Formulated NOY Values
[ ...Illustrations appear here... ]
[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as amended by Amdt. 36-5, 41 FR
35058, Aug. 19, 1976; Amdt. 36-9, 43 FR 8748, Mar. 2, 1978; Amdt. 36-14, 53
FR 3541, Feb. 5, 1988; Amdt. 36-15, 53 FR 16368, May 6, 1988]
Appendix C--Noise Levels for Transport Category and Turbojet Powered
Airplanes Under Sec. 36.201
Sec.
C36.1 Noise measurement and evaluation.
C36.3 Noise measuring points.
C36.5 Noise levels.
C36.7 Takeoff reference and test limitations.
C36.9 Approach reference and test limitations.
Section C36.1 Noise measurement and evaluation. Compliance with this
appendix must be shown with noise levels measured and evaluated as
prescribed, respectively, by Appendix A and Appendix B of this part, or under
approved equivalent procedures.
Section C36.3 Noise measuring points. Compliance with the noise level
standards of section C36.5 must be shown--
(a) For takeoff, at a point 21, 325 feet (6,500 meters) from the start of
the takeoff roll on the extended centerline of the runway;
(b) For approach, at a point 6,562 feet (2,000 meters) from the threshold
on the extended centerline of the runway; and
(c) For the sideline, at the point, on a line parallel to and 1,476 feet
(450 meters) from the extended centerline of the runway, where the noise
level after liftoff is greatest, except that, for an airplane powered by more
than three turbojet engines, this distance must be 0.35 nautical miles for
the purpose of showing compliance with Stage 1 or Stage 2 noise limits (as
applicable).
Sec. C36.5 Noise levels.
(a) Limits. Except as provided in paragraphs (b) and (c) of this section,
it must be shown by flight test that the noise levels of the airplane, at the
measuring points described in section C36.3, do not exceed the following
(with appropriate interpolation between weights);
(1) Stage 1 noise limits for acoustical changes for airplanes regardless of
the number of engines are those noise levels prescribed under Sec. 36.7(c) of
this part.
(2) Stage 2 noise limits for airplanes regardless of the number of engines
are as follows:
(i) For takeoff. 108 EPNdB for maximum weights of 600,000 pounds or more,
reduced by 5 EPNdB per halving of the 600,000 pounds maximum weight down to
93 EPNdB for maximum weights of 75,000 pounds and less.
(ii) For sideline and approach.--108 EPNdB for maximum weights of 600,000
pounds or more, reduced by 2 EPNdB per halving of the 600,000 pounds maximum
weight down to 102 EPNdB for maximum weights of 75,000 pounds and less.
(3) Stage 3 noise limits are as follows:
(i) For takeoff.
(A) For airplanes with more than 3 engines. 106 EPNdB for maximum weights
of 850,000 pounds or more, reduced by 4 EPNdB per halving of the 850,000
pounds maximum weight down to 89 EPNdB for maximum weights of 44,673 pounds
or less;
(B) For airplanes with 3 engines--104 EPNdB for maximum weights of 850,000
pounds or more, reduced by 4 EPNdB per halving of the 850,000 pounds maximum
weight down to 89 EPNdB for maximum weights of 63,177 pounds and less; and
(C) For airplanes with fewer than 3 engines--101 EPNdB for maximum weights
of 850,000 pounds or more, reduced by 4 EPNdB per halving of the 850,000
pounds maximum weight down to 89 EPNdB for maximum weights of 106,250 pounds
and less.
(ii) For sideline, regardless of the number of engines. 103 EPNdB for
maximum weights of 882,000 pounds or more, reduced by 2.56 EPNdB per halving
of the 882,000 pounds maximum weight down to 94 EPNdB for maximum weights of
77,200 pounds or less.
(iii) For approach, regardless of the number of engines--105 EPNdB for
maximum weights of 617,300 pounds or more, reduced by 2.33 EPNdB per halving
of the 617,300 pounds weight down to 98 EPNdB for maximum weights of 77,200
pounds or less.
(b) Tradeoffs. Except to the extent limited under Secs. 36.7(c)(1) and
36.7(d)(3)(i)(B) of this part, the noise level limits prescribed in paragraph
(a) of this section may be exceeded at one or two of the measuring points
specified in section C36.3 of this appendix, if--
(1) The sum of the exceedances is not greater than 3 EPNdB;
(2) No exceedance is greater than 2 EPNdB; and
(3) The exceedances are completely offset by reductions at other required
measuring points.
Sec. C36.7 Takeoff Reference and Test Limitations.
(a) This section applies to all takeoff noise tests conducted under this
appendix in showing compliance with this part.
(b) Takeoff power or thrust must be used from the start of takeoff roll to
at least the following altitude above the runway:
(1) For Stage 1 airplanes and for Stage 2 airplanes that do not have
turbojet engines with a bypass ratio of 2 or more, the following apply:
(i) For airplanes with more than three turbojet engines--700 feet (214
meters).
(ii) For all other airplanes--1,000 feet (305 meters).
(2) For Stage 2 airplanes that have turbojet engines with a bypass ratio of
2 or more and for Stage 3 airplane, the following apply:
(i) For airplanes with more than three turbojet engines--689 feet (210
meters).
(ii) For airplanes with three turbojet engines--853 feet (260 meters).
(iii) For airplanes with fewer than three turbojet engines--984 feet (300
meters).
(iv) For airplanes not powered by turbojet engines--1,000 feet (305
meters).
(c) Upon reaching the altitude specified in paragraph (b) of this section,
the power or thrust may not be reduced below that needed to maintain level
flight with one engine inoperative, or to maintain a four percent climb
gradient, whichever power or thrust is greater.
(d) A constant takeoff configuration, selected by the applicant, must be
maintained throughout the takeoff noise test, except that the landing gear
may be retracted.
(e) For applications made for subsonic airplanes after September 17, 1971,
and for Concorde airplanes, the following apply:
(1) For subsonic airplanes the test day speeds and the acoustic day
reference speed must be the minimum approved value of V2+10 knots, or the
all-engines-operating speed at 35 feet (for turbine engine powered airplanes)
or 50 feet (for reciprocating engine powered airplanes), whichever speed is
greater as determined under the regulations constituting the type
certification basis of the airplane. These tests must be conducted at the
test day speeds+/-3 knots. Noise values measured at the test day speeds must
be corrected to the acoustic day reference speed.
(2) For Concorde airplanes, the test day speeds and the acoustic day
reference speed must be the minimum approved value of V2 +35 knots, or the
all-engines-operating speed at 35 feet, whichever speed is greater as
determined under the regulations constituting the type certification basis of
the airplane, except that the reference speed may not exceed 250 knot. These
tests must be conducted at the test day speeds +3 knots. Noise values
measured at the test day speeds must be corrected to the acoustic day
reference speed.
(3) If a negative runway gradient exists in the direction of takeoff,
performance and acoustic data must be corrected to the zero slope condition.
Sec. C36.9 Approach reference and test limitations.
(a) This section applies to all approaches conducted in showing compliance
with this part.
(b) The airplane's configuration must be that used in showing compliance
with the landing requirements in the airworthiness regulations constituting
the type certification basis of the airplane. If more than one configuration
is used in showing compliance with the landing requirements in the
airworthiness regulations constituting the type certification basis of the
airplane, the configuration that is most critical from a noise standpoint
must be used.
(c) The approaches must be conducted with a steady glide angle of 3
deg.+0.5 deg. and must be continued to a normal touchdown with no airframe
configuration change.
(d) All engines must be operating at approximately the same power or
thrust.
(e) For applications made for subsonic airplanes after September 17, 1971,
and for Concorde airplanes, the following apply:
(1) For subsonic airplanes a steady approach speed, that is either 1.30 Vs
+10 knots or the speed used in establishing the approved landing distance
under the airworthiness regulations constituting the type certification basis
of the airplane, whichever speed is greatest, must be established and
maintained over the approach measuring point.
(2) For Concorde airplanes a steady approach speed, that is either the
landing reference speed + 10 knots or the speed used in establishing the
approved landing distance under the airworthiness regulations constituting
the type certification basis of the airplane, whichever speed is greater,
must be established and maintained over the approach measuring point.
(3) A tolerance of +3 knots may be used throughout the approach noise
testing.
[Doc. No. 9337, 34 FR 18364, Nov. 18, 1969, as amended by Amdt. 36-1, 34 FR
18815, Nov. 25, 1969; 34 FR 19025, Nov. 29, 1969; Amdt. 36-5, 41 FR 35058,
Aug. 19, 1976, Amdt. 36-7, 42 FR 12371, Mar. 3, 1977; Amdt. 36-8, 43 FR 8730,
Mar. 2, 1978; Amdt. 36-10, 43 FR 28420, June 29, 1978; 43 FR 44475, Sept. 28,
1978; 43 FR 47489, Oct. 16, 1978; Amdt. 36-12, 46 FR 33465, June 29, 1981;
Amdt. 36-15, 53 FR 16372, May 6, 1988]
Appendices D-E--[Reserved]
Appendix F--Flyover Noise Requirements for Propeller-Driven Small Airplane
and Propeller-Driven, Commuter Category Airplane Certification Tests
Prior to December 22, 1988
PART A--GENERAL
Sec.
F36.1 Scope.
PART B--NOISE MEASUREMENT
F36.101 General test conditions.
F36.103 Acoustical measurement system.
F36.105 Sensing, recording, and reproducing equipment.
F36.107 Noise measurement procedures.
F36.109 Data recording, reporting, and approval.
F36.111 Flight procedures.
PART C--DATA CORRECTION
F36.201 Correction of data.
F36.203 Validity of results.
PART D--NOISE LIMITS
F36.301 Aircraft noise limits.
PART A--GENERAL
Section F36.1 Scope. This appendix prescribes noise level limits and
procedures for measuring and correcting noise data for the propeller driven
small airplanes specified in Secs. 36.1 and 36.501(b).
PART B--NOISE MEASUREMENT
Sec. F36.101 General test conditions.
(a) The test area must be relatively flat terrain having no excessive sound
absorption characteristics such as those caused by thick, matted, or tall
grass, by shrubs, or by wooded areas. No obstructions which significantly
influence the sound field from the airplane may exist within a conical space
above the measurement position, the cone being defined by an axis normal to
the ground and by a half-angle 75 degrees from this axis.
(b) The tests must be carried out under the following conditions:
(1) There may be no precipitation.
(2) Relative humidity may not be higher than 90 percent or lower than 30
percent.
(3) Ambient temperature may not be above 86 degrees F. or below 41 degrees
F. at 33' above ground. If the measurement site is within 1 n.m. of an
airport thermometer the airport reported temperature may be used.
(4) Reported wind may not be above 10 knots at 33' above ground. If wind
velocities of more than 4 knots are reported, the flight direction must be
aligned to within +15 degrees of wind direction and flights with tail wind
and head wind must be made in equal numbers. If the measurement site is
within 1 n.m. of an airport anemometer, the airport reported wind may be
used.
(5) There may be no temperature inversion or anomalous wind conditions that
would significantly alter the noise level of the airplane when the noise is
recorded at the required measuring point.
(6) The flight test procedures, measuring equipment, and noise measurement
procedures must be approved by the FAA.
(7) Sound pressure level data for noise evaluation purposes must be
obtained with acoustical equipment that complies with section F36.103 of this
appendix.
Sec. F36.103 Acoustical measurement system. The acoustical measurement
system must consist of approved equipment equivalent to the following:
(a) A microphone system with frequency response compatible with measurement
and analysis system accuracy as prescribed in section F36.105 of this
appendix.
(b) Tripods or similar microphone mountings that minimize interference with
the sound being measured.
(c) Recording and reproducing equipment characteristics, frequency
response, and dynamic range compatible with the response and accuracy
requirements of section F36.105 of this appendix.
(d) Acoustic calibrators using sine wave or broadband noise of known sound
pressure level. If broadband noise is used, the signal must be described in
terms of its average and maximum root-mean-square (rms) value for nonoverload
signal level.
Sec. F36.105 Sensing, recording, and reproducing equipment.
(a) The noise produced by the airplane must be recorded. A magnetic tape
recorder is acceptable.
(b) The characteristics of the system must comply with the recommendations
in International Electrotechnical Commission (IEC) Publication No. 179,
entitled "Precision Sound Level Meters" as incorporated by reference in Part
36 under Sec. 36.6 of this part.
(c) The response of the complete system to a sensibly plane progressive
sinusoidal wave of constant amplitude must lie within the tolerance limits
specified in IEC Publication No. 179, dated 1973, over the frequency range 45
to 11,200 Hz.
(d) If limitations of the dynamic range of the equipment make it necessary,
high frequency pre-emphasis must be added to the recording channel with the
converse de-emphasis on playback. The pre-emphasis must be applied such that
the instantaneous recorded sound pressure level of the noise signal between
800 and 11,200 Hz does not vary more than 20 dB between the maximum and
minimum one-third octave bands.
(e) If requested by the Administrator, the recorded noise signal must be
read through an "A" filter with dynamic characteristics designated "slow," as
defined in IEC Publication No. 179, dated 1973. The output signal from the
filter must be fed to a rectifying circuit with square law rectification,
integrated with time constants for charge and discharge of about 1 second or
800 milliseconds.
(f) The equipment must be acoustically calibrated using facilities for
acoustic freefield calibration and if analysis of the tape recording is
requested by the Administrator, the analysis equipment shall be
electronically calibrated by a method approved by the FAA.
(g) A windscreen must be employed with microphone during all measurements
of aircraft noise when the wind speed is in excess of 6 knots.
Sec. F36.107 Noise measurement procedures.
(a) The microphones must be oriented in a known direction so that the
maximum sound received arrives as nearly as possible in the direction for
which the microphones are calibrated. The microphone sensing elements must be
approximately 4' above ground.
(b) Immediately prior to and after each test; a recorded acoustic
calibration of the system must be made in the field with an acoustic
calibrator for the two purposes of checking system sensitivity and providing
an acoustic reference level for the analysis of the sound level data.
(c) The ambient noise, including both acoustical background and electrical
noise of the measurement systems, must be recorded and determined in the test
area with the system gain set at levels that will be used for aircraft noise
measurements. If aircraft sound pressure levels do not exceed the background
sound pressure levels by at least 10 dB(A), approved corrections for the
contribution of background sound pressure level to the observed sound
pressure level must be applied.
Sec. F36.109 Data recording, reporting, and approval.
(a) Data representing physical measurements or corrections to measured data
must be recorded in permanent form and appended to the record except that
corrections to measurements for normal equipment response deviations need not
be reported. All other corrections must be approved. Estimates must be made
of the individual errors inherent in each of the operations employed in
obtaining the final data.
(b) Measured and corrected sound pressure levels obtained with equipment
conforming to the specifications described in section F36.105 of this
appendix must be reported.
(c) The type of equipment used for measurement and analysis of all
acoustic, airplane performance, and meteorological data must be reported.
(d) The following atmospheric data, measured immediately before, after, or
during each test at the observation points prescribed in section F36.101 of
this appendix must be reported:
(1) Air temperature and relative humidity.
(2) Maximum, minimum, and average wind velocities.
(e) Comments on local topography, ground cover, and events that might
interfere with sound recordings must be reported.
(f) The following airplane information must be reported:
(1) Type, model and serial numbers (if any) of airplanes, engines, and
propellers.
(2) Any modifications or nonstandard equipment likely to affect the noise
characteristics of the airplane.
(3) Maximum certificated takeoff weights.
(4) Airspeed in knots for each overflight of the measuring point.
(5) Engine performance in terms of revolutions per minute and other
relevant parameters for each overflight.
(6) Aircraft height in feet determined by a calibrated altimeter in the
aircraft, approved photographic techniques, or approved tracking facilities.
(g) Aircraft speed and position and engine performance parameters must be
recorded at an approved sampling rate sufficient to ensure compliance with
the test procedures and conditions of this appendix.
Sec. F36.111 Flight procedures.
(a) Tests to demonstrate compliance with the noise level requirements of
this appendix must include at least six level flights over the measuring
station at a height of 1,000' +30' and +10 degrees from the zenith when
passing overhead.
(b) Each test over flight must be conducted:
(1) At not less than the highest power in the normal operating range
provided in an Airplane Flight Manual, or in any combination of approved
manual material, approved placard, or approved instrument markings; and
(2) At stabilized speed with propellers synchronized and with the airplane
in cruise configuration, except that if the speed at the power setting
prescribed in this paragraph would exceed the maximum speed authorized in
level flight, accelerated flight is acceptable.
PART C--DATA CORRECTION
Sec. F36.201 Correction of data.
(a) Noise data obtained when the temperature is outside the range of 68
degrees F. +/-9 degrees F., or the relative humidity is below 40 percent,
must be corrected to 77 degrees F. and 70 percent relative humidity by a
method approved by the FAA.
(b) The performance correction prescribed in paragraph (c) of this section
must be used. It must be determined by the method described in this appendix,
and must be added algebraically to the measured value. It is limited to
5dB(A).
(c) The performance correction must be computed by using the following
formula:
R/C
DdB = 60-20 log 10 E(11,430-D50 ------ + 50F
Vy
Where:
D50=Takeoff distance to 50 feet at maximum certificated takeoff weight.
R/C=Certificated best rate of climb (fpm).
Vy =Speed for best rate of climb in the same units as rate of climb.
(d) When takeoff distance to 50' is not listed as approved performance
information, the figures of 2000 for single-engine airplanes and 1600' for
multi-engine airplanes must be used.
Sec. F36.203 Validity of results.
(a) The test results must produce an average dB(A) and its 90 percent
confidence limits, the noise level being the arithmetic average of the
corrected acoustical measurements for all valid test runs over the measuring
point.
(b) The samples must be large enough to establish statistically a 90 pecent
confidence limit not to exceed +/-1.5 dB(A). No test result may be omitted
from the averaging process, unless omission is approved by the FAA.
PART D--NOISE LIMITS
Sec. F36.301 Aircraft noise limits.
(a) Compliance with this section must be shown with noise data measured and
corrected as prescribed in Parts B and C of this appendix.
(b) For airplanes for which application for a type certificate is made on
or after October 10, 1973, the noise level must not exceed 68 dB(A) up to and
including aircraft weights of 1,320 pounds (600 kg.). For weights greater
than 1,320 pounds up to and including 3,630 pounds (1.650 kg.) the limit
increases at the rate of 1 dB/165 pounds (1 dB/75 kg.) to 82 dB(A) at 3,630
pounds, after which it is constant at 82 dB(A). However, airplanes produced
under type certificates covered by this paragraph must also meet paragraph
(d) of this section for the original issuance of standard airworthiness
certificates or restricted category airworthiness certificates if those
airplanes have not had flight time before the date specified in that
paragraph.
(c) For airplanes for which application for a type certificate is made on
or after January 1, 1975, the noise levels may not exceed the noise limit
curve prescribed in paragraph (b) of this section, except that 80 dB(A) may
not be exceeded.
(d) For airplanes for which application is made for a standard
airworthiness certificate or for a restricted category airworthiness
certificate, and that have not had any flight time before January 1, 1980,
the requirements of paragraph (c) of this section apply, regardless of date
of application, to the original issuance of the certificate for that
airplane.
[Doc. No. 13243, 40 FR 1035, Jan. 6, 1975; 40 FR 6347, Feb. 11, 1975, as
amended by Amdt. 36-6, 41 FR 56064, Dec. 23, 1976; Amdt. 36-6, 42 FR 4113,
Jan. 24, 1977; Amdt. 36-9, 43 FR 8754, Mar. 2, 1978; Amdt. 36-13, 52 FR 1836,
Jan. 15, 1987; Amdt. 36-16, 53 FR 47400, Nov. 22, 1988]
Appendix G--Takeoff Noise Requirements for Propeller-Driven Small Airplane
and Propeller-Driven, Commuter Category Airplane Certification Tests on
or After December 22, 1988
PART A--GENERAL
Sec.
G36.1 Scope.
PART B--NOISE MEASUREMENT
G36.101 General Test Conditions.
G36.103 Acoustical measurement system.
G36.105 Sensing, recording, and reproducing equipment.
G36.107 Noise measurement procedures.
G36.109 Data recording, reporting, and approval.
G36.111 Flight procedures.
PART C--DATA CORRECTIONS
G36.201 Corrections to Test Results.
G36.203 Validity of results.
PART D--NOISE LIMITS
G36.301 Aircraft Noise Limits.
PART A--GENERAL
Section G36.1 Scope. This appendix prescribes limiting noise levels and
procedures for measuring noise and adjusting these data to standard
conditions, for propeller driven small airplanes and propeller-driven,
commuter category airplanes specified in Secs. 36.1 and 36.501(c).
PART B--NOISE MEASUREMENT
Sec. G36.101 General Test Conditions.
(a) The test area must be relatively flat terrain having no excessive sound
absorption characteristics such as those caused by thick, matted, or tall
grass, by shrubs, or by wooded areas. No obstructions which significantly
influence the sound field from the airplane may exist within a conical space
above the measurement position, the cone being defined by an axis normal to
the ground and by a half-angle 75 degrees from the normal ground axis.
(b) The tests must be carried out under the following conditions:
(1) No precipitation;
(2) Ambient air temperature between 36 and 95 degrees F (2.2 and 35 degrees
C);
(3) Relative humidity between 20 percent and 95 percent, inclusively;
(4) Wind speed may not exceed 10 knots (19 km/h) and cross wind may not
exceed 5 knots (9 km/h), using a 30-second average;
(5) No temperature inversion or anomalous wind condition that would
significantly alter the noise level of the airplane when the nose is recorded
at the required measuring point, and
(6) The meteorological measurements must be made between 4 ft. (1.2 m) and
33 ft. (10 m) above ground level. If the measurement site is within 1 n.m. of
an airport meteorological station, measurements from that station may be
used.
(c) The flight test procedures, measuring equipment, and noise measurement
procedures must be approved by the FAA.
(d) Sound pressure level data for noise evaluation purposes must be
obtained with acoustical equipment that complies with section G36.103 of this
appendix.
Sec. G36.103 Acoustical Measurement System.
The acoustical measurement system must consist of approved equipment with
the following characteristics: (a) A microphone system with frequency
response compatible with measurement and analysis system accuracy as
prescribed in section G36.105 of this appendix.
(b) Tripods or similar microphone mountings that minimize interference with
the sound being measured.
(c) Recording and reproducing equipment characteristics, frequency
response, and dynamic range compatible with the response and accuracy
requirements of section G36.105 of this appendix.
(d) Acoustic calibrators using sine wave or broadband noise of known sound
pressure level. If broadband noise is used, the signal must be described in
terms of its average and maximum root-mean-square (rms) value for non-
overload signal level.
Sec. G36.105 Sensing, Recording, and Reproducing Equipment.
(a) The noise produced by the airplane must be recorded. A magnetic tape
recorder, graphic level recorder, or sound level meter is acceptable when
approved by the regional certificating authority.
(b) The characteristics of the complete system must comply with the
requirements in International Electrotechnical Commission (IEC) Publications
No. 651, entitled "Sound Level Meters" and No. 561, entitled "Electro-
acoustical Measuring Equipment for Aircraft Noise Certification" as
incorporated by reference under Sec. 36.6 of this part. Sound level meters
must comply with the requirements for Type 1 sound level meters as specified
in IEC Publication No. 651.
(c) The response of the complete system to a sensibly plane progressive
sinusoidal wave of constant amplitude must be within the tolerance limits
specified in IEC Publication No. 651, over the frequency range 45 to 11,200
Hz.
(d) If equipment dynamic range limitations make it necessary, high
frequency pre-emphasis must be added to the recording channel with the
converse de-emphasis on playback. The pre-emphasis must be applied such that
the instantaneous recorded sound pressure level of the noise signal between
800 and 11,200 Hz does not vary more than 20 dB between the maximum and
minimum one-third octave bands.
(e) The output noise signal must be read through an "A" filter with dynamic
characteristics designated "slow" as defined in IEC Publication No. 651. A
graphic level recorder, sound level meter, or digital equivalent may be used.
(f) The equipment must be acoustically calibrated using facilities for
acoustic free-field calibration and if analysis of the tape recording is
requested by the Administrator, the analysis equipment shall be
electronically calibrated by a method approved by the FAA. Calibrations shall
be performed, as appropriate, in accordance with paragraph A36.3(e) of
Appendix A of this part.
(g) A windscreen must be employed with the microphone during all
measurements of aircraft noise when the wind speed is in excess of 5 knots (9
km/hr).
Sec. G36.107 Noise Measurement Procedures.
(a) The microphones must be oriented in a known direction so that the
maximum sound received arrives as nearly as possible in the direction for
which the microphones are calibrated. The microphone sensing elements must be
4 ft. (1.2m) above ground level.
(b) Immediately prior to and after each test, a recorded acoustic
calibration of the system must be made in the field with an acoustic
calibrator for the purposes of checking system sensitivity and providing an
acoustic reference level for the analysis of the sound level data. If a tape
recorder or graphic level recorder is used, the frequency response of the
electrical system must be determined at a level within 10 dB of the full-
scale reading used during the test, utilizing pink or pseudorandom noise.
(c) The ambient noise, including both acoustic background and electrical
systems noise, must be recorded and determined in the test area with the
system gain set at levels which will be used for aircraft noise measurements.
If aircraft sound pressure levels do not exceed the background sound pressure
levels by at least 10 dB(A), a takeoff measurement point nearer to the start
of the takeoff roll must be used and the results must be adjusted to the
reference measurement point by an approved method.
Sec. G36.109 Data Recording, Reporting, and Approval.
(a) Data representing physical measurements and adjustments to measured
data must be recorded in permanent form and appended to the record, except
that corrections to measurements for normal equipment response deviations
need not be reported. All other adjustments must be approved. Estimates must
be made of the individual errors inherent in each of the operations employed
in obtaining the final data.
(b) Measured and corrected sound pressure levels obtained with equipment
conforming to the specifications in section G36.105 of this appendix must be
reported.
(c) The type of equipment used for measurement and analysis of all
acoustical, airplane performance, and meteorological data must be reported.
(d) The following atmospheric data, measured immediately before, after, or
during each test at the observation points prescribed in section G36.101 of
this appendix must be reported:
(1) Ambient temperature and relative humidity.
(2) Maximum and average wind speeds and directions for each run.
(e) Comments on local topography, ground cover, and events that might
interfere with sound recordings must be reported.
(f) The aircraft position relative to the takeoff reference flight path
must be determined by an approved method independent of normal flight
instrumentation, such as radar tracking, theodolite triangulation, or
photographic scaling techniques.
(g) The following airplane information must be reported:
(1) Type, model, and serial numbers (if any) of airplanes, engines, and
propellers;
(2) Any modifications or nonstandard equipment likely to affect the noise
characteristics of the airplane;
(3) Maximum certificated takeoff weight;
(4) For each test flight, airspeed and ambient temperature at the flyover
altitude over the measuring site determined by properly calibrated
instruments;
(5) For each test flight, engine performance parameters, such as manifold
pressure or power, propeller speed (rpm) and other relevant parameters. Each
parameter must be determined by properly calibrated instruments. For
instance, propeller RPM must be validated by an independent device accurate
to within +/-1 percent, when the airplane is equipped with a mechanical
tachometer.
(6) Airspeed, position, and performance data necessary to make the
corrections required in section G36.201 of this appendix must be recorded by
an approved method when the airplane is directly over the measuring site.
Sec. G36.111 Flight Procedures.
(a) The noise measurement point is on the extended centerline of the runway
at a distance of 8200 ft (2500 m) from the start of takeoff roll. The
aircraft must pass over the measurement point within +/-10 degrees from the
vertical and within 20% of the reference altitude. The flight test program
shall be initiated at the maximum approved takeoff weight and the weight
shall be adjusted back to this maximum weight after each hour of flight time.
Each flight test must be conducted at the speed for the best rate of climb
(Vy) +/-5 knots (+/-9 km/hour) indicated airspeed. All test, measurement, and
data correction procedures must be approved by the FAA.
(b) The takeoff reference flight path must be calculated for the following
atmospheric conditions:
(1) Sea level atmospheric pressure of 1013.25 mb (013.25 hPa);
(2) Ambient air temperature of 59 deg.F (15 deg.C);
(3) Relative humidity of 70 percent; and
(4) Zero wind.
(c) The takeoff reference flight path must be calculated assuming the
following two segments:
(1) First segment.
(i) Takeoff power must be used from the brake release point to the point at
which the height of 50 ft (15m) above the runway is reached.
(ii) A constant takeoff configuration selected by the applicant must be
maintained through this segment.
(iii) The maximum weight of the airplane at brake-release must be the
maximum for which noise certification is requested.
(iv) The length of this first segment must correspond to the airworthiness
approved value for a takeoff on a level paved runway (or the corresponding
value for seaplanes).
(2) Second segment.
(i) The beginning of the second segment corresponds to the end of the first
segment.
(ii) The airplane must be in the climb configuration with landing gear up,
if retractable, and flap setting corresponding to normal climb position
throughout this second segment.
(iii) The airplane speed must be the speed for the best rate of climb (Vy).
(iv) Maximum continuous installed power and rpm for variable pitch
propeller(s) shall be used. For fixed pitch propeller(s), the maximum power
and rpm that can be delivered by the engine(s) must be maintained throughout
the second segment.
PART C--DATA CORRECTIONS
Sec. G36.201 Corrections to Test Results.
(a) These corrections account for the effects of:
(1) Differences in atmospheric absorption of sound between meteorological
test conditions and reference conditions.
(2) Differences in the noise path length between the actual airplane flight
path and the reference flight path.
(3) The change in the helical tip Mach number between test and reference
conditions.
(4) The change in the engine power between test and reference conditions.
(b) Atmospheric absorption correction is required for noise data obtained
when the test conditions are outside those specified in Figure G1. Noise data
outside the applicable range must be corrected to 77 F and 70 percent
relative humidity by a FAA approved method.
(c) Helical tip Mach number and power corrections must be made if:
(1) The propeller is a variable pitch type, or
(2) The propeller is a fixed pitch type and the test power is not within 5
percent of the reference power.
(d) When the test conditions are outside those specified, corrections must
be applied by an approved procedure or by the following simplified procedure:
(1) Measured sound levels must be corrected from test day meteorological
conditions to reference conditions by adding an increment equal to
Delta (M) = (]]-0.7) HT/1000
where HT is the height in feet of the test aircraft when directly over the
noise measurement point and ]] is the rate of absorption for the test day
conditions at 500 Hz as specified in SAE ARP 866A, entitled "Standard Values
of Atmospheric Absorption as a function of Temperature and Humidity for use
in Evaluating Aircraft Flyover Noise" as incorporated by reference under Sec.
36.6 of this part.
(2) Measured sound levels in decibels must be corrected for height by
algebraically adding an increment equal to Delta (1). When test day
conditions are within those specified in figure G1:
Delta (1) = 22 log (HT/HR)
where HT is the height of the test aircraft when directly over the noise
measurement point and HR is the reference height.
When test day conditions are outside those specified in figure G1:
Delta (1) = 20 log (HT/HR)
(3) Measured sound levels in decibels must be corrected for helical tip
Mach number by algebraically adding an increment equal to:
Delta (2) = k log (MR/MT)
where MT and MR are the test and reference helical tip Mach numbers,
respectively. The constant "k" is equal to the slope of the line obtained for
measured values of the sound level in dB(A) versus helical tip Mach number.
The value of k may be determined from approved data. A nominal value of k =
150 may be used when MT is smaller than
Figure G1 -- Measurement Window For No Absorption Correction
[ ...Illustration appears here... ]
MR. No correction may be made using the nominal value of k when MT is larger
than MR. The reference helical tip Mach number MR is the Mach number
corresponding to the reference conditions (RPM, airspeed, temperature) above
the measurement point.
(4) Measured sound levels in decibels must be corrected for engine power by
algebraically adding an increment equal to:
Delta (3) = 17 log (PR/PT)
where PT and PR are the test and reference engine powers respectively.
Sec. G36.203 Validity of Results.
(a) The measuring point must be overflown at least six times. The test
results must produce an average noise level (LAmax) value within a 90 percent
confidence limit. The average noise level is the arithmetic average of the
corrected acoustical measurements for all valid test runs over the measuring
point.
(b) The samples must be large enough to establish statistically a 90
percent confidence limit not exceeding +/-1.5 dB(A). No test results may be
omitted from the averaging process unless omission is approved by the FAA.
PART D--NOISE LIMITS
Sec. G36.301 Aircraft noise limits.
(a) Compliance with this section must be shown with noise data measured and
corrected as prescribed in Parts B and C of this appendix.
(b) The noise level must not exceed 73 dB(A) up to and including aircraft
weights of 1,320 pounds (600 kg). For weights greater than 1,320 pounds the
limit increases at the rate of 1 dB/165
Figure G2 -- Noise Level Vs. Airplane Weight
[ ...Illustration appears here... ]
pounds (1 dB/75 kg) up to 85 dB(A) at 3,300 pounds (1,500 kg), after which it
is constant at 85 dB(A) up to and including 19,000 pounds (8,640). Figure G2
shows noise level limits vs airplane weight.
(Secs. 313(a), 603, and 611(b), Federal Aviation Act of 1958 as amended (49
U.S.C. 1354(a), 1423, and 1431(b)); sec. 6(c), Department of Transportation
Act (49 U.S.C. 1655 (c)); Title I, National Environmental Policy Act of 1969
(42 U.S.C. 4321 et seq.); E. O. 11514, March 5, 1970 and 14 CFR 11.45).
[Amdt. 36-16, 53 FR 47400, Nov. 22, 1988; 53 FR 50157, Dec. 13, 1988]
Appendix H--Noise Requirements For Helicopters Under Subpart H
Part A--Reference Conditions
Sec.
H36.1 General.
H36.3 Reference Test Conditions.
H36.5 Symbols and Units.
Part B--Noise Measurement Under Sec. 36.801
H36.101 Noise certification test and measurement conditions.
H36.103 Takeoff test conditions.
H36.105 Flyover test conditions.
H36.107 Approach test conditions.
H36.109 Measurement of helicopter noise received on the ground.
H36.111 Reporting and correcting measured data.
H36.113 Atmospheric attenuation of sound.
Part C--Noise Evaluation and Calculation Under Sec. 36.803
H36.201 Noise evaluation in EPNdB.
H36.203 Calculation of noise levels.
H36.205 Detailed data correction procedures.
Part D--Noise Limits Under Sec. 36.805
H36.301 Noise measurement, evaluation, and calculation.
H36.303 [Reserved]
H36.305 Noise levels.
Part A--Reference Conditions
Section H36.1 General. This appendix prescribes noise requirements for
helicopters specified under Sec. 36.1, including:
(a) The conditions under which helicopter noise certification tests under
Part H must be conducted and the measurement procedures that must be used
under Sec. 36.801 to measure helicopter noise during each test;
(b) The procedures which must be used under Sec. 36.803 to correct the
measured data to the reference conditions and to calculate the noise
evaluation quantity designated as Effective Perceived Noise Level (EPNL); and
(c) The noise limits for which compliance must be shown under Sec. 36.805.
Section H36.3 Reference Test Conditions.
(a) Meteorological conditions. Aircraft position, performance data and
noise measurements must be corrected to the following noise certification
reference atmospheric conditions which shall be assumed to exist from the
surface to the aircraft altitude:
(1) Sea level pressure of 2116 psf (76 cm mercury).
(2) Ambient temperature of 77 degrees F (25 degrees C).
(3) Relative humidity of 70 percent.
(4) Zero wind.
(b) Reference test site. The reference test site is flat and without line-
of-sight obstructions across the flight path that encompasses the 10 dB down
points.
(c) Takeoff reference profile. (1) Figure H1 illustrates a typical takeoff
profile, including reference conditions.
(2) The reference flight path is defined as a straight line segment
inclined from the starting point (1640 feet prior to the center microphone
location at 65 feet above ground level) at an angleb defined by the
certificated best rate of climb and Vy for minimum engine performance. The
constant climb angle B is derived from the manufacturer's data (FAA-approved
by the FAA) to define the flight profile for the reference conditions. The
constant climb angle b is drawn through Cr and continues, crossing over
station A, to the position corresponding to the end of the type certification
takeoff path represented by position Ir.
(d) Level flyover reference profile. The beginning of the level flyover
reference profile is represented by helicopter position D (Figure H2). The
helicopter approaches position D in level flight 492 feet above ground level
as measured at station A. Airspeed is stabilized at either 0.9 VH or 0.45 VH
+ 65 knots (0.45 VH + 120 km/hr), whichever speed is less. Rotor speed is
stabilized at the maximum continuous RPM throughout the 10 dB down time
period. The helicopter crosses station A in level flight and proceeds to
position J.
(e) For noise certification purposes, VH is defined as the airspeed in
level flight obtained using the minimum specification engine torque
corresponding to maximum continuous power available for sea level, 25 deg. C
ambient conditions at the relevant maximum certificated weight. The value of
VH thus defined must be listed in the Rotorcraft Flight Manual.
(f) Approach reference profile. (1) Figure H3 illustrates approach profile,
including reference conditions.
(i) The beginning of the approach profile is represented by helicopter
position E. The position of the helicopter is recorded for a sufficient
distance (EK) to ensure recording of the entire interval during which the
measured helicopter noise level is within 10 dB of Maximum Tone Corrected
Perceived Noise Level (PNLTM), as required. EK represents a stable flight
condition in terms of torque, rpm, indicated airspeed, and rate of descent
resulting in a 6 deg. +/- 0.5 deg. approach angle.
(ii) The approach profile is defined by the approach angle b passing
directly over the station A at a height of AH, to position K, which
terminates the approach noise certification profile.
(2) The helicopter approaches position H along a constant 6 deg. approach
slope throughout the 10 dB down time period. The helicopter crosses position
E and proceeds along the approach slope crossing over station A until it
reaches position K.
Section H36.5 Symbols and units. The following symbols and units as used in
this appendix for helicopter noise certification have the following meanings.
Flight Profile Identification--Positions
Position Description
A Location of the noise measuring point at the flight-track noise
measuring station vertically below the reference (takeoff,
flyover, or approach) flight path.
C Start of noise certification takeoff flight path.
Cr Start of noise certification reference takeoff flight path.
D Start of noise certification flyover flight path.
Dr Start of noise certification reference flyover path.
E Start of noise certification approach flight path.
Er Start of noise certification reference approach flight path.
F Position on takeoff flight path directly above noise measuring
station A.
G Position on flyover flight path directly above noise measuring
station A.
H Position on approach flight path directly above noise measuring
station A.
I End of noise type certification takeoff flight path.
Ir End of noise type certification reference takeoff flight path.
J End of noise type certification flyover flight path.
Jr End of noise type certification reference flyover flight path.
K End of noise certification approach type flight path.
Kr End of noise type certification reference approach flight path.
L Position on measured takeoff flight path corresponding to PNLTM at
station A.
Lr Position on reference takeoff flight path corresponding to PNLTM of
station A.
M Position on measured flyover flight path corresponding to PNLTM of
station A.
Mr Position on reference flyover flight path corresponding to PNLTM of
station A.
N Position on measured approach flight path corresponding to PNLTM at
station A.
Nr Position on reference approach flight path corresponding to PNLTM
at station A.
S Position on measured approach path nearest to station A.
Sr Position on reference approach path nearest to station A.
T Position on measured takeoff path nearest to station A.
Tr Position on reference takeoff path nearest to station A.
Flight Profile Distances
Distance Unit Meaning
AF Feet Takeoff Height. The vertical distance between helicopter and
station A.
AG Feet Flyover Height. The vertical distance between the helicopter
and station A.
AH Feet Approach Height. The vertical distance between the helicopter
and station A.
AL Feet Measured Takeoff Noise Path. The distance from station A to
the measured helicopter position L.
ALr Feet Reference Takeoff Noise Path. The distance from station A to
the reference helicopter position Lr.
AM Feet Measured Flyover Noise Path. The distance from station A to
the measured helicopter position M.
AMr Feet Reference Flyover Noise Path. The distance from station A to
helicopter position Mr on the reference flyover flight path.
AN Feet Measured Approach Noise Path. The distance from station A to
the measured helicopter noise position N.
ANr Feet Reference Approach Noise Path. The distance from station A to
the reference helicopter position Nr.
AS Feet Measured Approach Minimum Distance. The distance from station
A to the position S on the measured approach flight path.
ASr Feet Reference Approach Minimum Distance. The distance from
station A to the position Sr on the reference approach
flight path.
AT Feet Measured Takeoff Minimum Distance. The distance from station
A to the position T on the measured takeoff flight path.
ATr Feet Reference Takeoff Minimum Distance. The distance from station
A to the position Tr on the reference takeoff flight path.
CI Feet Takeoff Flight Path Distance. The distance from position C at
which the helicopter establishes a constant climb angle on
the takeoff flight path passing over station A and
continuing to position I at which the position of the
helicopter need no longer be recorded.
DJ Feet Flyover Flight Path Distance. The distance from position D at
which the helicopter is established on the flyover flight
path passing over station A and continuing to position J at
which the position of the helicopter need no longer be
recorded.
EK Feet Approach Flight Path Distance. The distance from position E
at which the helicopter establishes a constant angle on the
approach flight path passing over station A and continuing
to position K at which the position of the helicopter need
no longer be recorded.
Part B--Noise Measurement Under Sec. 36.801
Section H36.101 Noise certification test and measurement conditions.
(a) General. This section prescribes the conditions under which aircraft
noise certification tests must be conducted and the measurement procedures
that must be used to measure helicopter noise during each test.
(b) Test site requirements. (1) Tests to show compliance with established
helicopter noise certification levels must consist of a series of takeoffs,
level flyovers, and approaches during which measurement must be taken at
noise measuring stations located at the measuring points prescribed in this
section.
(2) Each takeoff test, flyover test, and approach test includes
simultaneous measurements at the flight-track noise measuring station
vertically below the reference flight path and at two sideline noise
measuring stations, one on each side of the reference flight track 492 feet
(150m) from, and on a line perpendicular to, the flight track of the noise
measuring station.
(3) The difference between the elevation of either sideline noise measuring
station may not differ from the flight-track noise measuring station by more
than 20 feet.
(4) Each noise measuring station must be surrounded by terrain having no
excessive sound absorption characteristics, such as might be caused by thick,
matted, or tall grass, shrubs, or wooded areas.
(5) During the period when the takeoff, flyover, or approach noise/time
record indicates the noise measurement is within 10 dB of PNLTM, no
obstruction that significantly influences the sound field from the aircraft
may exist--
(i) For any flight-track or sideline noise measuring station, within a
conical space above the measuring position (the point on the ground
vertically below the microphone), the cone being defined by an axis normal to
the ground and by half-angle 80 deg. from this axis; and
(ii) For any sideline noise measuring station, above the line of sight
between the microphone and the helicopter.
(6) If a takeoff or flyover test series is conducted at weights other than
the maximum takeoff weight for which noise certification is requested, the
following additional requirements apply:
(i) At least one takeoff test must be conducted at a weight at, or above,
the maximum certification weight.
(ii) Each test weight must be within +5 percent or -10 percent of the
maximum certification weight.
(iii) FAA-approved data must be used to determine the variation of EPNL
with weight for takeoff test conditions.
(7) Each approach test must be conducted with the aircraft stabilized and
following a 6.0 degree +/-0.5 degree approach angle and must meet the
requirements of section H36.107 of this part.
(8) If an approach test series is conducted at weights other than the
maximum landing weight for which certification is requested, the following
additional requirements apply:
(i) At least one approach test must be conducted at a weight at, or above,
the maximum landing weight.
(ii) Each test weight must exceed 90 percent of the maximum landing weight.
(iii) FAA-approved data must be used to determine the variation of EPNL
with weight for approach test conditions.
(9) Aircraft performance data sufficient to make the corrections required
under section H36.205 of this appendix must be recorded at an FAA-approved
sampling rate using FAA approved equipment.
(c) Weather restrictions. The tests must be conducted under the following
atmospheric conditions:
(1) No rain or other precipitation.
(2) Ambient air temperature between 36 deg. F and 95 deg. F (2.2 C deg. and
35 deg. C), inclusively, over that portion of the sound propagation path
between the aircraft and a point 10 meters above the ground at the noise
measuring station. The temperature and relative humidity measured at aircraft
altitude and at 10 meters above ground shall be averaged and used to adjust
for propagation path absorption.
(3) Relative humidity and ambient temperature over the portion of the sound
propagation path between the aircraft and a point 10 meters above the ground
at the noise measuring station is such that the sound attenuation in the one-
third octave band centered at 8 kHz is not greater than 12 dB/100 meters and
the relative humidity is between 20 percent and 95 percent, inclusively.
(4) Wind velocity as measured at 10 meters above ground does not exceed 10
knots (19 km/h) and the crosswind component does not exceed 5 knots (9 km/h).
The wind shall be determined using a continuous thirty-second averaging
period spanning the 10dB down time interval.
(5) No anomalous wind conditions (including turbulence) which will
significantly affect the noise level of the aircraft when the noise is
recorded at each noise measuring station.
(6) The wind velocity, temperature, and relative humidity measurements
required under the appendix must be measured in the vicinity of noise
measuring stations 10 meters above the ground. The location of the
meteorological measurements must be approved by the FAA as representative of
those atmospheric conditions existing near the surface over the geographical
area which aircraft noise measurements are made. In some cases, a fixed
meteorological station (such as those found at airports or other facilities)
may meet this requirement.
(7) Temperature and relative humidity measurements must be obtained within
25 minutes of each noise test measurement. Meteorological data must be
interpolated to actual times of each noise measurement.
(d) Aircraft testing procedures. (1) The aircraft testing procedures and
noise measurements must be conducted and processed in a manner which yields
the noise evaluation measure designated as Effective Perceived Noise Level
(EPNL) in units of EPNdB, as prescribed in Appendix B of this part.
(2) The aircraft height and lateral position relative to the centerline of
the reference flight-track (which passes through the noise measuring point)
must be determined by an FAA approved method which is independent of normal
flight instrumentation, such as radar tracking, theodolite triangulation,
laser trajectography, or photographic scaling techniques.
(3) The aircraft position along the flight path must be related to the
noise recorded at the noise measuring stations by means of synchronizing
signals at an approved sampling rate. The position of the aircraft must be
recorded relative to the runway during the entire time period in which the
recorded signal is within 10 dB of PNLTM. Measuring and sampling equipment
must be approved by the FAA.
Section H36.103 Takeoff test conditions.
(a) This section, in addition to the applicable requirements of sections
H36.101 and H36.205(b) of this appendix, applies to all takeoff noise tests
conducted under this appendix to show compliance with Part 36.
(b) A test series must consist of at least six flights over the flight-
track noise measuring station (with simultaneous measurements at all three
noise measuring stations) as follows:
(1) An airspeed of either Vy +/-5 knots or the lowest approved speed +/-5
knots for the climb after takeoff, whichever speed is greater, must be
established during the horizontal portion of each test flight and maintained
during the remainder of the test flight.
(2) The horizontal portion of each test flight must be conducted at an
altitude of 65 feet (20 meters) above the ground level at the flight-track
noise measuring station.
(3) Upon reaching a point 1,640 feet (500 meters) from the noise measuring
station, the helicopter shall be stabilized at:
(i) The torque used to establish the takeoff distance for an ambient
temperature at sea level of 25 deg. C for helicopters for which the
determination of takeoff performance is required by airworthiness
regulations; or
(ii) The torque corresponding to minimum installed power available for an
ambient temperature at sea level of 25 deg. C for all other helicopters.
(4) The helicopter shall be maintained throughout the takeoff reference
procedure at:
(i) The speed used +/-5 knots to establish takeoff distance for an ambient
temperature at sea level of 25 deg. C for helicopters for which the
determination of takeoff performance is required by airworthiness
regulations; or
(ii) The best rate of climb speed Vy +/-5 knots, or the lowest approved
speed for climb after takeoff, whichever is greater, for an ambient
temperature at sea level of 25 deg. C for all other helicopters.
(5) The rotor speed must be stabilized at the normal operating RPM (+/-1%)
during the entire period of the test flight when the measured helicopter
noise level is within 10 dB of PNLTM.
(6) The helicopter must pass over the flight-track noise measuring station
within +/-10 deg. from the zenith.
Section H36.105 Flyover test conditions.
(a) This section, in addition to the applicable requirements of sections
H36.101 and H36.205(c) of this appendix, applies to all flyover noise tests
conducted under this appendix to show compliance with Part 36.
(b) A test series must consist of at least six flights (three in each
direction) over the flight-track noise measuring station (with simultaneous
measurements at all three noise measuring stations)--
(1) In level flight;
(2) At a height of 492 feet +/-30 feet (150+/-9 meters) above the ground
level at the flight-track noise measuring station; and
(3) Within +/-5 deg. from the zenith.
(c) Each flyover noise test must be conducted--
(1) At a speed of 0.9 VH or 0.45 VH+120 km/hr (0.45 VH+65 kt), whichever is
less, maintained throughout the measured portion of the flyover;
(2) At rotor speed stabilized at the normal operating rotor RPM (+/-1
percent); and
(3) With the power stabilized during the period when the measured
helicopter noise level is within 10 dB of PNLTM.
(d) The airspeed shall not vary from the reference airspeed by more than
+/-5 knots (9 km/hr).
Section H36.107 Approach test conditions.
(a) This section, in addition to the requirements of sections H36.101 and
H36.205(d) of this appendix, applies to all approach tests conducted under
this appendix to show compliance with Part 36.
(b) A test series must consist of at least six flights over the flight-
track noise measuring station (with simultaneous measurements at the three
noise measuring stations)--
(1) On an approach slope of 6 deg.+/-0.5 deg.;
(2) At a height of 394+/-30 feet (120+/-9 meters) above the ground level at
the flight-track noise measuring station;
(3) Within +/-10 deg. of the zenith;
(4) At stabilized airspeed equal to the certificated best rate of climb Vy,
or the lowest approved speed for approach, whichever is greater, with power
stabilized during the approach and over the flight path reference point, and
continued to a normal touchdown; and
(5) At rotor speed stabilized at the maximum normal operating rotor RPM
(+/-1 percent).
(c) The airspeed shall not vary from the reference airspeed by more than
+/-5 knots (+/-9 km/hr).
Section H36.109 Measurement of helicopter noise received on the ground.
(a) General. (1) The measurements prescribed in this section provide the
data needed to determine the one-third octave band noise produced by an
aircraft during testing, at specific noise measuring stations, as a function
of time.
(2) Sound pressure level data for aircraft noise certification purposes
must be obtained with FAA-approved acoustical equipment and measurement
practices.
(3) Paragraphs (b), (c), and (d) of this section prescribe the required
equipment specifications. Paragraphs (e) and (f) prescribe the calibration
and measurement procedures required for each certification test series.
(b) Measurement system. The acoustical measurement system must consist of
FAA-approved equipment equivalent to the following:
(1) A microphone system with frequency response and directivity which are
compatible with the measurement and analysis system accuracy prescribed in
paragraph (c) of this section.
(2) Tripods or similar microphone mountings that minimize interference with
the sound energy being measured.
(3) Recording and reproducing equipment, the characteristics, frequency
response, and dynamic range of which are compatible with the response and
accuracy requirements of paragraph (c) of this section.
(4) Calibrators using sine wave, or pink noise, of known levels. When pink
noise (defined in paragraph (e)(1) of this section) is used, the signal must
be described in terms of its root-mean-square (rms) value.
(5) Analysis equipment with the response and accuracy which meets or
exceeds the requirements of paragraph (d) of this section.
(6) Attenuators used for range changing in sensing, recording, reproducing,
or analyzing aircraft sound must be capable of being operated in equal-
interval decibel steps with no error between any two settings which exceeds
0.2 dB.
(c) Sensing, recording, and reproducing equipment. (1) The sound produced
by the aircraft must be recorded in such a way that the complete information,
including time history, is retained. A magnetic tape recorder is acceptable.
(2) The microphone must be a pressure-sensitive capacitive type, or its
FAA-approved equivalent, such as a free-field type with incidence corrector.
(i) The variation of microphone and preamplifier system sensitivity within
an angle of +/-30 degrees of grazing (60-120 degrees from the normal to the
diaphragm) must not exceed the following values:
Change in
sensitivity
Frequency (Hz) (dB)
45 to 1,120 1
1,120 to 2,240 1.5
2,240 to 4,500 2.5
4,500 to 7,100 4
7,100 to 11,200 5
With the windscreen in place, the sensitivity variation in the plane of the
microphone diaphragm shall not exceed 1.0 dB over the frequency range 45 to
11,200 Hz.
(ii) The overall free-field frequency response at 90 degrees (grazing
incidence) of the combined microphone (including incidence corrector, if
applicable) preamplifier, and windscreen must be determined by using either
(A) an electrostatic calibrator in combination with manufacturer-provided
corrections, or (B) an anechoic free-field facility. The calibration unit
must include pure tones at each preferred one-third octave frequency from 50
Hz to 10,000 Hz. The frequency response (after corrections based on that
determination) must be flat and within the following tolerances:
44-3,549 Hz........................................................+/-0.25 dB
3,550-7,099 Hz......................................................+/-0.5 dB
7,100-11,200 Hz.....................................................+/-1.0 dB
(iii) Specifications concerning sensitivity to environmental factors such
as temperature, relative humidity, and vibration must be in conformity with
the recommendations of International Electrotechnical Commission (IEC)
Publication No. 179, entitled "Precision Sound Level Meters", as incorporated
by reference under Sec. 36.6 of this part.
(iv) If the wind speed exceeds 6 knots, a windscreen must be employed with
the microphone during each measurement of aircraft noise. Correction for any
insertion loss produced by the windscreen, as a function of frequency, must
be applied to the measured data and any correction applied must be reported.
(3) If a magnetic tape recorder is used to store data for subsequent
analysis, the record/replay system (including tape) must conform to the
following:
(i) The electric background noise produced by the system in each one-third
octave must be at least 35 dB below the standard recording level, which is
defined as the level that is either 10 dB below the 3 percent harmonic
distortion level for direct recording or +/-40 percent deviation for
frequency modulation (FM) recording.
(ii) At the standard recording level, the corrected frequency response in
each selected one-third octave band between 44 Hz and 180 Hz must be flat and
within +/-0.75 dB, and in each band between 180 Hz and 11,200 Hz must be flat
and within +/-0.25 dB.
(iii) If the overall system satisfies the requirements of paragraph
(c)(2)(ii) of this section, and if the limitations of the dynamic range of
the equipment are insufficient to obtain adequate spectral information, high
frequency pre-emphasis may be added to the recording channel with the
converse de-emphasis on playback. If pre-emphasis is added, the
instantaneously recorded sound-pressure level between 800 Hz and 11,200 Hz of
the maximum measured noise signal must not vary more than 20 dB between the
levels of the maximum and minimum one-third octave bands.
(d) Analysis equipment. (1) A frequency analysis of the acoustic signal
must be performed using one-third octave filters which conform to the
recommendations of International Electrotechnical Commission (IEC)
Publication No. 225, entitled "Octave, Half-Octave, and Third-Octave Band
Filters Intended for Analysis of Sound and Vibrations," as incorporated by
reference under Sec. 36.6 of this part.
(2) A set of 24 consecutive one-third octave filters must be used. The
first filter of the set must be centered at a geometric mean frequency of 50
Hz and the last filter at 10,000 Hz. The output of each filter must contain
less than 0.5 dB ripple.
(3) The analyzer indicating device may be either analog or digital, or a
combination of both. The preferred sequence of signal processing is:
(i) Squaring the one-third octave filter outputs;
(ii) Averaging or integrating; and
(iii) Converting linear formulation to logarithmic.
(4) Each detector must operate over a minimum dynamic range of 60 dB and
perform as a root-mean-square device for sinusoidal tone bursts having crest
factors of at least 3 over the following dynamic range:
(i) Up to 30 dB below full-scale reading must be accurate within +/-0.5 dB;
(ii) Between 30 dB and 40 dB below full-scale reading must be accurate
within +/-1.0 dB; and
(iii) In excess of 40 dB below full-scale reading must be accurate within
+/-2.5 dB.
(5) The averaging properties of the integrator must be tested as follows:
(i) White noise must be passed through the 200 Hz one-third octave band
filter and the output fed in turn to each detector/integrator. The standard
deviation of the measured levels must then be determined from a statistically
significant number of samples of the filtered white noise taken at intervals
of not less than 5 seconds. The value of the standard deviation must be
within the interval 0.48+/-0.06 dB for a probability limit of 95 percent. An
approved equivalent method may be substituted for this test on those
analyzers where the test signal cannot readily be fed directly to each
detector/integrator.
(ii) For each detector/integrator, the response to a sudden onset or
interruption of a constant amplitude sinusoidal signal at the respective one-
third octave band center frequency must be measured at sampling times 0.5,
1.0, 1.5, and 2.0 seconds after the onset or interruption. The rising
responses must be in the following amounts before the steady-state level:
0.5 seconds, 4.0+/-1.0 dB
1.0 seconds, 1.75+/-0.5 dB
1.5 seconds, 1.0+/-0.5 dB
2.0 seconds, 0.6+/-0.25 dB
(iii) The falling response must be such that the sum of the decibel
readings below the initial steady-state level, and the corresponding rising
response reading is 6.5+/- 1.0 dB, at both 0.5 and 1.0 seconds and, on
subsequent records, the sum of the onset plus decay must be greater than 7.5
decibels.
Note 1: For analyzers with linear detection, an approximation of this
response would be given by:
SPL (i, k)-10 log [0.17 (100.1 (Li, k-3))
+10.21 (00.1 (Li, k-2))
+0.24 (100.1 (Li, k-1))
+0.33 (100.1 (Li, k))]
When this approximation is used, the calibration signal should be
established without this weighting.
Note 2: Some analyzers have been shown to have signal sampling rates that
are insufficiently accurate to detect signals with crest factor ratios
greater than three which is common to helicopter noise. Preferably, such
analyzers should not be used for helicopter certification. Use of analysis
systems with high signal sampling rates (greater than 40KHz) or those with
analog detectors prior to digitization at the output of each one-third octave
filter is encouraged.
(iv) Analyzers using true integration cannot meet the requirements of (i),
(ii), and (iii) directly, because their overall average time is greater than
the sampling interval. For these analyzers, compliance must be demonstrated
in terms of the equivalent output of the data processor. Further, in cases
where readout and resetting require a dead-time during acquisition, the
percentage loss of the total data must not exceed one percent.
(6) The sampling interval between successive readouts shall not exceed 500
milliseconds and its precise value must be known to within +/-1 one percent.
The instant in time by which a readout is characterized shall be the midpoint
of the average period where the averaging period is defined as twice the
effective time constant of the analyzer.
(7) The amplitude resolution of the analyzer must be at least 0.25 dB.
(8) After all systematic errors have been eliminated, each output level
from the analyzer must be accurate within +/-1.0 dB of the level of the input
signal. The total systematic errors for each of the output levels must not
exceed +/-3.0 dB. For contiguous filter systems, the systematic corrections
between adjacent one-third octave channels must not exceed 4.0 dB.
(9) The dynamic range capability of the analyzer to display a single
aircraft noise event, in terms of the difference between full-scale output
level and the maximum noise level of the analyzer equipment, must be at least
60 dB.
(e) Calibrations. (1) Within five days prior to beginning each test series,
the complete electronic system, as installed in field including cables, must
be electronically calibrated for frequency and amplitude by the use of a pink
noise signal of known amplitudes covering the range of signal levels
furnished by the microphone. For purposes of this section, "pink noise" means
a noise whose noise-power/unit-frequency is inversely proportional to
frequency at frequencies within the range of 44 Hz to 11,200 Hz. The signal
used must be described in terms of its average root-mean-square (rms) values
for a nonoverload signal level. This system calibration must be repeated
within five days of the end of each test series, or as required by the FAA.
(2) Immediately before and after each day's testing, a recorded acoustic
calibration of the system must be made in the field with an acoustic
calibrator to check the system sensitivity and provide an acoustic reference
level for the sound level data analysis. The performance of equipment in the
system will be considered satisfactory if, during each day's testing, the
variation in the calibration value does not exceed 0.5 dB.
(3) A normal incidence pressure calibration of the combined microphone/
preamplifier must be performed with pure tones at each preferred one-third
octave frequency from 50 Hz to 10,000 Hz. This calibration must be completed
within 90 days prior to the beginning of each test series.
(4) Each reel of magnetic tape must:
(i) Be pistonphone calibrated; and
(ii) At its beginning and end, carry a calibration signal consisting of at
least a 15 second burst of pink noise, as defined in paragraph (e)(1) of this
section.
(5) Data obtained from tape recorded signals are not considered reliable if
the difference between the pink noise signal levels, before and after the
tests in each one-third octave band, exceeds 0.75 dB.
(6) The one-third octave filters must have been demonstrated to be in
conformity with the recommendations of IEC Publication 225 as incorporated by
reference under Sec. 36.6 of this part, during the six calendar months
preceding the beginning of each test series. However, the correction for
effective bandwidth relative to the center frequency response may be
determined for each filter by:
(i) Measuring the filter response to sinusoidal signals at a minimum of
twenty frequencies equally spaced between the two adjacent preferred one-
third octave frequencies; or
(ii) Using an FAA approved equivalent technique.
(7) A performance calibration analysis of each piece of calibration
equipment, including pistonphones, reference microphones, and voltage insert
devices, must have been made during the six calendar months preceding the
beginning of each day's test series. Each calibration must be traceable to
the National Bureau of Standards.
(f) Noise measurement procedures. (1) Each microphone must be oriented so
that the diaphragm is substantially in the plane defined by the flight path
of the aircraft and the measuring station. The microphone located at each
noise measuring station must be placed so that its sensing element is
approximately 4 feet above ground.
(2) Immediately before and immediately after each series of test runs and
each day's testing, acoustic calibrations of the system prescribed in this
section of this appendix must be recorded in the field to check the acoustic
reference level for the analysis of the sound level data. Ambient noise must
be recorded for at least 10 seconds and be representative of the acoustical
background, including system noise, that exists during the flyover test run.
During that recorded period, each component of the system must be set at the
gain-levels used for aircraft noise measurement.
(3) The mean background noise spectrum must contain the sound pressure
levels, which, in each preferred third octave band in the range of 50 Hz to
10,000 Hz, are the averages of the energy of the sound pressure levels in
every preferred third octave. When analyzed in PNL, the resulting mean
background noise level must be at least 20 PNdB below the maximum PNL of the
helicopter.
(4) Corrections for recorded levels of background noise are allowed, within
the limits prescribed in section H36.111(c)(3) of this appendix.
Section H36.111 Reporting and correcting measured data
(a) General. Data representing physical measurements, and corrections to
measured data, including corrections to measurements for equipment response
deviations, must be recorded in permanent form and appended to the record.
Each correction must be reported and is subject to FAA approval. An estimate
must be made of each individual error inherent in each of the operations
employed in obtaining the final data.
(b) Data reporting. (1) Measured and corrected sound pressure levels must
be presented in one-third octave band levels obtained with equipment
conforming to the standards prescribed in section H36.109 of this appendix.
(2) The type of equipment used for measurement and analysis of all
acoustic, aircraft performance, and meteorological data must be reported.
(3) The atmospheric environmental data required to demonstrate compliance
with this appendix, measured throughout the test period, must be reported.
(4) Conditions of local topography, ground cover, or events which may
interfere with sound recording must be reported.
(5) The following aircraft information must be reported:
(i) Type, model, and serial numbers, if any, of aircraft engines and
rotors.
(ii) Gross dimensions of aircraft and location of engines.
(iii) Aircraft gross weight for each test run.
(iv) Aircraft configuration, including landing gear positions.
(v) Airspeed in knots.
(vi) Helicopter engine performance as determined from aircraft instruments
and manufacturer's data.
(vii) Aircraft flight path, above ground level in feet, determined by an
FAA approved method which is independent of normal flight instrumentation,
such as radar tracking, theodolite triangulation, laser trajectography, or
photographic scaling techniques.
(6) Aircraft speed, and position, and engine performance parameters must be
recorded at an approved sampling rate sufficient to correct to the noise
certification reference test conditions prescribed in section H36.3 of this
appendix. Lateral position relative to the reference flight-track must be
reported.
(c) Data corrections. (1) Aircraft position, performance data and noise
measurement must be corrected to the noise certification reference conditions
as prescribed in sections H36.3 and H36.205 of this appendix.
(2) The measured flight path must be corrected by an amount equal to the
difference between the applicant's predicted flight path for the
certification reference conditions and the measured flight path at the test
conditions. Necessary corrections relating to aircraft flight path or
performance may be derived from FAA-approved data for the difference between
measured and reference engine conditions, together with appropriate
allowances for sound attenuation with distance. The Effective Perceived Noise
Level (EPNL) correction must be less than 2.0 EPNdB for any combination of
the following:
(i) The aircraft's not passing vertically above the measuring station.
(ii) Any difference between the reference flight-track and the actual
minimum distance of the aircraft's ILS antenna from the approach measuring
station.
(iii) Any difference between the actual approach angle and the noise
certification reference approach flight path.
(iv) Any correction of the measured level flyover noise levels which
accounts for any difference between the test engine thrust or power and the
reference engine thrust or power.
Detailed correction requirements are prescribed in section H36.205 of this
appendix.
(3) Aircraft sound pressure levels within the 10 dB-down points must exceed
the mean background sound pressure levels determined under section
A36.3(f)(3) by at least 5 dB in each one-third octave band or be corrected
under an FAA approved method to be included in the computation of the overall
noise level of the aircraft. An EPNL may not be computed or reported from
data from which more than four one-third octave bands in any spectrum within
the 10 dB-down points have been excluded under this paragraph.
(d) Validity of results. (1) The test results must produce three average
EPNL values within the 90 percent confidence limits, each value consisting of
the arithmetic average of the corrected noise measurements for all valid test
runs at the takeoff, level flyovers, and approach conditions. The 90 percent
confidence limit applies separately to takeoff, flyover, and approach.
(2) The minimum sample size acceptable for each takeoff, approach, and
flyover certification measurements is six. The number of samples must be
large enough to establish statistically for each of the three average noise
certification levels a 90 percent confidence limit which does not exceed +/-
1.5 EPNdB. No test result may be omitted from the averaging process, unless
otherwise specified by the FAA.
(3) To comply with this appendix, a minimum of six takeoffs, six
approaches, and six level flyovers is required. To be counted toward this
requirement, each flight event must be validly recorded at all three noise
measuring stations.
(4) The approved values of VH and Vy used in calculating test and reference
conditions and flight profiles must be reported along with measured and
corrected sound pressure levels.
Section H36.113 Atmospheric attenuation of sound.
(a) The values of the one-third octave band spectra measured during
helicopter noise certification tests under this appendix must conform, or be
corrected, to the reference conditions prescribed in section H36.3(a). Each
correction must account for any differences in the atmospheric attenuation of
sound between the test-day conditions and the reference-day conditions along
the sound propagation path between the aircraft and the microphone. Unless
the meteorological conditions are within the test window prescribed in this
appendix, the test data are not acceptable.
(b) Attenuation rates. The atmospheric attenuation rates of sound with
distance for each one-third octave band from 50 Hz to 10,000 Hz must be
determined in accordance with the formulations and tabulations of SAE ARP
866A, entitled "Standard Values of Atmospheric Absorption as a Function of
Temperatures and Humidity for Use in Evaluating Aircraft Flyover Noise", as
incorporated by reference under Sec. 36.6 of this part.
(c) Correction for atmospheric attenuation. (1) EPNL values calculated for
measured data must be corrected whenever--
(i) The ambient atmospheric conditions of temperature and relative humidity
do not conform to the reference conditions, 77 deg.F and 70%, respectively,
or
(ii) The measured flight paths do not conform to the reference flight
paths.
(iii) The temperature and relative humidity measured at aircraft altitude
and at 10 meters above the ground shall be averaged and used to adjust for
propagation path absorption.
(2) The mean attenuation rate over the complete sound propagation path from
the aircraft to the microphone must be computed for each one-third octave
band from 50 Hz to 10,000 Hz. These rates must be used in computing the
corrections required in section H36.111(d) of this appendix.
Part C--Noise Evaluation and Calculation Under Sec. 36.803
Section H36.201 Noise Evaluation in EPNdB.
(a) Effective Perceived Noise Level (EPNL), in units of effective perceived
noise decibels (EPNdB), shall be used for evaluating noise level values under
Sec. 36.803 of this part. Except as provided in paragraph (b) of this
section, the procedures in Appendix B of Part 36 must be used for computing
EPNL. Appendix B includes requirements governing determination of noise
values, including calculations of:
(1) Instantaneous perceived noise levels;
(2) Corrections for spectral irregularities;
(3) Tone corrections;
(4) Duration corrections;
(5) Effective perceived noise levels; and
(6) Mathematical formulation of noy tables.
(b) Notwithstanding the provisions of section B36.5(a), for helicopter
noise certification, corrections for spectral irregularities shall start with
the corrected sound pressure level in the 50 Hz one-third octave band.
Section H36.203 Calculation of noise levels.
(a) To demonstrate compliance with the noise level limits of section
H36.305, the noise values measured simultaneously at the three noise
measuring points must be arithmetically averaged to obtain a single EPNdB
value for each flight.
(b) The calculated noise level for each noise test series, i.e., takeoff,
flyover, or approach must be the numerical average of at least six separate
flight EPNdB values. The 90 percent confidence limit for all valid test runs
under section H36.111(d) of this appendix applies separately to the EPNdB
values for each noise test series.
Section H36.205 Detailed data correction procedures
(a) General. If the test conditions do not conform to those prescribed as
noise certification reference conditions under section H36.305 of this
appendix, the following correction procedure shall apply:
(1) If a positive value results from any difference between reference and
test conditions, an appropriate positive correction must be made to the EPNL
calculated from the measured data. Conditions which can result in a positive
value include:
(i) Atmospheric absorption of sound under test conditions which is greater
than the reference;
(ii) Test flight path at an altitude which is higher than the reference; or
(iii) Test weight which is less than maximum certification weight.
(2) If a negative value results from any difference between reference and
test conditions, no correction may be made to the EPNL calculated from the
measured data, unless the difference results from:
(i) An atmospheric absorption of sound under test conditions which is less
than the reference; or
(ii) A test flight path at an altitude which is lower than the reference.
(3) The following correction procedures may produce one or more possible
correction values which must be added algebraically to the calculated EPNL to
bring it to reference conditions:
(i) The flight profiles must be determined for both reference and test
conditions. The procedures require noise and flight path recording with a
synchronized time signal from which the test profile can be delineated,
including the aircraft position for which PNLTM is observed at the noise
measuring station. For takeoff, the flight profile corrected to reference
conditions may be derived from FAA approved manufacturer's data.
(ii) The sound propagation paths to the microphone from the aircraft
position corresponding to PNLTM are determined for both the test and
reference profiles. The SPL values in the spectrum of PNLTM must then be
corrected for the effects of--
(A) Change in atmospheric sound absorption;
(B) Atmospheric sound absorption on the linear difference between the two
sound path lengths; and
(C) Inverse square law on the difference in sound propagation path length.
The corrected values of SPL are then converted to PNLTM from which PNLTM must
be subtracted. The resulting difference represents the correction which must
be added algebraically to the EPNL calculated from the measured data.
(iii) The minimum distances from both the test and reference profiles to
the noise measuring station must be calculated and used to determine a noise
duration correction due to any change in the altitude of aircraft flyover.
The duration correction must be added algebraically to the EPNL calculated
from the measured data.
(iv) From FAA approved data in the form of curves or tables giving the
variation of EPNL with rotor rpm and test speed, corrections are determined
and must be added to the EPNL, which is calculated from the measured data to
account for noise level changes due to differences between test conditions
and reference conditions.
(v) From FAA approved data in the form of curves or tables giving the
variation of EPNL with approach angle, corrections are determined and must be
added algebraically to the EPNL, which is calculated from measured data, to
account for noise level changes due to differences between the 6 degree and
the test approach angle.
(b) Takeoff profiles. (1) Figure H1 illustrates a typical takeoff profile,
including reference conditions.
(i) The reference takeoff flight path is described in section H36.3(c).
(ii) The test parameters are functions of the helicopter's performance and
weight and the atmospheric conditions of temperature, pressure, wind velocity
and direction.
(2) For the actual takeoff, the helicopter approaches position C in level
flight at 65 feet (20 meters) above ground level at the flight track noise
measuring station and at either Vy+/-5 knots (+/-9 km/hr) or the maximum
speed of the curve tangential at the ordinate of the height-speed envelope
plus 3.0 knots (+/-5 knots), whichever speed is greater. Rotor speed is
stabilized at the normal operating RPM (+/-1 percent), specified in the
flight manual. The helicopter is stabilized in level flight at the speed for
best rate of climb using minimum engine specifications (power or torque and
rpm) along a path starting from a point located 1640 feet (500 meters)
forward of the flight-track noise measuring station and 65 feet (20 meters)
above the ground. Starting at point B, the helicopter climbs through point C
to the end of the noise certification takeoff flight path represented by
position I. The position of point C may vary within limits allowed by the
FAA. The position of the helicopter shall be recorded for a distance (CI)
sufficient to ensure recording of the entire interval during which the
measured helicopter noise level is within 10 dB of PNLTM, as required by this
rule. Station A is the flight-track noise measuring station. The
relationships between the measured and corrected takeoff flight profiles can
be used to determine the corrections which must be applied to the EPNL
calculated from the measured data.
(3) Figure H1 also illustrates the significant geometrical relationships
influencing sound propagation. Position L represents the helicopter location
on the measured takeoff flight path from which PNLTM is observed at station
A, and Lr is the A and Nr corresponding position on the reference sound
propagation path. AL and ALr both form the angle F with their respective
flight paths. Position T represents the point on the measured takeoff flight
path nearest station A, and Tr is the corresponding position on the reference
flight path. The minimum distance to the measured and reference flight paths
are indicated by the lines AT and ATr, respectively, which are normal to
their flight paths.
(c) Level flyover profiles. (1) The noise type certification level flyover
profile is shown in Figure H2. Airspeed must be stabilized within +/-5 knots
of the reference airspeed given in section H36.3(d). For each run, the
difference between airspeed and ground speed shall not exceed 10 knots
between the 10 dB down points. Rotor speed must be stabilized at the maximum
continuous RPM within one percent, throughout the 10 dB down time period. If
the test requirements are otherwise met, flight direction may be reversed for
each subsequent flyover, to obtain three test runs in each direction.
Figure H1. Comparison of Measured and Corrected Takeoff Profiles
[ ...Illustrations appear here... ]
Figure H2. Comparison of Measured and Corrected Flyover Profiles
[ ...Illustrations appear here... ]
(2) Figure H2 illustrates comparative flyover profiles when test conditions
do not conform to prescribed reference conditions. The position of the
helicopter shall be recorded for a distance (DJ) sufficient to ensure
recording of the entire interval during which the measured helicopter noise
level is within 10 dB of PNLTM, as required. The flyover profile is defined
by the height AG which is a function of the operating conditions controlled
by the pilot. Position M represents the helicopter location on the measured
flyover flight path for which PNLTM is observed at station A, and Mr is the
corresponding position on the reference flight path.
(d) Approach profiles. (1) Figure H3 illustrates a typical approach
profile, including reference conditions.
(2) The helicopter approaches position H along a 6 deg. (+/-0.5 deg.)
average approach slope throughout the 10 dB down period. The approach
procedure shall be acceptable to the FAA and shall be included in the Flight
Manual.
(3) Figure H3 illustrates portions of the measured and reference approach
flight paths including the significant geometrical relationships influencing
sound propagation. EK represents the measured approach path with approach
angle h, and Er and Kr represent the reference approach angle of 6 deg..
Position N represents the helicopter location on the measured approach flight
path for which PNLTM is observed at station A, and Nr is the corresponding
position on the reference approach flight path. The measured and corrected
noise propagation paths are AN and ANr, respectively, both of which form the
same angle with their flight paths. Position S represents the point on the
measured approach flight path nearest station A, and Sr is the corresponding
point on the reference approach flight path. The minimum distance to the
measured and reference flight paths are indicated by the lines AS and ASr,
respectively, which are normal to their flight paths.
Figure H3. Comparison of Measured and Corrected Approach Profiles
[ ...Illustration appears here... ]
(e) Correction of noise at source during level flyover. (1) For level
overflight, if any combination of the following three factors, 1) airspeed
deviation from reference, 2) rotor speed deviation from reference, and 3)
temperature deviation from reference, results in an advancing blade tip Mach
number which deviates from the reference Mach value, then source noise
adjustments shall be determined. This adjustment shall be determined from the
manufacturer supplied data approved by the FAA.
(2) Off-reference tip Mach number adjustments shall be based upon a
sensitivity curve of PNLTM versus advancing blade tip Mach number, deduced
from overflights carried out at different airspeeds around the reference
airspeed. If the test aircraft is unable to attain the reference value, then
an extrapolation of the sensitivity curve is permitted if data cover at least
a range of 0.3 Mach units. The advancing blade tip Mach number shall be
computed using true airspeed, onboard outside air temperature, and rotor
speed. A separate PNLTM versus advancing blade tip Mach number function shall
be derived for each of the three certification microphone locations, i.e.,
centerline, sideline left, and sideline right. Sideline left and right are
defined relative to the direction of the flight on each run. PNLTM
adjustments are to be applied to each microphone datum using the appropriate
PNLTM function.
(f) PNLT corrections. If the ambient atmospheric conditions of temperature
and relative humidity are not those prescribed as reference conditions under
this appendix (77 degrees F and 70 percent, respectively), corrections to the
EPNL values must be calculated from the measured data under paragraph (a) of
this section as follows:
(1) Takeoff flight path. For the takeoff flight path shown in Figure H1,
the spectrum of PNLTM observed at station A for the aircraft at position Lr
is decomposed into its individual SPLi values.
(i) Step 1. A set of corrected values are then computed as follows:
SPLic = SPLi + (a i-a io)AL
+ (a io)AL-ALr)
+ 20 log(AL/ALr)
Where SPLi and SPLic are the measured and corrected sound pressure levels,
respectively, in the i-th one-third octave band. The first correction term
accounts for the effects of change in atmospheric sound absorption where ai
and aio are the sound absorption coefficients for the test and reference
atmospheric conditions, respectively, for the -ith one-third octave band and
LrA is the measured takeoff sound propagation path. The second correction
term accounts for the effects of atmospheric sound absorption on the change
in the sound propagation path length where LrA is the corrected takeoff sound
propagation path. The third correction term accounts for the effects of the
inverse square law on the change in the sound propagation path length.
(ii) Step 2. The corrected values of the SPLic are then converted to PNLT
and a correction term calculated as follows:
D1=PNLT-PNLTM
Which represents the correction to be added algebraically to the EPNL
calculated from the measured data.
(2) Approach flight path. (i) The procedure described in paragraph (f)(1)
of this section for takeoff flight paths is also used for the approach flight
path, except that the value for SPLic relate to the approach sound
propagation paths shown in Figure H3 as follows:
SPLic = SPLi+(a-aio) AM+
a (AM-AMr)+ 20 log (AM/AMr)
Where the lines NS and NrSr are the measured and referenced approach sound
propagation paths, respectively.
(ii) The remainder of the procedure is the same as that prescribed in
paragraph (d)(1)(ii) of this section, regarding takeoff flight path.
(3) Sideline microphones. The procedure prescribed in paragraph (f)(1) of
this section for takeoff flight paths is also used for the propagation to the
sideline microphones, except that the values of SPLic relate only in the
measured sideline sound propagation path as follows:
SPLic - SPLi + (aio-a+io)KX
+ aio (KX-KXr) + 20 log (KX/KXr)
K is the sideline measuring station where
X=L and Xr=Ln for takeoff
X=M and Xr=Mn for approach
X=N and Xr=Nr for flyover
(4) Level flyover flight path. The procedure prescribed in paragraph (f)(1)
of this section for takeoff flight paths is also used for the level flyover
flight path, except that the values of SPLic relate only to the flyover sound
propagation paths as follows:
SPLic=SPLi+(a-aio) AN + aio (AN-ANr)+20 log (AN/ANr)
(g) Duration corrections. (1) If the measured takeoff and approach flight
paths do not conform to those prescribed as the corrected and reference
flight paths, respectively, under section A36.5(d)(2) it will be necessary to
apply duration corrections to the EPNL values calculated from the measured
data. Such corrections must be calculated as follows:
(i) Takeoff flight path. For the takeoff flight path shown in Figure H1,
the correction term is calculated using the formula--
D 2 = -10 log (AT/ATr) + 10 log (V/Vr)
which represents the correction which must be added algebraically to the EPNL
calculated from the measured data. The lengths AT and ATr are the measured
and corrected takeoff minimum distances from the noise measuring station A to
the measured and the corrected flight paths, respectively. A negative sign
indicates that, for the particular case of a duration correction, the EPNL
calculated from the measured data must be reduced if the measured flight path
is at greater altitude than the corrected flight path.
(ii) Approach flight path. For the approach flight path shown in Figure H3,
the correction term is calculated using the formula--
D 2 = -10 log (AS/ASr) + 10 log (V/Vr)
where AS is the measured approach minimum distance from the noise measuring
station A to the measured flight path and 394 feet is the minimum distance
from station A to the reference flight path.
(iii) Sideline microphones. For the sideline flight path, the correction
term is calculated using the formula--
D 2 = -10 log (KX/KXr)+10 log (V/Vr)
K is the sideline measuring station
where X=T and Xr=Tr for takeoff
where X=S and Xr=Sr for approach
where X=G and Xr=Gr for flyover
(iv) Level flyover flight paths. For the level flyover flight path, the
correction term is calculated using the formula--
D 2 = -10 log (AG/AGr)+10 log (V/Vr)
where AG is the measured flyover altitude over the noise measuring station A.
(2) The adjustment procedure described in this section shall apply to the
sideline microphones in the take-off, overflight, and approach cases.
Although the noise emission is strongly dependent on the directivity pattern,
variable from one helicopter type to another, the propagation angle u shall
be the same for test and reference flight paths. The elevation angle c shall
not be constrained but must be determined and reported. The certification
authority shall specify the acceptable limitations on c. Corrections to data
obtained when these limits are exceeded shall be applied using FAA approved
procedures.
Part D--Noise Limits Under Sec. 36.805
Section H36.301 Noise measurement, evaluation, and calculation
Compliance with this part of this appendix must be shown with noise levels
measured, evaluated, and calculated as prescribed under Parts B and C of this
appendix.
Section H36.303 [Reserved]
Section H36.305 Noise levels
(a) Limits. For compliance with this appendix, it must be shown by flight
test that the calculated noise levels of the helicopter, at the measuring
points described in section H36.305 (a) of this appendix, do not exceed the
following, with appropriate interpolation between weights:
(1) Stage 1 noise limits for acoustical changes for helicopters are as
follows:
(i) For takeoff, flyover, and approach calculated noise levels, the noise
levels of each Stage 1 helicopter that exceed the Stage 2 noise limits plus 2
EPNdB may not, after a change in type design, exceed the noise levels created
prior to the change in type design.
(ii) For takeoff, flyover, and approach calculated noise levels, the noise
levels of each Stage 1 helicopter that do not exceed the Stage 2 noise limits
plus 2 EPNdB may not, after the change in type design, exceed the Stage 2
noise limits plus 2 EPNdB.
(2) Stage 2 noise limits are as follows:
(i) For takeoff calculated noise levels--109 EPNdB for maximum takeoff
weights of 176,370 pounds or more, reduced by 3.01 EPNdB per halving of the
weight down to 89 EPNdB for maximum weights of 1,764 pounds or less.
(ii) For flyover calculated noise levels--108 EPNdB for maximum weights of
176,370 pounds or more, reduced by 3.01 EPNdB per halving of the weight down
to 88 EPNdB for maximum weights of 1,764 pounds or less.
(iii) For approach calculated noise levels--110 EPNdB for maximum weights
of 176,370 pounds or more, reduced by 3.01 EPNdB per halving of the weight
down 90 EPNdB for maximum weight of 1,764 pounds or less.
(b) Tradeoffs. Except to the extent limited under Sec. 36.11(b) of this
part, the noise limits prescribed in paragraph (a) of this section may be
exceeded by one or two of the takeoff, flyover, or approach calculated noise
levels determined under section H36.203 of this appendix if
(1) The sum of the exceedances is not greater than 4 EPNdB;
(2) No exceedance is greater than 3 EPNdB; and
(3) The exceedances are completely offset by reduction in the other
required calculated noise levels.
[Amdt. 36-14, 53 FR 3541, Feb. 5, 1988; 53 FR 4099, Feb. 11, 1988; 53 FR
7728, Mar. 10, 1988]
Appendix I--[Reserved. Amdt. 36-20, 57 FR 42855, Sept. 16, 1992]
Appendix J--Alternative Noise Certification Procedure For Helicopters Under
Subpart H Having A Maximum Certificated Takeoff Weight Of Not More Than 6,000
Pounds
Part A--Reference Conditions
J36.1 General.
J36.3 Reference Test Conditions.
J36.5 [Reserved]
Part B--Noise Measurement Procedure Under Sec. 36.801
J36.101 Noise certification test and measurement conditions.
J36.103 [Reserved]
J36.105 Flyover test conditions.
J36.107 [Reserved]
J36.109 Measurement of helicopter noise received on the ground.
J36.111 Reporting requirements.
J36.113 [Reserved]
Part C--Noise Evaluation and Calculation Under Sec. 36.803
J36.201 Noise evaluation in SEL.
J36.203 Calculation of noise levels.
J36.205 Detailed data correction procedures.
Part D--Noise Limits Procedure Under Sec. 36.805
J36.301 Noise measurement, evaluation, and calculation.
J36.303 [Reserved]
J36.305 Noise limits.
Part A--Reference Conditions
Section J36.1 General
This appendix prescribes the alternative noise certification requirements
identified under Sec. 36.1 of this part and subpart H of this part for
helicopters in the primary, normal, transport, and restricted categories
having maximum certificated takeoff weight of not more than 6,000 pounds
including:
(a) The conditions under which an alternative noise certification test
under subpart H of this part must be conducted and the alternative
measurement procedure that must be used under Sec. 36.801 of this part to
measure the helicopter noise during the test;
(b) The alternative procedures which must be used under Sec. 36.803 of this
part to correct the measured data to the reference conditions and to
calculate the noise evaluation quantity designated as Sound Exposure Level
(SEL); and
(c) The noise limits for which compliance must be shown under Sec. 36.805
of this part.
Section J36.3 Reference Test Conditions
(a) Meteorological conditions. The following are the noise certification
reference atmospheric conditions which shall be assumed to exist from the
surface to the helicopter altitude:
(1) Sea level pressure of 2116 pounds per square foot (76 centimeters
mercury);
(2) Ambient temperature of 77 degrees Fahrenheit (25 degrees Celsius);
(3) Relative humidity of 70 percent; and
(4) Zero wind.
(b) Reference test site. The reference test site is flat and without line-
of-sight obstructions across the flight path that encompasses the 10 dB down
points of the A-weighted time history.
(c) Level flyover reference profile. The reference flyover profile is a
level flight 492 feet (150 meters) above ground level as measured at the
noise measuring station. The reference flyover profile has a linear flight
track and passes directly over the noise monitoring station. Airspeed is
stabilized at 0.9VH; 0.9VNE; 0.45VH + 65 kts (0.45VH + 120 km/h); or 0.45VNE
+ 65 kts (0.45VNE + 120 km/h), whichever of the four speeds is least. Rotor
speed is stabilized at the power on maximum normal operating RPM throughout
the 10 dB down time period.
(1) For noise certification purposes, VH is defined as the airspeed in
level flight obtained using the minimum specification engine power
corresponding to maximum continuous power available for sea level, 77 degree
Fahrenheit (25 degrees Celsius) ambient conditions at the relevant maximum
certificated weight. The value of VH thus defined must be listed in the
Rotorcraft Flight Manual.
(2) VNE is the never-exceed airspeed.
(d) The weight of the helicopter shall be the maximum takeoff weight at
which noise certification is requested.
Section J36.5 [Reserved]
Part B--Noise Measurement Procedure Under Sec. 36.801
Section J36.101 Noise certification test and measurement conditions
(a) General. This section prescribes the conditions under which helicopter
noise certification tests must be conducted and the measurement procedures
that must be used to measure helicopter noise during each test.
(b) Test site requirements. (1) The noise measuring station must be
surrounded by terrain having no excessive sound absorption characteristics,
such as might be caused by thick, matted, or tall grass, shrubs, or wooded
areas.
(2) During the period when the flyover noise measurement is within 10 dB of
the maximum A-weighted sound level, no obstruction that significantly
influences the sound field from the helicopter may exist within a conical
space above the noise measuring position (the point on the ground vertically
below the microphone), the cone is defined by an axis normal to the ground
and by half-angle 80 degrees from this axis.
(c) Weather restrictions. The test must be conducted under the following
atmospheric conditions:
(1) No rain or other precipitation;
(2) Ambient air temperature between 36 degrees and 95 degrees Fahrenheit (2
degrees and 35 degrees Celsius), inclusively, and relative humidity between
20 percent and 95 percent inclusively, except that testing may not take place
where combinations of temperature and relative humidity result in a rate of
atmospheric attenuation greater than 10 dB per 100 meters (30.5 dB per 1000
ft) in the one-third octave band centered at 8 kiloHertz.
(3) Wind velocity that does not exceed 10 knots (19 km/h) and a crosswind
component that does not exceed 5 knots (9 km/h). The wind shall be determined
using a continuous averaging process of no greater than 30 seconds;
(4) Measurements of ambient temperature, relative humidity, wind speed, and
wind direction must be made between 4 feet (1.2 meters) and 33 feet (10
meters) at the noise monitoring station. Unless otherwise approved by the
FAA, ambient temperature and relative humidity must be measured at the noise
measuring station at the same height above the ground.
(5) No anomalous wind conditions (including turbulence) or other anomalous
meteorological conditions that will significantly affect the noise level of
the helicopter when the noise is recorded at the noise measuring station; and
(6) The location of the meteorological instruments must be approved by the
FAA as representative of those atmospheric conditions existing near the
surface over the geographical area where the helicopter noise measurements
are made. In some cases, a fixed meteorological station (such as those found
at airports or other facilities) may meet this requirement.
(d) Helicopter testing procedures. (1) The helicopter testing procedures
and noise measurements must be conducted and processed in a manner which
yields the noise evaluation measure designated Sound Exposure Level (SEL) as
defined in section J36.109(b) of this appendix.
(2) The helicopter height relative to the noise measurement point
sufficient to make corrections required under section J36.205 of this
appendix must be determined by an FAA-approved method that is independent of
normal flight instrumentation, such as radar tracking, theodolite
triangulation, laser trajectography, or photographic scaling techniques.
(3) If an applicant demonstrates that the design characteristics of the
helicopter would prevent flight from being conducted in accordance with the
reference test conditions prescribed under section J36.3 of this appendix,
then with FAA approval, the reference test conditions used under this
appendix may vary from the standard reference test conditions, but only to
the extent demanded by those design characteristics which make compliance
with the reference test conditions impossible.
Section J36.103 [Reserved]
Section J36.105 Flyover test conditions
(a) This section prescribes the flight test conditions and allowable random
deviations for flyover noise tests conducted under this appendix.
(b) A test series must consist of at least six flights with equal numbers
of flights in opposite directions over the noise measuring station:
(1) In level flight and in cruise configuration;
(2) At a height of 492 feet +/-50 feet (150 +/-15 meters) above the ground
level at the noise measuring station; and
(3) Within +/-10 degrees from the zenith.
(c) Each flyover noise test must be conducted:
(1) At the reference airspeed specified in section J36.3(c) of this
appendix, with such airspeed adjusted as necessary to produce the same
advancing blade tip Mach number as associated with the reference conditions;
(i) Advancing blade tip Mach number (MAT) is defined as the ratio of the
arithmetic sum of blade tip rotational speed (VR) and the helicopter true air
speed (VT) over the speed of sound (c) at 77 degrees Fahrenheit (1135.6 ft/
sec or 346.13 m/sec) such that MAT = (VR + VT)/c; and
(ii) The airspeed shall not vary from the adjusted reference airspeed by
more than +/-3 knots (+/-5 km/hr) or an equivalent FAA-approved variation
from the reference advancing blade tip Mach number. The adjusted reference
airspeed shall be maintained throughout the measured portion of the flyover.
(2) At rotor speed stabilized at the power on maximum normal operating
rotor RPM (+/-1 percent); and
(3) With the power stabilized during the period when the measured
helicopter noise level is within 10 dB of the maximum A-weighted sound level
(LAMAX).
(d) The helicopter test weight for each flyover test must be within plus 5
percent or minus 10 percent of the maximum takeoff weight for which
certification under this part is requested.
(e) The requirements of paragraph (b)(2) of this section notwithstanding,
flyovers at an FAA-approved lower height may be used and the results adjusted
to the reference measurement point by an FAA-approved method if the ambient
noise in the test area, measured in accordance with the requirements
prescribed in section J36.109 of this appendix, is found to be within 15
dB(A) of the maximum A-weighted helicopter noise level (LAMAX) measured at
the noise measurement station in accordance with section J36.109 of this
appendix.
Section J36.107 [Reserved]
Section J36.109 Measurement of helicopter noise received on the ground
(a) General. (1) The helicopter noise measured under this appendix for
noise certification purposes must be obtained with FAA-approved acoustical
equipment and measurement practices.
(2) Paragraph (b) of this section identifies and prescribes the
specifications for the noise evaluation measurements required under this
appendix. Paragraphs (c) and (d) of this section prescribe the required
acoustical equipment specifications. Paragraphs (e) and (f) of this section
prescribe the calibration and measurement procedures required under this
appendix.
(b) Noise unit definition. (1) The value of sound exposure level (SEL, or
as denoted by symbol, LAE), is defined as the level, in decibels, of the time
integral of squared 'A'-weighted sound pressure (PA) over a given time period
or event, with reference to the square of the standard reference sound
pressure (PO) of 20 micropascals and a reference duration of one second.
(2) This unit is defined by the expression:
[ ...Illustration appears here... ]
Where TO is the reference integration time of one second and (t2-t1) is the
integration time interval.
(3) The integral equation of paragraph (b)(2) of this section can also be
expressed as:
[ ...Illustration appears here... ]
Where LA(t) is the time varying A-weighted sound level.
(4) The integration time (t2-t1) in practice shall not be less than the
time interval during which LA(t) first rises to within 10 dB(A) of its
maximum value (LAMAX) and last falls below 10 dB(A) of its maximum value.
(5) The SEL may be approximated by the following expression:
LAE = LAMAX + <delta> A
where <delta> A is the duration allowance given by:
<delta> A = 10 log10 (T)
where T = (t2-t1)/2 and LAMAX is defined as the maximum level, in decibels,
of the A-weighted sound pressure (slow response) with reference to the square
of the standard reference sound pressure (P0).
(c) Measurement system. The acoustical measurement system must consist of
FAA-approved equipment equivalent to the following:
(1) A microphone system with frequency response that is compatible with the
measurement and analysis system accuracy prescribed in paragraph (d) of this
section;
(2) Tripods or similar microphone mountings that minimize interference with
the sound energy being measured;
(3) Recording and reproducing equipment with characteristics, frequency
response, and dynamic range that are compatible with the response and
accuracy requirements of paragraph (d) of this section; and
(4) Acoustic calibrators using sine wave noise and, if a tape recording
system is used, pink noise, of known levels. When pink noise (defined in
section H36.109(e)(1) of Appendix H of this part) is used, the signal must be
described in terms of its root-mean-square (rms) value.
(d) Sensing, recording, and reproducing equipment. (1) The noise levels
measured from helicopter flyovers under this appendix may be determined
directly by an integrating sound level meter, or the A-weighted sound level
time history may be written onto a graphic level recorder set at "slow"
response from which the SEL value may be determined. With the approval of the
FAA, the noise signal may be tape recorded for subsequent analysis.
(i) The SEL values from each flyover test may be directly determined from
an integrating sound level meter complying with the Standards of the
International Electrotechnical Commission (IEC) Publication No. 804,
"Integrating-averaging Sound Level Meters," as incorporated by reference
under Sec. 36.6 of this part, for a Type 1 instrument set at "slow" response.
(ii) The acoustic signal from the helicopter, along with the calibration
signals specified under paragraph (e) of this section and the background
noise signal required under paragraph (f) of this section may be recorded on
a magnetic tape recorder for subsequent analysis by an integrating sound
level meter identified in paragraph (d)(1)(i) of this section. The record/
playback system (including the audio tape) of the tape recorder must conform
to the requirements prescribed in section H36.109(c)(3) of Appendix H of this
part. The tape recorder shall comply with specifications of IEC Publication
No. 561, "Electro-acoustical Measuring Equipment for Aircraft Noise
Certification," as incorporated by reference under Sec. 36.6 of this part.
(iii) The characteristics of the complete system shall comply with the
recommendations given in IEC Publication No. 651, "Sound Level Meters," as
incorporated by reference under Sec. 36.6 of this part, with regard to the
specifications concerning microphone, amplifier, and indicating instrument
characteristics.
(iv) The response of the complete system to a sensibly plane progressive
wave of constant amplitude shall lie within the tolerance limits specified in
Table IV and Table V for Type 1 instruments in IEC Publication No. 651,
"Sound Level Meters," as incorporated by reference under Sec. 36.6 of this
part, for weighting curve "A" over the frequency range of 45 Hz to 11500 Hz.
(v) A windscreen must be used with the microphone during each measurement
of the helicopter flyover noise. Correction for any insertion loss produced
by the windscreen, as a function of the frequency of the acoustic calibration
required under paragraph (e) of this section, must be applied to the measured
data and any correction applied must be reported.
(e) Calibrations. (1) If the helicopter acoustic signal is tape recorded
for subsequent analysis, the measuring system and components of the recording
system must be calibrated as prescribed under section H36.109(e) of Appendix
H of this part.
(2) If the helicopter acoustic signal is directly measured by an
integrating sound level meter:
(i) The overall sensitivity of the measuring system shall be checked before
and after the series of flyover tests and at intervals (not exceeding one-
hour duration) during the flyover tests using an acoustic calibrator using
sine wave noise generating a known sound pressure level at a known frequency.
(ii) The performance of equipment in the system will be considered
satisfactory if, during each day's testing, the variation in the calibration
value does not exceed 0.5 dB. The SEL data collected during the flyover tests
shall be adjusted to account for any variation in the calibration value.
(iii) A performance calibration analysis of each piece of calibration
equipment, including acoustic calibrators, reference microphones, and voltage
insertion devices, must have been made during the six calendar months
proceeding the beginning of the helicopter flyover series. Each calibration
shall be traceable to the National Institute of Standards and Technology.
(f) Noise measurement procedures. (1) The microphone shall be of the
pressure-sensitive capacitive type designed for nearly uniform grazing
incidence response. The microphone shall be mounted with the center of the
sensing element 4 feet (1.2 meters) above the local ground surface and shall
be oriented for grazing incidence such that the sensing element, the
diaphragm, is substantially in the plane defined by the nominal flight path
of the helicopter and the noise measurement station.
(2) If a tape recorder is used, the frequency response of the electrical
system must be determined at a level within 10 dB of the full-scale reading
used during the test, utilizing pink or pseudorandom noise.
(3) The ambient noise, including both acoustical background and electrical
noise of the measurement systems shall be determined in the test area and the
system gain set at levels which will be used for helicopter noise
measurements. If helicopter sound levels do not exceed the background sound
levels by at least 15 dB(A), flyovers at an FAA-approved lower height may be
used and the results adjusted to the reference measurement point by an FAA-
approved method.
(4) If an integrating sound level meter is used to measure the helicopter
noise, the instrument operator shall monitor the continuous A-weighted (slow
response) noise levels throughout each flyover to ensure that the SEL
integration process includes, at minimum, all of the noise signal between the
maximum A-weighted sound level (LAMAX) and the 10 dB down points in the
flyover time history. The instrument operator shall note the actual db(A)
levels at the start and stop of the SEL integration interval and document
these levels along with the value of LAMAX and the integration interval (in
seconds) for inclusion in the noise data submitted as part of the reporting
requirements under section J36.111(b) of this appendix.
Section J36.111 Reporting Requirements
(a) General. Data representing physical measurements, and corrections to
measured data, including corrections to measurements for equipment response
deviations, must be recorded in permanent form and appended to the record.
Each correction is subject to FAA approval.
(b) Data reporting. After the completion of the test the following data
must be included in the test report furnished to the FAA:
(1) Measured and corrected sound levels obtained with equipment conforming
to the standards prescribed in section J36.109 of this appendix;
(2) The type of equipment used for measurement and analysis of all
acoustic, aircraft performance and flight path, and meteorological data;
(3) The atmospheric environmental data required to demonstrate compliance
with this appendix, measured throughout the test period;
(4) Conditions of local topography, ground cover, or events which may
interfere with the sound recording;
(5) The following helicopter information:
(i) Type, model, and serial numbers, if any, of helicopter, engine(s) and
rotor(s);
(ii) Gross dimensions of helicopter, location of engines, rotors, type of
antitorque system, number of blades for each rotor, and reference operating
conditions for each engine and rotor;
(iii) Any modifications of non-standard equipment likely to affect the
noise characteristics of the helicopter;
(iv) Maximum takeoff weight for which certification under this appendix is
requested;
(v) Aircraft configuration, including landing gear positions;
(vi) VH or VNE (whichever is less) and the adjusted reference airspeed;
(vii) Aircraft gross weight for each test run;
(viii) Indicated and true airspeed for each test run;
(ix) Ground speed, if measured, for each run;
(x) Helicopter engine performance as determined from aircraft instruments
and manufacturer's data; and
(xi) Aircraft flight path above ground level, referenced to the elevation
of the noise measurement station, in feet, determined by an FAA-approved
method which is independent of normal flight instrumentation, such as radar
tracking, theodolite triangulation, laser trajectography, or photoscaling
techniques; and
(6) Helicopter position and performance data required to make the
adjustments prescribed under section J36.205 of this appendix and to
demonstrate compliance with the performance and position restrictions
prescribed under section J36.105 of this appendix must be recorded at an FAA-
approved sampling rate.
Section J36.113 [Reserved]
Part C--Noise Evaluation and Calculations Under Sec. 36.803
Section J36.201 Noise Evaluation in SEL
The noise evaluation measure shall be the sound exposure level (SEL) in
units of dB(A) as prescribed under section J36.109(b) of this appendix. The
SEL value for each flyover may be directly determined by use of an
integrating sound level meter. Specifications for the integrating sound level
meter and requirements governing the use of such instrumentation are
prescribed under section J36.109 of this appendix.
Section J36.203 Calculation of Noise Levels
(a) To demonstrate compliance with the noise level limits specified under
section J36.305 of this appendix, the SEL noise levels from each valid
flyover, corrected as necessary to reference conditions under section J36.205
of this appendix, must be arithmetically averaged to obtain a single SEL
dB(A) mean value for the flyover series. No individual flyover run may be
omitted from the averaging process, unless otherwise specified or approved by
the FAA.
(b) The minimum sample size acceptable for the helicopter flyover
certification measurements is six. The number of samples must be large enough
to establish statistically a 90 percent confidence limit that does not exceed
+/-1.5 dB(A).
(c) All data used and calculations performed under this section, including
the calculated 90 percent confidence limits, must be documented and provided
under the reporting requirements of section J36.111 of this appendix.
Section J36.205 Detailed Data Correction Procedures
(a) When certification test conditions measured under part B of this
appendix differ from the reference test conditions prescribed under section
J36.3 of this appendix, appropriate adjustments shall be made to the measured
noise data in accordance with the methods set out in paragraphs (b) and (c)
of this section. At minimum, appropriate adjustments shall be made for off-
reference altitude and for the difference between reference airspeed and
adjusted reference airspeed.
(b) The adjustment for off-reference altitude may be approximated from:
<delta>J1=12.5 log10(HT/492) dB;
where <delta>J1 is the quantity in decibels that must be algebraically added
to the measured SEL noise level to correct for an off-reference flight path,
HT is the height, in feet, of the test helicopter when directly over the
noise measurement point, and the constant (12.5) accounts for the effects on
spherical spreading and duration from the off-reference altitude.
(c) The adjustment for the difference between reference airspeed and
adjusted reference airspeed is calculated from:
<delta>J3=10 log10(VRA/VR) dB;
Where <delta>J3 is the quantity in decibels that must be algebraically added
to the measured SEL noise level to correct for the influence of the
adjustment of the reference airspeed on the duration of the measured flyover
event as perceived at the noise measurement station, VR is the reference
airspeed as prescribed under section J36.3.(c) of this appendix, and VRA is
the adjusted reference airspeed as prescribed under section J36.105(c) of
this appendix.
(d) No correction for source noise during the flyover other than the
variation of source noise accounted for by the adjustment of the reference
airspeed prescribed for under section J36.105(c) of this appendix need be
applied.
(e) No correction for the difference between the reference ground speed and
the actual ground speed need be applied.
(f) No correction for off-reference atmospheric attenuation need be
applied.
(g) The SEL adjustments must be less than 2.0 dB(A) for differences between
test and reference flight procedures prescribed under section J36.105 of this
appendix unless a larger adjustment value is approved by the FAA.
(h) All data used and calculations performed under this section must be
documented and provided under the reporting requirements specified under
section J36.111 of this appendix.
Part D--Noise Limits Procedure Under Sec. 36.805
Section J36.301 Noise Measurement, Evaluation, and Calculation
Compliance with this part of this appendix must be shown with noise levels
measured, evaluated, and calculated as prescribed under parts B and C of this
appendix.
Section J36.303 [Reserved]
Section J36.305 Noise Limits
For compliance with this appendix, the calculated noise levels of the
helicopter, at the measuring point described in section J36.101 of this
appendix, must be shown to not exceed the following (with appropriate
interpolation between weights):
(a) For primary, normal, transport, and restricted category helicopters
having a maximum certificated takeoff weight of not more than 6,000 pounds
and noise tested under this appendix, the Stage 2 noise limit is 82 decibels
SEL for helicopters with maximum certificated takeoff weight at which the
noise certification is requested, of up to 1,764 pounds and increasing at a
rate of 3.01 decibels per doubling of weight thereafter. The limit may be
calculated by the equation:
LAE(limit)=82+3.01[log10(MTOW/1764)/log10(2)] dB;
where MTOW is the maximum takeoff weight, in pounds, for which certification
under this appendix is requested.
(b) The procedures required in this amendment shall be done in accordance
with the International Electrotechnical Commission IEC Publication No. 804,
entitled "Integrating-averaging Sound Level Meters," First Edition, dated
1985. This incorporation by reference was approved by the Director of the
Federal Register in accordance with 5 U.S.C. 552(a) and 1 CFR part 51. Copies
may be obtained from the Bureau Central de la Commission Electrotechnique
Internationale, 1, rue de Varembe, Geneva, Switzerland or the American
National Standard Institute, 1430 Broadway, New York City, New York 10018,
and can be inspected at the Office of the Federal Register, 800 North Capitol
Street NW., suite 700, Washington, DC.
[Amdt. 36-20, 57 FR 42855, Sept. 16, 1992; 57 FR 46243, Oct. 7, 1992]
