Appendix F to Part 36 - Flyover Noise Requirements for Propeller-Driven Small Airplane and Propeller-Driven, Commuter Category Airplane Certification Tests Prior to December 22, 1988
14:1.0.1.3.20.14.283.1.39 : Appendix F
Appendix F to Part 36 - 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 §§ 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 IEC 179 (incorporated by reference, see §
36.6).
(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:
Where: D50 = Takeoff distance to 50 feet at
maximum certificated takeoff weight. R/C = Certificated best rate
of climb (fpm). V
y = 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; FAA Doc. No. FAA-2015-3782, Amdt. No. 36-31,
82 FR 46131, Oct. 4, 2017]