Appendix G to Part 36 - Takeoff Noise Requirements for Propeller-Driven Small Airplane and Propeller-Driven, Commuter Category Airplane Certification Tests on or After December 22, 1988
14:1.0.1.3.20.14.283.1.40 : Appendix G
Appendix G to Part 36 - 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 §§
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 IEC 651 and IEC 561 (incorporated by reference,
see § 36.6). Sound level meters must comply with the requirements
for Type 1 sound level meters as specified in IEC 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 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
651. A graphic recorder, sound level meter, or digital equipment
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 paragraphs A36.3.8 and A36.3.9 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 microphone must be a pressure type, 12.7 mm in diameter,
with a protective grid, mounted in an inverted position such that
the microphone diaphragm is 7 mm above and parallel to a
white-painted metal circular plate. This white-painted metal plate
shall be 40 cm in diameter and at least 2.5 mm thick. The plate
shall be placed horizontally and flush with the surrounding ground
surface with no cavities below the plate. The microphone must be
located three-quarters of the distance from the center to the back
edge of the plate along a radius normal to the line of flight of
the test airplane.
(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 °F (15 °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) For airplanes equipped with fixed pitch propellers, takeoff
power must be maintained throughout the second segment. For
airplanes equipped with variable pitch or constant speed
propellers, takeoff power and rpm must be maintained throughout the
second segment. If airworthiness limitations do not allow the
application of takeoff power and rpm up to the reference point,
then takeoff power and rpm must be maintained for as long as is
permitted by such limitations; thereafter, maximum continuous power
and rpm must be maintained. Maximum time allowed at takeoff power
under the airworthiness standards must be used in the second
segment. The reference height must be calculated assuming climb
gradients appropriate to each power setting used.
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 59 F and 70 percent relative humidity by an FAA
approved method.
(c) No corrections for helical tip Mach number variation need to
be made if the propeller helical tip Mach number is:
(1) At or below 0.70 and the test helical tip Mach number is
within 0.014 of the reference helical tip Mach number.
(2) Above 0.70 and at or below 0.80 and the test helical tip
Mach number is within 0.007 of the reference helical tip Mach
number.
(3) Above 0.80 and the test helical tip Mach number is within
0.005 of the reference helical tip Mach number. For mechanical
tachometers, if the helical tip Mach number is above 0.8 and the
test helical tip Mach number is within 0.008 of the reference
helical tip Mach number.
(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) = (HT α - 0.7 HR)/1000 where HT is the height in feet
under test conditions, HR is the height in feet under reference
conditions when the aircraft is directly over the noise measurement
point and α 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 § 36.6.
(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 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) = K3 log (PR/PT) where PR and PT are the test and
reference engine powers respectively obtained from the manifold
pressure/torque gauges and engine rpm. The value of K3 shall be
determined from approved data from the test airplane. In the
absence of flight test data and at the discretion of the
Administrator, a value of K3 = 17 may be used. 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) For single-engine airplanes for which the original type
certification application is received before February 3, 2006 and
multi-engine airplanes, the noise level must not exceed 76 dB(A) up
to and including aircraft weights of 1,320 pounds (600 kg). For
aircraft weights greater than 1,320 pounds, the limit increases
from that point with the logarithm of airplane weight at the rate
of 9.83 dB (A) per doubling of weight, until the limit of 88 dB (A)
is reached, after which the limit is constant up to and including
19,000 pounds (8,618 kg). Figure G2 shows noise level limits vs
airplane weight.
(c) For single-engine airplanes for which the original type
certification application is received on or after February 3, 2006,
the noise level must not exceed 70dB(A) for aircraft having a
maximum certificated takeoff weight of 1,257 pounds (570 kg) or
less. For aircraft weights greater than 1,257 pounds, the noise
limit increases from that point with the logarithm of airplane
weight at the rate of 10.75dB(A) per doubling of weight, until the
limit of 85dB(A) is reached, after which the limit is constant up
to and including 19,000 pounds (8,618 kg). Figure G2 depicts noise
level limits for airplane weights for single-engine airplanes.
(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, as amended by
Amdt. 36-22, 64 FR 55602, Oct. 13, 1999; Amdt. 36-54, 67 FR 45236,
July 8, 2002; Amdt. 36-27, 70 FR 45504, Aug. 5, 2005; Amdt. 36-28,
71 FR 532, Jan. 4, 2006; FAA Doc. No. FAA-2015-3782, Amdt. No.
36-31, 82 FR 46131, Oct. 4, 2017]