Federal Aviation Administration, DOT

Pt. 36, App. H

rotor RPM by more than Section1.0 percent during
the 10 dB-down time interval; and
(6) The constant approach configuration
used in airworthiness certification tests,
with the landing gear extended, must be
maintained throughout the approach reference procedure.
(c) The airspeed shall not vary from the
reference airspeed by more than Section5 knots (Section9
km/hr).
Section H36.109 Measurement of Helicopter
Noise Received on the Ground.
The measurement system and the measurement, calibration and general analysis procedures to be used are provided in Appendix
A, section A36.3 of this part.

spaschal on DSK3GDR082PROD with CFR

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 helicopter flight path or performance may be derived from FAA-approved data for the difference between measured and reference conditions, together with appropriate allowances for sound attenuation with distance.
The Effective Perceived Noise Level (EPNL)
correction may not exceed 2.0 EPNdB except
for takeoff flight condition, where the correction may not exceed 4.0 EPNdB, of which
the arithmetic sum of D1 (described in section H36.205(f)(1)) and the term Section7.5 log (AL/
ALr) from D2 term (described in section
H36.205(g)(1)(i)) may not exceed 2.0 EPNdB,
for any combination of the following:
(i) The helicopter not passing vertically
above the measuring station.
(ii) Any difference between the reference
flight track and the actual test flight track;
and
(iii) Detailed correction requirements prescribed in section H36.205 of this appendix.
(3) Helicopter sound pressure levels within
the 10 dB-down time interval must exceed
the mean background sound pressure levels
determined under section B36.3.9.11 by at
least 3 dB in each one-third octave band, or
must be corrected under an FAA-approved
method.
(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 Section1.5
EPNdB. No test result may be omitted from
the averaging process, unless otherwise specified by the FAA.

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