792 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 36, App. A 

A36.5.2.4 The applicant must report condi-

tions of local topography, ground cover, and 
events that might interfere with sound re-
cordings. 

A36.5.2.5 The applicant must report the fol-

lowing: 

(a) Type, model and serial numbers (if any) 

of airplane, engine(s), or propeller(s) (as ap-
plicable); 

(b) Gross dimensions of airplane and loca-

tion of engines; 

(c) Airplane gross weight for each test run 

and center of gravity range for each series of 
test runs; 

(d) Airplane configuration such as flap, air-

brakes and landing gear positions for each 
test run; 

(e) Whether auxiliary power units (APU), 

when fitted, are operating for each test run; 

(f) Status of pneumatic engine bleeds and 

engine power take-offs for each test run; 

(g) Indicated airspeed in knots or kilo-

meters per hour for each test run; 

(h) Engine performance data: 
(1) For jet airplanes: engine performance in 

terms of net thrust, engine pressure ratios, 
jet exhaust temperatures and fan or com-
pressor shaft rotational speeds as determined 
from airplane instruments and manufactur-
er’s data for each test run; 

(2) For propeller-driven airplanes: engine 

performance in terms of brake horsepower 
and residual thrust; or equivalent shaft 
horsepower; or engine torque and propeller 
rotational speed; as determined from air-
plane instruments and manufacturer’s data 
for each test run; 

(i) Airplane flight path and ground speed 

during each test run; and 

(j) The applicant must report whether the 

airplane has any modifications or non-stand-
ard equipment likely to affect the noise 
characteristics of the airplane. The FAA 
must approve any such modifications or non- 
standard equipment. 

A36.5.3 

Reporting of noise certification ref-

erence conditions. 

A36.5.3.1 Airplane position and perform-

ance data and the noise measurements must 
be corrected to the noise certification ref-
erence conditions specified in the relevant 
sections of appendix B of this part. The ap-
plicant must report these conditions, includ-
ing reference parameters, procedures and 
configurations. 

A36.5.4 

Validity of results. 

A36.5.4.1 Three average reference EPNL 

values and their 90 percent confidence limits 
must be produced from the test results and 
reported, each such value being the arith-
metical average of the adjusted acoustical 
measurements for all valid test runs at each 
measurement point (flyover, lateral, or ap-
proach). If more than one acoustic measure-
ment system is used at any single measure-
ment location, the resulting data for each 
test run must be averaged as a single meas-

urement. The calculation must be performed 
by: 

(a) Computing the arithmetic average for 

each flight phase using the values from each 
microphone point; and 

(b) Computing the overall arithmetic aver-

age for each reference condition (flyover, lat-
eral or approach) using the values in para-
graph (a) of this section and the related 90 
percent confidence limits. 

A36.5.4.2 For each of the three certification 

measuring points, the minimum sample size 
is six. The sample size must be large enough 
to establish statistically for each of the 
three average noise certification levels a 90 
percent confidence limit not exceeding 

±

1.5 

EPNdB. No test result may be omitted from 
the averaging process unless approved by the 
FAA. 

N

OTE

: Permitted methods for calculating 

the 90 percent confidence interval are shown 
in the current advisory circular for this part. 

A36.5.4.3 The average EPNL figures ob-

tained by the process described in section 
A36.5.4.1 must be those by which the noise 
performance of the airplane is assessed 
against the noise certification criteria. 

Section A36.6 Nomenclature: Symbols and Units 

Symbol Unit 

Meaning 

antilog ..........

.....................

Antilogarithm to the base 10. 

C(k) ..............

dB ................

Tone correction factor. 

The 

factor to be added to 
PNL(k) to account for the 
presence of spectral irreg-
ularities such as tones at 
the k-th increment of time. 

d ...................

s ..................

Duration time. 

The time inter-

val between the limits of 
t(1) and t(2) to the nearest 
0.5 second. 

D ..................

dB ................

Duration correction. 

The fac-

tor to be added to PNLTM 
to account for the duration 
of the noise. 

EPNL ...........

EPNdB ........

Effective perceived noise 

level. 

The value of PNL ad-

justed for both spectral 
irregularities and duration of 
the noise. (The unit EPNdB 
is used instead of the unit 
dB). 

EPNL

r

..........

EPNdB ........

Effective perceived noise 

level adjusted for reference 
conditions. 

f(i) ................

Hz ................

Frequency. 

The geometrical 

mean frequency for the i-th 
one-third octave band. 

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