801 

Federal Aviation Administration, DOT 

Pt. 36, App. A 

(1) The term 0.01[

a

(i) 

¥ 

a

(i)

0

]QK is the ad-

justment for the effect of the change in 
sound attenuation coefficient, and 

a

(i) and 

a

(i)

0

are the coefficients for the test and ref-

erence atmospheric conditions respectively, 
determined under section A36.7 of this appen-
dix; 

(2) The term 0.01

a

(i)

0

(QK 

¥ 

Q

r

K

r

) is the ad-

justment for the effect of the change in the 
noise path length on the sound attenuation; 

(3) The term 20 log(QK/Q

r

K

r

) is the adjust-

ment for the effect of the change in the noise 
path length due to the inverse square law; 

(4) QK and Q

r

K

r

are measured in meters and 

a

(i) and 

a

(i)

0

are expressed in dB/100 m. 

A36.9.3.2.1.1 

PNLT Correction. 

(a) Convert the corrected values, SPL(i)

r

, 

to PNLT

r

; 

(b) Calculate the correction term 

D

1

using 

the following equation: 

D

1

= PNLT

r

¥ 

PNLTM 

A36.9.3.2.1.2 Add 

D

1

arithmetically to the 

EPNL calculated from the measured data. 

A36.9.3.2.2 If, during a test flight, several 

peak values of PNLT that are within 2 dB of 
PNLTM are observed, the procedure defined 
in section A36.9.3.2.1 must be applied at each 
peak, and the adjustment term, calculated 
according to section A36.9.3.2.1, must be 
added to each peak to give corresponding ad-
justed peak values of PNLT. If these peak 
values exceed the value at the moment of 
PNLTM, the maximum value of such exceed-
ance must be added as a further adjustment 
to the EPNL calculated from the measured 
data. 

A36.9.3.3 

Adjustments to duration correction. 

A36.9.3.3.1 Whenever the measured flight 

paths and/or the ground velocities of the test 
conditions differ from the reference flight 
paths and/or the ground velocities of the ref-
erence conditions, duration adjustments 
must be applied to the EPNL values cal-
culated from the measured data. The adjust-
ments must be calculated as described below. 

A36.9.3.3.2 For the flight path shown in Fig-

ure A36–6, the adjustment term is calculated 
as follows: 

D

2

= 

¥

7.5 log(QK/Q

r

K

r

) + 10 log(V/V

r

) 

(a) Add 

D

2

arithmetically to the EPNL cal-

culated from the measured data. 

A36.9.3.4 

Source noise adjustments. 

A36.9.3.4.1 To account for differences be-

tween the parameters affecting engine noise 
as measured in the certification flight tests, 
and those calculated or specified in the ref-
erence conditions, the source noise adjust-
ment must be calculated and applied. The 
adjustment is determined from the manufac-
turer’s data approved by the FAA. Typical 
data used for this adjustment are illustrated 
in Figure A36–8 that shows a curve of EPNL 
versus the engine control parameter 

µ

, with 

the EPNL data being corrected to all the 
other relevant reference conditions (airplane 
mass, speed and altitude, air temperature) 
and for the difference in noise between the 
test engine and the average engine (as de-
fined in section B36.7(b)(7)). A sufficient 
number of data points over a range of values 
of 

µ

r

is required to calculate the source noise 

adjustments for lateral, flyover and ap-
proach noise measurements. 

A36.9.3.4.2 Calculate adjustment term 

D

3

by 

subtracting the EPNL value corresponding 

to the parameter 

µ 

from the EPNL value cor-

responding to the parameter 

µ

r

. Add 

D

3

 

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