802 

14 CFR Ch. I (1–1–19 Edition) 

Pt. 36, App. A 

arithmetically to the EPNL value calculated 
from the measured data. 

A36.9.3.5 

Symmetry adjustments. 

A36.9.3.5.1 A symmetry adjustment to each 

lateral noise value (determined at the sec-
tion B36.4(b) measurement points), is to be 
made as follows: 

(a) If the symmetrical measurement point 

is opposite the point where the highest noise 
level is obtained on the main lateral meas-
urement line, the certification noise level is 
the arithmetic mean of the noise levels 

measured at these two points (see Figure 
A36–9(a)); 

(b) If the condition described in paragraph 

(a) of this section is not met, then it is as-
sumed that the variation of noise with the 
altitude of the airplane is the same on both 
sides; there is a constant difference between 
the lines of noise versus altitude on both 
sides (see figure A36–9(b)). The certification 
noise level is the maximum value of the 
mean between these lines. 

A36.9.4 

Integrated method of adjustment 

A36.9.4.1 

General. 

As described in this sec-

tion, the integrated adjustment method con-
sists of recomputing under reference condi-
tions points on the PNLT time history cor-
responding to measured points obtained dur-
ing the tests, and computing EPNL directly 
for the new time history obtained in this 

way. The main principles are described in 
sections A36.9.4.2 through A36.9.4.4.1. 

A36.9.4.2 

PNLT computations. 

(a) The portions of the test flight path and 

the reference flight path described in para-
graph (a)(1) and (2), and illustrated in Figure 
A36–10, include the noise time history that is 
relevant to the calculation of flyover and ap-
proach EPNL. In figure A36–10: 

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