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of p. Data of this type are required around the values of p used
for lateral, flyover and approach noise measurements.
9.3.4.2 The adjustment term A3 shall be obtained by subtracting
the EPNL value corresponding to the parameter p
from the EPNL value corresponding to the parameter pr and
shall be added algebraically to the EPNL value calculated
from the measured data.
Note.- See Figure A2-12 in which p is the value of the
engine control parameter in theflight test conditions, J+ is the
corresponding value in the reference conditions.
9.3.5 Symmetry adjustments
For the lateral noise, a symmetry adjustment shall be made
(see Part 11, Chapter 3, 3.3.2.2) as follows:
a) if the symmetrical measurement point is opposite the
point where the highest noise level is obtained on
the main lateral measurement line, the certification
noise level shall be the (arithmetical) mean of the
noise levels measured at these two points (see
Figure A2- 13 a));
b) if not, it shall be assumed that the variation of noise with
the altitude of the aeroplane is the same on both
sides (i.e. there is a constant difference between the
lines of noise versus altitude on the two sides (see
Figure A2- 13 b)). The certification noise level shall then
be the maximum value of the mean between these lines.
9.4 "Integrated" method
of adjustment
9.4.1 General
Note.- The "integrated" adjustment method consists of
recomputir~g under reJerence cunditiuns points on the PNLT
time history corresponding to measuredpoints obtained during
the tests, and computing EPNL directly for the new rime
histog. obtained in this way. The main principles are described
below.
APP 2-29 2411 1105
Annex 16 - Environmental Protection Volume I
9.4.2 PNLT computations
Note 1.- The portions of the test flight path and the reference
profile which are significant for the EPNL computation
are i1luslrult.J in Figure A2-14 for the flyover; fill-power and
approach noise measurements.
a) XY represents the usefir1 portion of the measured flight
path and XrYr that of the corresponding referenceflight
path.
b) The points Qo, Q1, Q, represent aeroplane positions on
the measuredflight path at time to, tl and t, respectively.
Consider the point Q1 at which the noise was emitted
and observed as one-third octave values SPL(i)l at the
noise measuring station K at time tl. The point Qrl
represents the corresponding position on the reference
flight path for noise observed as SPL(i),l at the reference
measuring station Kr at time t r l QIK and QrlKr
are respectively the measured and reference noise
propagation paths which in each case form the angle 8,
with their respective flight paths. Q,,, and Q, are similarly
the points on the reference flight path corresponding
to Qo and Q, on the measuredflight path. Qo and Q,
are chosen so that between Qd and Qrn all values of
PNLT, (computed and described below) within 10 dB of
the peak value are included.
Note 2.- The portions of the testflight path and the reference
profile which are signijicant for the EPNL computation
are illustrated in Figures A2-1.5 a) and b) for the lateral noise
measurements.
a) XY represents the useful portion of the measured
flight path and X,Y, that of the corresponding reference
flight path.
b) The points Qo, Q,, Q, represent aeroplane positions on
the measuredflight path at time to, tl and t, respectively.
Consider the point Q, at which the noise was emitted
and observed as one-third octave values SPL(ij1 at the
noise measuring station K at time tl. The point Qrl
represents the corresponding position on the reference
flight path for noise observed as SPL(i),l at the
measuring station K, at time t,,. QIK and QrIK, are
respectively the measured and reference noise propagation
paths. Q,,, and Q, are similarly the points on the
reference flight path corresponding to Qn and Q, on the
measured flight path. Qo and Q, are chosen so that
between QA and Q, aN values of PNLT (computed and
described below) within 10 dB of the peak value are
included. In this case Kr is only specified as being on a
particular lateral line. The position of Y and Qrl are
foundfim the assumptions that:
1) QIK and QrlKr form the same angle 81 with their
respective flight paths for all times tl; and
2) the dzfferences between the angles v1 and vrl are
minimized over the relevant part of the time
histoly by a method approved by the cerfijicating
authorities.
Note 3.- In the particular case of lateral noise measurement,
sound propagation is affected not only by "inverse
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