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the effects of:
a) change in atmospheric sound absorption;
b) atmospheric sound absorption on the change in noise
path length; and
c) inverse square law on the change in noise path length.
9.1.2.4 The corrected values of SPL shall then be converted
to PNLT from which PNLTM is subtracted.
Note.- The difference represents the correction to be
added algebraically to the EPNL calculated from the
measured dala.
9.1.3 The minimum distances fiom both the test and reference
profiles to the noise measuring station shall be calculated
and used to determine a noise duration correction due to
the change in the altitude of aeroplane flyover. The duration
correction shall be added algebraically to the EPNL calculated
from the measured data.
9.1.4 From manufacturer's data (approved by the certificating
authority) in the form of curves, tables or in some other
manner giving the variation of EPNL with take-off mass and
also for landing mass, corrections shall be determined to be
added to the EPNL calculated fiom the measured data to
account for noise level changes due to differences between
maximum take-off mass and landing mass and test aeroplane
mass.
9.1.5 From ma~~ufaclurerd'sa ta (approved by the certificating
authority) in the form of curves, tables or in some
manner giving the variation of EPNL with approach anglc,
corrections shall be determined to be added algebraically to
the EPNL calculated from measured data to account for noise
level changes due to differences between the reference and
the test approach angles.
9.2 Take-off profiles
a) Figure AI-4 illustrates a typical take-off profile. The
aeroplane begins the take-off roll at point A, lifts o f at
point B, and initiates the first constant climb at point C
at an angle J. The noise abatement thrust cutback is
started at point D and completed at point E where the
second constant climb is defined by the angle y (usually
expressed in terms of the gradient in per cent).
b) The end of the noise certification take-offflight path is
represented by aeroplane position F whose vertical projection
on the flight track (extended centre line of the
runway) is point M. The position of the aeroplane is
recorded-for a distance AM of at least 11 km (6 NW.
c) Position K is the take-off noise measuring station whose
distance AK is the specified take-off measurement distance.
Position L is the sideline noise measuring station
located on a line parallel to and the specified distance
fi-om the runway centre line where the noise level during
take-off is greatest.
d) The thrust settings afler thrust reduction, ifused, under
the test conditions are such as would produce at least
the minimum certification gradient for the reference
conditions of atmosphere and mass.
e) The take-ofprofile is associated with the following five
parameters: AB, the length of take-off roll; P, the fist
constant climb angle; y, the second constant climb
angle; and 6 and E, the thrust cutback angles. These five
parameters are finctions of the aeroplane peflormance,
mass and atmospheric conditions (ambient air
temperature, pressure, and wind velocity). If the test
atmospheric conditions are not equal to the reference
atmospheric conditions, the corresponding test and ref
erence profile parameters will be drferent as shown in
Figure AI-5. The profile parameter changes (identified
as AAB, AB, Ay, A6 arid A&) can be derived from (he
manufacturer S data (approved by the certificating
authority) and are used to define the flight profile
corrected to the atmospheric reference conditions, the
aeroplane mass being unchangedfiom that of the test.
The relationships between the measured and corrected
take-offflight profiles can then be used to determine the
corrections which are applied to the EPNL calculated
from the measured data.
jl Figure A1-6 illustrates portions of the measured and
corrected take-offlight paths including the signiJicant
geometrical relationships influencing sound propagation.
EF represents the second constant measured
APP 1-27 24/11/05
Annex 16 - Environmental Protection Volume I
flight path with climb angle y, and E, F, represents the
second constant correctedflight path at different altitude
and with dryerent climb angle y + Ay.
g) Position Q represents the aeroplane location on the
measured take-of flight path for which PNLTM is
observed at the noise measuring station K, and Q, is the
corresponding position on the correctedflight path. The
measured and corrected noise propagation paths are
KQ and KQ,, respectively, which are assumed to form
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