(a) The conditions under which helicopter noise certification tests under Part H must be conducted and the measurement procedures that must be used under §36.801 to measure helicopter noise during each test;
Section H36.3 Reference Test Conditions.
(a) Meteorological conditions. Aircraft position, performance data and noise measurements must be corrected to the following noise certification reference atmospheric conditions which shall be assumed to exist from the surface to the aircraft altitude:
(1) Sea level pressure of 2116 psf (76 cm mercury).
(2) Ambient temperature of 77 degrees F (25 degrees C).
(3) Relative humidity of 70 percent.
(4) Zero wind.
(b) Reference test site. The reference test site is flat and without line-of-sight obstructions across the flight path that encompasses the 10 dB down points.
(c) Takeoff reference profile. (1) Figure H1 illustrates a typical takeoff profile, including reference conditions.
(2) The reference flight path is defined as a straight line segment inclined from the starting point (1640 feet prior to the center microphone location at 65 feet above ground level) at an angleβ defined by the certificated best rate of climb and Vy for minimum engine performance. The constant climb angleβ is derived from the manufacturer's data (FAA-approved by the FAA) to define the flight profile for the reference conditions. The constant climb angleβ is drawn through Cr and continues, crossing over station A, to the position corresponding to the end of the type certification takeoff path represented by position Ir.
(d) Level flyover reference profile. The beginning of the level flyover reference profile is represented by helicopter position D (Figure H2). The helicopter approaches position D in level flight 492 feet above ground level as measured at station A. Airspeed is stabilized at either 0.9 VH or 0.45 VH + 65 knots (0.45 VH + 120 km/hr), whichever speed is less. Rotor speed is stabilized at the maximum continuous RPM throughout the 10 dB down time period. The helicopter crosses station A in level flight and proceeds to position J.
(e) For noise certification purposes, VH is defined as the airspeed in level flight obtained using the minimum specification engine torque corresponding to maximum continuous power available for sea level, 25 °C ambient conditions at the relevant maximum certificated weight. The value of VH thus defined must be listed in the Rotorcraft Flight Manual.
(f) Approach reference profile. (1) Figure H3 illustrates approach profile, including reference conditions.
(i) The beginning of the approach profile is represented by helicopter position E. The position of the helicopter is recorded for a sufficient distance (EK) to ensure recording of the entire interval during which the measured helicopter noise level is within 10 dB of Maximum Tone Corrected Perceived Noise Level (PNLTM), as required. EK represents a stable flight condition in terms of torque, rpm, indicated airspeed, and rate of descent resulting in a 6° ±0.5° approach angle.
(ii) The approach profile is defined by the approach angle β passing directly over the station A at a height of AH, to position K, which terminates the approach noise certification profile.
(2) The helicopter approaches position H along a constant 6° approach slope throughout the 10 dB down time period. The helicopter crosses position E and proceeds along the approach slope crossing over station A until it reaches position K.
Section H36.5 Symbols and units. The following symbols and units as used in this appendix for helicopter noise certification have the following meanings.
Flight Profile Identification_Positions
------------------------------------------------------------------------
Position Description
------------------------------------------------------------------------
A................................ Location of the noise measuring point
at the flight-track noise measuring
station vertically below the
reference (takeoff, flyover, or
approach) flight path.
C................................ Start of noise certification takeoff
flight path.
C[INF]r[/INF].................... Start of noise certification
reference takeoff flight path.
D................................ Start of noise certification flyover
flight path.
D[INF]r[/INF].................... Start of noise certification
reference flyover path.
E................................ Start of noise certification approach
flight path.
E[INF]r[/INF].................... Start of noise certification
reference approach flight path.
F................................ Position on takeoff flight path
directly above noise measuring
station A.
G................................ Position on flyover flight path
directly above noise measuring
station A.
H................................ Position on approach flight path
directly above noise measuring
station A.
I................................ End of noise type certification
takeoff flight path.
I[INF]r[/INF].................... End of noise type certification
reference takeoff flight path.
J................................ End of noise type certification
flyover flight path.
J[INF]r[/INF].................... End of noise type certification
reference flyover flight path.
K................................ End of noise certification approach
type flight path.
K[INF]r[/INF].................... End of noise type certification
reference approach flight path.
L................................ Position on measured takeoff flight
path corresponding to PNLTM at
station A.
L[INF]r[/INF].................... Position on reference takeoff flight
path corresponding to PNLTM of
station A.
M................................ Position on measured flyover flight
path corresponding to PNLTM of
station A.
M[INF]r[/INF].................... Position on reference flyover flight
path corresponding to PNLTM of
station A.
N................................ Position on measured approach flight
path corresponding to PNLTM at
station A.
N[INF]r[/INF].................... Position on reference approach flight
path corresponding to PNLTM at
station A.
S................................ Position on measured approach path
nearest to station A.
S[INF]r[/INF].................... Position on reference approach path
nearest to station A.
T................................ Position on measured takeoff path
nearest to station A.
T[INF]r[/INF].................... Position on reference takeoff path
nearest to station A.
------------------------------------------------------------------------
Flight Profile Distances
------------------------------------------------------------------------
Distance Unit Meaning
------------------------------------------------------------------------
AF..................... Feet.............. Takeoff Height. The
vertical distance between
helicopter and station A.
AG..................... Feet.............. Flyover Height. The
vertical distance between
the helicopter and station
A.
AH..................... Feet.............. Approach Height. The
vertical distance between
the helicopter and station
A.
AL..................... Feet.............. Measured Takeoff Noise
Path. The distance from
station A to the measured
helicopter position L.
AL[INF]r[/INF]......... Feet.............. Reference Takeoff Noise
Path. The distance from
station A to the reference
helicopter position
L[INF]r[/INF].
AM..................... Feet.............. Measured Flyover Noise
Path. The distance from
station A to the measured
helicopter position M.
AM[INF]r[/INF]......... Feet.............. Reference Flyover Noise
Path. The distance from
station A to helicopter
position M[INF]r[/INF] on
the reference flyover
flight path.
AN..................... Feet.............. Measured Approach Noise
Path. The distance from
station A to the measured
helicopter noise position
N.
AN[INF]r[/INF]......... Feet.............. Reference Approach Noise
Path. The distance from
station A to the reference
helicopter position
N[INF]r[/INF].
AS..................... Feet.............. Measured Approach Minimum
Distance. The distance
from station A to the
position S on the measured
approach flight path.
AS[INF]r[/INF]......... Feet.............. Reference Approach Minimum
Distance. The distance
from station A to the
position S[INF]r[/INF] on
the reference approach
flight path.
AT..................... Feet.............. Measured Takeoff Minimum
Distance. The distance
from station A to the
position T on the measured
takeoff flight path.
AT[INF]r[/INF]......... Feet.............. Reference Takeoff Minimum
Distance. The distance
from station A to the
position T[INF]r[/INF] on
the reference takeoff
flight path.
CI..................... Feet.............. Takeoff Flight Path
Distance. The distance
from position C at which
the helicopter establishes
a constant climb angle on
the takeoff flight path
passing over station A and
continuing to position I
at which the position of
the helicopter need no
longer be recorded.
DJ..................... Feet.............. Flyover Flight Path
Distance. The distance
from position D at which
the helicopter is
established on the flyover
flight path passing over
station A and continuing
to position J at which the
position of the helicopter
need no longer be
recorded.
EK..................... Feet.............. Approach Flight Path
Distance. The distance
from position E at which
the helicopter establishes
a constant angle on the
approach flight path
passing over station A and
continuing to position K
at which the position of
the helicopter need no
longer be recorded.
------------------------------------------------------------------------
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