TM55-2840-251-23
Section X ENGINE TESTING (Continued)
1-95
GROUND TESTING OF ENGINE ON
MOBILE TRAILER ASSEMBLY (AVIM) (Cont)
4.
Check No. 3 - Part Power Trim Check. (Cont)
CAUTION
Part power trim stop must be properly
stowed after completion of part power trim
checks. Insure that attaching screw is
tightened and lockwired.
d. Data Plate Speed. Data plate speed is gas
generator speed (Ng) obtained with engine running at
reference power on a standard day (59
F) (15
C). This
value is determined from acceptance running, and
each engine has its individual value stamped on data
plate speed plate in rpm and a percentage of
maximum gas generator speed. The reference power
in shp/(Shp corrected) is also stamped on the data
plate.
5.
Check No. 4 - Engine Performance Check.
a. Engine performance check should be
carried out and changes in engine performance noted
prior to installation in airframe. The engine
performance check curve is presented as constant
torque versus ambient temperature so that engine
performance can be checked over a wide range of
ambient temperatures without overtorquing the
reduction gearbox.
NOTE
The performance check curve is presented on page
opposite paragraph 1-94.5a.
b. All forms of engine deterioration are
accompanied by an increase in interturbine
temperature and fuel flow at a given power.
Compressor deterioration is, in most cases, due to dirt
deposits and causes an increase in gas generator
speed at a given power setting. This form of
deterioration can be remedied by compressor wash
(Section VIII, Paragraph 1-77).
c. Hot section deterioration results in
decreased gas generator speed at a given power
setting. To determine engine performance check
parameters, proceed as follows (see curve).
(1) Obtain ambient air temperature.
(2) Obtain field barometric pressure
(not corrected to sea level).
(3) Obtain reference rpm from engine
data plate.
(4) Enter engine performance check
curve with ambient temperature and proceed vertically
upward to intersect appropriate field barometric
pressure line. From this intersection, proceed
horizontally to left to read torquemeter pressure.
Record desired torque pressure.
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