TM55-2840-251-23
Section X ENGINE TESTING (Continued )
1-94
GROUND TEST ON ENGINE
INSTALLED IN AIRCRAFT
(Cont)
5.
Check No. 4 - Engine Performance Check
(Turbine Engine Analysis Check).
a.
Periodic engine performance checks must be
performed and changes in engine performance noted.
The engine performance check curve (refer to figure
opposite) 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 gear- box.
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 aircraft manufacturer's engine
performance check 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 torquemeter
pressure.
(5)
Enter curve with ambient temperature
and proceed vertically upward to intersect appropriate
field barometric pressure line. From this inter- section,
proceed horizontally to left to read fuel flow in lbs/hr.
Record desired fuel flow.
(6)
Enter curve with ambient temperature
and proceed vertically upward to intersect gas generator
data plate speed line. From this intersection, proceed
horizontally to left to read desired ratio (gas generator
speed + data plate speed). Record desired ratio.
(7)
Enter curve with ambient temperature
and proceed vertically upward to intersect interturbine
temperature line. From this intersection, proceed
horizontally to left to read interturbine temperature.
Record desired interturbine temperature.
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