Engine and Related Systems
T-45C TS, ADV & IUT ENG-04
(3) Shuts down GTS and engine ignition when
engine N2 rpm reaches 45%
2.
Engine starting component function
a.
Bleed air valve: relieves pressure from N2
compressor to ease engine starting and
prevent compressor stalls
(1) Engine off and initial acceleration
(a) Electrically actuated, spring-operated
valve opens when low differential fuel
pressure signal is received during
engine start (initially with engine off,
valve is open)
(b) Valve held open by spring and
differential air pressure (between
N2 and bypass duct) during start
and initial engine acceleration
(c) Valve closed pneumatically by P3 air
when N2 rpm reaches 61 +/- 4%
NOTE: When the valve closes,
rpm increases approximately 3%
and EGT decreases approximately
50 degrees C.
(2) Engine running: valve held closed
pneumatically by P3 air after engine start
and all other throttle movements
(3) Engine shutdown: spring opens valve
when engine speed reaches approximately
45% rpm during rundown
(4) Starting with manual fuel selected (FUEL
CONTROL switch set to MANUAL): bleed
air valve opened electrically by pressing
GTS start button—valve held open for
60 seconds
Original (9-98)
Page 4-17
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