T-45A UJPT, E2-C2, ADV, & IUT Eng-02
Engine
3.
Other engine starting component functions
a.
Engine bleed air valve: relieves
engine starting and revent compressor
stalls
(1) Operates with engine off and
during initial acceleration
(a) It is an electrically actuated,
spring-operated valve which
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
(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
engine rundown
(8-03) Original
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