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other engine. Figure 2-24 shows the components associated
with the engine start system.
2.9.1 External Airstart. Ahigh-pressure(75psi)air
source and 115 volt, 400 Hz ac power are required for
engine start on the deck.
The air hose is connected to the aircraA fitting in the
left sponson area, behind the main gear strut. Ground
start air is ducted into a central bleed air (9th stage)
manifold, which interconnectst he air turbine starterso n
both engines. The air supply to each air turbine starter
is pressure regulated (52.5 psi) and controlled by a
shutoff and regulating valve at the turbine. Each pneumatic
starter is composed of a turbine, gear train, sprag
clutch with a speed-sensingd evice, and an overspeed
disengagemenmt echanismw ith a shears ection.S hutoff
valves in the bleed air manifold selectively isolate the
other starter, subsidiary bleed lines, and the environmental
control system air supply for effecting a start.
Maximum engine motoring speed with the pneumatic
starter is approximately 30-percent ‘pm.
2.9.2 Engine Crank. Placing the ENG CRANK
switch in either L or R openst he correspondings tarter
pressure shutoff valve to allow pressurized air to drive
the turbine. The ENG CRANK switch, energizes the
appropnate shutoff valves to condition the bleed manifold
for starting.
2.9.2.1 Engine Crank Switch. The ENG CRANK
switch is held in L or R by a holding coil. At approximately
50-percent ‘pm, a centrifugal cutoff switch
closes the turbine shutoff valve and returns the ENG
CRANK to the center or off position. A START VALVE
caution light illuminates if the starter valve remains in
the open position after the ENG CRANK switch automatically
returns to the center (on) position.
l If the starter valve does not close during
engine acceleration to idle rpm, continued
airflow through the air turbine starter
could result in catastrophic failure of the
starter turbine.
a If the START VALVE caution light illuminates
after the ENG CRANK switch is
OFF, select AIR SOURCE to OFF to preclude
starter overspeed.
a If the ENG CRANK switch does not automatically
return to the OFF position by 50
percent, ensure that the ENG CRANK
switch is off by 60-percent ‘pm to avoid
starter turbine failure as a result of an inoperative
automatic starter cutout.
ORIGINAL 2-32
NAVAIR 01.F14AAD.1
Figure 2-24. Engine Start System
2-33 ORIGINAL
NAVAIR QW14AAD1
This action, in turn, resets the bleed air manifold
valves to permit 9th-stage bleed air to flow to the environmental
cooling system and ejectors in the engine
compartment.
Starter cranking limits:
1. Crossbleed - 2 minutes continuous then 10
minutes OFF.
2. Start cart - 5 minutes continuous then 10
minutes OFF.
2.9.3 Crossbleed Start. Engine cranking procedures
during a crossbleed start are the same as with a ground
start cart. Engine crossbleed start on the ground can be
accomplished with the throttle on the operating engine
at or above idle rpm. When high-residual EGT (remains
from a hot start) and/or throttles are advanced from OFF
to IDLE prior to 20-percent mm, higher than normal
EGT readings may occur.
When initiating crossbleed starts with ambient temperature
less than 40 “F (4 “C), the starter torque load is
increased. Above 80 “F (27 “C), engine bleed air provides
less energy potential to the starter turbine. Either
extreme can affect engine starting acceleration rates,
resulting in hotter-than-normal starts. When crossbleed
starting with an operating engine at idle, the operator
should be aware of either condition and increase the
operating engine rpm in S-percent increments until normal
starting acceleration rate is achieved. Low percentage
rpm-to-EGT ratio can increase turbine distress
without necessarily exceeding the EGT limit.
When performing an idle crossbleed start, advance
the throttles from OFF to IDLE at 20-percent ‘pm or
greater while monitoring EGT. If EGT rises rapidly,
advance the operating engine rpm to slightly above idle.
The exhaust nozzles start to close when rpm is slightly
above idle.
Note
To prevent possible engine overtemperature
during crossbleed and backup ignition
start attempts, select AIR SOURCE
for the operating engine and return to
BOTH after ‘pm stabilizes at idle or
above.
If attempting a ground restart after a hot
stat, windmill the engine until EGT is
below 250 ‘C prior to advancing the throttle
from OFF to IDLE to avoid a subsequent
　
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