POWERPLANT
AIRPLANE
OPERATIONS
MANUAL
2-10-30
Page
2
Code
01
REVISION 37
AOM-145/1114
PNEUMATIC STARTING SYSTEM
The engine starting system comprises the Air Turbine Starter and the
Starting Control Valve. The starting system has the function of
supplying airflow for pneumatic engine starting, converting the
pneumatic energy into gearbox driving torque.
Pneumatic power source can be selected from the APU, ground air
supply source, or cross bleed from the opposite engine.
AIR TURBINE STARTER (ATS)
The ATS is installed in a dedicated engine accessory gearbox pad and
consists basically of an air inlet, an impeller turbine, a reduction
gearset, a clutch, and an output shaft.
The ATS converts pneumatic energy into driving torque for engine gas
generator spool acceleration up to the self-sustained speed during the
starting cycle. The air exhaust from the turbine is discharged into the
engine nacelle compartment.
STARTING CONTROL VALVE (SCV)
The SCV regulates the pressure supplied to the ATS and provides
isolation from the pneumatic system following start completion. The
valve is electrically controlled and pneumatically actuated.
A SCV visual position indication is available on the valve housing.
A manual override adapter is available on the valve housing, enabling
engine start in the case of a valve or associated electrical system
failure. The valve is spring-loaded to the closed position.
If the ATS shutoff valve remains open after 53% N2, a caution
message is presented on the EICAS.
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