MAINTENANCE MANUAL-CF6-80C SERIES

民航论坛

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民航论坛

STARTING SYSTEM - DESCRIPTION AND OPERATION 1 . General (Fig. 1) A. The engine starting system provides the means of rotating the engine N2 compressor on the ground or in flight to an rpm at which engine start can occur. The starting system assists the engine to accelerate to approximately 50% N2 rpm, at which time the starting system will stop operating. For inflight start, the system can be energized to supplement a windmilling engine if required. System components for each engine include the starter, start valve, start valve disagreement light, pneumatic ducting, and necessary control circuitry (Fig. 1). Switches on the engine start and ignition control module located on the pilots' overhead panel P5, control the engine starting system operation. B. Power for the system is 28 volts dc supplied from the overhead circuit breaker panel P11 battery bus. C. Pneumatic power can be obtained from three separate compressed air sources: the airplane auxiliary power unit (APU), ground carts through service connections, or cross-bleed air from an operating engine. 2 . Component Details A. Starter (Fig. 2) (1) The engine starter converts high energy compressed air to starter shaft torque sufficient to accelerate the engine to starting speed. The starter is a lightweight, single stage, axial flow, turbine air motor consisting of a nozzle, turbine wheel and shaft, reduction gear train, exhaust screen, housing assembly, clutch mechanism, and output drive shaft. Starter operation is controlled by the start valve which opens on demand to permit air to flow into the starter inlet. (2) The starter is mounted on the aft face of the accessory gearbox at the 6 o'clock drive pad. It is secured to an adapter pad by a V-band coupling and accurately located by two locator pins on the starter flange. (3) The starter gears and bearings are splash-lubricated by a self-contained oil system. Fill and drain ports are provided in the housing for servicing. The magnetic drain plug assembly consists of an inner magnetic probe and an outer drain plug. The magnetic probe can be removed to check for metallic chips without draining the oil. A check valve in the drain plug prevents draining when the magnetic probe is removed. B. Start Valve (Fig. 3 and Fig. 4) (1) The start valve controls compressed air flow to the engine starter. The valve is a spring loaded closed, electrically controlled, pneumatically operated shutoff valve. The start valve has two major components, the valve body and the actuator