MANUAL BACKUP FOR ELECTRONIC FUEL CONTROL

摘要

A manual backup system (10) for a fuel control incorporating a metering valve (108) controlled by an electronic computer has a power piston (34) and a loading piston (60) in confronting relationship adapted to engage each other upon power being withdrawn from a solenoid operated valve (72). The loading piston acts to maintain an arm (28) in engagement with the power piston so that it follows the power piston's movements as controlled by a servo valve (48), incorporating a fuel flow to compressor discharge pressure schedule (54) operated by a PLA lever (74). The position of the arm represents a requested fuel flow to discharge pressure ratio. The arm is mechanically connected to the meterin valve through a multiplier linkage (96) which is also connected to a compressor discharge pressure transducer (98) so that the meterin valve is positioned in accordance with the requested fuel flow to discharge pressure ratio as multiplied by the sensed compressor discharge pressure. Fuel flow is metered on the basis of an adjustable manual fuel flow to compressor discharge pressure schedule with the PLA lever operating in its normal quadrant. The PLA lever is not susceptible to being back driven during changeover or manual operation.