Chandler Evans Inc.

Colt Industries Inc.

Cnandler Evans Inc.

Albert H White

Raymond D Zagranski

Robert E Peck

Raymond H Devanney

Gene Meyer

This invention relates generally to fuel control systems for combustion engines such as gas turbines used in helicopters and the like, and more specifically relates to a fuel control transfer system which permits the substitution of one fuel control device for another which is supplying fuel to an operating combustion engine, without interruption of, or adverse effect on continued operation of the engine.

Transfer system for combustion engine fuel control devices

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a power piston (34) and a loading piston (60) in confronting relationship adapted to engage each other upon power being withdrawn from a solenoid operated valve (72).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 metering valve through a multiplier linkage (96) which is also connected to a compressor discharge pressure transducer (98) so that the metering 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.

Manual backup for electronic fuel control

A fuel control for a gas turbine engine has an actuator (24) for a fuel metering valve (22) which includes two stepper motors (46 and 48) which selectively drive a differential mechanism operatively connected to the valve. The differential mechanism includes two identical gear assemblies (60, 64) which are mounted for rotation upon a shaft (26) connected to the valve. The gear assemblies include worm gears (58, 62) in engagement with worms (54, 56) driven by the stepper motors and bevel gears (68, 70). A spider bevel gear (66), carried by the shaft, is in meshing engagement with the bevel gears of the gear assemblies such that rotation of one of the gear assemblies with the other at rest causes a circumferential movement of the spider bevel gear which rotates the shaft and positions the valve. Two identical electronic control units (A, B), which each sense selected engine parameters are respectively connected to the stepper motors for controlling their operation. Only one of the electronic control units functions to control its stepper motor during normal operation while the positions worm and gear assembly associated with the other stepper motor remain frozen without any backdriving. Changeover to the other electronic control unit because of a malfunction or other reason may be effected by switching logic or operation of a selector switch (100).

Dual stepper motor actuator for fuel metering valve

A fuel control for a gas turbine engine has a positive displacement pump (28) for supplying fuel to the engine. Fuel flow from the pump is metered by a metering valve (30) which has a constant pressure head held across it by a metering head regulator valve (48) adapted to bypass flow around the pump in a conduit (50). An overspeed valve and solenoid assembly (42) is positioned in the control downstream of the metering valve for shutting off fuel flow to the engine in the event of an overspeed of a turbine of the engine. The metering head regulator valve is referenced to a pressure downstream of the overspeed valve and solenoid assembly by a pressure sense line (68). The solenoid (96) is controlled by a dual channel overspeed valve control circuit (102) having proportional plus derivative gains (108, 110). When the overspeed valve (76) of the assembly is operated, the pump is not deadheaded because the metering head regulator valve is referenced to a lower pressure downstream of the overspeed valve. By not deadheading the pump, faster fuel shutoff can be achieved and leakage across the overspeed valve minimized.

Overspeed limiter for gas turbine fuel control

The failure of a gas turbine engine, particularly flame-out or output drive train breakage, is immediately detected and a warning signal generated. Engine flame-out is defined as an unacceptably fast gas turbine deceleration rate while output shaft failure is determined by sensing a mismatch between the engine output shaft speed and load speed.

Engine failure detector

A method of controlling fuel flow to a gas turbine engine includes computing the compressor discharge pressure from signals indicative of engine inlet temperature, engine speed and the computed scheduled fuel flow. The method permits accurate scheduling of fuel flow without employing a compressor discharge pressure sensor or continued engine operation in the event of sensor failure.

Backup control

A fuel control for a gas turbine engine has a fuel flow limiting valve located in series flow relationship with a main fuel metering valve, which is manually operable, to prevent engine overspeed and overtemperature conditions. A pulse-modulated solenoid valve, responsive to error signals indicative of engine overspeeds or overtemperature conditions, modulates the pressure in an actuation cylinder which positions the flow-limiting valve so that it limits flow in accordance with the magnitude of the error signals. The solenoid valve is pulsed by a redundant analog control so that, during manual operation of the main fuel metering valve, overspeed and overtemperature protection is provided to the engine. An indicator is furnished to apprise the operator of overspeed or overtemperature conditions.

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Wethersfield, CT, United States of America

Albert H White