Abstract: An acceleration schedule, from which data is derived for use in calculating fuel flow during acceleration of a gas turbine engine, is modified each time the engine surges so as to avoid future surges.

Abstract: A digital fuel control (53) for a helicopter engine (20) controls fuel flow (52) to the engine in response to a turbine reference speed (62) determined in a normal mode (FIG. 5) to be a rated speed, in a fade-in mode (FIG. 6) to be incremented (117, 120) to an estimated optimum minimum speed (114, 115, 125), in an optimizer mode (FIG. 7) to be incremented (138) in a direction (137) leading to least fuel consumption (135), and in a fade-out mode (FIG. 8) to be incremented (151, 153) back to rated speed (154). The invention provides an engine reference speed which results in minimum fuel consumption during cruise flight.

Abstract: The ability of a gas turbine engine to recover from surge is enhanced by implementing a closed loop control mode wherein fuel flow is varied as a function of the ratio of the rate of change of engine gas generator speed to compressor discharge pressure.

Abstract: The power available from a gas turbine engine is accurately determined by correcting predicted torque and gas generator speed for variations from normal of engine performance. The correction function is adaptively updated on-line by comparing actual and predicted values of torque and speed, storing any differences and summing the stored differences with the predicted values during the determination of power available.

Abstract: The prompt starting of a gas turbine engine is achieved, even when utilizing comparatively poor grade fuel with relatively high viscosity, by modulating the fuel flow between high and low flow rates during the ignition portion of a start schedule. The fuel flow modulation is accomplished by delivering a pulse width modulated control signal to a fuel metering device and modulation is terminated when ignition is verified.