Title: Helicopter power plant control

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Abstract: A control system for a helicopter power plant with three power units driving the lifting rotor system. Each power unit comprises a gas-coupled gas turbine engine, a hydromechanical fuel control receiving electrical inputs to set a gas generator governor, an engine electronic control, and engine accessories. Power plant operation is normally controlled by the pilot through condition levers and switches on a control quadrant, through a collective pitch control for the rotor blades, and through a master beeper switch which is operable to trim the setting of a rotor speed governor and the gas generator governors. A condition lever transmits a speed command signal through the electronic control of each power unit to its gas generator governor. A collective pitch signal from the rotor control system is another factor in setting the gas generator governor of each unit. The power plant includes a power management control which equalizes the power outputs of the engines and includes the rotor isochronous governor. The power management control receives inputs of rotor system speed command and actual rotor speed, and of the torques of the individual power plants and transmits a governor trim signal to the several electronic controls. All signals are transmitted electrically between the rotor system, control panel, power management control, and engine electronic controls. The signal representing condition lever power setting decreases with increasing power demand. The collective pitch signal decreases with increasing pitch. A failure to transmit either signal thus represents a high power request -- a fail-safe feature. A starting system for each engine includes logic circuits to test the operation of the electrical signal transmission system and closure of a fuel shutoff valve as a prerequisite to starting of the engine.


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