Helicopter control systems

A helicopter having at least one engine for driving a main sustaining rotor and an anti-torque tail rotor each comprising a plurality of rotor blades, a flight control system comprising a flight control computer for receiving pilot flight control input signals and generating output signals for adjusting the pitch of the main and tail rotor blades, an engine control computer for receiving a pilot engine control input signal and generating output signals for controlling the speed of rotation of an engine output shaft, and an integrated flight and engine control computer receiving said output signals from the flight control computer, a signal representative of engine state information and signals representative of helicopter flight state information, said integrated flight and engine control computer including helicopter and engine mathematical models for predicting the torque required from the engine to maintain substantially a constant datum speed of rotation of the main sustaining rotor and generating output signals for summing with the pilot engine control input signal to the engine output shaft to meet the predicted torque requirement and for summing with the pilot flight control input signals to the flight control computer to adjust said signals if the engine cannot respond quickly to meet the predicted torque demand or the predicted torque demand is greater than that available.