Propeller phase control apparatus

Apparatus for controlling the relative phase between propellers of a multi-engine aircraft having, for each engine, a speed and phase control (SPC) unit and an electronic engine control (EEC) unit, the SPC unit controlling the propeller blade pitch angle in dependence on a difference magnitude between the spatial positioning of the signal pulses of a pulsed command speed and phase (S/P) signal from the EEC unit and that of a sensed pulse signal indicative of the propeller's actual blade positioning, the SPC unit controlling propeller shaft speed in dependence on a difference magnitude of each S/P signal's pulse repetition frequency (PRF), the EEC unit calculating the EEC pulsed command S/P signal spatial positioning of pulses and the PRF using a model algorithm responsive to the magnitude of sensed flight data signals received from an aircraft data bus and on throttle lever angle (TLA) position signals from the aircraft flight deck, comprising:

• SYNCHROPHASER Reference Unit (SRU) means, including signal processing means having signal memory means for storing signals definitive of the model algorithm used in the EEC unit, said signal processing means being responsive to the sensed flight data signals and TLA position signal information presented to the EEC unit, for calculating a SRU command S/P signal value having a desired pulse spatial positioning and a desired PRF;
• and
• switch means associated with each SPC unit for selecting, alternately in dependence on operator control, said SRU command S/P signal or the associated engine's EEC command S/P signal for presentation to the SPC unit.