Adaptive synchrophaser for reducing aircraft cabin noise and vibration

A method of reducing vibration in an aircraft cabin during flight, the aircraft having at least two propellers, said method comprising the steps of:

• a. setting a phase angle relationship between the aircraft propellers by using an associated synchrophaser;
• b. sensing a vibration signal at each of a plurality of vibration sensors in the cabin, each vibration signal being indicative of the vibration level based on flight conditions at the set phase angle;
• c. converting each vibration signal from analog to digital and transmitting the converted vibration signal to a digital signal processor;
• d. comparing each converted vibration signal in the processor to identify the maximum vibration level signal generated at any vibration sensor at that phase angle and storing a resulting signal which characterizes that maximum vibration level and associated angle;
• e. repeating steps (b)-(d) for each of a plurality of other, incremental phase angles;
• f. determining, from among all of the resulting signals, the signal indicative of both a lowest maximum vibration level and its associated propeller shaft phase angle;
• and
• g. generating a control signal from the processor to the synchrophaser to set the phase angle relationship between the propellers to that value determined in step (f) above, thereby reducing the cabin vibration to the lowest maximum vibration level at any of the sensor locations.

Apparatus, disposed on an aircraft having at least two propellers, operable to set a phase angle between the propellers to an desired value, said apparatus comprising:

• a. sensing means, disposed throughout various locations on the aircraft, for sensing a predetermined aircraft parameter at each of the aircraft locations and for providing a corresponding sensed signal for each of the aircraft locations;
• b. synchrophaser means, responsive to a phase angle signal, for setting a phase angle between the propellers to a predetermined value;
• and
• c. signal processing means, responsive to each of the sensed signals, for incrementally setting the phase angle signal to a series of values, for comparing, at each incremental value of the phase angle signal, the sensed signals to determine the sensed signal with a predetermined characteristic, and for comparing all of the sensed signals with the predetermined characteristic to determine the sensed signal having a predetermined quality and for setting an in-flight value of the phase angle signal equal to the phase angle associated with the determined sensed signal with the predetermined quality.