A phase and speed control system for synchronizing the speed and controlling the phase relationship between a pair of aircraft engines, each engine having associated therewith a centrifugal governor, includes a phase comparator circuit which provides a pulse width modulated signal only to the governor coil of the engine having the slower initial rotational velocity. A variable delay on one input of the phase comparator may be adjusted to determine the relative rotational phase relationship between the engines.

Digital systems for synchronizing prime movers equipped with magnetic ball head speed governors provide smooth and continuous synchronizing control. A plurality of prime movers may be synchronized by operating one as a "master" and the other as "slaves," in which event each "slave" is equipped with a magnetic ball head speed governor and the bias coil of each such governor is supplied with a digital control signal which is modulated in accordance with any difference between the speed of the associated "slave" and that of the "master." Alternatively, a pair of prime movers may be synchronized by equipping each of them with a magnetic ball head speed governor and by supplying the bias coils of those governors with digital signals which are complementarily modulated in accordance with any difference between the speeds of the prime movers. The reference level of the digital control pulses may be adjusted manually or automatically to establish and maintain a desired phase relationship between the synchronized prime movers.

System for reducing vibrations in the cabin of an aircraft driven by two or more propellers each having n blades (n being an integer equal or larger than 2) of which the relative phase angle can be adjusted, said system comprising synchrophase means for adjusting said relative phase angle such that a predetermined relative phase angle is maintained. The system furthermore comprises means supplying information about the vibration level at one or more positions within the cabin or thereto related information and for generating a thereto corresponding level signal, and a control unit which in response to said level signal supplies an error signal to the synchrophase means causing the synchrophase means to adjust the blades of the various propellers such that a new relative phase angle is maintained which differs m.(2.pi./n) radians (m being an integer) from the previous relative phase angle. Each propeller comprises at least one recognizing means attached to one of its propeller blades, the recognizing means being detectable by a sensor in order to establish the absolute position of the various propeller blades.

The pitch of a rotating propeller blade is adjusted to selectively increase the pitch of the blade or to selectively decrease the pitch of the blade. The blade is connected to a rotating hub by bearings that allow the blade to change pitch. A two-direction D.C. motor mounted on the rotating hub is selectively energized to increase or decrease the pitch of the blade. A pair of sensors are mounted on the rotating hub at different distances from the hub's axis of rotation. The first sensor is adapted to generate a signal for energizing the motor in a first direction and increase the pitch of the blade. The second sensor is adapted to generate a signal for energizing the motor in a second direction and decrease the pitch of the blade. An energy source spaced from the rotating blade selectively directs a first beam of energy onto said first sensor thereby causing said first sensor to generate a signal and energize the motor and selectively directs a second beam of energy onto said second sensor thereby causing said second sensor to generate a signal and energize the motor.

An engine synchronization system for a pair of turbo jet engines in a twin jet aircraft includes a subsystem for selecting a power output, a signal generator for producing a first output signal in response to the speed of a first engine and a signal generator for producing a second output signal in response to the speed of a second engine. The system also includes a selector for selecting the fan speed or compressor speed of the engines as a control. The system incorporating an averaging device for calculating the average of the engine speeds and causing the servo driven throttle controller to retard the faster and advance the slower throttles toward the average. The engine synchronization system also includes a split shaft assembly including first and second output shafts which are disposed on a common axis. Each of the output shafts is locked to a servo motor and are free to rotate with respect to one another. The servo driven throttle control also includes a pair of sprag clutches with one of the clutches disposed between each of the shafts and a manual throttle control. The sprag clutch allows the manual throttle control to rotate about the shaft without rotating the shaft and for providing authority to the manual throttle control.