Shaft breakage detection apparatus

An apparatus for detecting breakage of a turbine shaft in a gas turbine engine, comprising two detection devices for producing first and second pulse trains whose frequencies are responsive to speeds of a turbine and a compressor, respectively, on the shaft, an up-down counter, means for causing said counter to count up and down in response to pulses from the first and second trains, respectively, means for providing an indicating signal if the value in said counter exceeds a predetermined level, means for causing a magnitude of a count in response to the pulses in the second train to exceed that in response to the pulses in the first train, and means for resetting said counter each time a down count thereby equals a preceding up count.

An apparatus for detecting breakage of a rotary shaft, comprising first and second sensors for producing first and second signals whose frequencies are dependent on first and second speeds of first and second regions, respectively, of the shaft, an up-down counter, first and second control pulse forming means for providing first and second control pulses of first and second predetermined durations, respectively, in response to the first and second signals, respectively, the second control pulse being longer than the first control pulse, control means causing said counter to count in opposite directions in response to the first and second control pulses, respectively, and signaling means for signaling if the count in said counter passes a first predetermined threshold.