There is described a shaft shear event detection method. The method comprises storing in memory a shaft oscillation signature determined as a function of known characteristics of the shaft and associated with a shaft shear event; monitoring a rotational speed of the shaft; detecting from the rotational speed an oscillation wave superimposed on the rotational speed by detecting a first period below a lower threshold and a second period above an upper threshold, and detecting a rate of occurrence of the first period and the second period, the oscillation wave having a wave modulation frequency corresponding to the rate of occurrence and a wave modulation amplitude; comparing the oscillation signature to the oscillation wave; and detecting the shaft shear event when the oscillation wave corresponds to the oscillation signature.

There is described a shaft shear event detection method. The method comprises storing in memory a shaft oscillation signature determined as a function of known characteristics of the shaft and associated with a shaft shear event; monitoring a rotational speed of the shaft; detecting from the rotational speed an oscillation wave superimposed on the rotational speed by detecting a first period below a lower threshold and a second period above an upper threshold, and detecting a rate of occurrence of the first period and the second period, the oscillation wave having a wave modulation frequency corresponding to the rate of occurrence and a wave modulation amplitude; comparing the oscillation signature to the oscillation wave; and detecting the shaft shear event when the oscillation wave corresponds to the oscillation signature.

A gas turbine engine, includes: an engine core including a turbine, compressor, and shaft system connecting the turbine to the compressor, and forming a torque path therebetween. The shaft system is axially located by a thrust bearing located forward of the turbine, and the engine is configured, in the event of a shaft break which divides the shaft system into a front portion located by the thrust bearing and a rear portion unlocated by the thrust bearing, the rear portion is free to move axially rearwardly under a gas load. The engine further includes a shaft break detector having a forward speed sensor configured to measure a rotational speed of the front portion of the shaft system, and a rear microwave sensor configured to measure a rotational speed of the rear portion of the shaft system, wherein a shaft break can be detected based on differences in the measured speeds.

A gas turbine engine, includes: an engine core including a turbine, compressor, and shaft system connecting the turbine to the compressor, and forming a torque path therebetween. The shaft system is axially located by a thrust bearing located forward of the turbine, and the engine is configured, in the event of a shaft break which divides the shaft system into a front portion located by the thrust bearing and a rear portion unlocated by the thrust bearing, the rear portion is free to move axially rearwardly under a gas load. The engine further includes a shaft break detector having a forward speed sensor configured to measure a rotational speed of the front portion of the shaft system, and a rear microwave sensor configured to measure a rotational speed of the rear portion of the shaft system, wherein a shaft break can be detected based on differences in the measured speeds.

The invention relates to a torque limiting device in a torque bearing connecting structure between a gearbox and a stationary structure in a gas turbine engine, wherein the torque limiting device comprises a mechanical fuse in the connection structure comprising an at least partially circumferential weakening of the material. The invention also relates to a gas turbine engine.

The invention relates to a torque limiting device in a torque bearing connecting structure between a gearbox and a stationary structure in a gas turbine engine, wherein the torque limiting device comprises a mechanical fuse in the connection structure comprising an at least partially circumferential weakening of the material. The invention also relates to a gas turbine engine.

A method of reducing rotor bow in a high pressure rotor of a gas turbine engine that has in axial flow a low pressure rotor and a high pressure rotor. The method involves storing bleed air from the gas turbine engine when the engine is running to provide stored pneumatic energy; and using that stored pneumatic energy after the engine has been shut-down to rotate the high pressure rotor at a speed and for a duration that reduces rotor bow. A gas turbine engine wherein rotor bow in the high pressure rotor after engine shut-down has been reduced by carrying out the aforesaid method is also disclosed.

A method of reducing rotor bow in a high pressure rotor of a gas turbine engine that has in axial flow a low pressure rotor and a high pressure rotor. The method involves storing bleed air from the gas turbine engine when the engine is running to provide stored pneumatic energy; and using that stored pneumatic energy after the engine has been shut-down to rotate the high pressure rotor at a speed and for a duration that reduces rotor bow. A gas turbine engine wherein rotor bow in the high pressure rotor after engine shut-down has been reduced by carrying out the aforesaid method is also disclosed.

Methods and systems for operating a gas turbine engine having variable geometry mechanisms are described. The method comprises detecting a failure event associated with the gas turbine engine, identifying a location of the failure event, selecting an aerodynamic load modulation schedule for the variable geometry mechanisms of the gas turbine engine as a function of the location of the failure event, and applying the aerodynamic load modulation schedule as selected to the variable geometry mechanisms during the failure event.

An abnormality treatment apparatus includes: a sensor which outputs a signal upon detecting an event caused by contact of a rotor of a rotating machine during rotation of the rotor; and a control unit which executes at least one of rotation number control of reducing the number of rotations of the rotor step by step, liquid injection control of injecting liquid into a housing chamber of the rotor step by step, and pressure control of lowering a discharge pressure of the rotating machine step by step based on reception of the signal output from the sensor.