Shaft event detection in gas turbine engines

1. A method for detecting a shaft event in a gas turbine engine of an aircraft, the method comprising:

obtaining a first speed measurement at a first location along a first shaft extending between a power turbine of the gas turbine engine and a first load and a second speed measurement at a second location along a second shaft extending between the power turbine and a second load;

determining a speed ratio between the first speed measurement and the second speed measurement;

comparing the speed ratio to a detection threshold;

detecting the shaft event when the speed ratio is beyond the detection threshold; and

issuing a signal indicative of the shaft event in response to detecting the shaft event.

2. The method of claim 1 , wherein the detection threshold comprises a maximum allowed variation between the speed ratio and at least one previously obtained speed ratio of the gas turbine engine.

3. The method of claim 2 , wherein the at least one previously obtained speed ratio is obtained immediately prior to the first speed measurement and the second speed measurement.

4. The method of claim 1 , further comprising determining the detection threshold as a function of at least one of a mode of operation of the engine and a flight phase of the aircraft.

5. The method of claim 4 , wherein the detection threshold changes dynamically as a function of changes to the at least one of a mode of operation of the engine and a flight phase of the aircraft.

6. The method of claim 1 , wherein the first location is at a first end of the first shaft and the second location is at a second end of the second shaft.

7. The method of claim 1 , wherein the gas turbine engine is a reverse flow split compressor engine.

8. The method of claim 7 , wherein the first shaft and the second shaft form an integral one-piece shaft.

9. The method of claim 1 , wherein the first shaft extends in a first direction and the second shaft extends in a second direction opposite from the first direction.

10. A system for detecting a shaft event in a gas turbine engine, the system comprising:

a processing unit; and

a non-transitory memory communicatively coupled to the processing unit and comprising computer-readable program instructions executable by the processing unit for:

obtaining a first speed measurement at a first location along a first shaft extending between a power turbine of the gas turbine engine and a first load and a second speed measurement at a second location along a second shaft extending between the power turbine and a second load;

determining a speed ratio between the first speed measurement and the second speed measurement;

comparing the speed ratio to a detection threshold;

detecting the shaft event when the speed ratio is beyond the detection threshold; and

issuing a signal indicative of the shaft event in response to detecting the shaft event.

11. The system of claim 10 , wherein the detection threshold comprises a maximum allowed variation between the speed ratio and at least one previously obtained speed ratio of the gas turbine engine.

12. The system of claim 11 , wherein the at least one previously obtained speed ratio is obtained immediately prior to the first speed measurement and the second speed measurement.

13. The system of claim 10 , further comprising determining the detection threshold as a function of at least one of a mode of operation of the engine and a flight phase of the aircraft.

14. The system of claim 13 , wherein the detection threshold changes dynamically as a function of changes to the at least one of a mode of operation of the engine and a flight phase of the aircraft.

15. The system of claim 10 , wherein the first location is at a first end of the first shaft and the second location is at a second end of the second shaft.

16. The system of claim 10 , wherein the gas turbine engine is a reverse flow split compressor engine.

17. The system of claim 16 , wherein the first shaft and the second shaft form an integral one-piece shaft.

18. The system of claim 10 , wherein the first shaft extends in a first direction and the second shaft extends in a second direction opposite from the first direction.

19. A gas turbine engine comprising:

a power turbine having a first shaft extending between the power turbine and a first load and a second shaft extending between the power turbine and a second load;

at least one first speed sensor located at a first location along the first shaft;

at least one second speed sensor located at a second location along the second shaft; and

a shaft shear event detection system operatively coupled to the at least one first speed sensor and the at least one second speed sensor and configured for:

obtaining a first speed measurement at the first location and a second speed measurement at the second location from the at least one first speed sensor and the at least one second speed sensor, respectively;

determining a speed ratio between the first speed measurement and the second speed measurement;

comparing the speed ratio to a detection threshold; and

detecting the shaft event when the speed ratio is beyond the detection threshold.

20. The gas turbine engine of claim 19 , wherein the first location is at a first end of the first shaft and the second location is at a second end of the second shaft.