Condition determination of a gas turbine engine

1. A method of automatically determining an operating condition of at least part of a gas turbine engine for an aircraft, the method comprising:

measuring one or more gas pressure waves by a gas pressure detector, wherein the gas pressure detector is located in the gas turbine engine and comprises an acoustic element, and the acoustic element has a directional sensitivity; and

automatically determining, by a computing system, an operating condition of the at least part of the gas turbine engine in dependence on an output signal of the gas pressure detector, wherein:

the gas pressure detector comprises a plurality of acoustic elements;

each acoustic element has directional sensitivity; and

all of the acoustic elements have different orientations such that the gas pressure detector is able to detect gas pressure waves with substantially the same sensitivity in all of the directions that a respective acoustic element is orientated in.

2. The method according to claim 1 , further comprising

measuring one or more gas pressure waves by one or more further gas pressure detectors, wherein:

the one or more further gas pressure detectors are located in the gas turbine engine; and

said automatically determining of the operating condition is also dependent on the output signal from each of the one or more further gas pressure detectors.

3. The method according to claim 1 , wherein the computing system performs a Fourier Transform on the output signal of the gas pressure detector to generate a frequency domain version of the output signal.

4. The method according to claim 1 , wherein said automatically determining of the operating condition comprises comparing, by the computing system, the output signal of the gas pressure detector with one or more predetermined signals.

5. The method according to claim 4 , wherein:

the computing system performs a Fourier Transform on the output signal of the gas pressure detector to generate a frequency domain version of the output signal; and

said comparing of the output signal of the gas pressure detector with the one or more predetermined signals is a comparison of the frequency domain version of the output signal with the one or more predetermined signals.

6. The method according to claim 1 , further comprising filtering, by the computing system, the output signal of the gas pressure detector.

7. The method according to claim 1 , further comprising:

monitoring, by the computing system, the operating condition of the at least part of the gas turbine engine; and

detecting, by the computing system, a change in the operating condition.

8. The method according to claim 7 , further comprising

determining, by the computing system, a type of the change in the operating condition of the at least part of the gas turbine engine in dependence on comparison of the output signal of the gas pressure detector with one or more predetermined signals.

9. The method according to claim 8 , wherein:

the determined type of the change includes a pipe cracking, bursting and/or leaking; and/or

the determined type of the change comprises a type of pipe that a change has occurred in, including at least one of a cabin air pipe, anti-ice air pipe or handling bleed pipe.

10. The method according to claim 7 , further comprising

determining a location of the change.

11. The method according to claim 10 , further comprising

measuring one or more gas pressure waves by one or more further gas pressure detectors, wherein:

the one or more further gas pressure detectors are located in the gas turbine engine;

said automatically determining of the operating condition is also dependent on the output signal from each of the one or more further gas pressure detectors; and

the location of the change is determined in dependence on a difference in time of arrival of gas pressure waves received at two or more of the gas pressure detectors.

12. The method according to claim 1 , wherein the acoustic elements are arranged to form a substantially spherical shape such that the sensitivity of the gas pressure detector is substantially the same in all directions around the gas pressure detector.

13. The method according to claim 1 , wherein:

each acoustic element comprises an acoustic sensor and a housing; and

the housing is a horn wave guide.

14. The method according to claim 1 , wherein the gas pressure detector is located in a fire zone of the gas turbine engine.

15. The method according to claim 1 , further comprising

impacting the gas turbine engine,

wherein the automatically determining of the operating condition of the at least part of the gas turbine engine is dependent on one or more gas pressure waves caused by the impact.

16. A system comprising a gas turbine engine for an aircraft and a computing system, wherein:

the gas turbine engine comprises one or more gas pressure wave detectors; and

the computing system is arranged to automatically detect the operating condition of the at least part of the gas turbine engine according to the method of claim 1 .

17. The system according to claim 16 , wherein the gas turbine engine further comprises:

an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;

a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and

a gearbox that receives an input from the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft.

18. The system according to claim 17 , wherein:

the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft;

the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor; and

the second turbine, second compressor, and second core shaft are arranged to rotate at a higher rotational speed than the first core shaft.

19. A gas pressure detector comprising:

a plurality of acoustic elements, wherein sensitivity of detection of a gas pressure wave by each acoustic element is dependent on a direction that the acoustic element is aligned in relative to a direction of propagation of the gas pressure wave,

wherein:

all of the acoustic elements have different orientations such that the gas pressure detector is able to detect gas pressure waves with substantially the same sensitivity in all of the directions that an acoustic element is orientated in; and

the acoustic elements are arranged to form a substantially spherical shape such that the sensitivity of the gas pressure detector is substantially the same in all directions around the gas pressure detector.

20. The gas pressure detector according to claim 19 , wherein:

each acoustic element comprises an acoustic sensor and a horn wave guide;

the acoustic element is arranged at a first end of the horn wave guide; and

a second end of the horn wave guide, that is opposite the first end of the horn wave guide, is shaped as a polygon in a cross-section that is orthogonal to a longitudinal axis of the horn wave guide.

21. The gas pressure detector according to claim 19 , wherein the acoustic elements are arranged such that a shape of the gas pressure detector is a dodecahedron.