Gas turbine engine with heat exchanger diagnostics

1. A gas turbine engine comprising:

a compressor section and a turbine section, said compressor section including a low pressure compressor and a high pressure compressor, and said turbine section including a low pressure turbine and a high pressure turbine;

a fan rotor, said low pressure turbine driving said low pressure compressor, and said low pressure turbine driving said fan rotor through a gear reduction such that said fan rotor rotates at a lower speed than said low pressure turbine;

said high pressure turbine driving said high pressure compressor;

a cooling air system including a first fluid connection to tap cooling air and pass the cooling air through a heat exchanger, and a second fluid connection for returning air from the heat exchanger back to at least one of the compressor section and the turbine section for cooling; and

a first sensor for sensing a pressure of the cooling air downstream of the heat exchanger and a control to compare the sensed pressure of the cooling air to an expected pressure, and said control is programmed to identify a condition of the cooling air system when the sensed pressure differs from the expected pressure by more than a predetermined amount, said condition being indicative of a failure in said heat exchanger, said first fluid connection, or said second fluid connection, and said control setting a maintenance flag such that when cooling air is not properly passing to the at least one of the compressor section and the turbine section the maintenance flag is set; and

wherein said first fluid connection and said second fluid connection are fluid conduits.

2. The gas turbine engine as set forth in claim 1 , wherein said pressure is sensed downstream of said second fluid connection.

3. The gas turbine engine as set forth in claim 2 , wherein said cooling air is returned into a diffuser downstream of said compressor section for transfer to at least one of the turbine section and the compressor section.

4. The gas turbine engine as set forth in claim 3 , wherein said first sensor senses the pressure within a part of said diffuser which is connected to pass cooling air to at least one of the turbine section and the compressor section.

5. The gas turbine engine as set forth in claim 4 , wherein said first sensor is positioned on said diffuser.

6. The gas turbine engine as set forth in claim 4 , wherein a pressure tap taps air from within said diffuser to said first sensor, said first sensor being remote from said diffuser.

7. The gas turbine engine as set forth in claim 1 , wherein said first sensor is located to be line replaceable.

8. The gas turbine engine as set forth in claim 1 , wherein a reference pressure is also sensed and said pressure sensed by said first sensor is compared to said reference pressure as said expected condition.

9. The gas turbine engine as set forth in claim 8 , wherein said reference pressure is a pressure sensed downstream of said compressor section.

10. The gas turbine engine as set forth in claim 1 , wherein said expected condition is an artificially determined reference pressure.

11. The gas turbine engine as set forth in claim 1 , wherein said control is programmed such that the comparison results in varying levels of the maintenance flag.

12. The gas turbine engine as set forth in claim 11 , wherein said control is programmed such that when the comparison results in the pressure sensed by the first sensor differing from said expected pressure by a first amount, then the maintenance flag indicates routine maintenance whereas when said pressure sensed by said first sensor differs from said expected pressure by a second greater amount, then the maintenance flag indicates a more drastic step than routine maintenance.

13. The gas turbine engine as set forth in claim 12 , wherein said more drastic step is a power reduction of the gas turbine engine.

14. A gas turbine engine comprising:

a compressor section and a turbine section;

a cooling air system including a first fluid connection to tap cooling air and pass the cooling air through a heat exchanger, and a second fluid connection for returning air from the heat exchanger back to at least one of the compressor section and the turbine section for cooling;

a first sensor for sensing a pressure of the cooling air downstream of the heat exchanger and a control to compare the sensed pressure of the cooling air to an expected pressure, and said control is programmed to identify a condition of the cooling air system when the sensed pressure differs from the expected pressure by more than a predetermined amount; and

said control is programmed such that condition being indicative of a failure in said heat exchanger, said first fluid connection, or said second fluid connection, and said control setting a maintenance flag such that when cooling air is not properly passing to the at least one of the compressor section and the turbine section the maintenance flag is set;

wherein a reference pressure is also sensed and said pressure sensed by said first sensor is compared by said control to said reference pressure as said expected pressure;

wherein said reference pressure is a pressure sensed downstream of said compressor section;

wherein said control is programmed such that said comparison results in varying levels of the maintenance flag; and

wherein said control programmed such that when the comparison results in the pressure sensed by the first sensor differing from said expected pressure by a first amount, then the maintenance flag indicates routine maintenance whereas when said pressure sensed by said first sensor differs from said expected pressure by a second greater amount, then the maintenance flag indicates a more drastic step than routine maintenance.

15. The gas turbine engine as set forth in claim 14 , wherein said expected pressure is an artificially determined reference pressure.

16. The gas turbine engine as set forth in claim 14 , wherein said pressure is sensed downstream of said second fluid connection.

17. The gas turbine engine as set forth in claim 14 , wherein said more drastic step is a power reduction of the gas turbine engine.

18. A gas turbine engine comprising:

a compressor section and a turbine section;

a cooling air system including a first fluid connection to tap cooling air and pass the cooling air through a heat exchanger, and a second fluid connection for returning air from the heat exchanger back to at least one of the compressor section and the turbine section for cooling; and

a first sensor for sensing a pressure of the cooling air downstream of the heat exchanger and a control to compare the sensed pressure of the cooling air to an expected pressure, and said control is programmed to identify a condition of the cooling air system when the sensed pressure differs from the expected pressure by more than a predetermined amount, said condition being indicative of a failure in said heat exchanger, said first fluid connection, or said second fluid connection, and said control setting a maintenance flag such that when cooling air is not properly passing to the at least one of the compressor section and the turbine section the maintenance flag is set, wherein when a difference between said sensed pressure and said expected pressure exceeds a maximum, said maintenance flag includes a reduction to of power of the gas turbine engine.