Diagnostic system and method for monitoring hydraulic pump

1. A diagnostic system comprising:

a hydraulic system onboard an aircraft, the hydraulic system comprising a pump configured to pump hydraulic fluid on the aircraft, the pump including an inlet, a discharge outlet, and a case drain outlet, wherein the inlet is fluidly connected to a reservoir and receives an incoming flow stream of the hydraulic fluid from the reservoir, the discharge outlet emits a high pressure flow stream of the hydraulic fluid configured to be conveyed to a hydraulic load to perform work, and the case drain outlet emits a cooling flow stream of the hydraulic fluid that is discrete from the high pressure flow stream, wherein the cooling flow stream has a lower pressure than the high pressure flow stream;

a first temperature sensor configured to measure a first temperature of the incoming flow stream upstream of the inlet of the pump;

a second temperature sensor configured to measure a second temperature of the cooling flow stream downstream of the case drain outlet of the pump; and

a controller including one or more processors and configured to:

determine a value of a temperature rise of the hydraulic fluid across the pump as a difference between the first temperature and the second temperature;

obtain an expected range for the temperature rise of the hydraulic fluid across the pump based on a speed of the pump; and

in response to the value of the temperature rise being outside of the expected range, generate a maintenance message for communication to one or more devices that are off-board the aircraft, wherein the maintenance message indicates that the pump is operating in a degraded state.

2. The diagnostic system of claim 1 , wherein the controller is further configured to:

obtain the expected range for the temperature rise based on a flight condition of the aircraft; and

determine the value of the temperature rise while the aircraft is in the flight condition.

3. The diagnostic system of claim 2 , wherein the controller is further configured to determine that the aircraft is in a cruise state as the flight condition.

4. The diagnostic system of claim 1 , wherein the controller is further configured to obtain the expected range for the temperature rise based on an ambient temperature of an environment surrounding the aircraft.

5. The diagnostic system of claim 1 , wherein the controller is further configured to generate the maintenance message to identify the pump and request scheduling a maintenance appointment for the aircraft.

6. The diagnostic system of claim 1 , wherein the pump is powered by a driver component that is one of a fuel combustion engine, an electric motor, or a ram air turbine, and wherein the controller is configured to determine the speed of the pump based on a measured rotational speed of the driver component.

7. The diagnostic system of claim 1 , wherein the controller is configured to obtain the expected range by calculating the expected range, the controller configured to obtain a volumetric flow rate of the hydraulic fluid based on the speed of the pump, calculate a mass flow rate of the hydraulic fluid based on the volumetric flow rate and a density property of the hydraulic fluid, and calculate both an upper limit of the expected range for the temperature rise and a lower limit of the expected range for the temperature rise based, at least in part, on the mass flow rate.

8. The diagnostic system of claim 1 , wherein the controller is configured to obtain the expected range by accessing a look-up table stored in a memory storage device, the look-up table listing a respective upper limit of the expected range and a respective lower limit of the expected range for each of multiple different ranges of the speed of the pump.

9. The diagnostic system of claim 1 , wherein, after determining the value of the temperature rise of the hydraulic fluid across the pump, the controller is further configured to determine multiple updated values of the temperature rise of the hydraulic fluid across the pump over an extended time period and to record the value and the updated values.

10. The diagnostic system of claim 9 , wherein the controller is further configured to predict a remaining operational life of the pump based on a variation in the value and the updated values over the extended time period.

11. The diagnostic system of claim 10 , wherein the controller is further configured to predict the remaining operational life of the pump by extrapolating, based on the variation in the value and the updated values, a time at which a future value of the temperature rise will exceed a designated overheat threshold for the pump.

12. The diagnostic system of claim 1 , wherein an upper limit of the expected range for the temperature rise is below a designated overheat threshold for the pump, wherein the controller is configured to generate a restriction message in response to the value of the temperature rise exceeding the designated overheat threshold, and wherein the restriction message prohibits subsequent flights of the aircraft until maintenance is performed on the aircraft to address the pump.

13. A method comprising:

providing a hydraulic system that includes a pump configured to pump hydraulic fluid on an aircraft, the pump including an inlet, a discharge outlet, and a case drain outlet, wherein the inlet is fluidly connected to a reservoir and receives an incoming flow stream of the hydraulic fluid from the reservoir, the discharge outlet emits a high pressure flow stream of the hydraulic fluid configured to be conveyed to a hydraulic load to perform work, and the case drain outlet emits a cooling flow stream of the hydraulic fluid that is discrete from the high pressure flow stream, wherein the cooling flow stream has a lower pressure than the high pressure flow stream;

receiving a first sensor signal, generated by a first temperature sensor located upstream of the inlet of the pump, indicating a temperature of the incoming flow stream;

receiving a second sensor signal, generated by a second temperature sensor located downstream of the case drain outlet of the pump, indicating a temperature of the cooling flow stream;

determining a value of a temperature rise of the hydraulic fluid across the pump of the hydraulic system as a difference between the temperature of the incoming flow stream and the temperature of the cooling flow stream;

obtaining an expected range for the temperature rise of the hydraulic fluid across the pump based on a speed of the pump; and

in response to the value of the temperature rise being outside of the expected range, generating a maintenance message for communication to one or more devices that are off-board the aircraft, wherein the maintenance message indicates that the pump is operating in a degraded state.

14. The method of claim 13 , wherein the expected range for the temperature rise is based on a flight condition of the aircraft, and wherein the value of the temperature rise is determined while the aircraft is in the flight condition on which the expected range is based.

15. The method of claim 14 , further comprising determining the flight condition of the aircraft based, at least in part, on control signals received from a user input device that controls movement of the aircraft.

16. The method of claim 13 , wherein said obtaining the expected range of the temperature rise comprises accessing a look-up table stored in a memory storage device, and wherein the look-up table lists a respective upper limit of the expected range and a respective lower limit of the expected range for each of multiple different ranges of the speed of the pump.

17. The method of claim 13 , wherein, after determining the value of the temperature rise of the hydraulic fluid across the pump, the method further comprises:

determining updated values of the temperature rise of the hydraulic fluid across the pump over an extended time period; and

predicting a remaining operational life of the pump based on a variation in the value and the updated values over the extended time period.

18. The method of claim 17 , wherein said predicting the remaining life span comprises extrapolating, based on the variation in the value and the updated values, a time at which a future value of the temperature rise will exceed a designated overheat threshold for the pump.

19. A diagnostic system comprising:

a pump of a hydraulic system, the pump including an inlet, a discharge outlet, and a case drain outlet, wherein the inlet is fluidly connected to a reservoir and receives an incoming flow stream of hydraulic fluid from the reservoir, the discharge outlet emits a high pressure flow stream of the hydraulic fluid configured to be conveyed to a hydraulic load to perform work, and the case drain outlet emits a cooling flow stream of the hydraulic fluid that is discrete from the high pressure flow stream, wherein the cooling flow stream has a lower pressure than the high pressure flow stream;

a first temperature sensor configured to measure a first temperature of the incoming flow stream upstream of the inlet of the pump;

a second temperature sensor configured to measure a second temperature of the cooling flow stream downstream of the case drain outlet of the pump; and

a controller including one or more processors and configured to:

determine a flight condition of the aircraft based, at least in part, on an absence of control signals received from a user input device that controls movement of the aircraft;

determine a value of a temperature rise of the hydraulic fluid across the pump as a difference between the first temperature and the second temperature, wherein the value of the temperature rise is determined while the aircraft is in the flight condition that is determined;

obtain an expected range for the temperature rise of the hydraulic fluid across the pump based on the flight condition of the aircraft and a speed of the pump; and

in response to the value of the temperature rise being outside of the expected range, generate a maintenance message for communication to one or more devices that are off-board the aircraft, wherein the maintenance message identifies the pump, indicates that the pump is operating in a degraded state, and requests scheduling a maintenance appointment for the aircraft.

20. The diagnostic system of claim 19 , wherein the controller is configured to determine that the aircraft is in cruise mode as the flight condition, and is configured to obtain the expected range for the temperature rise of the hydraulic fluid across the pump based on the aircraft being in the cruise mode.