Method for diagnosing an auxiliary power unit fault

A method of diagnosing an auxiliary power unit fault in an aircraft having an auxiliary power unit and multiple sensors related to the auxiliary power unit, components thereof, and systems related thereto, the method comprising:

• receiving, during pre-flight or post-flight, a sensor signal from at least one of the multiple sensors to define a sensor output;
• comparing, by a controller, the sensor output to a reference value for the sensor output;
• and
• diagnosing, by a controller, a fault in the auxiliary power unit based on the comparison;
• and
• providing, by a controller, an indication of the diagnosed fault.