Patent ID: 7487029

Claim:
A method of monitoring the performance of an aircraft-mounted gas turbine engine, the method comprising the steps of: selecting at least one engine parameter to monitor, wherein the engine parameter is indicative of a deterioration condition of the engine as the engine is operated; selecting an engine at-limit point corresponding to the parameter; selecting an engine warn point corresponding to the at-limit point, where the warn point is different than the at-limit point and provides an operating margin for the parameter between the warn point and the at-limit point; monitoring the engine parameter; determining a difference in the engine parameter between an actual value and an expected value; adjusting a counter value based on the engine parameter actual-expected difference; comparing the counter value to the warn point; setting a warning flag indicative of an impending maintenance condition when the counter value meets at least a first criterion based on said comparison; and indicating to an operator of the aircraft that the warning flag has been set.