Patent ID: 7702447

Claim:
A method for distinguishing between gas turbine engine case cooling (TCC) and high pressure turbine (HPT) performance faults comprising: monitoring a plurality of gas path parameters of an operating gas turbine engine so as to acquire in-flight gas path data samples from said gas turbine engine, said in-flight gas path data samples corresponding to a predetermined number of engine parameter percent Δs from nominal; inputting said in-flight gas path data samples into a computer; determining if a percent Δ shift has occurred in a gas path engine parameter percent Δ; if a percent Δ signature shift has occurred, determining whether a shift ΔΔ is from an HPT or TCC performance fault, said shift ΔΔ determining step comprising: extracting exhaust gas temperature shift magnitudes from the predetermined number of engine parameters; converting said exhaust gas temperature shift magnitudes from percent to degrees; obtaining take-off EGT margin calculations for present flight time and previous flight time; calculating an exhaust gas temperature differential between in-flight and take-off exhaust gas temperature margin calculations, wherein the exhaust gas temperature differential is the difference between the change in exhaust gas temperature margin and the exhaust gas temperature shift magnitudes; calculating a TCC event likelihood and a non-TCC event likelihood; obtaining a mean and standard deviation for gas turbine engines not experiencing TCC faults; obtaining a mean and standard deviation for gas turbine engines experiencing TCC faults; and calculating an exhaust gas temperature difference between cruise and take-off conditions comparing said calculated TCC event likelihood to said calculated non-TCC event likelihood; and declaring a TCC performance fault if the calculated TCC event likelihood is greater than or equal to the calculated non-TCC event likelihood, wherein calculating the likelihood of a TCC or non-TCC event further comprises: obtaining a mean and standard deviation for gas turbine engines not experiencing TCC faults; obtaining a mean and standard deviation for gas turbine engines experiencing TCC faults, and calculating an exhaust gas temperature difference between cruise and take-off conditions.