Abstract: A system for detecting the failure of a control system and its object includes a mathematical model of the control system and its object which continuously predicts the output of the object. An error signal is continuously calculated which is the difference between the model output and the actual output of the object. Error signals exceeding a predetermined minimum value or deadband are integrated; but the integral is reset to zero whenever the error signal value falls within a predetermined range indicative of normal steady state operating tolerances. If the value of the integral reaches a specified level before being reset to zero, a failure signal is triggered. This failure detection system can be made sensitive to relatively small error signals without triggering a false failure signal if the small error was the result of only a temporary problem or due to inaccuracies in model simulation.

Abstract: A thrust augmented twin spool turbofan engine system to control instability at high altitude, low Mach number conditions wherein an engine electronic control monitors engine inlet temperature, engine burner pressure and Mach number, and inhibits fuel flow to the outermost augmentor segment when the engine inlet temp drops below 25.degree. F, when engine burner pressure drops below 120 psia or when the Mach number drops below 0.4. When fuel flow to the outermost augmentor is inhibited, upmatch logic modifies the variable nozzle AJ trim signal closed 8% and the power level angle trim signal up 4.degree..