Retrospective cost model refinement for aircraft fault signature detection

Retrospective cost model refinement is applied to on-board identification of a linearized aircraft model, and it is shown that with altitude and airspeed measurements, the aircraft stability derivatives can be estimated. These estimates are then compared to the nominal values at the same flight condition. The comparison between identified and nominal stability derivatives provides a fault signature. We also describe a methodology for updating the flight envelope based on identified stability derivatives.