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The major emphasis in Fault-Tolerant Flight Control (FTFC) System is towards Fault Detection and Diagnosis (FDD). FDD is used to isolate the aircraft’s fault and provides information for reconfiguration mechanisms to recover the system from a faulty state. In this paper, based on the classification of faults in actuators and sensors, FTFC system design methods are proposed while retaining the existing flight control system (FCS) architecture. Fault scenarios broadly can be classified as one that can be identified and addressed using a sensor or actuator redundancy management (RM) algorithm and the other that need to be identified using real-time system identification techniques. The reconfiguration carried out for the former is termed as passive FTFC, whereas the latter as active FTFC.

Aerodynamic database update from the flight tests using system identification techniques is a crucial tool for the development of control laws and high fidelity simulators. For the certification of aircraft under test, aero-database needs to be validated from flight tests throughout the flight envelope and also to certain levels beyond the envelope boundaries. Validation of aero-database close to envelope boundaries entails additional complexities which necessitates careful handling of flight data identification and update process. This paper discusses the approach adopted for aero-database update and flight clearance, followed by a discussion on the issues relevant in the extreme flight test regimes, such as, flow angle accuracy at higher angles-of-attack, center-of-gravity variation with fuel pitch angle for high-g maneuvering conditions and inaccuracies in Mach number at transonic speeds.