Validation and Update of Aerodynamic Database at Extreme Flight Regimes

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. Results from flight data identification of a high performance aircraft with relaxed static stability are presented to highlight the impact of each of these factors on aero-database update.