High Angle-of-Attack Departure Criteria for High Agility Fighters

Fighter agility is comprised of both maneuverability and controllability. Inadequate controllability can limit the agility potential through a combination of reduced control power and/or a lack of bare airframe departure resistance. Typical departure criteria include only static aerodynamic terms and are not adequate predictors for modern fighter aircraft performing high-agility maneuvers such as loaded roll motions. The development of a reliable departure resistance design criteria for highly agile, highly augmented fighter aircraft and the exploration of validation methods using 6-DOF computations and comparisons to existing flight data from the F/A-18 HARV is the subject of this study The innovation in Phase I is the inclusion of appropriate dynamic aerodynamic terms and the effects of flight control system inputs to evaluate the departure characteristics of a highly augmented high agility aircraft. Phase I will develop the enhanced criteria and demonstrate methodologies for validation. Phase II will accomplish the validation with flight test data from NASA Ames/Dryden for the F/A-18 HARV, x-31 and X-29A aircraft. The expected payoff will be a validated tool to evaluate agility and departure tradeoffs in preliminary design that will result in significant cost and time savings in the development of new configurations and will provide an additional means of evaluating the performance characteristics of augmented aircraft prior to flight.