Optimal tiltrotor aircraft operations during power failure

The most dangerous time for civil tiltrotor aircraft is during takeoff and landing procedures. Potential and kinetic energy are the lowest at these times and the power requirement is high. Because of the danger and because of their one engine inoperative (OEI) options, they must satisfy specific requirements during takeoff and landing. These requirements are determined by the FAA through flight test certification, a time consuming, costly, and potentially dangerous process.; Optimal control theory has been shown to give results consistent with flight tests. Using optimization in conjunction with flight tests can reduce their cost and improve their safety. Optimization can be used to determine performance limits, flight procedures, and design sensitivities. These results can be helpful as a benchmark for flight tests and as a design tool.; This thesis investigates the use of trajectory optimization as a method to study civil tiltrotor aircraft flight during power failure situations. A longitudinal rigid body tiltrotor model is first developed. Tabular aerodynamic data from the XV-15 Research Tiltrotor Aircraft are fit to smooth functions to realistically represent tiltrotor aerodynamics. Numerical methods are investigated, and a direct approach is implemented. Steady-state analysis is conducted to determine initial conditions arising from flight procedures. Numerical simulation is conducted to account for pilot response delay. Height-Velocity diagrams are theoretically calculated to determine the region of unsafe height and velocity conditions for both OEI and AEI situations. Problems are also formulated and solved to study Category A “type” OEI takeoff procedures for both runway and confined area operations. Sensitivity analyses are conducted to investigate the sensitivity of solutions to uncertainties.; Exact procedures for civil tiltrotor aircraft have not yet been decided. One of the key issues during engine failure is the rotor speed and its control. The rotor speed governor control system can be disengaged to use the energy in the rotors for thrust during engine failure situations. There is however a danger of the blades reaching stall. Results of this thesis are calculated both with and without the use of rotor speed energy to study the its affect on performance.