This thesis investigates the utilization of differential thrust to help a
commercial aircraft with a damaged vertical stabilizer regain its lateral/directional
stability. In the event of an aircraft losing its vertical stabilizer, the consequential
loss of the lateral/directional stability is likely to cause a fatal crash. In this thesis,
the damaged aircraft model is constructed, and the lateral/directional dynamic
stability and frequency domain analyses are conducted. The propulsion dynamics of
the aircraft are modeled as a system of differential equations with engine time
constant and time delay terms to study the engine response time with respect to a
differential thrust input. The novel differential thrust control module is presented to
map the rudder input to differential thrust input. Then, the differential thrust
based control strategies such as linear quadratic regulator (LQR), model reference
adaptive system (MRAS), and H∞ loop-shaping based robust control system are
proposed to be utilized to help maintain stability and control of the damaged
aircraft. For each type of control system design, robustness and sensitivity analysis
is also conducted to test the performance of each control system in the presence of
noise and uncertainty. Results demonstrate successful applications of such control
methodologies as the damaged aircraft can achieve stability under feasible control
efforts and without any actuator saturation. Finally, a comparison study of three
control systems is conducted to investigate the merits and limits of each control
system. Overall, the H∞ loop-shaping based robust control system was found to
have the most remarkable results for stabilizing and saving the damaged aircraft
