Publication Date

Fall 2015

Degree Type


Degree Name

Master of Science (MS)


Aerospace Engineering


Kamran Turkoglu


Damaged vertical stabilizer, Differential thrust, H-infinity loop-shaping based robust control systems, Lateral/directional stability, Linear quadratic regulator, Model reference adaptive systems

Subject Areas

Aerospace engineering


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.