Advisor: Dr. Dimitri Mavris

Milestone: MS Thesis Final Examination (Defense)

Degree Program: Aerospace Engineering

Title: A Methodology to Assess Trimmability During Early-Stage Conceptual Design for Advanced Concepts with Multiple, Redundant Control Effectors

Abstract: The Blended Wing Body (BWB) is one of the most promising configurations for reducing the fuel consumption of transport aircraft, but several challenges remain before it can enter service. One of them is trimming the aircraft at low speed after an engine failure, a condition required for certification. This is hard to assess early in design. The BWB has many redundant control effectors that share the same surfaces. The tail volume coefficient, the conventional way to size a vertical tail, rests on statistics of tube-and-wing aircraft that do not apply to it. This thesis develops a methodology to assess the trimmability of aircraft with multiple, redundant control effectors during conceptual design. Trim in each low-speed condition is posed as a constrained control allocation problem. The deflection of every effector, together with the angle of attack, sideslip and bank angle, is chosen to satisfy the equilibrium equations with the least control effort, within the limits of each surface. The control margin this leaves, and the effector that limits it, measure how close the aircraft is to losing control authority. The aerodynamic loads come from a vortex lattice model with empirical corrections for the control surfaces. The methodology is verified on the NASA Common Research Model. It is then applied to size a twin, canted vertical tail for a BWB by trimming 750 tail designs in the one-engine-inoperative takeoff and in crosswind. Without a tail, the BWB cannot be trimmed after an engine failure. The fin area is the most important design variable, followed by the cant angle, which trades margin in one condition against the other. Above a certain fin size the margin no longer grows. It is then limited by the roll authority of the outboard ailerons in crosswind, not by the tail. The volume coefficient of conventional transports gives a fin several times larger than the smallest tails whose margin is close to the best, so the conventional method oversizes the BWB tail. The methodology is intended as a module for conceptual design and multidisciplinary design optimization frameworks.

Date and time: 2026-11-25, 2:00 pm - 4:00 pm

Location: CoVE

Committee:
Dr. Dimitri Mavris (advisor), School of Aerospace Engineering
Dr. Jimmy Tai, School of Aerospace Engineering
Dr. Daniel Schrage, School of Aerospace Engineering
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