Integrated Flight Control Design and Handling Qualities Analysis for a Tiltrotor Aircraft

Open Access
Yomchinda, Thanan
Graduate Program:
Aerospace Engineering
Master of Science
Document Type:
Master Thesis
Date of Defense:
Committee Members:
  • Joseph Francis Horn, Thesis Advisor
  • Model Inversion Control Law
  • Flight Control
  • Aircraft Handling Qualities
Tiltrotor aircraft present a challenge for flight control designers and handling qualities engineers. Achieving consistent handling qualities throughout an operational flight envelope is difficult since the aircraft’s flight dynamics change significantly at different operating conditions (e.g. speed, attitudes, etc.) and configurations (e.g. helicopter mode, conversion mode or airplane mode). The requirement to meet both helicopter and fixed-wing flying qualities specifications always results in substantial cost and time. Development of integrated methods for flight control design and handling qualities analysis could greatly enhance the future of tiltrotor aircraft. In 2008, the University of Liverpool conducted a competition on flight control design for tiltrotor aircraft. The goal is to deliver level one handling qualities across the flight envelope for a predefined search and rescue (SAR) mission for the XV-15 tiltrotor aircraft. The competitors were provided linear models of XV-15 simulation model and specifications together with the following tasks to submit: • The predicted bare-airframe handling qualities • A flight control system achieving predicted level one handling qualities • A full report of the flight control design and handling qualities results This thesis will present the integrated methodology of model following based flight control design and handling qualities analysis developed at the Penn State University and the test pilot evaluation conducted at the University of Liverpool. In this research, a linear model analysis was developed in MATLAB to evaluate predicted handling qualities based on assigned specifications and the dynamic model. A controller was designed to meet level one handling qualities and also have maneuvering stability. The results of predicted handling qualities were determined and showed the control concept was effective. A few criteria showed degraded handling qualities below level one. These criteria were investigated and discussed. The pilot evaluation showed that the model following / inversion controller with airspeed-scheduled inversion model was effective in delivering level one handling qualities to the tiltrotor aircraft in helicopter configuration.