Design of a manual roll control for a trainer aircraft

Turbo-prop trainer aircraft are designed to offer a cost effective alternative to military jet training aircraft. As a design objective of such aircraft, the Military Specifications of handling qualities applicable to jet trainer aircraft should be satisfied. However, in line with the philosophy of low purchase and maintenance costs, the added complexity of a hydraulic power boost system for the control surfaces cannot be accepted. The objective of this work was to optimise the roll control system so as to achieve an optimum of ergonomic design combined with the performance goals of the military specifications, using purely aerodynamic means of balance. Relevant British and American civilian and military specifications and simulator studies have been reviewed to select the detailed design objectives of the study. The American Mil. Specs. were selected as a baseline, with modifications derived from the results of simulator experiments. A Baseline Aircraft was selected on which to apply the optimisation. The highest performance turbo-prop trainer of the time was selected. A mathematical model of the roll response was derived for the extrapolation of flight test data and to allow an evaluation and optimisation of the critical aileron parameters. A description of the model and comparison to flight test results is given in the text. Literature was searched to examine the availability of information for the aerodynamicist to conduct such an optimisation. The results were disappointing, showing that very little work had been conducted on aileron design since the late 1940's and that the work of that time was not entirely relevant to today's requirements. Because the literature search was not conclusive, further flight tests had to be conducted on the Baseline Aircraft to investigate different forms of aerodynamic balance. The performance of the ailerons and some of the problems encountered in their usage are reported in this thesis and forms a data bank from which to conduct the optimisation. Finally, a selection process is conducted to size the aileron to satisfy the performance goals and to select the best aerodynamic balance to achieve the ergonomic goals. The achieved performance is summarised and compared with the original design goals. It is concluded that the optimised aileron is capable of achieving the design goals over the major portion of the design envelope. The design optimisation process is not limited to turbo-prop aircraft but can be applied to any high performance aircraft with reversible controls.