Tilt Rotor Pitch/Flight-Path Handling Qualities

Interest in so-called ‘bare-airframe’ handling qualities stems from the need to quantify the level of degradation following failures in the control augmentation functions. For tilt rotor aircraft the issue is complicated by the lack of dedicated criteria and supporting test data. The University of Liverpool is a member of a team working to fill the criteria gaps and to develop a database of piloted simulation results, in support of the design of the European civil tilt rotor. During one of a series of piloted trials, the Cooper-Harper handling qualities ratings did not show good agreement with the predicted pitch/flightpath handling qualities analysis for the aircraft in aeroplane mode. Further investigation revealed that this was due to a large pitch rate overshoot, leading to a correspondingly large pitch attitude dropback in attitude/flight-path capture tasks. Current fixed-wing handling qualities criteria such as CAP and bandwidth need supplementary dropback parameters to accord with pilot opinion. This paper reports progress in the development of more unified short period mode handling qualities criteria, which properly integrate the pitch dropback phenomenon. Handling qualities boundaries are proposed for both flightpath and pitch attitude tracking requirements.