Six Degree of Freedom Flight Dynamics Model of a Tilt-Wing Aircraft with Trim and Stability Analysis

Abstract

One of the biggest trade-offs in aviation is between a vehicle’s ability to take-off and land vertically and its efficiency in cruising flight. The recent drive for electric vehicles creates space to consider new solutions to this trade-off. Tilt wing aircraft offer significant advantages in vertical take-off and landing (VTOL) operations due to their versatile design. One of the difficulties in designing configurations with little historical data is that they are difficult to predict. The challenge of formulating a flight dynamics model valid through the transition phase from vertical to horizontal flight is undertaken in this study. This research aims to investigate the tilt wing aircraft behaviour through the wing tilt transition, as well as the stability characteristics. A six degree of freedom model implemented on the Canadair CL-84 Dynavert compares favourably to flight test data, albeit with low-fidelity especially around hovering flight. The likely cause is the simple rotor to wing slipstream interference modelled. The stability characteristics reveal large spikes in positive stability of the longitudinal derivative Cmu and Cmw due to the behaviour of the wings and the slipstream effect on the horizontal tail, with normalized values up to 5.5 and 150 respectively. Some unstable flight configurations are found within the flight envelope at 41 degrees and 28 degrees due to wing stall.