Dr Douglas Thomson, Dr Stewart Houston
Following a spate of unexplained fatal accidents involving light gyroplanes between 1989 and 1991, the UK Air Accident Investigation Branch funded a research programme at the University of Glasgow to improve the understanding of aerodynamics and flight mechanics of gyroplanes. At the outset of the research programme in 1993, the aim was to establish the general stability characteristics of a gyroplane and then determine which aspects of its design were most influential on its dynamic characteristics. The primary output of the research with the CAA was an engineering mathematical model of the aircraft so that design features, changes and hypothetical situations could be examined in safety. The mathematical model, RASCAL, is a high-order, high-fidelity simulation previously developed at the University of Glasgow to investigate helicopter-related problems.
Ongoing research checked the fidelity of the model against flight test data gathered during a number of campaigns with two fully-instrumented light gyroplanes. The research demonstrated that the vertical location of the centre of mass in relation to the assumed propeller thrust line is the key parameter leading to aircraft instability. This was a particularly important finding since the incorporation of more powerful engines and larger propellers into gyroplane design had resulted in the propeller being raised to ensure clearance with the craft’s keel, thereby raising the centre of mass. The key output was the 2008 report to the CAA (http://www.caa.co.uk/application.aspx?catid=33&pagetype=65&appid=11&mode=detail&id=4184) recommending gyroplane design changes including lowering the keel. The report’s findings were integrated into CAA’s current British Civil Airworthiness Requirements (BCAR) Section T: Light Gyroplanes, legislation which governs the safety of gyroplanes.
As well as directed research for CAA, researchers in Glasgow have used the aircraft, and the data it produced, in studies of autogyro handling qualities, rotor aeroelastic modelling, validation of rotor inflow models, and currently, autogyro control studies.