Application Of The Westland CRFD Program To Total Helicopter Dynamics

The Vestland CRFD (Coupled Rotor-Fuselage Dynamics) program is a module providing modal degrees of freedom within the Coupled Rotor-Fuselage Model, the development of which is the subject of collaborative research with the Royal Aerospace Establishment, UK, for the prediction of rotor loads and fuselage vibration in both level and manoeuvring flight, as well as application to stability, performance and handling qualities. Applications of CRFD are described, to examples of total dynamic systems involving combinations of significant sub-systems with the main rotor. In particular, predicted natural frequencies and mode shapes of a rotor-fuselage model are presented, and compared with results from a more conventional approach which considers the rotor and fuselage separately. The form of the results is supported qualitatively by flight test measurements. Results suggest that effects of the rotor on fuselage. modes and of hub motion on rotor modes are both significant. The contributions of other components, namely the transmission system, control system and blade lag dampers to the rotor dynamic characteristics are also assessed by application of CRFD and consideration of test measurements.