ADVERSE ROTORCRAFT-PILOT COUPLINGS: MODELLING AND PREDICTION RIGID BODY RPC: SKETCHES FROM THE WORK OF ARISTOTEL

摘要

This paper is about the European Commission 7th Framework Programme project ARISTOTEL. This is the extended abstract. Today's high performance aircraft and rotorcraft are a product of the ever increasing demands of operator requirements. They are faster and more capable, but are consequently more complex than their predecessors. During their development and subsequent operation, it appears that both, engineers and pilots must be prepared to deal with unfavourable phenomena, so-called 'Aircraft/Rotorcraft Pilot Couplings' (A/RPCs). In the past frequently called 'pilot induced oscillations/pilot assisted oscillations' (PIO/PAO), A/RPC are defined as 'inadvertent, sustained aircraft oscillations as a consequence of an abnormal joint enterprise between the aircraft and the pilof. These undesirable oscillations may result in potential instabilities and limit cycle oscillations, degrading aircraft handling qualities and exceeding the vehicle structural strength limits. In 2010 the European Commission launched, under the umbrella of the 7th Framework Programme (FP7), the ARISTOTEL project (Aircraft and Rotorcraft Pilot Couplings - Tools and Techniques for Alleviation and Detection ), the aim of which is to advance the state-of-the-art of A/RPC prediction and suppression. With a duration of 3 years (2010-2013), and involving partners from across Europe, the ARISTOTEL project's objectives were to improve the understanding of present and future A/RPCs. Based on the experience of previous projects related to A/RPCs in both Europe and United States of America, the ARISTOTEL project has divided the A/RPC range of incidents into two categories (see Figure 1): 1) lower frequency range A/RPC or 'rigid-body A/RPC' involving adverse coupling phenomena dominated by helicopter low frequency dynamics i.e. flight mechanics characteristics, by the flight control system and by an active pilot 'keen' to fulfil the mission task by actively controlling the rotorcraft; 2) high frequency range A/RPC or 'aeroelastic A/RPC' corresponding to higher frequency dynamics, i.e. elastic airframe and main rotor blades modes, which involve more a passive pilot subjected to vibrations. Extended rigid body RPC underlines the importance of higher order rotor dynamics on the flight mechanics modelling for rotorcraft capturing vehicle-pilot coupling phenomena up to 3Hz. The goal of the present paper is to give an overview of the progress in the work performed by the ARISTOTEL project on understanding, modelling and predicting rigid body RPC.