Rotorcraft pilot coupling susceptibility accompanying handling qualities prospects in preliminary rotorcraft design

Due to expensive and risky Rotorcraft-Pilot Couplings (RPC) that can develop during flight testing phases of any new prototype aircraft, it is beneficial to crosscheck the RPC susceptibility of the vehicle as early as possible during the design process. One of the objectives of the European project ARISTOTEL (2010-2013) is to provide guidelines to designers and simulator programs to reveal RPC aspects of the vehicle to be designed. First, a methodology to assess the sensitivity of Handling Qualities (HQs) and RPCs to design parameters is presented: a design envelope is created around a baseline configuration while considering various parameter constraints and simulation models in state space representation are developed. Second, three PIO criteria are applied to predict the susceptibility to PIO of a set of configurations belonging to the design envelope. Assessment based on Bandwidth-Phase Delay (BPD) reveals that the lowest tip speed values and the lowest disc loading values have the best HQs. Category II PIO assessment based on Open Loop Onset Point (OLOP) shows that lowest actuator rate limits are obtained for the configurations with high tip speed values and high disc loading values. PIO prediction based on the newly developed Predictive Phase-Aggression Criterion (PRE-PAC) shows that results for models tested reflect those of the BPD criteria.