Handling qualities studies into the interaction between active sidestick parameters and helicopter response types

Active inceptors offer great potential for improving the handling qualities of fly-by-wire rotorcraft. In a cooperative research effort, the DLR Institute of Flight Systems in Germany and the US Army Aeroflightdynamics Directorate (AFDD) conducted several in-flight experiments to study the influence of the dynamic characteristics (natural frequency and damping) of the cyclic stick on the overall handling qualities of a rotorcraft. Experiments were performed looking at sidestick (DLR) and centerstick (AFDD) inceptors for Rate and Attitude Command response types. The results of two different experiments are presented in this paper. The first experiment evaluated the roll handling in forward flight and was only performed with a sidestick inceptor. The task used in this experiment was designed during exercises of the Empire Test Pilots’ School (ETPS) on DLR’s Flying Helicopter Simulator EC135 ACT/FHS. ETPS also contributed to the optimization of the static sidestick characteristics that were used for the testing. The second, more comprehensive experiment, evaluating ADS-33 Hover and Slalom Mission Task Elements, was performed both with a sidestick and a centerstick allowing a direct comparison of both types of inceptors. Regression analyses were performed on the collected pilot ratings to gain a systematic insight into the preferred stick characteristics for the different inceptor and response types. The test results consistently suggest that the preferred characteristics are best described by a first-order response model.