FLIGHT CONTROL-SYSTEM MODE TRANSITIONS INFLUENCE ON HANDLING QUALITIES AND TASK-PERFORMANCE

The Flight Research Simulator of the University of Toronto Institute f or Aerospace Studies was modified to represent a fly-by-wire helicopte r with a digital flight control system (FCS) and a side-arm controller . Three FCS modes were employed (in addition to the basic airframe ver sion of the helicopter): rate command/attitude hold, attitude command/ attitude hold, and translation rate command. A smooth FCS mode selecti on algorithm was developed and successfully tested. Three types of mod e transition were evaluated: 1) transition selected manually by the pi lot, 2) transition selected by the FCS accompanied by an audio warning , and 3) transition initiated without warning by a system failure. The pilot/helicopter response to mode transitions was studied for formati on flying and precision hover. Both normal- and failure-induced transi tions were investigated by a group of 9 evaluation pilots. The results were obtained in the form of Cooper-Harper handling qualities ratings (HQR) and stationkeeping performance measurements. It was found that for the present mode selection algorithm, the type of mode transition from the initial FCS mode to the final FCS mode (i.e., within a mode p air) did not significantly influence the experimental results. However , the mode pair itself was found to influence both HQRs and performanc e. The mode pairs producing most of the significant effects on HQR and performance contained as one of their elements, the FCS mode having t he poorest handling qualities. For mode pairs producing significant ef fects, it was found in some instances that the mode in place before tr ansition actually influenced the HQRs and performance after transition .