Pilot model development and human manual control considerations for helicopter hover displays

Abstract

Head-down hover displays and instrument panels theoretically provide all necessary flight data information to control low-speed helicopter manoeuvring. However, past experiments have shown that head-down displays can incur high workload, control instability, and even loss of control when used as the sole flight data source. This paper investigates the reasons for this instability incurred by replacing good outside visuals with a head-down hover display and an instrument panel. A pilot model based on crossover theory is developed for a linear six-degree-of-freedom B0105 helicopter model. Utilising a target trajectory based ?-theory and assuming perfect information availability, the developed model can perform the required manoeuvring task with a control time-delay stability margin of 0,15s (with SAS) or 0,17s (without SAS). Then, the actual information availability based on human perception methods and limitations is discussed. A pilot-in-the-loop experiment in the SIMONA Research Simulator qualitatively validates the developed pilot model for good outside visuals. However, the pilot model does not capture the added difficulties of having to utilise the hover display and instrument panel instead of good outside visuals; during the experiment, the task was impossible to complete with only these displays. This is likely caused by an increase in control time-delay, which in turn is caused by the loss of peripheral and flow field information, a more abstract information representation compared to good outside visuals, and the fact that the pilot now needs to scan multiple displays to acquire all necessary flight state information. Improving head-down hover display symbology and scaling factors might rectify some, but probably not all of these effects.