Pilot performance evaluation of tunnel-in-the-sky Head Mounted Display - Results of the 2nd HMD flight experiments with Dornier 228 -

The Institute of Flight Guidance of the Deutsches Zentrum fuer Luft- und Raumfahrt (DLR) in Bruns-wick has been researching a perspective display format called “pathway-in-the-sky”, which provides the pilot with navigation and guidance cue using a perspective image of the nominal trajectory. This display format is the result of the enhanced vision research program ADvanced VIsual system for Situation awareness Enhancement – PROtotype (ADVISE-PRO). Although the pathway-in-the-sky displays enables pilots to accurately fly difficult trajectories, these displays may drive pilot’s attention to the aircraft guidance task at the expense of other tasks particularly when the pathway display is lo-cated head-down. A pathway Head-Up Display (HUD) may be a viable solution to overcome this dis-advantage. Moreover, the pathway may mitigate the perceptual segregation between the static near domain and the dynamic far domain and hence, may improve attention switching between both sources. In order to more comprehensively overcome the perceptual near-to-far domain disconnect alphanumeric symbols could be attached to the pathway leading to a HUD design concept called “scene-linking”. In a preceding study of the ADVISE-PRO program, a scene-linked pathway concept was implemented on a monocular retinal scanning Head-Mounted Display (HMD) and tested in real flights on a Dornier (Do) 228 involving 5 test pilots. The flight test mainly focused at usability issues of the display in combination with an optical head tracker. The flight test results indicated limitation of the HMD usability in relation to readability, see-through capability, field of view and wearing comfort as well as the display symbology that has to be improved regarding attitude awareness, commencing turning cue and symbol overlap. Some pilots sometimes deviated from pathway with scene-linked pathway HMD. As a result of the study, improved new display symbology was implemented the HMD and a second series of flight experiments was conducted with Dornier (Do) 228 involving 4 test pilots in April 2006. The main purpose of the experiments was to evaluate the effectiveness of the proposed new HMD symbology. Flight scenario includes some climb, descent phases that have variable rate of climb, descent and path angle and turning phases that has left and right turn with different bank an-gles. The pilot tasks were evaluated comparing HMD navigation with Global Positioning System (GPS), i.e. without HMD, navigation. The study revealed the display symbology resulted in good flight path performance, helping the pilots with on-going and/or next pilot’s action and giving pilot the aware-ness of changing flight phases. However, some degraded flight performance relation to exceeding reference bank angle and difficulty to return reference trajectory in case of flying far off the track, high pilot workload regarding fully attended control in the “tunnel-in-the-sky” flight and degraded situation awareness, visual attention fixation and display clutter were observed with HMD flight in the pilot evaluation. Usability results are consistent with the latest human factors literature on the HMD regard-ing visual discomfort, headache and human visual capability limitation for visual focus, brightness ad-aptation and visual switching between HMD and Head-Down Display (HDD) and/or external view