Head-Mounted Display – Evaluation in Simulation and Flight Trials

Pathway-in-the-sky displays enable pilots to accurately fly difficult trajectories. However, these displays may drive pilots’ attention to the aircraft guidance task at the expense of other tasks particularly when the pathway display is located head-down. A pathway HUD may be a viable solution to overcome this disadvantage. 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’. A scene-linked pathway-predictor concept was implemented on a monocular retinal scanning HMD in combination with an optical head tracker and tested in flight on a Do228. The display concept had been tested in the DLR’s generic cockpit simulator where curved CAT I approaches were investigated in a high fidelity environment as well as a part task simulation had been developed to provide results about the benefits of ‘scene-linking’. Completing the set of experiments two different flight tests have been conducted. The flight tests were limited to 5 test pilots in the first and 4 test pilots in the second study. The first mainly focused at usability issues of the display and its peripheral equipment. Visual and instrument departure and approach tasks were evaluated comparing HMD navigation with standard instrument or terrestrial navigation. The study revealed limitations of the HMD regarding its see-through capability, field of view, weight and wearing comfort that showed to have a strong influence on pilot acceptance rather than rebutting the approach of the display concept as such. Additionally to the precision analysis the pilot’s behavior in altitude tracking as well as their timing pattern of turning into and out of curves was investigated. It was found that pilots had difficulties during segment transitions while using the HMD. In a second flight test a redesigned pathway-predictor-director concept was implemented. The trials were designed as a high workload curved departure and approach task. The results exposed more or less the same difficulties regarding the usability of the display but showed a much better pathway following especially during segment transitions