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Scanning the head-up display

By Captain Matthew Gray
Commercial (Qantas Airways) and Military (RAAF) Pilot and Instructor, ret.

Bombardier Global 7500’s Vision flight deck with dual HUDs based on Collins Aerospace Pro Line Fusion avionics suite.
Head-up displays (HUDs) are becoming more commonplace, but is HUD use intuitive, or do pilots need specific eye scan training? Can eye-tracking technology assist the pilot and the instructor? The HUD glass, called a combiner, presents critical flight information projected with unique features that make it distinct from the primary flight display (PFD).

One of the great benefits of the HUD is that the information is presented in the pilot’s eyeline, allowing him/her to access this info while keeping a view of the outside world.

For example, a HUD is particularly beneficial when landing with reduced visibility, as pilots adjust their focus to look at the runway through the HUD without making significant changes to their scan.

New technology usually comes with questions on how to use it, and the HUD is no exception. Pilots derive up to 90% of information from the instruments by sequentially scanning the flight instruments and cognitively processing what they have seen.

So, does the pilot adopt a different HUD scan pattern compared to the PFD? If this is the case, how different is the scan? Is it important? Using the HUD requires training and line flying experience, but can targeted training accelerate pilot skill acquisition on the HUD? Is the HUD easier to use, or does it require different cognitive processing? There are significant differences between the information displays of the HUD and PFD.

The HUD is a monochromatic presentation in green, whereas the PFD presents information in blue and brown coloration. The field of view (FOV) is much wider on the HUD – up to 34º versus 12º in the PFD. And the PFD depicts aircraft attitude, while the HUD shows flightpath information.

The wide FOV has benefits for viewing the outside world, particularly in a crosswind, where the runway and projected information can still be seen. However, the pilot now has a much greater area to scan to get the information that is needed. Knowing where to look, and when, means the eyes have to travel further.

In addition, some HUDs have up to 4 different modes. “Primary” mode shows a more traditional style of display, with speed and altitude info on the edges of the display. “Decluttered” mode simplifies some information into digital readouts, but often the information is presented in a slightly different location, which means the pilot needs to adjust the scan to these different and sometimes dispersed locations.

Both the HUD and PFD have different symbology. The central display of the HUD is the flightpath vector (FPV) and guidance cue. The FPV shows the path of the aircraft, in contrast to the PFD, which displays aircraft attitude.

Furthermore, the FPV/guidance cue combination is very sensitive, and appears to the pilot as exaggerated movement in the combiner. Meanwhile, the PFD attitude display is far less sensitive and can lead the inexperienced on the HUD to chase the guidance cue and overcontrol the aircraft.

Pilots may have a preference between the HUD and PFD, particularly when prioritizing aircraft attitude. This may result in a “split” scan between the PFD and the HUD, depending on the maneuver.

As an example, the PFD attitude display has a more realistic horizon display. Some pilots prefer to use the PFD at selected times, since it is perhaps more intuitive. All these factors combined require the pilot to recognize and understand the differences, and suggest a different scan technique between the HUD and PFD. Qantas Airways flies Boeing 787-9s fitted with dual HUDs.

Since many pilots transitioning to this type have never operated a HUD before and therefore are not aware of these scan differences, Qantas has fitted a Seeing Machines device to its 787-9 simulator which tracks the eye movements of trainee pilots in real time, enabling the instructor to provide feedback to the trainee.

The combination and correct operation of these technologies has the potential to unlock a range of benefits that have not previously been available. Qantas is examining how this combination may influence the speed of skills acquisition, the possibility of optimized training duration, and the benefit to the instructor in terms of gaze position and analysis.

Instructors are critical to both flight training and the assessment of ongoing pilot performance. The simulator environment is complex and very busy, with the highly-trained instructor bringing enormous experience into a training session.

The eye tracker will provide an accurate position of the pilot’s eyes, and Qantas is focusing on how this technology can be used to assist the flight instructor with an additional visual perspective to assist performance analysis.

The unique Boeing 787-9 simulator and eye-tracking combination is providing a new and exciting path in 21st-century flight training for current and future pilots, and for the instructors who will train them.

GrayMatt Gray trained as a pilot and instructor in the Royal Australian Air Force. He spent 32 years with Qantas flying Boeing 747s, and flying and examining on the Boeing 767, 787, and 737. He holds a master’s degree in aviation and is currently doing a PhD in pilot eye scan behavior.