human factors issue associated with heads-up display (HUD)

What is HUD and the functions

Theoretically, automation is designed to reduce the number of operational human errors that made from both physical and mental performance. Although the replacement of automation from

operational performance is increasing dramatically in the aviation industry but the total elimination of humans is still not feasible. If the concept of automation used appropriately, it could be a

valuable tool to reduce physical and mental workload, and even more, the head-up display (HUD) is one of such design (Wells & Rodrigues, 2003). An aircraft flying with HUD simply means that

the “head-up” guidance will be provide to the pilot through on a transparent screen, the guidance commonly including flight guidance, air data, navigation, airspeed and so on. The picture of modern

HUD showing on Figure 2 . The concept of HUD provides all available information which virtually in the flight computer, in order to reduce the shift from looking at the flight computer and outside

window (Aviation glossary, 2010).

(Firgure 2 image embedded from aviation glossary on 01 September 2010)

Human factors issue associated with head-up display

The concept of head-up display has gain widely acceptance being used for military aviation and seems spreading to the commercial aviation (Stuart & McAnally & Meehan, 2005). There are many

applied researches focus on exploring the human factors issue associated with the basic “head-up” display, the phenomenon of “attention capture” which pilots could pay more attention on the

events, and reduce the needs of scanning a number showing on the head-down instrument panel. Not only reduce the risk of workload management but also the increasing the situational

awareness by providing conformal, scene-linked symbology depicting the centreline and edges of the taxiways and runways (AndFoyle & Adre & McCann, 1996). Some aviation experts hypothesized

that if pilots were allowed to maintain their spatial orientation the workload and situation awareness may highly reduced compare to the basic “head-down” display which focal vision and active

interpretation are required to pilots.

Perceptual factors and attentional factors

Perceptual factors:

There are two major elements of perceptual factors within HUD; first one is collimation of the image, the main advantage of collimation is the reduction of the eye movement

from looking at external environment and display. The second element is the size of the symbols, some research has shown that the eye movements can be reduced by presenting symbology in a

heads-up display. However, it has been widely argue because the size of symbology is too small which makes the eye movements necessary.

Attentional factors:

The phenomenon of “change blindness” would most occur when rapid eye movements, or the interval is too short. A number of studies demonstrated that the changes from

external environment could be missed during “change blindness”. The potential advantage of HUD is the less possibilities of the phenomenon occur, due to less eye movements.

Failure of parallel attentional or efficient switching – attentional capture

One of the potential drawbacks of HUDs is the problem of the display may capture attention, where is more relevant and seems to be an unavoidable factor in the HMDs. Attentional capture has been

most found in unexpected events, for instance, pilots could simply land an aircraft by using virtual symbology and do not need to pay attention to the external environment, because the real runway

can be overlapped from virtual symbology, in this case runway incursions may happened during simulated instrument landing.

The research of Fischer, Haines and Price (1980, p30) has found that “several pilots admitted that from time to time they caught themselves totally fixating on the symbology, oblivious of anything

else, and had to consciously force their attention to the outside scene.” In the future designation of HUDs, the key concept understands the word of “attention” in order to reduce the possibility of

attentional capture (Stuart & McAnally & Meehan, 2005).

(Figure 3 showing the screen of HUD, embedded from blogspot, on 01 September 2010)

How to avoid attentional capture?


Some aviation experts argued if the HUD can segregated from the external environment, that the attentional capture could be avoid, because the spatial can be selected when the single field were

made from the combination of display elements and the outside scene.

Peripheral symbology

The display of information could provide parallel attention by segregating perceptual modes. This is because some of the information can be seen in peripheral vision, which allows pilots to keep

focuses on the important feature, and search for other elements without deliberately look away.

Multiple resources and workload

The visual attention is divided into multiple tasks in some modern theories. North (1977) has provide some evidences shows that to perform two different type of tasks at the same time is more easier

than perform two same type of tasks. Less attention will be made when pilots suffering high workload.

Training and practice

Stuart & McAnally & Meehan (2005), suggested that the ability of work efficiency in parallel can be affected by the factor of training and practice. They considered that the outside environment can be

viewed while operating HUD in parallel, if more trainings provided to pilots.

(Video shows the F16 HUD, embedded from Youyube, on 11September 2010)


Although there has been plenty of theoretical and applied research found that heads-up display may provides more safety and work efficiency than heads-down display, but neither of those research

has been convincingly demonstrated to be universally true (Stuart & McAnally & Meehan, 2005). The potential advantages of HUD has shown in both perceptual and attentional factors, but the

potential drawbacks which are still needs further training and practices to be done to ensure cockpit safety.

Further information on Current and Future development of HUD:

New heads-up display helmet for F35 fighter:

Heads-up display for air traffic controllers:

The super cockpit:


Aviation glossary. (2010). HUD-head up display. Retrieved 06 September 2010. From:

Foyle, D, C & Andre, A, D & McCann, R, S & Wenzel, E & Begault, D & Battiste, V. (1996). //Taxiway navigation and situation awareness (T-NASA) system: problem, design philosophy and description of

an integrated display suite for low-visibility airport surface operations//. SAE transactions: Journal of Aerospace, 105, 1411-1418.

Skybrary. (2010). ICAO SHELL Model. Retrieved 06 September 2010. From:

Stuart, W, G & McAnally, I, K & Meehan, W, J. (2003). Head-up displays and visual attention : integrating data and theory. In Wells, T, A & Rodrigues, C, C. (2003). Commercial aviation safety (4th

eds). New York : McGraw-Hill, Inc. Pp25-46

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