LOOKOUT
MET INSIGHT
EYE SEE...
You’ll probably know much of thiS already, but it’s worth a quick reminder of how the eye works to understand why a regulated scan is good.
where colliding aircraft have a relative bearing constant to each other until impact. The subjective effect of this is that the collision threat remains in the same place on the canopy (stationary) unless you move your head to stimulate the eye’s ambient visual system (the ‘cones’ in the periphery of the retina) that relies on an object’s motion in the outside world to attract the focal system’s attention. An unfortunate consequence of ‘constant relative bearing’ is that no other aircraft that the pilot has ever seen will have possessed the same characteristic as that of a colliding one…
So moving your head, relative to the canopy or windscreen, is an important aid to the lookout front and side and, of course, it helps to take out the blind spots such as canopy furniture, pillars, high/low wings etc.
A quick bit more science shows that as a collision threat approaches, its size on the retina roughly doubles with each halving of the separation distance, so colliding aircraft stay relatively small until shortly before impact when, as pointed out earlier, it all happens rather quickly. This presents a bit of a challenge even if you do perform a good ‘lookout’, and underlines the importance of apportioning the correct
amount of time for a systematic and repetitious scan pattern. One of the best ways to lookout is to use a series of small eye and head movements with intervening rests, the latter being the only time when the outside world is really being interrogated. Carrying out regulated scans might sound a bit formulaic and, let’s be honest, boring, but they do work much better than looking ‘here, there and everywhere’.
That said there’s no one technique that suits all pilots and it’s important to have a comfortable and workable scan, although horizontal back-and-forth eye movements seem preferred by most. First, you obviously need to concentrate on the most critical areas at any given time, which in normal flight are the areas at least 60° left and right of the intended flight path. This doesn’t mean the rest of the visual area should be forgotten, at least 10° above and below the projected flight path also needs interrogating.
One of the simplest and effective scans is the rule of threes as detailed in the graphic. No one’s immune to a mid-air collision,
but keeping in-cockpit time to a minimum, understanding of the limitations of vision, collision geometry and using visual scanning techniques will help to avoid one.
Essentially, the lens focuses light to form an image on the retina which is made up of more than 100 million light sensitive cells that convert the light (image) to electrical impulses which are then sent to the brain. So to develop an effective lookout it’s important to understand the distribution and function of the retina’s two types of cells, rods and cones. What you see might seem like one big
picture, but detailed interrogation of the world is only provided by rods in the central, focal, part of the visual system, an area no larger than a thumbnail held at arm’s length. Not only is this area small compared with the whole visual field, but an image falling on this portion of the retina has to be stable and the pilot’s attention directed towards it for active interpretation. Meanwhile, the cones in the periphery
of the retina are responsible for the ambient visual system that relies on an object’s motion in the outside world to attract the focal system’s attention, so movement is a very important attention-getter.
With no visual cues to attract the LOR LOR LOR LOR
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Scan technique - Rule of 3s - Allow eyes 1 sec per pause - 3 zones, 3 areas in each • centre 3 – 3 hops left – centre 3 – 3 hops right – centre 3 – look inside • Start scan on centreline (head-on threat greatest) • Return through centreline (head-on threat greatest)
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eye’s attention, there’s a tendency for it to focus at a point in space one to two metres away, making you effectively short-sighted so you’re not necessarily going to see something at a distance; one good way to get around this is to periodically glance at objects such as the wingtips to stop this ‘empty field myopia’. Quite apart from the physiological limitations, the eyes are vulnerable to other visual distractions, not all of which are confined to flight; lighting, foreign objects, illness, fatigue, emotion, the effect of alcohol, certain medications and, as you probably expect, age all play their part. Then there are additional challenges such as atmospheric conditions, glare, deterioration of transparencies, aircraft design and cabin temperature, which all take their toll on your eyes and what you can see.
18 CLUED UP SPRING 2021
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