The Eyes Have It

Lay the magazine down where you can still read it. Then, raise the index fingers on both hands and hold them both out in front of you pointing vertically up. Make believe it's some sort of weird dance move. Hold them at arm's length and about a foot apart. Now, turn your head and focus on your left index finger. Got it? Okay, now, without moving your head or your eyes, continue staring at your left finger and notice how sharp your right finger is in your peripheral vision. Pretty fuzzy isn't it?

Now, still staring at your left finger move your right hand/finger towards it and see how close your right finger has to be to your left finger before they're both sharp. Generally, they have to be within a few inches for both of them to be sharp. So, what did we just prove? We just proved that as soon as something is even slightly outside of our point of focus, the visual information being generated by it gets very vague, very quickly.

We're talking about this because one school of thought says that you should be staring straight ahead when landing, and relying on your peripheral vision to keep you straight and give you height information during flare. This is especially prevalent in taildraggers, where often you can't actually see over the nose, but you hear it mentioned in nosedraggers from time to time, too. In fact, for decades, yours truly taught landings that way. However, at some point in the last 10 years, it became obvious that everything out in the fringes of vision is fuzzy and a different approach was needed.

According to the FAA, as soon as we get five degrees outside of the point of focus, 20/20 vision degrades to 20/100. That's right: While some of us are landing, the visual information that we're depending on is being generated by 20/100 vision or less. If we were walking, that would qualify us for a white cane. But, we're hurtling at the ground at 80 mph where 20/100 vision just doesn't cut it. So, what do we do about it?

Since we only have about a narrow cone of 20/20 vision, it's practical that we conduct ourselves as if we were looking at the world through a soda straw. We need to recognize that the information coming from that narrow cone of focus is the best we're going to get. That doesn't mean, however, that we totally ignore our peripheral vision. As far as that goes, we couldn't ignore our peripheral vision even if we wanted to, because our mind will subconsciously see what's out there in the fringes whether we want it to or not.

In essence, our field of vision resembles a shooting target where our sharpest focus is on the bull's-eye and our peripheral vision encircles it. Our peripheral vision spreads out to cover the rest of the target, quickly getting weaker the further out it goes. Our mind sees the entire target, but concentrates on the bull's-eye. Knowing that's how our eyes and our brain work, we then need to make a conscious effort to use our eyes differently in different parts of every flight.

At the same time that we're recognizing the target-like structure of our vision, we should also recognize that it's very possible to "look" but not "see," even though we think we're concentrating on the bull's-eye. This is the super-common tendency to look through the windshield and think we're seeing what's happening out there but we really aren't. Our eyes are seeing a generalized picture of the scene that's in the windshield, but we aren't really focused on any of the small details that would be giving us vital information IF we saw them. Which we often don't.

The tendency to "look" but not "see" affects us in two different areas: the first is when looking over the nose and judging the nose's motion against the background, as in takeoff and landing, or while making turns. The other is when looking over the nose (and out the side windows) while trying to see what's out there, collision avoidance being the most critical of those.

Even though surveying ground references, as when on a cross-country, fits into this conversation on visual acuity, that's a form of "looking" in that pilots innately understand the difference between "looking" and "seeing" and, without realizing it, use their eyes differently.

It's a given that if the eyes aren't focused on a point, i.e., if they aren't picking out something specific, they get lazy and tend to focus short. This is apparently what happens, when using a casual, constantly moving scan while looking for traffic in a featureless sky. According to the FAA, this focusing-short phenomenon is called "eye myopia." In slowly moving our eyes across the sky, as most of us do, we're not giving the eyes anything to focus on, so they've focused short, and we're not likely to see another airplane even if it's in plain sight. This doesn't happen when looking at the ground checking for checkpoints because we're asking our eyes to focus on and identify features of the landscape. They're constantly picking out new features, so they're continually changing focus and we're basically ignoring our peripheral vision even though it's there. It's not applicable, so we don't use it.

When scanning for traffic, the FAA tells us that our eyes work better if we separate the sky into roughly 10-degree sections. We should then spend 10 or 15 seconds (according to them: seems like a long time to us) examining each section before moving on to the next one. The theory behind this kind of visual scanning is that by concentrating on small segments we've given our eyes the task of focusing on that specific section so they focus much better. We also can apply the same concept to other parts of the flight. Which brings us back to taking off and landing, making turns and the difference between "looking" and "seeing."

Let's use landing flare as an example of where it may be a good idea to remember that only the middle 5% of our vision is giving us accurate information. So during flare, we're going to force ourselves to direct that narrow visual cone to look at and analyze specific areas.

When we're pulling the airplane level in ground effect, one visual method often used is to fixate on the far end of the runway for as long as we can see it. This works, but the information isn't as finite as it would be if we picked far, distant points on both sides of the runway and continually shifted our focus from one to the other. This triangulation gives us more exact visual information and forces our peripheral vision further to the side, so even more information is gathered.

As the airplane settles into ground effect and we hold it off, often the nose comes up and covers the middle of the runway. At that exact moment, our focal point moves to the side of the cowling where the edge of the runway hits it. It's the apex of the triangle formed by the leading edge of the wing, the side of the nose and the edge of the runway. In effect, we're using the nose as if it were the rear sight on a rifle, and the edge of the runway is the front sight, and we're trying to keep the intersection of the two in a specific alignment. The way in which the side of the runway moves up and down the side of the cowling tells us exactly what our airplane is doing both while in ground effect and while in final flare.

If for instance, while in flare, the airplane turns even slightly left, the point where the runway edge hits the cowling will move down the side of the cowling, and the visual triangle will get smaller. The point moves up if we turn right, and the fuzzy triangle in our left peripheral vision will get bigger (we "sense" the change more than seeing it).

While we're holding the aircraft off and it's settling into ground effect, the point moves up the side of the nose as the airplane moves. The visual triangle, however, remains pretty much the same size because our nose has moved neither left nor right.

That point is continually talking to us. If we're looking straight ahead and depending on our peripheral vision to tell us what's happening, our 20/100 vision field will include that point, and the information we receive from it will, at best, be an approximation.

The ability to direct our 20/20 visual cone at the exact points where the most accurate visual information is being generated is what defines our visual acuity. And our visual acuity is often what defines us as pilots. The old saying says, "You can't fix what you can't see," and no truer words were ever spoken.