In the September 2020 issue of EAA's Sport Aviation, Budd Davisson writes

Runway width becomes a problem for some taildraggers when it gets to be less than 35-40 feet because of the lack of visibility.

Sure. When you can't see the centerline, it's nice to have some lateral margin of error.
But later in the article (p. 74) in the caption of an overhead photo of a small airplane on a runway seven times wider than its wingspan, he writes

Oddly enough, super-wide runways can cause as many problems as very narrow ones, especially for taildraggers.

What might such problems be? (Not wandering into the grass. Even if you can neither look over the nose nor locate the runway's edges, if during takeoff or rollout you drift to one side, wouldn't you still notice the center stripe or the edge or the lights in time to correct?)

Do any NTSB reports mention a too-wide runway as the cause of an incident?

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    $\begingroup$ There's an old joke about the pilot and copilot landing and having to bring the plane to a very abrupt stop. "That's the shortest runway I've ever seen!" said the pilot. The co-pilot looked from side to side and said "yeah, it's also the widest ..." $\endgroup$ – Jason Oct 1 '20 at 14:35
  • $\begingroup$ The way I heard it, @Jason, was much less "politically correct", but it's still funny. :) $\endgroup$ – FreeMan Oct 1 '20 at 15:28
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    $\begingroup$ "Tower to Speedbird, you were a bit to the left of the centerline on that landing." "Speedbird to Tower, yes, and my co-pilot was a bit to the right." $\endgroup$ – Camille Goudeseune Oct 1 '20 at 16:14
  • $\begingroup$ At the former Kelly Air Force Base, a taxiway had "TAXIWAY" painted in HUGH letters easily seen on final to the adjacent runway. Over the years too many had, or attempted to, land on the taxiway. $\endgroup$ – radarbob Oct 7 '20 at 2:32

The issue has always been human perception. Pilots are tasked with trying to make great landings. One way they do that is with peripheral vision. If the runway is too wide, they lose that extra clue on when to roundout and flare. They may flare too early and stall the aircraft too high above the runway. This perceptual clue is more important for tailwheel pilots than tricycle gear pilots.

From the FAA AIM 8-1-5.

  1. Illusions Leading to Landing Errors.

(a) Various surface features and atmospheric conditions encountered in landing can create illusions of incorrect height above and distance from the runway threshold. Landing errors from these illusions can be prevented by anticipating them during approaches, aerial visual inspection of unfamiliar airports before landing, using electronic glide slope or VASI systems when available, and maintaining optimum proficiency in landing procedures.

(b)Runway width illusion. A narrower‐than‐usual runway can create the illusion that the aircraft is at a higher altitude than it actually is. The pilot who does not recognize this illusion will fly a lower approach, with the risk of striking objects along the approach path or landing short. A wider‐than‐usual runway can have the opposite effect, with the risk of leveling out high and landing hard or overshooting the runway.

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    $\begingroup$ Though it perhaps be mentioned that this is to some extent a matter of habit, e.g. judging flare by the perceived width. If you occasionally land on dry lakes and such (or wet ones, I understand, though I have no personal experience of seaplanes), you learn to deal with the illusions. $\endgroup$ – jamesqf Oct 1 '20 at 16:58
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    $\begingroup$ The base I currently fly out of has a 10,000x150ft runway. One of our emergency divert fields is 5,000x75ft. The perception would be that it is the same as the runway we land on everyday, when in reality it is half the length. In pilot training, we had a 13,000x300ft runway next to an 8,000x150ft. I'd always find myself flaring high when landing on the 300ft wide runway. $\endgroup$ – Keegan Oct 2 '20 at 0:34
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    $\begingroup$ @Keegan: Perhaps that's a consequence of not landing at enough different runways? So you've unconsciously trained yourself to use the perception of runway width as a cue to flare. So it's not that the runway width is inherently a problem, it's the habit that's been formed. $\endgroup$ – jamesqf Oct 2 '20 at 4:47
  • $\begingroup$ @jamesqf: In the context of safety, the human factor cannot be understated. Consider the opposite effect, of a pilot used to a wide runway landing at a narrower one. Can you see the CFIT in the making? $\endgroup$ – dotancohen Oct 3 '20 at 23:49
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    $\begingroup$ @dotancohen: Sure, and that's why I suggested becoming used to different sorts of runways so you DON'T get into the habit of using the perceived size as a cue. $\endgroup$ – jamesqf Oct 5 '20 at 2:35

When landing an airplane you get used to visual reference points to evaluate your position relative to the ground. Optical illusion are therefore quite common.

A narrower-than-usual runway can create an illusion that the aircraft is higher than it actually is, leading to a lower approach. A wider-than-usual runway can create an illusion that the aircraft is lower than it actually is, leading to a higher approach and greater slope.

On a very wide runway you might flare too early and even stall the airplane a few meters above ground. Taildraggers are quite tricky at landing in those condition as you don't want to overshoot the 3 points pitch attitude of the aircraft or you will hit the tail first which is not designed to handle it.

The opposite might happen on narrow runway for nose wheel plane where you might miss your flare and touchdown with the nose gear first who might collapse under you. This risk adds obviously to the risk of hitting ground obstacle while flying a low approach.

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  • $\begingroup$ Thanks for explaining why it's a problem "especially for taildraggers" as Budd wrote. $\endgroup$ – Camille Goudeseune Oct 1 '20 at 16:20
  • $\begingroup$ It's a problem for everyone, but consequences might be a bit worse in a taildragger ^^ $\endgroup$ – MaximEck Oct 4 '20 at 21:22
  • $\begingroup$ At the former NAS Dallas, about 1/4 of the runway juts out into a lake on a peninsula just wide enough for a taxiway on one side. My first time on short final I felt slightly unnerved with a "what's wrong with this picture?" I got used to it, but it recurred a couple of times. The OLS meatball was my friend! Years later I was not surprised when Asiana 214 hit the runway approach end at SFO for want of referencing the visual approach lights. Who hasn't landed with one VASI light red? They were not "just a little low." $\endgroup$ – radarbob Oct 7 '20 at 3:07

As a pilot, switching from my training on a 50 ft runway to landing frequently on a 150 ft wide runway was slightly challenging.

The FAA describes two illusions:

Wide Runway

Looks closer on final and you will tend to float and flare high.

Narrow Runway

Looks farther away on final and you will tend to approach at a higher rate of descent.

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    $\begingroup$ Is it feasible to land away from the centerline, and closer to one side of the runway? Separately, is that even permitted ? $\endgroup$ – Criggie Oct 1 '20 at 9:51
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    $\begingroup$ @Criggie Surely it ispossible and authorised assuming your not entierly missing the runway, but the real question is why would you do it ? Flying in close formation is the only valid reason I can find, and we often do it with aicraft landing on each side of the runway to reduce the time and space between landings. Othervise, the centerlinegive a perfect reference, give you the more security in case of crosswind landings where the plane light woble left to right or any other problem. $\endgroup$ – MaximEck Oct 1 '20 at 11:57
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    $\begingroup$ Does the size of runway markings help with this? Probably not an urgent problem, but in a theoretical world maybe a fixed-size marking further out on the runway, so that it can be a reference point for height. $\endgroup$ – user3067860 Oct 1 '20 at 13:38
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    $\begingroup$ Larger runways are made for larger airplanes - therefore, the markings are more complex and designed for a longer TDZ(touch down zone) for aircraft moving a lot faster than 65 knots. $\endgroup$ – Grayson Bertaina Oct 1 '20 at 18:17
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    $\begingroup$ The issue with the FAA illusions is that as a trainee pilot you learn a mental "picture" of what your whole visual field should look like, and how it should be located relative to the edges of your windshield, when flying a visual approach. If the runway is a different width from what you expect, your brain will misjudge the width and/or the length and/or your angle of descent, to make what you see match up with your internal "picture" of how you should be moving in three dimensions. $\endgroup$ – alephzero Oct 1 '20 at 23:28

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