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Comment by jcrawfordor | Hacker News Reader

Build-up of rubber from the tires of landing airplanes is a routine problem with runway maintenance. Typically the airport authority will use a friction-measurement device at regular intervals to determine when the surface friction of the runway has fallen below required parameters, and resurface. But rain makes things much worse and might have combined with rubber build-up to produce a particularly slick section.

Flying light aircraft, I was taught to avoid landing right in the touchdown zone just to have better traction. I'm not sure if this is actually useful or just Old Pilot Superstition but it has some logic to it, and putting a Skyhawk down on a 14k foot runway you have a lot of room for eccentric opinions (similar to landing just a touch off centerline so the nosewheel isn't on the painted stripes, another one I've heard people mention as a "best bad practice").

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My dad was a commercial pilot, and taught me to fly at a young age. One of the bits of sage advice was something along the lines of "if your nosegear has two or more wheels, try to get it bang on the centre line, every time. Otherwise, miss a little tiny bit. The lights go THUMP-THUMP-THUMP and eventually drive you mad or, combined with a little gust of wind, cause you to hop once more".

I think there's a lot of Old Pilot Superstition with more than a dollop of truth in it.

I don't think anything too bad could happen when landing light aircraft on slippery but long runway. I was doing some winter flying and was landing pa28 on slippery runway (compressed snow) and I didn't noticed any difference until i started pressing brakes which had virtually no effect on deceleration. On touchdown you have a lot of aerodynamic authority on your controls so runway friction doesn't really matter unless you have super strong crosswind that could blow you out the runway i guess.

If I recall rightly Concorde pilots often took control from autoland and landed it slightly off the center line.

This was to avoid upsetting the passengers and to ensure the champagne didn't get shaken too much.

I don't think you were allowed any service items during landing, so this can't have been true.

Could be referring to the champagne still in bottles. How long does it take for a "shaken" bottle to return to "won't explode everywhere when you open it" state, anyway? Does the low pressure in the cabin make it more prone to erupt?

It's very odd they don't do anything to speed up the wheels or apply a coating of water to them on dry days to avoid extreme wear and excess rubber for future planes landing.

Even a passive design with the shape of the tread could help substantially reduce the amount of rubber scraped off the wheel on each landing.

Apparatus to spin up wheels was analyzed exhaustively, early on. They determined that the added weight and complexity did not pay.

That is not to say that some clever physical design could not help. But the idea of spinning up wheels is well-known to gear engineers. Tire wear is a substantial expense, so any bright ideas would be welcomed, and eventually tried out.

Seems like one could design the tread (or an extra rubber tab) to catch the wind and self spin.

And, as I said, these ideas have been explored in depth, and abandoned. Nothing has changed in tires or landing gear, since, to merit going back over everything that was tried.

Suppose your stuff got the tire spinning at the circumferential rate of 20 knots. The plane touches down at 130+ knots. Is the decrease in rubber deposited noticeable? How fast would you need the tire to be spinning to make a noticeable difference? How much does your extra apparatus weigh? How much extra space does it take in the wheel well?

The extra weight has to be carried throughout the flight. Space in the wheel well is tightly constrained, because it is near the center of gravity of the aircraft, where cargo space is most valuable, and where the wing spar crosses through the fuselage.

Everybody thinks of spinning up wheels. Thus far nobody has had answers to the questions that led to acting on the idea.

Thanks, more or less the reality check I was hoping for :)

Well using sprinklers to wet the initial part of the tarmac would work. But the safety folks don't have an understanding of nuance that a runway where just the first 300 feet is wet is different from the runway being fully wet.

So you are suggesting hydroplaning?

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