Hydroplaning prevention technique

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Thanks for the links tribo.

I found the report from the Dutch transport safety board interesting, both for the circumstances contributing to the accident, and also the reference to the Boeing article.

I suppose the point I found most interesting about the accident and which has occured to me in the past is that the braking condition of the runway is very often not consistant along the entire length of the runway. In this case Runway 01L offered good/medium braking action at the start of the landing roll and virtually zero braking action toward the other end. So in those circumstances perhaps it's better to "make hay while the sun shines". In other words, if they had slowed to taxi speed before reaching the last third of the runway, we wouldn't be reading about them now.


Reading the Boeing article raised a question in my mind.

There is a graph on page 86 of the accident report (page 10 of the Boeing article) and on page 88 of the accident report (page 12 of the Boeing article) which shows the braking and cornering capability of the tyres when compared to the tyre slip.

What I don't undertand is why the braking capability is zero when the the tyre slip is zero, but at the same time the cornering capability is high. Wouldn't the braking capability be the same as the cornering capability. ie the tyres offer the same grip in all directions. How much slip is there when autobrakes 1 is selected on a dry runway? Virtually zero I would have thought. What about when the aircraft is stationary with the park brake set. No slip there either, however the tyres are capable of resisting quite a force before there is any slip and aircraft movement. Same thing when you park a car on the side of a hill. No slip but there is much braking and cornering resistance preventing the car from sliding down the hill. In fact the braking and cornering capability would be the same. That is to say, it would be just as hard to push the parked car forwards or backwards as it would be side to side.

Just thinking aloud.

P.S. Thanks for raising the question punkalouver.

To answer your question. Yes we are told not to attempt a smooth landing. Just put her on nice and positive to achieve a good wheel spin-up. If after the inital flare, the main wheels don't go on the runway, just a slight easing of the back pressure on the control column will lower the nose just enough (maybe half to one degree in pitch at a guess) to establish again a descent rate towards the runway. Sometimes this can be over done somewhat and before you know it, the passengers are telling themselves under their breaths that you can't fly (or land) an aeroplane!