I have been observing several aircraft landings and have noticed that when the aircraft's landing gear touches down, it precipitates the rising of a cloud of smoke. Why is this?
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Because the tires are momentarily skidding on the pavement as they rapidly spin up from standstill to the jet’s touchdown speed. It’s just a puff of burnt rubber but the tire tread itself becomes quite warm, reaching 600-700°F for an instant. It’s also the reason a pilot does not ride the brakes upon touchdown as this could cause a blowout as the tire is ground up rapidly.
Imagine yourself driving your car at a speed of 60mph (96 kmph) and suddenly you apply the brakes completely and notice that it produces smoke. THIS IS FRICTION.
Now, when the aircraft lands at 180 knots (324 kmph) it creates friction too.
Anytime a tire's bottom is moving at a significantly different speed than the roadway, it'll make smoke. An example is a burnout, where the tire is spinning at high speed with a vehicle and road going 0 mph. Roads generally go 0 mph.
Prior to aircraft touchdown, the tires are not turning, so the top and bottom of its tires are going at the same speed - aircraft ground speed, say 120 knots for a 737 in a bit of a headwind. Not all runways have a ground speed of 0 knots, but the ones that land 737s do.
When the 120-knot tire bottom touches the 0-knot runway, that's a big difference, so as said, there'll be smoke. This reveals drag on the tire, which will very quickly spin the tire up so its bottom is going 0 knots relative to the ground. At that point the smoke will stop.
Planes land at somewhere in the ballpark of 150mph (230km/h). At the moment when the plane lands, the wheels aren't spinning, and the only thing that can make them spin is the contact with the runway. So, at the moment the plane lands, the wheels are skidding at 150mph, and they'll continue to partially skid until their rotation speed matches the speed of the plane. And it takes a little while for that to happen, because aircraft wheels are pretty heavy: according to Lufthansa, a wheel and tyre on a 737 weighs about 112kg, and about 185kg on a 747.
So, the smoke you see is material being worn off the tyres as they skid up to speed. They're designed to be used this way and are regularly inspected and replaced to ensure that not too much of the rubber is worn away.
It is kind of the reverse of burning tires on a car. There is a limit to static friction and tires spin. Even when they spin there is kinetic friction. When the tires spin they get hot from friction and burn (more like the rubber vaporizes).
The tires have mass and it takes energy to spin them up the speed of the plane. Initially the speed difference is so great they spin and smoke. The kinetic friction quickly brings the tire up to the speed of the plane.