Why do landing gear tires smoke upon touchdown? 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?


(Source: airliners.net)
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.