What is the mist coming off the wing off a plane when taking off?
Answers:
It's moisture in the atmosphere, which condenses when the pressure changes due to the airfoil's effect. You see the same things on the wings of racing cars, for example, at high speeds on damp days. The physics are simple -- as air pressure drops, water vapor condenses into larger droplets, and if they get large enough, you can see them.
The Sources link has a REALLY dramatic example of the same effect -- a cloud forming as an aircraft breaks the sound barrier about 50 feet over the surface of the water as it flies by an aircraft carrier. Awesome!
Possibly moisture in the air being whipped up by air turbulence? Or maybe there is mist there all the time but you only notice it during take-off? If you watch Formula One cars at high speed then you can see a little vortex of air coming off each corner of the wing at the back of the car, so maybe it is something like that?
Low pressure regions trailing the wing cause water vapour to condense.
The low pressure area created over the wing at high angles of attack make water vapour condense out of the air. this is what you can see.
Low level moisture that condenses over the wings leading edge
the moister
Fuel leak usually!
The wingtip vortex created, creates a low pressure area, which causes the water vapour to condense.
To elaborate on previous answers. Low pressure is correct and moisture does condense to form a temporary cloud you could say. Low pressure creates lower temperatures. All that needs to happen is the temperature to reach the dew point or lower. The dew point being the temperature at which moisture in the air condenses to form a cloud.
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