On wingtips and outboard flaptips, I always notice vapor trails emerging during takeoff and most especially during approachs. I especially admire the way the vapor trail follows the shape of the outermost edge of the fully extended outboard flaps ( it happens on alomst all airplanes). I've also noticed that the more Gs an airplane 'pulls', the more prominent or pronounced the vapor trails become. On one particular flight -way back in the 1980s- I noticed that the CF-60 turbofans (on the DC-10-30 I was flying on) were creating a curved "vapor vortex" at the front of the engine...when ever the pilots throttled up to inch further on the crowded taxiway -to the runway. Then, if one looks closely at hefty turboprop engines, throttled-up to "TO" for the takeoff run, you notice sets of whirling vapor vortices coming off each blade tip as they spin round. I've seen these coming off the Allison T56-A-15s of several C-130H planes.
My question: Why the vapor trails/vortices on all those tips?
2006-11-29 17:45:54 · 5 answers · asked by Fulani Filot 3 in Cars & Transportation ➔ Aircraft
Basically the water in the air is condensing out when the pressure drops. This effect is increased by local disturbances in the air flow. On a damp day you will sometimes see vapor over the whole wing. Propellors have tip vortices that also enhance the effect, I watched a Transall take off one day and it looked like she was trailing two tubes from her props.
Check out the F-18 in the link below, she's dragging her own personal cloud around.
This is a low pressure effect, it's sort of analogous to keeping CO2 in a soda bottle, when you take off the cap the pressure drops and the CO2 is liberated from the water because the water can not keep it in solution at the lower pressure.
2006-11-30 02:54:59 · answer #1 · answered by Chris H 6 · 1⤊ 0⤋
Happens with helicopters, too. If you're in a hover in extremely moist air, with little or no temperature/dew point spread, you can create your own cloud.
I've gone near IFR at the top of mountains when setting down external loads in freezing weather. Makes life pretty interesting.
2006-11-30 13:59:53 · answer #2 · answered by lowflyer1 5 · 0⤊ 0⤋
It is air being compressed.
When air is compressed it "squeezes" the moisture out of the air and becomes visible.
When there is a light fog or haze in the air it is really noticeable. I have even left some in a hard turn doing aerobatics when the air was saturated with moisture.
Even props will leave trails that spiral. That is really something to see.
It is just the science of air. The more compressed it gets the less moisture it will hold.
2006-11-30 09:40:54 · answer #3 · answered by dyke_in_heat 4 · 0⤊ 3⤋
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2006-11-30 02:05:33 · answer #4 · answered by Anonymous · 0⤊ 0⤋
The vapor has nothing better to do.
2006-11-30 07:13:28 · answer #5 · answered by Anonymous · 0⤊ 1⤋