What causes this to happen?

Question

http://www.airliners.net/open.file?id=0728247&size=L&width=1200&height=812&sok=JURER%20%20%28%20cubgb_vq%20%3D%20%271316136%27%20BE%20cubgb_vq%20%3D%20%271289034%27%20BE%20cubgb_vq%20%3D%20%27893702%27%20BE%20cubgb_vq%20%3D%20%27893699%27%20BE%20cubgb_vq%20%3D%20%27820396%27%20BE%20cubgb_vq%20%3D%20%27748912%27%20BE%20cubgb_vq%20%3D%20%27728247%27%20BE%20cubgb_vq%20%3D%20%27695890%27%20BE%20cubgb_vq%20%3D%20%27558160%27%20BE%20cubgb_vq%20%3D%20%27507366%27%20BE%20cubgb_vq%20%3D%20%27282866%27%20BE%20cubgb_vq%20%3D%20%27282865%27%20BE%20cubgb_vq%20%3D%20%2727967%27%29%20%20beqre%20ol%20&photo_nr=7

When you see that white trail behind the wing what's going on? What causes that to happen?

Answer 1

how did u get that avatar??

Answer 2

Depending on atmospheric conditions, you are seeing what is referred to as a vapor trail;  a common occurrence. Sometimes, depending on the existing moisture in the air and varying lift coefficients, one or both wings, or the vertical stabilizer, passing through the air will cause a vapor trail.

Answer 3

Yes also knowing as water vapor

Answer 4

That's coming off the flap tip, not the wingtip.  The vortex [not "vortice"] of air is also expanding air.  --Thus EXPANSIONAL COOLING, with (invisible)  water vapor condensing into (visible) liquid water droplets.

It is a contrail.

It is not a "vapor trail."  Water vapor is not visible.

Answer 5

it is just air it happens when mix high altitude with high speed , it is very common

Answer 6

It is called contrails and is very common when an airplane is above 20,000 feet altitude It is water vapor condensing or actually tiny ice crystals.

Answer 7

I believe that it is water vapor created from low pressure on the trailing side of the wing.

Answer 8

Technically they are called contrails, but people are not wrong when they say water vapor. It happens at higher altitudes because of the turbos in jet engines condensing the air and water molecules and releasing them into a less dense environment (high altitude), where they condense even more (into ice crystals specifically) to form a contrail.

Edit - Oh, maybe I should look at the picture first... In that case, it is the movement of air/water molecules passing under the wing, where the pressure increases due to wing design (to create lift) and as they leave the wing the water vapor will condense to a supersaturated state into ice crystal form (the contrail look). And in the second picture you have posted, you have a great shot of what air is actually doing behind a plane. My guess would be that he is landing near some water and he is kicking  the vapor up. Pretty cool though, but that exact effect right there is why they have regulations on how close a plane can be behind another that is landing like that. Causes pressure to drop and the planes wings cannot create the lift that keeps it in the air... in case you wanted that info too haha.

Edit 2 - To the lady down below... I have been flying for 22 years, I think I would know what a contrail is... Your description is correct, but it IS a contrail, because contrail is a conjuntion of two words, "condense" and "trail". Someone above has posted a link to info on contrails, maybe you should go read up before ya bag on a real pilot :).

Answer 9

It's called "vapor" and it occurs when the airflow across any surface of the airplane becomes superheated and mixes with a high moisture atmosphere (condensation) and it is more pronounced when two things happen, high G's and high humidity. You see this quite often at airshows when military flight demo teams demonstrate low altitude high performance maneuvering. Here is such an example

[IMG]http://i36.photobucket.com/albums...

Answer 10

Whenever air is compressed, it is heated.  The higher the temperature of the air, the more water vapor it can absorb.  Under the right atmospheric conditions (that is, a lot of moisture in the surrounding air), the compressing force of a wing or control surface passing through the air can compress and heat the air so that it will absorb significant moisture,

Then when the air has passed behind the wing or control surface, it cools with equal suddenness, releasing the moisture and resulting in a visible trail of ice crystals.

This is not the same as a contrail, which is a high-speed, high-altitude phenomenon.

As always, it is amazing how many people post answers on topics they know little or nothing about.

Answer 11

Thats not a contrail, which occurs at high altitudes. Contrails are isicles.

Its a VORTICE...Its condensation.

It occurs more often at low speeds, when drag is high. That plane is approaching the runway, ...at a low speed. Thats when this occurs.

Woops basically what he said above.. :)