Identify the phenomenon...?

Question

http://i7.photobucket.com/albums/y293/marballe/053.jpg

I don't know what this phenomenon called. Anyone know about it... It appears at the side wing of the jet, and it's amazing.

What is this stream; What caused it; How does it appear?

Thanks.

Answer 1

That's water vapor. What's happening is that the wing is doing what it's designed to, and lowering the air pressure. When the airpressure is suddenly lowered, the moisture in the air condenses and creates that little vapor stream you see.

Answer 2

To be more specific than the answerer above, it is water vapor condensing in the low pressure area above the wing.  It is commonly known as a vapor trail or "contrail" (condensation trail). To make an airplane fly, wings must create lift, which is a combination of the pressure differential above and below the wing, the shape of the airfoil, the angle at which it meets the airflow, and the speed of the aircraft.  In flight, the air pressure above the wing is substantially lower than that below the wing. Anytime the air pressure drops, temperature also drops, and IF atmospheric conditions are right, water vapor will condense (think tornado or hurricane). The phenomenon pictured was created by a small disturbance of air on the engine nacell or pylon ahead of the wing. This disturbence was just enough to lower the pressure along that narrow band of airflow and create a vapor trail. This is much more common at the wingtips, which create rapidly spinning vortices of low pressure that are especially strong during take off and landing. You also see such phenomena when acrobatic or military aircraft perform a high-G maneuver such as a hard pull-up or tight turn. at high speed.

Answer 3

It's not a contrail.  The vapor is caused solely by a drop in pressure and the condensing out of the water vapor.  Contrails are similar but need engine exhaust.  

You can see the same thing on any F-16 picture when it's pulling Gs.  We called it ectoplasm, but it's also around on the net in pictures of Tomcats and Hornets about to go supersonic (caused by the pressure drop per the transonic air over the fuselage).

Sometimes you'll see this rolling around the flaps or off the entire top surface of the wing.