Purpose of winglets on airplanes?
 

Does anyone know the purpose of putting the winglets on airplanes? I know the obvious answer is that aeronautical engineers found that wings fly better with them there. But could someone tell me how that works? I'm curious in the concepts of aeronautical engineering without the detailed equations. What exactly do they do for the airflow over the wings? Does any one have any recommendations about a book or webpage to view on this?

Thanks for your help!

They help reduce wingtip vortices and induced drag.
They reduce air being "spilt" off the end of the wing.

Plus they look cool!

Kind of like a spoiler on a Honda Accord!

The most efficient wing, aerodynamically speaking, is infinitely long. The reason is the nasty stuff that happens at the wingtip, basically as the result of lazy air. Air wants to go around the end of the wing, instead of over the wing where it has to do the heavy lifting.

An infinitely long wing raises problems of fitting into airports, structural strength, and so on, so real wings are somewhat shorter than that. This is a design compromise: designers make them as long as possible, until the added weight you need to hold things together exceeds the added lift you get from making the wing longer.

Winglets recreate some of the effect of an infinitely long wing by creating a "wall" that makes it harder for air to go around the end. Some of the air now finds it easier to stay on the wing, despite having to do some lifting there. A bit still spills over because the winglets aren't infinitely tall. Another design compromise.

a bit off topic here but

nice name/handle

AFAIK winglets improve fuel efficiency during flight but increase fuel consumption for take off and climb.

why aren't there winglets attached to some of the bigger planes like 747, 777, A330, A340, A380? thnx in advance

I think he confused user name and password ;)

The 747-400 has winglets. The 777 has a special wing geometry which doesn't need winglets. Same with the A380. The A330 and A340 have winglets.

Not sure about the A380 however I believe they are similarly beneficial to bigger planes, have definitely seen the on the newer QANTAS 747's that I have flown on over the past few years...

A-380 does have winglets (the kind that go above and below the wing - similar to A-320).

Although the 747-400 does have winglets, the upcoming 747-8 will not (similar wing design philosophy as 787).

Any chemists want to translate?

"Are you lonely? Don't be. You have a friend in tape hiss, in the background creak of wooden chairs, in the crackle and click of four-track recordings. And besides, I'm coming over later tonight, and I'm bringing S1C3R1A1B3B3L1E1 and mojitos. [Info]

Posted by Jordan at August 4, 2006 2:37 PM "

There is a plan to have 777 winglets as a retrofit package.

That's the best explanation. ^ It keeps the air from high pressure region to leak into low pressure region., which leads to loss of lift, vortices, which produce lift induced drag.

I think the user name is meant to evoke a reading of booking-class availability - not a chemical compound.