Winglets, how do they work?

[bentandtwisted]

I know they provide a 3-4% saving in fuel burn and reduce induced drag, but why/how do they work?

Why don't the 777, 767 and 757 have them?

Do "Blended" winglets work better than normal winglets?

Thanks in advance.

[gas path]

A nice and simple description can be found HERE (http://www.airandspacemagazine.com/ASM/Mag/Index/2001/AS/htww.html)

[dolly737]

You could also look here (http://www.mandhsoaring.com/articles/WL-Soaring.pdf) or here (http://www.boeing.com/commercial/aeromagazine/aero_17/winglet_story.html) :)

happy landings

[phnuff]

With the winglets reducing drag by reducing the vorticees, do they lead to a significant wake vortex reduction on landing/takeoff, or is the reduction too small compared to the turbulence caused by higher angles of attack ?

[Bre901]

You could also perform some searches on the PPRuNe Forums, lots of threads about winglets. See for instance :

http://www.pprune.org/forums/showthread.php?s=&threadid=66429&highlight=winglets
http://www.pprune.org/forums/showthread.php?s=&threadid=61636&highlight=winglets
http://www.pprune.org/forums/showthread.php?s=&threadid=61636&highlight=winglets

[hoss]

bentandtwisted,

haven't had a chance to check out all the above links,but try a search of 'supercritical wing' or 'reflex camber'.it may help answer your B777 etc question.

blended vs normal winglets, my guess would be blended wins.

safe flying, hoss