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Winglets Vs. No Winglets  
User currently offlineMike_mit From United States of America, joined Oct 2000, 81 posts, RR: 0
Posted (13 years 5 months 4 weeks 22 hours ago) and read 2615 times:

Hi,
Can someone explain to me what purpose winglets serve on an airplane? Why do most Airbus aircraft have winglet and nearly all Boeing aircraft (even the 777..a new design) do not have winglets?
Thanks ahead for your responses.


7 replies: All unread, jump to last
 
User currently offlineOldman From United States of America, joined Sep 2006, 0 posts, RR: 0
Reply 1, posted (13 years 5 months 4 weeks 21 hours ago) and read 2536 times:

Hello Mike,

If you look down on this page you will see a Post Winglets. You should find your answer there.  Smile


User currently offlineAeroGlobeAir7 From United States of America, joined Jan 2001, 586 posts, RR: 2
Reply 2, posted (13 years 5 months 4 weeks 21 hours ago) and read 2522 times:

The winglets are usually an option on Boeing aircraft. At least on the NG 737s. They increase the range of the aircraft slightly. ATA (AMerican Trans Air) and SAA have winglets on their 737s.

User currently offlineBuzz From United States of America, joined Nov 1999, 697 posts, RR: 21
Reply 3, posted (13 years 5 months 3 weeks 5 days 4 hours ago) and read 2485 times:

Hi Mike_mit, Buzz here. Winglets act like the wing should have more wingspan, without a few of the penalites (still fits in the hanger!)
The 767-400 has the wingtips modified, seems that winglets just weren't good for it, but it needed the extra wing area. So the extreme winglets of the 737 Buisness Jet are more for advertising than utility.
Notice the difference in shape between the A320 winglet, and the MD-11, and the 747-400 winglet: got to tailor the winglet to the wing. One size does not fit all.
g'day


User currently offlineB787 From Australia, joined May 2005, 152 posts, RR: 0
Reply 4, posted (13 years 5 months 3 weeks 1 day ago) and read 2454 times:

There is an on-going debate over what is the "best" way to do wingtip treatments. For a more efficient wing you can add span and aspect ratio, the winglet adds "effective" span but is not quite as efficient because it does so by reducing induced drag, where as a raked tip like the 767-400ER adds lift and increases aspect ratio. The advantage winglets like the BBJ and Airbus winglets(A330/340) is that they add effective span without inncreasing the actuall span. this is helpful when you are trying to get into small gates and airports. Boeing recently flew a 747 with API winglets(same guys as the BBJ) and a raked tip similar to the 767-400ER and the rumor was that there was negligible benifit for either one, the differences come down to integration, flutter, gate clearence, and what not.

hope that helps


User currently offlineSpoiler From Spain, joined Apr 2007, 0 posts, RR: 0
Reply 5, posted (13 years 5 months 2 weeks 5 days 17 hours ago) and read 2420 times:

Another reason for winglets: The way that wings produce lift is by creating a low air pressure area on the upper surface of the wing, hence the term 'airfoil.' That much I'm sure you are well aware of. Because of this, there an area of relatively higher air pressure underneath the wing. High pressure flows to low, and the high pressure air tends to curl up over the wingtip to the low pressure area, creating a vortex (as well as drag). This is known as a wingtip vortex, or wake turbulence. Winglets don't eliminate this vortex, they just move the location that it occurs to the top of the wingtip. The theory is that this diminishes some of the drag associated with the vortex by decreasing the size of the vortex itself, thus increasing range. Anyway, that's just how I heard it. You can actually see these vortices when it is humid enough. 757/767s have one coming off the wingtip, as well as the outside edge of the flap (which was what was causing all those crashes behind the 757s)


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Photo © George Polfliet



All that aspect ratio stuff might be true, but it doesn't make to much sense to me because all a winglet could do is produce horizontal force, like the vertical stabilizer. And a lot of business jets have winglets, and I'm sure that they don't care about gate clearance.


User currently offlineKeycaukr From , joined Dec 1969, posts, RR:
Reply 6, posted (13 years 5 months 2 weeks 3 days 9 hours ago) and read 2388 times:

Actually Mik_mit already has the answer by simply looking at the 777. This design was the result of the very best in science and technology can contribute. I'm quite sure Boeing didn't simply forget about winglets.

It is possible that others are flying with winglets because the theory is logical from a several prospectives. But considering everything there is to consider, Boeing decided not to go with it, and remember, they squeezed every oz. of efficiency into there design.



User currently offlineB787 From Australia, joined May 2005, 152 posts, RR: 0
Reply 7, posted (13 years 5 months 2 weeks 17 hours ago) and read 2373 times:

take a look at the new 777-200LR and -300ER they both have an extended wing and raked tips, the gate limits again show up because the span is limited to 213 ft. or class F gate (which is a 747-400)

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