Mike_mit From United States of America, joined Oct 2000, 81 posts, RR: 0 Posted (14 years 7 months 2 weeks 5 days ago) and read 3448 times:
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.
Buzz From United States of America, joined Nov 1999, 697 posts, RR: 20
Reply 3, posted (14 years 7 months 2 weeks 2 days 6 hours ago) and read 3318 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.
B787 From Australia, joined May 2005, 155 posts, RR: 0
Reply 4, posted (14 years 7 months 1 week 5 days 3 hours ago) and read 3287 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.
Spoiler From Spain, joined Apr 2007, 0 posts, RR: 0
Reply 5, posted (14 years 7 months 1 week 2 days 19 hours ago) and read 3253 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)
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.
Keycaukr From , joined Dec 1969, posts, RR:
Reply 6, posted (14 years 7 months 1 week 11 hours ago) and read 3221 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.