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User currently offlineTarantine From United States of America, joined Sep 2000, 210 posts, RR: 0
Posted (15 years 8 months 2 weeks 1 day 6 hours ago) and read 1335 times:

Most of the new aircraft from the 1980's like the 747-400, MD-11 & all the Airbus types were equipped with winglets. I thought that they reduced fuel burn. Why then did Boeing (and also Douglas on the MD-90) decide not to put them on their newer aircraft?

2 replies: All unread, jump to last
User currently offlineMD11Nut From , joined Dec 1969, posts, RR:
Reply 1, posted (15 years 8 months 2 weeks 18 hours ago) and read 1202 times:

I think there are several factors that affect the decisions whether to add winglets or not.

1. Cost is definitely the number one issue. To build a winglet you first have to design, build and test it then to certify it.

2. Advantages due to addition of winglets have in terms of fuel saving compared to cost and the addition of weight.

As I understand it, winglets can reduce drag only at one or two flying conditions (e.g., during cruise) and not during other phases. Depending on the design and type of operations, the net advantage of winglets may not be that great. I think in the case of the MD-90, McD Douglas simply did not want to deal with designing and building a new winglet for the MD-90 since it's a relatively short range aircraft anyway. In the case of the 777 , with a new wing (not modified from other models), Boeing feels that a winglet is not needed (keep in mind that if you can add, say 5 ft to a wing, it is more efficient to add it outward than upward (winglet)).

Best Regards,

User currently offlineBoomer From United States of America, joined May 1999, 102 posts, RR: 0
Reply 2, posted (15 years 8 months 1 week 6 days 7 hours ago) and read 1165 times:

Dead-on MD11Nut. I just wanted to add a note. There are many aerodynamic tricks that can be used to save fuel, not just winglets. Just look at the raked wingtips on the B767-400ER.

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The wing structure required to support the loads a winglet places on the wing is costly and is not easily recovered by the puddle jumper operation of short and mid-range aircraft. Even long-range aircraft like the 767 have obvious design related cost trade-offs that drove Boeing to decide to rake the wingtip instead of putting a winglet on it.

If there was only one right way to do things in this business, all aircraft would have wing mounted engines, fowler flaps, and cabin doors that retract inside the fuselage ceiling.

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