777 and Winglets

[citabriapilot]

How come the 777 doesn't have winglets? With all the talk about how great winglets are for economy and how some airlines are retrofitting the 757 with winglets, what's the deal with the 777?

 

[FurloughedTwice]

Some types of aircraft, especially airliners, have winglets, for example the Airbus A340, and the Boeing 747-400. Other designs such as the Boeing 777 omit them, because the gain available is very small and would make the aircraft just too large for a standard airport gate. The designers of the 777 considered folding wingtips to accommodate winglets, but in the end, customers decided that the extra complexity of the wing did not justify it. Recently, blended winglets have been offered as an aftermarket retrofit for Boeing 737 and 757 aircraft by Aviation Partners Inc., allowing these aircraft improved performance and efficiency characteristics.

I found this article but I'm not sure how old it is.

 

[pgcfii2002]

I wonder why not too....they have winglets on every other damn airframe nowadays.

 

[citabriapilot]

Hmmm....makes a lot of sense. Thanks!

 

[Cardinal]

The 777-200LR and -300ER do have winglets - they just happen to lie flat. The purpose of a winglet is to prevent the "spill" at the end of the wingtip and reduce drag by increasing aspect ratio. It doesn't really matter which direction you orient the "fence," you still derive a similar aerodynamic benefit.

 

[pgcfii2002]

Correct

 

[Patriot328]

If I remember right, the 777-100 was the 777 that had the folding wingtips (about 8-10 feet per side) for gate space.

Not too many (0) 777-100s running around

 

[pgcfii2002]

I think the 777 has "raked" winglets.

 

[8vATE]

I think the 777 has "raked" winglets.

as someone mentioned..

the "raked" wingtip achieves the same performance gains as the "elliptical" winglet...

 

[Gillegan]

You have to consider the wings on modern planes unique to their type with unique characteristics and performance. Winglets might be a benefit on one wing while not on another. A winglet is designed to recover some of the wing efficiency that is lost from wingtip vortices. The tradeoff is increased structural weight. On some aircraft types, the tradeoff may recommend winglets, while on others they may not. Winglets tend to be of more benefit the longer you fly the airplane. When operators are considering the whether to fit their B737NG's with winglets, I'm sure they look at the average stage length that the aircraft will be used on. On the B777, the wingtips have been carefully designed (rake, changing airfoil section etc.) to minimize the wingtip vortex so the winglet will not be beneficial to that particular wing. You can't draw a conclusion that just because the A340/A330/B747-400 benefit from winglets, that other types necessarily will also.