Why don't all new jets have winglets?

[HardDrive]

Why do I only see some aircraft with winglets? Do they only benefit certain wing designs?

[stevepaa]

They benefit all wings as the best wing is a tube. But there may be structural concerns at the ends.

[LeeH]

http://en.wikipedia.org/wiki/Winglet

[dd74]

So that's what they're called...

[rattlsnak]

With the exception of the 737, on which they absolutely look ridiculous, they definetely look cool..
This was taken leaving Buffalo, with Niagara Falls in the background..

[rattlsnak]

oops, heres the pic..

[Porsche-O-Phile]

Depending on the design (strictly from an engineering and not an aesthetic perspective here) the aerodynamic benefits of eliminating or reducing spanwise flow might be offset by the additional weight of the winglets, the structure needed to support them, or both. The whole design picture needs to be considered (which I'm sure it is).

[450knotOffice]

With the exception of the 737, on which they absolutely look ridiculous, they definetely look cool..

Yea, but those huge blended winglets on the 737NG's are actually the most efficient versions in existence. Beauty does not factor into the equation when it comes to airliner economics - just look at the A-380, probably the ugliest airliner I've ever seen, but probably the most efficient also.

[island911]

Originally posted by stevepaa
They benefit all wings as the best wing is a tube. But there may be structural concerns at the ends.

Are you sure about that? What about an elliptical wing? ( http://en.wikipedia.org/wiki/Elliptical_wing )

[island911]

Oh yeah . . the original Q...

Originally posted by HardDrive
Why do I only see some aircraft with winglets? Do they only benefit certain wing designs?

Cost.

... like replacing the P&C's on your 911 w/ higher compression ratio versions . .. you'll get better mpg & performance . .. but at what cost? Old planes, like old 911s (pre-SC) just may be headed for the scrap heap soon. Thus they don't get the upgrade.

[swa911]

737 winglets only weigh 200 lbs. I've changed a few out. They must really do something for fuel economy since SWA is installing them on our older 737-300's beginning in Jan. Biggest drawback from my perspective is that they are lightning rods. They have no static wicks and lightning strikes typically blow out the trailing edges.

[swa911]

[rattlsnak]

im sure on the 737s are quite worth it, but they are still ugly,.. That picture above doesnt show it that good. They stick up way above the body!

Scott, Im allowed to say so, because my plane has winglets, yours doesnt..

[artplumber]

Form follows function.

[IROC]

Originally posted by island911
Oh yeah . . the original Q... Cost.

island's right. Cost. We actually quoted building these here at our facility (Boeing) to retrofit onto older planes. It's being done (not here - we were too expensive), but it all boils down to cost.

Mike

[beepbeep]

The reason why spells: certification

Adding winglets to existing designs means that whole aircraft family would need to be re-certified, which isn't quite cheap och easy to do.

With other words, even if you can save 4% on fuel on a 737-100 or such old bird, expenses would be eaten up by gigantic costs of re-certification + additional work to install winglets.

Aircraft industry isn't car industry. You can have the mother of all smart solutions that could save you heaps of dollars in your hands, but you aren't allowed to put it on the plane as long as AC is certified without it.

[onewhippedpuppy]

Winglets can be rolled into an STC (secondary type certification). It's essentially an approved modification. Still has to be certified, but only the winglet and other affected structures/systems, not the entire aircraft.

I would suspect that beyond cost, in many cases they aren't installed because you hit the point of diminishing returns. If the drag reduction from the winglet is insignificant compared to the drag polar (entire aircraft), then the additional weight/cost/complexity wouldn't be justified. Part of the reason most smaller aircraft don't have them, the contribution to overall drag by the tip vorticies isn't that large. In an otherwise efficient design, they can make a very noticable difference.

Plus, releasing winglets on a new "improved" model of an aircraft can be a selling point. Just like sticking a more powerful engine in a car, aircraft companies upgrade their aircraft periodically to make them more appealing. I work at Raytheon Aircraft, several of our new Hawker jet and Beechcraft King Air models feature winglets. They're not all new aircraft, just derivatives of an existing one, so a much smaller investment by the company.

[slakjaw]

Originally posted by onewhippedpuppy
I work at Raytheon Aircraft, several of our new Hawker jet and Beechcraft King Air models feature winglets. They're not all new aircraft, just derivatives of an existing one, so a much smaller investment by the company.

OWP,

Do you know anything about the Raytheon jobs up in Antarctica? A friend of mine wants to go up there for the "winter term"

[swa911]

Here is a better picture. Winglets are cool.

[swa911]

I forgot how many pics of winglets I have. This is the last one, I promise.