Boeing 797 Take A Look

[Diapason]

It leads to smoother air flow, apparently. According to my fluid mechanics lecturer the story (maybe apocryphal) goes that somebody bumped a wing into a wall, pushing the end up a little. Said pilot thought it flew better, and when fluid mechanics gurus put that wing design into the Navier-Stokes equations they found that, sure enough, it gives a better air-flow profile. As I say, this story might be utter nonsense, but I liked it anyway.

Si

[Tango]

I was on a Boeing (something or other ) 700 series that had pointy up wing tips like in the picture in the first post.

Does anyone know why the tips point up? Is it for economy or dynamic stability or something else please?

They were originally designed by Burt Rutan and I first remember seeing them on Burt Rutans Voyager, and now they're pretty common on gliders, and a lot of powered aircraft. Also you can also see them on Wind Turbine blades...have a look at the new one near J12 on the M4 next time you're passing (or is it J11?).

Anyway...Google is your friend:

The wingtip devices increase the lift generated at the wingtip, and reduce the lift-induced drag caused by wingtip vortices, improving lift-to-drag ratio. This increases fuel efficiency in powered aircraft, and cross-country speed in gliders, in both cases increasing range.

They're called winglets. The upward angle (or cant) of the winglet, its inward angle (or toe), as well as its size and shape are critical for correct performance, and unique in each application. The vortex which rotates around from below the wing strikes the cambered surface of the winglet, generating a force that angles inward and slightly forward, analogous to a sailboat sailing close hauled. The winglet converts some of the otherwise wasted energy in the wing tip vortex to an apparent thrust.

[tdiplc]

I was on a Boeing (something or other ) 700 series that had pointy up wing tips like in the picture in the first post.

Does anyone know why the tips point up? Is it for economy or dynamic stability or something else please?

They were originally designed by Burt Rutan and I first remember seeing them on Burt Rutans Voyager, and now they're pretty common on gliders, and a lot of powered aircraft. Also you can also see them on Wind Turbine blades...have a look at the new one near J12 on the M4 next time you're passing (or is it J11?).

Anyway...Google is your friend:

The wingtip devices increase the lift generated at the wingtip, and reduce the lift-induced drag caused by wingtip vortices, improving lift-to-drag ratio. This increases fuel efficiency in powered aircraft, and cross-country speed in gliders, in both cases increasing range.

They're called winglets. The upward angle (or cant) of the winglet, its inward angle (or toe), as well as its size and shape are critical for correct performance, and unique in each application. The vortex which rotates around from below the wing strikes the cambered surface of the winglet, generating a force that angles inward and slightly forward, analogous to a sailboat sailing close hauled. The winglet converts some of the otherwise wasted energy in the wing tip vortex to an apparent thrust.

That is a fantastic answer - thank you Tango :)

Thanks to Diapason too :)

[Tango]

I was on a Boeing (something or other ) 700 series that had pointy up wing tips like in the picture in the first post.

Does anyone know why the tips point up? Is it for economy or dynamic stability or something else please?

They were originally designed by Burt Rutan and I first remember seeing them on Burt Rutans Voyager, and now they're pretty common on gliders, and a lot of powered aircraft. Also you can also see them on Wind Turbine blades...have a look at the new one near J12 on the M4 next time you're passing (or is it J11?).

Anyway...Google is your friend:

The wingtip devices increase the lift generated at the wingtip, and reduce the lift-induced drag caused by wingtip vortices, improving lift-to-drag ratio. This increases fuel efficiency in powered aircraft, and cross-country speed in gliders, in both cases increasing range.

They're called winglets. The upward angle (or cant) of the winglet, its inward angle (or toe), as well as its size and shape are critical for correct performance, and unique in each application. The vortex which rotates around from below the wing strikes the cambered surface of the winglet, generating a force that angles inward and slightly forward, analogous to a sailboat sailing close hauled. The winglet converts some of the otherwise wasted energy in the wing tip vortex to an apparent thrust.

That is a fantastic answer - thank you Tango :)

Thanks to Diapason too :)

Just found the first aircraft to have them fitted in 1975...it was the Rutan Varieze (similar to the type that John Denver was flying when he disappeared)