Re: objects on wing tips

From:         gregory@bcstec.ca.boeing.com (Greg Wright)
Organization: The Boeing Co. (Aerodynamics)
Date:         10 Dec 92 00:52:14 PST
References:   1 2 3 4
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I have a few questions for any of you passenger airplane gurus.
Several years ago, the aeropspace industry introduced vertical
flap-like things on the ends of their airplane wings. I've
only noticed these on 'larger' planes such Airbus, 747-400 and
MD-11.
Q1. What is the technical name for these flap-like things?

    Winglets....

Q2. Are they mobile or fixed?

 Fixed on our airframes....

Q3. Do they only serve to stabilize the flight?

 They help to reduce the induced drag by preventing the wingtip
 vorticies from forming...well keep them from being as strong at
 the tips anyway. They also produce lift since they are not 
 mounted absolutly vertical. In the same vain, they produce a little
 thrust.

Q4. Why haven't they appeared on smaller aircraft?

 The weight. Also, in theory they have big effect on the reduction of
 total drag, however, this has not been the case. The effect is small
 enough that we put them only on the long range planes. This is why
 we removed them from the wings of the 747-400D, which was made for
 short hauls..

Q5. The ones I saw on the Airbus were shaped like a 'V'
    and symmetric with the wing tip, ie. one leg of the 'V'
    was above the wing and the other pointed below the wing.
    Whereas the ones on the 747-400 looked like extensions
    of the actually wing, but bent 90 degrees upwards.
    Why the difference?

 Same principle, just different methods. As the technology advances
 you will see many different devices designed to to the same thing.
 NASA flew a plane that had six or seven winglets, all at different
 angles to the freestream....


I would greatly appreciate any answers.

-Cheers




 ________Greg Wright____________     High Lift Development     
| gregory@bcstec.ca.boeing.com  |    Aerodynamics    
|     gregory@halcyon.com       |                             
|____uunet!bcstec!gregory_______|               NOT A BOEING SPOKESPERSON.