Re: Why no wingtips for B777???

Date:         05 Aug 97 03:15:48 
From:         k_ish <kenish@ix.netcom..com>
Organization: Netcom
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jf mezei wrote:
>
> > C. Marin Faure wrote:
> > > Winglets are a compromise, used to improve the efficiency of an existing
> > > or flawed wing design.  If you have the opportunity to design a wing from
> > > scratch and you get it right, as was done with the 777 and the New
> > > Generation 737 family, there is no reason to install winglets.  While they
>
> k_ish wrote:
> > Also, the efficiency improvement from winglets is only fully realized at
> > high altitude sustained cruise.  Although winglets yield an efficiency
> > increase at any altitude/airspeed, this improvement does not offset the
> > weight and manufacturing penalties C. Marin describes.
>
> What about the other extreme of the 747-400, the Canadair Regional jet
> (flying skidoo).  It is designed for short hops, yet has winglets. Is
> this because Canadair didn't build the wing from scratch, using designs
> from its Challenger programme ?

Good point.  I don't know why the CRJ uses winglets, but here's a few
possibilities:

1.  The original wing may be common with the Canadair Challenger, and
optomized for a "mission profile" different than the CRJ.  An
improvement to an existing design, as C. Martin Faure stated.

2.  Winglets aerodynamically look like an increased-span wing, which may
be required for the heavier CRJ.  If the CRJ shares the production line
with the Challenger (I don't know if this is true), a longer span wing
might not work on the established production line.

3.  Variation on 2.  If the wing is common to both, the same tooling and
jigging can be used.  Add winglets, and voila.

4.  The marketing department thinks winglets look cool!  (Don't
underestimate this as a possibility).

> Or are the winglets on the CRJ purely for manoeuvrability/smooth ride
> purposes ?
> (do they make a difference ?)

Winglets have nothing to do with handling or ride characteristics.
(They do reduce the wake vorticies behind the wing, and could "improve"
the handling and ride for a Cessna 150 following behind!)  :-)

Ken Ishiguro