Re: Why no wingtips for B777???

Date:         13 Jul 97 01:25:56 
From:         kls@ohare.Chicago.NOSPAM.COM (Karl Swartz)
Organization: Chicago Software Works, Menlo Park, California
References:   1
Followups:    1
Next article
View raw article
  or MIME structure

>Why are winglets not used on the newer Boeing aircraft, for example the
>B777, and the originally proposed B747-500X/600X???

This has been discussed *many* times here -- see the newsgroup
archives at http://www.chicago.com/airliners/archives.html for those
previous discussions.

Bottom line: for a new design (not modifying an old one), Boeing feels
they can produce a better wing without winglets.  (Or wing fences, as
Airbus calls them.)

>And why are winglets used on the latest B767-400ERX????

This is where it gets interesting.  The latest iteration of the design
being considered (p. 34, AW&ST, June 30, 1997) does NOT have winglets.
Quoting from Aviation Week:

   The highly-swept, 8 ft. wing extensions save over a ton of weight
   and are substantially less complex to manufacture and maintain than
   the originally proposed 8 ft. canted winglets, Boeing said.

   The patent-pending, in-wingplane design also reduces the planned
   767-400ER wingspan to 170 ft. from 181 ft., with no loss in overall
   aircraft performance, according to John Quinlivan, 767-400ER
   program manager.

>From the photograph (of a 3.7% scale wind-tunnel model), it looks like
the line of the trailing edge is straight all the way to the wingtip,
but the leading edge sweep-back increases at a point near the wingtip
(presumably 8 ft. inboard, from the text.)

BTW, this page is also where the picture of the British Airways
747-400 with a fifth engine in a ferry pod can be found.

--
Karl Swartz	|Home	kls@chicago.com
		|Work	kls@netapp.com
		|WWW	http://www.chicago.com/~kls/
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills