Re: A3XX vs B747-600 (was: Airbus lawsuit coming?)

From:         drinkard@bcstec.ca.boeing.com (Terrell D. Drinkard)
Organization: The Boeing Company
Date:         25 Sep 96 13:40:13 
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In article <airliners.1996.1881@ohare.Chicago.COM>,
C. Marin Faure <faurecm@halcyon.com> wrote:
>In article <airliners.1996.1872@ohare.Chicago.COM>, jfmezei@videotron.ca wrote:
>
>> Ok, so in the case of the 747,  the old wing design had become a
>> "hindrance" to added pax and range, so the use of a totally new wing
>> with today's efficient designs is a "must" in order to acheive the
>> stated goals (range/pax).

I'm not sure what exactly is meant by "hindrance", but the current 747
wing, at 5500 sq ft, simply wasn't large enough to haul 500+ passengers
with bags 7400+ nmi.  Not enough fuel volume, and too much wing loading.
I won't even attempt to discuss the problems with manufacturing and
additional induced drag.

>> However, in the case of the potential A3XX, since the A340 already has a
>> modern wing, is it conceiveable that Airbus might be able to adapt the
>> existing 340 wing design instead of design a brand new one from scratch
>> ? Would such a "new" wing be all that different from the existing 340
>> wing ?
>
>I'm not an aerodynamics engineer, but I would imagine that Airbus might
>draw heavily on the wing design of the A-330/340 if they build an A-3XX,
>although they would probably like to get rid of the winglet.  However, the
>A-3XX would be considerably larger and heavier than the A-330/340, so the
>wing would have to be proportionately larger, which would necessitate
>designing a new internal structure even if the airfoil shape were similar
>or identical.  Also, the A-3XX would require larger and stronger landing
>gear, which means the wing spars and other associated components would
>have to be stronger.

I'm going to differ with Martin here for a moment.  Given the relatively
poor results of the A340 wing design (reduced LRC, flutter, etc) I don't
think anyone would really want to reproduce that particular wing on a
larger aircraft.  Further, the A340 wing is "corner" designed.  That is, it
doesn't have much (if any) room to grow as it sits.  It needs a total
structural redesign, or it'll end up with huge doublers on the wing upper
surface, same as the A300.  This is considered poor form amongst aero
performance types.

>> And taking this to another plane, if Boeing builds its new 747s, could
>> the 777s wings not be adapted to the new 747s ?

No.  There are huge differences between twin and four engine aircraft
wings, generated primarily by flutter response.

>> Even if the actual wing cannot be adapted litterally, wouldn't the
>> expertise and computer simulation programmes developped for the 777 not
>> reduce the costs of the 747s new wings ? Or would this knowledge already
>> be considered "old" and no longer state-of-the-art forcing Boeing to
>> start from "scratch" ?
>
>The 777 has one of the most advanced wings around, and Boeing has already
>stated that the 747 derivatives, if they are built, will use a similar
>wing.  However, it would have to be larger and stronger than the wing on
>the 777 because the new airplane itself will be larger and heavier.  But
>the aerodynamic and manufacturing advances that are incorporated in the
>777's wing would be used for the 747 derivative wing.  In that much of the
>airfoil and control surface research and development has already been done
>for the 777, you are correct in stating that the expertise gained from the
>777 program will help hold the costs down on a 747 derivative.

The airfoil technology is a good starting place, but airfoil development
rarely stands still.  The CFD techniques alluded to above are being used
by Boeing, and every other jet transport manufacturer, to hold down costs.
However, the controls requirements and layout would differ significantly
between the 777 and any 4-engined airplane, rendering much of the 777 data
irrelevant.  Suffice to say that the wing is the heart of the airplane's
performance, and each wing design is lovingly tweaked right up to drawing
release, and beyond in some cases.

--
Terry
drinkard@bcstec.ca.boeing.com
"Anyone who thinks they can hold the company responsible for what I say has
more lawyers than sense."