Re: Concorde Question?

From:         drinkard@bcstec.ca.boeing.com (Terrell D. Drinkard)
Organization: Boeing Commercial Airplane Group
Date:         26 May 94 12:14:43 
References:   1 2 3
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In article <airliners.1994.1251@ohare.chicago.com>,
Alex Lee  <alexlee@MIT.EDU> wrote:
>
>I talked to a 747-400 captain a while back, and asked him if they 
>transfer fuel in flight to the tank in the stabilizer to reduce trim 
>drag.  The answer, to my surprise, was NO.  He said unlike the MD-11's
>and the airbuses, the 747-400s only use the stabilizer tank to store 
>fuel, not to move the CG to reduce trim drag. Anyone out there who can
>verify that?

That is technically true.  The fuel from the tail tank is simply metered
into the center section tank at a specified rate.  There is no attempt to
determine the airplane's CG in flight and move it by pumping fuel.
I believe that is considered to be too complex for its expected benefit.

However, the 747-400 does derive a trim drag benefit from the tail fuel. 
The tail fuel does pull the airplane's CG aft, reducing the amount of trim
drag generated by the horizontal tail.  But, all of those calculations are
done on the ground.


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