Re: 747-400F

From: (Greg Wright)
Organization: Boeing
Date:         16 Mar 93 21:57:51 PST
References:   1 2
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In article <airliners.1993.223@ohare.Chicago.COM> (SSgt Scott Jacobson;93D APS/TROS;981-7441) writes:
>The 747-400F doesn't have the stretched upper deck due to the
>fact that the floor of the upper deck reduces the clear ceiling
>height available on the main deck, hence the available cargo
>volume is LESS than the unstretched version.

Not to be picky but in the -400F we don't put a floor in the upper
deck.  This lets us put in oversized cargo there and reduces the
overall empty weight of the airframe.

>I know it sounds backwards, but a 747-400F with a Stretched upper
>deck has LESS available cargo volume than a -400F without it...

We could actually get more cargo in without the floor but the
weight increase overcomes this advantage.

>Since no cargo is carried on the upper deck stretching it just adds
>dead weight. There might be aerodynamic advantages to the stretch
>but I'll bet there outweighed by the extra weight.

There is a incremental drag increase with the upper deck from the
added wet area of the plane. The only aero advantages from the
upper deck are at the critical mach number where, through a better
area ruling, the wave drag is decreased a little.  This is why 
the 747-100,-200 cruise at mach .84 and the -300, -400 cruise
at mach .86.



 ________Greg Wright____________     High Lift Development 
|  |    747/767 Aerodynamics 
|       |                             
|____uunet!bcstec!gregory_______|               NOT A BOEING SPOKESPERSON.