Newsgroups: sci.aeronautics.airliners
Date: 10 Sep 97 19:38:45
From: David Lednicer <dave@amiwest.com>
Subject: Re: 747 hump

Marc Schaeffer wrote:
>
> I wonder to what extend the hump of the 747 contributes to the total
> fuel consumption at cruise speed and cruise altitude. Can the
> aerodynamical disadvantages of the 747-hump be evaluated by some
> formula ?

	Actually, the hump slightly improves the drag of the 747.  If the hump
wasn't there, the cross-sectional area distribution would have a chunk
missing and the wave drag would be higher.  I have data showing that the
extended hump on the 747-300 and -400 improves the area distribution
slightly, further reducing wave drag.

-------------------------------------------------------------------
David Lednicer             | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc.   |   email:   dave@amiwest.com
2133 152nd Ave NE          |   tel:     (206) 643-9090
Redmond, WA  98052  USA    |   fax:     (206) 746-1299

Newsgroups: sci.aeronautics.airliners
Date: 25 Sep 97 01:39:42
From: David Lednicer <dave@amiwest.com>
Subject: Re: 747 hump

Joel S Cole wrote:
> Solution.  Boeing engineers designed a panel that deployed behind the
> Refueling Receptable, just in front of the windshield.  This panel has
> holes that breaks up the turblence from the boom and re-establishes
> laminar flow over the Hump.
> Next time you see a front view of the "Flying Fuhrer Bunker", look
> above the Refueling Receptable and you will see an outline of this panel.

	Not quite - one of the engineers who helped fix this explained it
to me years ago.  The presence of the boom created a flow separation that
was unstable.  They tried to get rid of it, but eventually came to the
conclusion that they were stuck with the separation.  This being the case,
the added the panel to stabilize the flow separation so that it doesn't
wander about.  There is no laminar flow on the hump!  Any laminar flow on
the 747 fuselage is gone by the time it tries to cross the radome joint,
the windshield joints, etc.

-------------------------------------------------------------------
David Lednicer             | "Applied Computational Fluid Dynamics"
Analytical Methods, Inc.   |   email:   dave@amiwest.com
2133 152nd Ave NE          |   tel:     (206) 643-9090
Redmond, WA  98052  USA    |   fax:     (206) 746-1299