Re: 747 hump

Date:         16 Sep 97 02:35:26 
From: (Joel S Cole)
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Newsgroups: sci.aeronautics.airliners

Quoting "Thomas Lindberg"

>>I wonder to what extend the hump of the 747 contributes to the total
>>fuel consumption at cruise speed and cruise altitude.

>I have been told (by Boeing during a visit??) that the hump actually
>contributes to the lift and that the longer hump (compared to the old
>original) is still better.

  Mr. Lindberg (hmm, I wonder),

     The contribution of the hump to the B747 aerodynamics was
demonstrated conclusively on the E-4 Airborne Command Post.  The Air
Force's requirements were that the E-4 would have aerial refueling
capabilities.  They conducted a feasibily test using the prototype B747
behind a tanker to verify that the bow wave of the jumbo would not lift
pick up the tail of the tanker.  This test also determined the best
location of the refueling receptable was just in front of the cockpit
windshield (and just above the President's bunk).
     Then the Universal In-Flight Refueling Receptable was designed and
installed during Phase I of the program, which converted a B747-200
fuselage for the Phase 2 electronics modification.
      About 1975, the Air Force performed a dry-run refueling test with
actual connects.  The E-4 pilot noticed the procedure required more
flight control inputs and the crew in the rear said they were being
bounced around during the refueling procedure.  After some analysis,
Boeing determined the problem.
      As the tanker's boom dropped down in front of the nose of the E-4,
the turbulance off the winglets on the boom disturbed the airflow over
the B747's Hump. As this airflow was disrupted, killing the lift off the
Hump, the pilot had to make a control input.  As the boom broke away, the
pilot then had to reverse the contol input.
    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.

      		STeve Cole~
			(ex-2nd Louie with E-4 SPO)

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