Re: TWA 800 question: fuel flow problem

Date:         11 Feb 98 04:26:33 
From:         "Matthew Lehde" <>
Organization: EarthLink Network, Inc.
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jf mezei <"[non-spam]jfmezei"> wrote in message ...
>OK. We know that centre fuel tank exploded. And 1.5 minutes prior to
>that explosion, there is a "crazy fuel flow indicator" for an engine.
>Couldn't the initial problems not have been caused by an electrical
>problem which eventually sparked the explosion ?

I don't think this could be the cause of the explosion... A fuel flow
indicator would probably be located out on the engine.  If it sparked, the
wing would have blown up first.

>Could someone put this "crazy fuel flow indicator" in perspective ? Is
>this something which is as common as someone sneezing and considered
>perfectly normal ?

I doubt it's very serious.  When I was fueling airliners they would have
inop fuel (level)guages every once in a while.  Just inconvenient... Lots of
extra calculations.
Of course it's possible that there may have been a fuel pump failure on that
engine, but that would only result in power loss and engine shut-down. Not a
CWT explosion.
Most likely a guage malfunction.

>Also, what exactly did the pilot mean by "where this thing's trimmed" ?

That is in reference to the trimming of the flight controls to "trim" the
airplane to fly level and at the desired pitch.  After fuel,cargo, and
passengers are loaded and the doors are closed. weight and balance
calculations are done to determine the proper trim setting for the horizonal
stabiliser.  If this setting is incorrect it could cause under or
over-rotation on take-off resulting in a catostrofic runway overrun or a
stall immediately after rotation.  The aircraft trim may have been off
slightly requiring the pilot to apply forward or back pressure on the
control yoke.  This doesn't seem like a big problem to me since they had
flown all that distance with no problems.  It was probably just annoying...
Hopefully an airline pilot will respond... I'm not one yet.

>Also, how is fuel distributed to each engine ?

On the 747-400 with the automated fuel system during take-off each
engine draws off its own wing tank, and after flap retraction draws all
fuel from the CenterWT.  After the CWT is empty it feeds from the Main
2 & 3 tanks... Main 1 is between Engine 1 & 2, main 2  between Eng 2 and
the CWT, main 3 is between the CWT and Eng 3, main 4 is between Eng 3 &
4.  Small reserve tanks are outboard of Eng 1 & 4.  After 2 & 3 are down
to the same level as 1 & 4 each Eng feeds from its own tank.
Of course on a 747-100 the fuel distribution is controlled by the flight
engineer, but I think on take-off and landing it's standard the for the Engs
to feed off their own tanks.

>Last question: with a wing tank almost full, what would happen if a pump
>in centre fuel tank were to start to pump air/fumes from an empty centre
>tank to a wing tank

If air/fumes were pumped into the wings it would just go out the fuel tank
vents, wouldn't it?   Hopefully some airline pilots will respond.

The main cause of the crash was the navy missile tearing through the
fuselage just forward of the CWT and the resulting rapid decompression.

[Moderator's Note:  The bit about the missile is of course totally
unsubstantiated speculation, not fact as implied.  -- Karl]
matt lehde