Re: What's that?

Date:         16 Oct 97 11:59:50 
From:         "john r." <john@guava.demon.co.uk>
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In article <airliners.1997.2456@ohare.Chicago.COM>, Gerhard Lenssen
<GLenssen@t-online.de> writes
>I saw a PIA-747 after starting from Frankfurt having something similar
>to condens-stripes outgoing from the outer edge of the right wing;
>only from this point.
>What may this have been?

Its venting fuel from the wing tip surge tanks. These are small
reservior tanks that catch overfuels and shuts down the refuel process,
when on the ground. Normaly this fuel slowly drains back into the tanks.

In flight, if the aircraft is tanked up to the limits and not flown
level it tends to slosh out into the surge tanks and then overboard and
thats what you see. I have watched a PIA leaving a trail over a mile
long out of Heathrow. They seem to make a habit of it !
Maybe they tanker fuel to Pakistan.
--
john r.