Leslie and others,
Fuel leaking from a surge tank vent is in 90% of the cases caused by overfilling one of the main tanks.
This can be caused by expanding fuel during a hot day, by towing the aircraft and 'rocking'the wing or by a malfunction in the volumetric topoff system.
In the other 10% of the cases it is likely to have a mechanical failure in the fuel distribution system inside the tanks, for example a ruptured fuel feeder tube.
As soon as you switch on the pumps you get a fuel transfer from one tank to another, causing an overflow.
Normal procedure is to return to the gate, have the surge tank drained (takes 30 minutes), switch on the pumps again for 15 minutes or so and see what happens.
If the fuel starts flowing again you're grounded for at least a day or two.
Regards, Ballpoint, LAE 743/744.
[ 20 January 2002: Message edited by: ballpoint ]
[ 20 January 2002: Message edited by: ballpoint ]</p>