quote:Originally posted by selector
I was on the VS53 from BOS to LON on Sun morning. According to what I heard there it was something to do with the fuel supply on VS20 which meant it could only use fuel from one wing and not balance out. There was talk of diverting to Montreal but the captain decided they could last until Boston.
Yeah, I can see how that will be a problem, and that it possibly won't manifest itself until in flight. The 747-400 carries fuel in the wings, the belly (in between the wings), and in the tail (vertical stabiliser), although it's unlikely there's anything loaded in the tail tank for SFO-LHR.
With an 11-12 hour fuel load, the fuel is drawn from the centre (belly) tank initially, which is topped up by any fuel in the tail tank draining into the centre tank. This feeds all four engines.
When the centre tank is empty, the engines then start drawing the fuel in the wings. I'd hazard a guess that this problem only became apparent when the fuel system switched from the centre tank to the wing tanks.
It could have been caused by a frozen valve, blocked feed pipe, or a leak in part of the fuel system which is triggered by drawing fuel in a certain way.
Based on the readings and alerts they recieved in the flight deck, the crew would elect to manually configure the fuel system to avoid the problem, work out how much fuel was then available to them, what their new endurance is, and based on that, elect where they would divert to.
The divert to BOS looks to have been operationally influenced - VS have local staff and handling agents, probably have MX agreements with a local operator, and access to onward flights for re-accomodation of the pax.
Cheers,
Mike