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Originally Posted by XabbaRus
I thought with water being denser than fuel it sinks and I'd imagine a scavenge system would pull it out from the bottom, but then if you have 5 litres in a thousands of litres of fuel it would be so dispersed that draining it off would be very difficult.
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It does sink to the bottom. But I can't think of a way a scavenge pump will take just the water and not the fuel or somehow seperate the 2 without adding one more complex system.
Again though, I'm not familiar with the 777, so maybe they do have something that can, but I'd be suprised though.
Normally, all aircraft have fuel sump drains in the lowest part of each tank for the purpose of draining water from the fuel. That might be part of the routine maintenance at BA. Who knows, if it is part of their checks, maybe they haven't been doing it.
I work for a charter company in Denver, CO. We maintain Lears, King Airs, Hawker 800's and a couple of Challenger 600 aircraft(biggest airplane we have) and we have a fuel sumping procedure to check for water that we do as part of our departure checks. Normally we'll find some globules of water floating around and those are not normally a problem. It is when the water becomes suspended in the fuel, that is when there can be a problem. There is a test that we then do and there is a limit on how much water can be suspended in the fuel sample. It is a fair amount though before it becomes out of limits.
I've taken a pint sample jar filled 3/4 of the way with jet fuel and filled it the rest of the way with water, mixed and did the test, and it still didn't show out of limits for suspended water. Normally, jet fuel is clear, maybe a slight straw tinge. If there is suspended water in it and you swirl a sample of fuel with suspended water, it is very cloudy. that is whe we normally do the test.
