Originally Posted by
hoss183
I was pax on a BA 747 back in the '90s sometime and seen fuel venting on take-off, the pilot later apologized and told us not to worry, but it struck me as strange as it would have contaminated the rwy i think and possibly given a good mist over hounslow. Never seen it since.
This just got me wondering, does that happen much? An over-filled tank, or a faulty vent?
Similarly, I was on a CX 747 out of Vancouver for Hong Kong back around that time and saw fuel venting on take-off. I presumed at the time that with full tanks and heavy acceleration, dynamic pressure in the system might be enough to crack a relief or vent valve.
Is that vent line opened to atmosphere during re-fuelling to avoid over-pressurisation? If so, perhaps whichever valve is involved in that process may not have closed completely after re-fuelling.
How are the 747 tanks pressurised? What are the consequences of not achieving pressurisation because a vent line is open?