Originally Posted by
MarkerInbound
Fuel flow is measured going into the engine. Hard to say from the video if the engines are running. Not enough spillage to show up on the quantity indicators. Not a 767 person but as said above, either a failed check valve in the dump system or the plane was topped off while cold and as the day's temperature climbed and the hydraulic pumps were turned on preflight the surge tank filled and vented outboard.
I have noticed fuel flow from the vent pipe on a 747 during acceleration on more than one occasion. I presumed that it was something that could happen normally for a fully-fueled aircraft.
The old CX and SQ long-hauls out of YVR notably took most of the runway to get up and away, frequently trailing a spray from the vent pipe; too much to just be condensation off the wing.
Is there a pressure relief function coming into play there, perhaps?