Originally Posted by Phu
...The only reason for that valve the valves in cell 8 and 6 that I can think of is so fuel does not quickly move from cell to cell during a non cruise attitude.
Hello Phu:
Your analysis is absolutely correct. The holes in the flapper valves in the cells which are not collector cells and not cells with refuelling provisions are there to allow an adequate quantity of fuel to flow into the lower manifold to support fuel transfer to the collector cell
via the ejector during normal operations.
As you pointed out, having a flapper valve with a hole in it permits rapid entry of fuel into the cell during refuelling operations (the flapper valve lifts up to allow fuel to enter from the manifold), but prevents noticeable center of gravity shifts from taking place during the climb and descent phases of flight.
The holes in the flapper valves also permit fuel to transfer to the collector cell (and from there to the engines) by gravity alone in the event of a failure of the normal motive flow system. This could be caused (for example) by blockage of the ejector cell, or a loss of all electrical power.
I have posted a photo of the actual contents of a collector cell below. This assembly is incomplete, but at least it will give you an idea of what all the parts shown in the collector cell schematic look like. I will try and get a picture of one of the flapper valves with a hole in it and post it here later this week (I might need to go down to the factory to find one).
Michael
Collector Cell Components (assembly is incomplete)
