Hi,
I am studying the Twin Otter and have a two part question regarding the flapper valves. I have inserted a diagram below of the aft tank, as it is essentially the same as the forward tank.
First off, what is the difference between the flapper valves in Cells 8 and 6 compared to the one located in Cell 5. The diagram depicts the first ones as two black lines, and the last one as a solid line (shown by two red circles, and one blue circle respectively). Am I correct to assume that the valves in cells 8 and 6 have a smaller hole in the middle of the valve to allow fuel to transfer out of the cell at a slower rate than into the cell (ie. fuel would be drawn out at a slower rate in flight, but would be added quickly while being refueled)?
My second question is what is the purpose of these same valves on cells 8 and 6. I can understand why 7 does not have one, as that is the cell which is connected to the aft refueling filler. And I can understand why 5 needs a valve, as it is the collector cell. 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.
I hope that makes some sense..
Cheers!
(Ps. I posted this question on avcanada as well)
