I'm in the middle of plumbing my all-electric fuel system for my 9A. Without turning this into a debate about the merits or dangers of an all-electric system, I'm seeking advice from the collective VAF brain on whether check valves need redundancy in a carb setup.
My fuel system will look like the following diagram:
The fuel pumps are Facet 40109 as mentioned elsewhere in the forums, and have built-in check valves. They will be fed by redundant power supplies and will be on independent switches, circuits, etc.
I've been thinking, if one pump fails AND its built-in check valve simultaneously fails open, the other pump will pump to the path of least resistance. That would probably be in a closed loop between the pumps, and not to the engine, which could lead to a fuel starvation event. To mitigate this risk, I could put an additional Andair check valve at the output of each pump, further reducing the possibility of fuel starvation.
Is this failure scenario realistic? Sure, one pump could fail during a given flight. One check valve could fail during a given flight. But both? Is this akin to losing both the vacuum system and the electrical system simultaneously in a spam can?
The pumps will be tested independently during the ground run-up, and as each pump is tested a failure of the opposite check valve would be immediately apparent as a loss of pressure. So the more I think about it, the more I think there would have to be two independent, simultaneous failures: one pump failure and one check valve failure on the FAILED pump.
Thoughts? Opinions? Thanks!
My fuel system will look like the following diagram:
The fuel pumps are Facet 40109 as mentioned elsewhere in the forums, and have built-in check valves. They will be fed by redundant power supplies and will be on independent switches, circuits, etc.
I've been thinking, if one pump fails AND its built-in check valve simultaneously fails open, the other pump will pump to the path of least resistance. That would probably be in a closed loop between the pumps, and not to the engine, which could lead to a fuel starvation event. To mitigate this risk, I could put an additional Andair check valve at the output of each pump, further reducing the possibility of fuel starvation.
Is this failure scenario realistic? Sure, one pump could fail during a given flight. One check valve could fail during a given flight. But both? Is this akin to losing both the vacuum system and the electrical system simultaneously in a spam can?
The pumps will be tested independently during the ground run-up, and as each pump is tested a failure of the opposite check valve would be immediately apparent as a loss of pressure. So the more I think about it, the more I think there would have to be two independent, simultaneous failures: one pump failure and one check valve failure on the FAILED pump.
Thoughts? Opinions? Thanks!