VW - Dual Fuel Pump - Anyone done it
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VW - Dual Fuel Pump - Anyone done it
Hi, I wonder if anyone has any experience in installing a dual fuel pump configuration in a VW powered light single seat A/C. I have a Colibri with just a single pump and it seems like a good idea to have two for redundancy. If there is any precedence I guess the MOD application will be much easier.
Best Regards
Tony Barber
Best Regards
Tony Barber
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I looked briefly into this. The standard engine driven pump won't flow if it dies, according to the VW car experts, so I stuck with gravity and a Facet 40105 which WILL flow fuel if it dies. (Usual Caveats here)
I have my fuel tank vent in a high pressure area so that I get a small speed/pressure boost on top of the 12 inches of gravity pressure. The pump will give an extra 1-to-4 psi and so far ir hasn't overwhelmed the needle valve.
It might be possble to run to 40105s in series or in parallel if you have 2 Andairesque non-return valves. All weigh a lot more than gravity, if you see what I mean.
I have my fuel tank vent in a high pressure area so that I get a small speed/pressure boost on top of the 12 inches of gravity pressure. The pump will give an extra 1-to-4 psi and so far ir hasn't overwhelmed the needle valve.
It might be possble to run to 40105s in series or in parallel if you have 2 Andairesque non-return valves. All weigh a lot more than gravity, if you see what I mean.
Rob Thomas
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On the pump I removed, if the drive fails then it becomes sealed and won't flow. If the diaphragm goes then I'm not sure. I ditched it because of known problems with flaking cadnium plating on the chambers, the extra fuel piping in the engine 'hot area' that was required to run from the tank to the front of the engine and back again to the carb plus the fact that it all weighed more than the facet.
I think I lost about 4 feet of armoured pipework this way.
I think I lost about 4 feet of armoured pipework this way.
Rob Thomas
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Hi All
I don't have an engine pump, just a single facet electric pump. This was how the airplane was when I to it. Its always worried me that a pump failure means I go gliding. There is no gravity available due to the design so its got to be another pump. Hence the question if anyone else had such a set up.
- dual electrical fuel pump.
Cheer
Tony
I don't have an engine pump, just a single facet electric pump. This was how the airplane was when I to it. Its always worried me that a pump failure means I go gliding. There is no gravity available due to the design so its got to be another pump. Hence the question if anyone else had such a set up.
- dual electrical fuel pump.
Cheer
Tony
Tony Barber
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I'd stick a standard VW mechanical one on, in parallel with the electric one, and put a non-return valve after each pump so neither can try to push fuel back through the other.
I'd then fly in the usual way, electric pump on to start, leave it on until at cruising altitude, and then turn it off. It goes on again as part of the approach procedure to keep the fuel flow up when the engine speed drops off with the winding down of the RPM. Of course it can be turned on again if CardiffRob's pessimism comes to fruition and the mechanical pump packs in!
Goes without saying that all this will be subject to a mod approval and discussion with your inspector. I am surprised that the aircraft was issued a permit to fly with just an electrical pump as the failure scenarios are legion, far more than for a mechanical one.
You are looking for redundancy: my suggestion above provides it.
A second electric pump can only provide this if it has a second backup battery giving a supply of volts should the main electrical system croak. If you have Leburg ignition then you have this already, otherwise you are looking at an increase in complexity and weight that is difficult to justify.
My only concern regarding the very pretty Colibri is whether the standard VW mechanical pump will fit under the cowlings. I think lower profile pumps might be available if this is an issue, but I couldn't say where for certain (Great Plains?)
I'd then fly in the usual way, electric pump on to start, leave it on until at cruising altitude, and then turn it off. It goes on again as part of the approach procedure to keep the fuel flow up when the engine speed drops off with the winding down of the RPM. Of course it can be turned on again if CardiffRob's pessimism comes to fruition and the mechanical pump packs in!
Goes without saying that all this will be subject to a mod approval and discussion with your inspector. I am surprised that the aircraft was issued a permit to fly with just an electrical pump as the failure scenarios are legion, far more than for a mechanical one.
You are looking for redundancy: my suggestion above provides it.
A second electric pump can only provide this if it has a second backup battery giving a supply of volts should the main electrical system croak. If you have Leburg ignition then you have this already, otherwise you are looking at an increase in complexity and weight that is difficult to justify.
My only concern regarding the very pretty Colibri is whether the standard VW mechanical pump will fit under the cowlings. I think lower profile pumps might be available if this is an issue, but I couldn't say where for certain (Great Plains?)
Rob Swain
If the good Lord had intended man to fly, He would have given him more money.
If the good Lord had intended man to fly, He would have given him more money.