romirez
Member
Hi folks,
I experienced a complete engine failure in my RV7 a few weeks ago, due to fuel system obstruction, and figured I'd share the experience with the community in case it helps prevents similar incidents. Luckily, the failure happened on downwind, so I was able to deadstick it to the runway with no damage to myself or the airplane. Once on the ground, with the help of a local mechanic, we quickly identified the cause: a piece of proseal separated from one of the tanks, and completely plugged up the inlet of my Red Cube fuel flow transducer, resulting in 0 fuel flow to the engine.
The bit of proseal in question, recovered out of the Red Cube, with a mm scale. It is almost exactly 3mm in diameter, same as the Red Cube flow inlet. It's possible it has been banging around the fuel lines for a while to achieve this very round shape and be able to cause the failure
Clearly, this is a design flaw with the plane's fuel system:
1. It has the aerobatic flop tube pickups in both tanks, so no mesh / screen in the tank (normal pickups possibly could have caught this).
2. From the tanks, fuel goes to an andair fuel selector valve, then into the redcube (in the footwell tunnel), then into the electric boost pump, and only then into a gascolator on the other side of the firewall, so there is a ~3mm narrowing of the fuel line before the first real filter.
I am not the builder of this airplane, and bought it already flying a little over a year ago with 100hr flown on it, and then added another 100hr before this failure. The builder says that the fuel system was designed and executed by a build-assist shop (in South Africa, now appears to be defunct), who apparently didn't consider the fact that there is a obstruction failure mode (which has, turns out, caused accidents in the past), or possibly were unaware of the flop tubes and expected the pickup mesh to act as the filter (still probably not the best idea). I myself also thought I had normal pickups until I started digging into the fuel system - the plane has a carburated O360, so sustained inverted flight is not really possible - there is no reason for the flop tubes. Turns out that the builder bought the kit partially complete (including completed and sealed tanks) and finished it - the flop tubes were installed by the original kit owner, who I guess was planning on a different engine.
I have added the TS Flightlines wing root fuel filters to prevent a repeat and am back to flying the airplane, but I would be lying if it didn't cause me to think long and hard about what other possible design issues might be hiding somewhere that are hard to identify on a prebuy / conditional inspection!
I experienced a complete engine failure in my RV7 a few weeks ago, due to fuel system obstruction, and figured I'd share the experience with the community in case it helps prevents similar incidents. Luckily, the failure happened on downwind, so I was able to deadstick it to the runway with no damage to myself or the airplane. Once on the ground, with the help of a local mechanic, we quickly identified the cause: a piece of proseal separated from one of the tanks, and completely plugged up the inlet of my Red Cube fuel flow transducer, resulting in 0 fuel flow to the engine.
The bit of proseal in question, recovered out of the Red Cube, with a mm scale. It is almost exactly 3mm in diameter, same as the Red Cube flow inlet. It's possible it has been banging around the fuel lines for a while to achieve this very round shape and be able to cause the failure
Clearly, this is a design flaw with the plane's fuel system:
1. It has the aerobatic flop tube pickups in both tanks, so no mesh / screen in the tank (normal pickups possibly could have caught this).
2. From the tanks, fuel goes to an andair fuel selector valve, then into the redcube (in the footwell tunnel), then into the electric boost pump, and only then into a gascolator on the other side of the firewall, so there is a ~3mm narrowing of the fuel line before the first real filter.
I am not the builder of this airplane, and bought it already flying a little over a year ago with 100hr flown on it, and then added another 100hr before this failure. The builder says that the fuel system was designed and executed by a build-assist shop (in South Africa, now appears to be defunct), who apparently didn't consider the fact that there is a obstruction failure mode (which has, turns out, caused accidents in the past), or possibly were unaware of the flop tubes and expected the pickup mesh to act as the filter (still probably not the best idea). I myself also thought I had normal pickups until I started digging into the fuel system - the plane has a carburated O360, so sustained inverted flight is not really possible - there is no reason for the flop tubes. Turns out that the builder bought the kit partially complete (including completed and sealed tanks) and finished it - the flop tubes were installed by the original kit owner, who I guess was planning on a different engine.
I have added the TS Flightlines wing root fuel filters to prevent a repeat and am back to flying the airplane, but I would be lying if it didn't cause me to think long and hard about what other possible design issues might be hiding somewhere that are hard to identify on a prebuy / conditional inspection!
