Roger Mellema:
Newsletter #14 (Dec. 86)
Finger Strainers
... Enough suspense - what caused the engine failure? I do not have finger strainers at the outlets of my wing tanks and someone pumped me a piece of junk big enough to plug the Flow Scan fuel transducer that I use with my Compu-cruise computer. I had it mounted under the cowl after the gascolator and a fuel filter but had trouble with bad readings probably as a result of some air or vapor lock in the transducer itself. I then mounted it under the instrument panel where the temperature and vibration are more controlled. The idea of using a Flow-Scan transducer rather than the one supplied with the Compu-Cruise was that it is supposed to be a full flow measuring system. I never really looked at the Flow-Scan but now I see that what looks like a large hole on the inlet side really tapers down to a very small hole inside the device. As it turns out the piece of crud that plugged it might also have plugged the top inlet to the gascolator. The answer to the whole problem is to put finger strainers in the fuel tanks or something like that. I can't get into that area now so I will be putting the see-through fuel filters in each of the tank outlet lines (4). I don't know whether they will be in the wing root or under the instrument panel.
I learned later that the FBO where I buy my gas had pumped several gallons of water to several customers about a week before my accident. They found and drained all affected aircraft so that solved the immediate problem. When they cleaned out the FBO tanks, they found that the fuel filters on the pumps had not been cleaned or changed for years. It would be hard to prove, but I think I now know where the crud came from. While at Oshkosh I bought one of the new funnels that filter the gas and separates out water. Gas will flow through the funnel at 6 gallons per minute and it seems to do a good job.
We talked about this at Oshkosh and it looks like less than half of the already built BD's have strainers in the fuel tanks. The idea is to have a coarse screen about 2 or more inches long in the tank and then let the gascolator and/or a fuel filter in the engine compartment catch the small stuff. In this way the small stuff will not slowly plug up the wing strainers. It would be nice if the wing strainers were easily removeable but I really don't thing it is necessary.
John Steere:
The sumps are fabricated from streamlined aluminum tubing which extends about 2" below the wing, and contain flush drain valves. At this location, they will catch any water that condenses in the tank because they are at the lowest point when the plane is on the ground.
Val Bernhardt:
Newsletter #24
1. This quick-drain allows you to get all water out of a non-sump type tank.
2. On a high wing aircraft there is nothing protruding to cut your head on.
3. "O" ring can be replaced through the drain hole (use a bent wire).
4. Drain can be bonded to fiberglass or aluminum tank (no rivets needed).
5. "O" ring is "Evinrude" quick disconnect gas line replacement ring.
6. Be sure to corrosion-proof the 4130 steel or the seat will rust and then leak.
7. The drain can be turned from aluminum or made from stainless steel.
8. The seat can be cleaned by pushing up the valve and "scrubbing" the seat area.
9. Be sure to use a strong enough spring or leaks will be frequent.
10. The drain can easily be removed by "cutting" the ProSeal around the base.
11. Use ProSeal sparingly when installing to avoid "squish up" in front of drain holes.
)
The
guy who built our BD4 told me that the local equivalent of the FAA in Australia
(nowadays CASA - Civil Aviation Safety Authority aka Commissariat Against Sane
Aviation) required him to add sumps to the fuel tank area on the fiberglass
wings. These are bumps that run from the spar area to the rear spar with fuel
drains at the back of them. One at the root end of the tank area, one at the
tip. Ok so thay cause a little drag but so does a bent airplane. In this case
they may have had a good point.
I think there is a row of a few half inch holes in the wing skin with the sump glued and glassed over. These really work.
I've had a drop of dew get in the tank when checking fuel levels (by dipping the
tank) in the morning. Shake the wing, let settle for a minute and hey presto you
get the same drop out of the drain. This convinces me they work.
)
When
I take the wings off for re-finishing(one of these centuries) I'll add a little
fairing to the top part of the rear above the fuel drains.