The inevitable fuel spill disaster

[WaiexB22]

Note: My Sonex centre tank, is filled vie either wing tank, so no fuel close to canopy.

What pump(s) are you using to transfer? How fast does it transfer?

[Skippydiesel]

A single Transfer pump, Facet Posi-Flow PN 60303. 7-10 psi,129 L/hr = 2.15L/min. It's slow but adequate. There is a wing tank selector valve - Left, Right, Off, that must be turned to the "active" tank.

I have 30 L in each wing tank and 35L in the fuselage tank. I mostly transfer in the air but on occasion, top up the fuselage tank on the ground and then fill both wing tanks.

My son has made me a semi automatic fuel transfer system (can be turned to manual) that works very well. I just select the wing tank I want to use, press the Auto Fill button and the Transfer pump starts. The Auto Fill works on fuel level and on time. If its taking to long for the fuel to get to the preset 35L level, it will time out and stop the pump.

My fuel return line, about 7L/hr, goes to the fuselage tank.

I can use my Boost pump ( Facet Cube PN 40135, 4-7psi, Flow 121.13L/hr = 2L/Min) on any of the three tanks for TO/Landings, however it's simpler to just use the fuselage tank.

[13brv3]

13brv3,

On the matter of pump priming - from the photo it looks very like your pump is a centrifugal type. Centrifugal do not easily self prim when mounted above the liquid source.

The Fill-Rite folks are very quick with replies to questions. Priming is indeed the issue. They said the automatic nozzle requires 4psi to actuate, and the centrifugal pump can't generate that much pressure if it's lost prime. I do have a few options to get it working, and I'll definitely be reinstalling the automatic nozzle.

[13brv3]

I think I've pretty much settled on the new fuel funnel. It seals to the inside of the tank neck with an o-ring, and should dump any overfill or spill harmlessly on the cowl. Now I just have to be vigilant about using it.

[4redwings]

I made this for my Onex although I haven't fueled with it yet. The material is Ottertex Waterproof 70D PVC Backed Nylon Taffeta from Fabric Wholesale Direct and is available in many colors. The flap is glued with HH-66 Vinyl Cement. I found that it works best when gluing the rough side to the rough side.

My next operation will be defueling. The Aerovee is coming off for a 912ULS.

Onex Fuel Funnel.jpeg (124.87 KiB) Viewed 632 times

[13brv3]

You certainly seem to have it covered, literally :-) I would add an o-ring groove on the outside to seal to the tank. Mine was an overfill accident, and if that happens, you'll still get some fuel spilling inside unless you seal the funnel part to the tank. Trust me, it doesn't take much.

BTW, I'll be interested to see how you work out the 912 installation. I'm really glad I went that route rather than the Aerovee.

[Skippydiesel]

I have asked this before - yet to get an answer.

Is there some reason why the fuel point can not be moved in front of the firewall ie forward into the the rear of engine bay. A suitably designed flap (size & hinge point), could open to prevent splash onto polycarbonate and any overfill, would drain out of the bottom of the engine bay OR be caught by a well/bund arrangement, that could drain through a pipe onto the ground.

I sure hope the new high wing comes up with a better, fueling, arrangement.

[4redwings]

Never thought about an overfill. Should be easy enough to add one or even two o-ring grooves although the downspout is a fairly snug fit and I printed it thin to preserve as much opening as possible. Have to think about this.

Wouldn't someone have to build a new fuel tank rotational mold to move the filler? The filler would also have to stick up above the upper cowl but then you'd lose the sonex canopy/cowl airfoil shape, unless you made the tank shorter in height. On a Onex there is the FWF real estate issue to think about as well especially with the Rotax.

[Skippydiesel]

What's wrong with a new tank design, to move the fill point to a location to one with less propensity to damaging the polycarbonate windscreen.
As for height - only have my Sonex Legacy as a reference - plenty of potential to lower the tank base/floor to preserve volume.

Full disclosure - My Sonex has wing tanks, that feed the large in fuselage header, located in the same position as a conventional tank but without any external fill point (no splash, no overfill worries)

[13brv3]

I'm sure it's possible to design your own tank, or modify the existing tank and firewall, but I don't think either of those are very feasible.

I also wonder if they didn't have a good reason to eliminate the fuel filler that extended forward of the firewall. If you think of where the engine will end up in a typical nose low crash landing, it seems a little risky to have part of your fuel tank right where the engine may end up. I'm betting that's why they got rid of it on the Onex and B models.

I seriously considered connecting one of the unused ports on the gascolator to to a fill line to the side of the cowl. Since I've never filled my plane anywhere but my hangar, it would be easy to use an electric fuel pump to fill the tank from that line. You'd still need to open the cap to monitor the fuel level during fill, but it's safer. The top fill option would still be there for fills away from home.