SonexBuilders.net

I had to declare an emergency today at our class D airport. I had fuel flowing down the firewall and flowing down the floor on the passenger side. When I stopped the plane just clear of the runway, fuel was standing the catch pan I had installed under the fuel cap. It had filled that pan and flowed thru the gaps into the cockpit.

I put the pan in there to catch the drips from the fuel nozzle when refueling. I never thought I needed to make it fuel tight to hold fuel at full capacity of the pan and a drain to get it overboard. It seems the fuel cap was not tight enough. I had just refueled and had a total of 11 gallons in the tank. The cap hits the fuel vent fitting on tightening so that may have contributed to it not being tight enough. I was coming downhill into the airport area when I started to smell a strong fuel oder.

I have now sanded the knobs off the fuel cap so it doesn't hit the vent fitting. I also sealed the catch pan the best I can. Now I can strong arm tighten the fuel cap when I install it. Next to do is add a fuel drain from the catch pan to out of the cowling.

I can't imagine this happening to someone building to plans so the fuel cap area is just open into the cockpit.

Rick Caldwell
Xenos 0057 36 hrs phase 1

Glad you landed uneventfully! I have an aluminum drain line from my catch pan, that exits out the bottom of the cowl. This also serves to drain water that gets into that pan. Even with a cover, rain sometimes goes where it wants to go!

You can start at this log entry to see what I did:
http://www.mykitlog.com/users/display_l ... 960&row=26

Rick I have also had this happen several times when descending with a near full tank. I also have the sealed tray thankfully but have not thought about adding a drain. I really really don’t want any fuel leaking. It stared happening when I was using the boat tank type fuel caps. It seemed like the cap would develop a crack in the rubber every year or so so I would replace. After talking to another builder who had same cap for 8 plus years with no failures he said he never fills his plan to near touching cap. I think my cap was getting fuel soaked to much might have been why mine were only lasting a year or so. I went to a Peter Anson aftermarket cap and that seemed to solve the issue till a few weeks ago when I had the same issue. I figured out that the o-ring on the cap was not compressing evenly around the slopped area as you tightened the cap. A little WD40 on the o-ring did the trick and is sealing nicely now.

I don't want this to happen again. Scary situation.

Here are a couple pics of the seal job and the overboard drain I put in today.

I'll test out the sealing of the fuel cap by picking up the tail in the hangar tomorrow. I guess I could also put a small balloon on the fuel vent tube.

Rick Caldwell
Xenos ph 1 36 hrs powered, 3 hrs gliding

Rick,
That's almost exactly how I sealed up the fuel-well. In my case I used a fire proof foam to fill all the gaps then sealed it all with pro-seal. Used a larger nylon drain elbo since the intended purpose was to drain off spilled fuel if/when over-filling. Not exactly pretty but functional.

As a follow up, I put a balloon on the fuel vent and could smell fumes coming from the cap even though it was tight. I had a 2nd fuel tank & cap in the hangar so I used that cap gasket to double gasket the cap. The extra rubber thickness then sealed the roughness on the plastic tank lip. A balloon then held pressure for over 45 min. and no smell of fuel at the cap.

That was the issue - the fuel cap gasket did not seal completely on the rough edge of the fuel tank. This was a spare tank I had bought from someone parting out their Sonex project. My tank from the kit was screwed up by me trying to install the opps fittings and it leaked after 35 hrs so I swapped out the tanks.
Rick Caldwell
Xenos 0057 ph 1