Wing fuel interconnect

Guys I'm placing this here in hopes people will spot it and comment. I also plan to post it in the building tips/techniques to see what people think of the idea. Background; I plan to use an alternate engine system with electronic fuel injection. (not here to argue the point this is a completely seperate idea suggested on another forum that would work with Lyc or alternate engine)

Fuel management and systems are a frequently dicussed item in all sorts of forums. Poor fuel management leads to engine outs and sometimes crashes. At the very least momentary panic as we struggle to restart the engine knowing there is still plenty of fuel in "at least one of the tanks" ((famous last words?) Rather than a selector valve, someone suggested why not run a big tube between both tanks and make them one big tank? I know that in long turns fuel could slosh between wings, and other problems but even in single wing tanks we will baffle to keep the fuel at the wing root. Why not put in a non-structural rib about 6" from the inside wall on both sides with inward facing trapdoors. This would trap about 5 gallons around the center pickup, almost like a header tank. It should keep the pickup covered in all but serious aerobatics. Comments? One line from the tank/s, one return, no selector valve. couldn't be simpler. Redundant pumps could still be used, the plumbing would just be simpler. The more I think about it the more I like the idea.
Bill Jepson
Rotary10-RV

Aleternate fuel system

I don't think it will work. As one of the other RV'rs put it once. Think of two straws in to separate glasses. Put less liquid in one glass and suck on the straws. As soon as you run out of liquid in one glass you just suck air. Even with Cessna gravity feed from both tanks one tank always feeds more fuel than the other and empties first. With the system you have described if you happen to fly with one wing high you will feed from that tank first, fuel will flow across to the other tank through the interconnect and when the high tank is empty your engine will quit. The only other simple alternative is to put in a header tank that both wings feed into and then out to the engine. The draw back to this is the tank is usually mounted in the cabin.
Believe me, I think if Piper and other low wing mfgs could figure out an easy way to feed from both thanks at once and prevent engine failure from forgetting to switch tanks they would have done it a long time ago.

Believe me, I think if Piper and other low wing mfgs could figure out an easy way to feed from both thanks at once and prevent engine failure from forgetting to switch tanks they would have done it a long time ago.[/QUOTE]

Ping,
I once asked my CFI why the cowl flaps weren't automated, (sensor for engine heat is easy, even air cooled VW's have a bi-metalic heat riser), He said, "The manual system is certified." The litigious society has caused innovation to be held back. That is why Piper doesn't do it.
Bill Jepson

Single aircraft tank

In general, it sounds like a good idea to interconnect the wing tanks. It's not much different from having a single tank in the fuselage, which many homebuilts have. I seriously considered doing this on my RV8.

However, I really doubt that doing this will save you any time or energy, or increase safety. The only time running a tank dry is dangerous is near to the ground. Usually, as part of your preflight and landing checklists you move the selector to the fullest tank. No problem there. During cruise, if you run a tank dry, you change to the other tank.

The thing I think you lose is a bit of flexiblity with having two tanks. It kind of forces you to think about your fuel usage, while you fly. On cross country flights, I put the selector on the right when the big hand on the clock is on the right side, and on the left the rest of the hour. Keeps reminding me that I don't want to run out of fuel. Also, you can use the fuel level to trim the aircraft when you are flying alone, or have an unbalanced left/right load.

In any case, take lots of pictures, and keep us posted on your progress. It's always interesting when people do new things - it advances the "state of the art".

Who's the test pilot?

No argument there. It costs a lot of money to certify new systems and components. Look at the Lycoming engine, basically a proven design from the 30&40s. But cost is not everything. Many new designs have come out over the years, gone through the certification process (lots of money and lots of engineering know how) and failed in the field. Many of these failures are also attributed to loss of life. As for me, I like building and tinkering. I'm getting very close to the first flight on my -9 and I have made many modifications to the plans but none to do with aerodynamics or the fuel supply system. I'm not willing to be the one to "take it up and see if it works".
There would be a lot of fabrication and testing to designing a new fuel system. You would have to make sure your check valves worked in all attitudes, venting system with all possible variations that could happen,(bug clogging a vent) uneven pressured, insure fuel flows to engine in all flight attitudes........
As for me???......
I'm too interested in flying to undertake such a critical modification.
Maybe you are not and would enjoy the challenge. If so good luck. And some personal advice....find a good test pilot!