Fuel System Peer Review

[Mich48041]

I hope it is alright to post here, even though the aircraft not a Van's, but is a Thurston-TA-16 with a LS1 fuel injected engine. VansAirforce is where all of the most knowledgeable people hang out. A friend of mine is building the TA16, which is at the stage where it is starting to look like an airplane. Below is a diagram of his fuel system which is already installed. I drew the filter and pressure regulator separately, but they are actually combined in one unit. The tank in the center holds about a quart. My friend calls it an accumulator, but I think that it is just a large-volume 4-way "T". I have concerns about the consequences of a pressure regulator failing. Is there a problem with turning on both solenoid valves but only one fuel pump? Comments, suggestions and criticism are welcome. PDF Version - ExpressSch Version

[rmartingt]

IMHO that systems seems needlessly complicated. Solenoid valves for selecting the tank? Why the "accumulator" tank? Why no filters before the pumps?

I assume an LS1 uses electronic ignition, so why not piggyback off the same setup used by EFII? See the last page here. Forget the solenoid valves and just use a manual duplex fuel valve.

Edit: Also make sure the fuel return goes all the way back to the tank. Don't just tee it back in.

[Jesse]

I agree with rmartingt. I wouldn't be a fan of the solenoid valves. I think the EFII setup should work perfect for that installation as well.

In response to the single pump on with both valves on, this should work since there are 2 pressure regulators and the check valves.

[Mich48041]

The owner of this project lives about 45 minutes away from me. I have just recently visited his project for the first time and the fuel system was already installed in the fuselage. It would be difficult to install return lines to the fuel tanks in the wings that are already built (but not yet attached to the fuselage). I agree with you guys that a manual fuel valve is less likely to fail than a solenoid valve. The solenoid valves do allow remote control without long fuel lines or the need to find room to install a manual selector valve within easy reach.
"Why the "accumulator" tank" That is the same question I asked. I see no useful purpose of that tank except perhaps to help cool the fuel. But I do not know if it has enough area to accomplish that. Do you guys think that the fuel will get too warm without returning to the wing tanks? I will forward your comments to my friend.

[Jesse]

The purpose of the "header" tank is almost certainly to keep the fuel cool. I would probably recommend that it be at least 2 gallons to avoid overheating the fuel. I had a vapor problem on an engine with no header with the fuel return going to a T in the line just on the engine side of the fuel selector. The fuel just kept getting hotter and hotter, as it cycled into the engine compartment, until it vaporized in the fuel pump and the engine wanted to quit in flight. Not a fun experience. We added fuel returns to the tanks and a stacked fuel selector and the problem was solved. That's certainly the best option. He could get a bung that rivets with proseal into the tank and then a threaded fitting in the bung and you have a return. That would definitely be my recommendation.

[DanH]

Originally Posted by Mich48041

I have just recently visited his project for the first time and the fuel system was already installed....

Joe, make enough TC calls, and this won't be the last time you hear that wail from a builder.

I agree with you guys that a manual fuel valve is less likely to fail than a solenoid valve.

Don't need any valve. Fuel is not going to flow uphill (from a wing tank to a high pusher engine pylon) all by itself. Without 'em you can simplify and add lightness.

Ditch the solenoid valves. Run return lines to the tanks. Put the filters before the pumps. Move the check valves. Now it's simply "both pumps on for takeoff", and if one unports or runs dry it makes no difference.

[rv6ejguy]

Duplex fuel valve, return lines to the tanks a very good idea to avoid hot start and vapor lock issues, filters before the pumps, use Walbro pumps mounted right on the floor (they re-prime much better and don't make metal like some other brands), they have built in check valves. Ditch the header tank and solenoid valves. Regs should ideally be on exit of 2nd fuel rail (again to purge out hot fuel as soon as pumps run).

If you have a sender access cover in metal tanks, you can use Earls Stat-O-Seals to mount the return fittings without the goop.

[N62XS]

Keep it super simple. If the builder wants an eternal repair/tinker project, embrace complexity. If the builder wants to fly and enjoy the fruits of his labor, keep it super simple.

[Mich48041]

Thanks for all of the comments and suggestions. I will pass them along to the builder.