A Cozy Fuel System for UL Power Engines

[@stolaircraftsuyanto9728]

hi greg.thank you for sharing..success always for you

[@GregoryACross]

Thank you!

[@foesfly3047]

I appreciate learning a little about fuel system requirements for the UL Power engine but also got some ideas for my own cold air inlet to engine air filter and oil cooler mounting. Thanks for posting.

[@GregoryACross]

I'm glad it was helpful to you.

[@pusherpilot]

Nice explanation Greg. Its looking good

[@GregoryACross]

Thank you, Paul!

[@NewEnglandForest]

clean install!

[@GregoryACross]

Thank you for the kind words, Preston!

[@andymckee53]

Hi Greg, I have never had that problem with my UL engine, the problem of the rpm drop when switching pumps/tanks. I see you have two fine filters and that may be the issue as there is now a path for the fuel to go backwards through the unused lines and fine filter when switching as they are after the pumps. Just a thought... Worth investigating as it should not do that.

[@GregoryACross]

Hi Andy, Thanks for the thoughts. The pumps have built in check valves, so the only back feeding route would be, as you state, back through the unused fine filter. But there is no where for the fuel to go because of the pump check valve. As the selector valve is rotated, there is a dead period when one pump is powered off and the next one is powered on. That's what is causing the momentary loss of pressure. The pressure regulator snaps closed at 43 p.s.i., but the injectors continue to drain off fuel and the pressure instantly drops since the fuel is incompressible. (I suppose one way to resolve that would be to install a pressure tank, where there would be trapped and pressurized air maintaining fuel pressure longer... but that seems like a bad idea in an airplane, with the possibility of getting air in the fuel lines!) As the system is currently, I understand how it works, and why, and don't really see it as a problem. If you turn a pump off, the engine stops, if you turn one on, it runs. If you do it relatively quickly, the engine just stumbles momentarily. Moving air through the propeller in flight should lessen the r.p.m. drop considerably (momentary windmilling).

[@Verb130]

Wow. Complexity. More to go wrong/fail; more weight. I can think of more than a dozen ways to simplify the system, and still have system redundancy. Your workmanship is excellent. I'm critiquing your system design; not your craftsmanship.

[@GregoryACross]

Thank you for your comments, K Verb! I tried to utilize the existing per-plans Cozy fuel tanks and plumbing, in conjunction with UL Power recommended and supplied pumps and filters. Regarding the UL Power recommended fuel system, my thinking was why have just redundant fuel pumps, when, for another set of filters, I can have two completely redundant fuel systems. This way, if anything goes wrong, a clogged filter, a failed pump, bad fuel, etc. all I have to do is switch to the opposite fuel system and find a good place to land. Nothing to figure out or troubleshoot while trying to fly the airplane. Of course, this is just one man's idea, not a recommendation for anyone to use. Your safety is ultimately up to you as the builder of your airplane.

[@Verb130]

@@GregoryACross I love the two fuel filter system on seperate lines. Some might say the two second filters is a bit much, and I could see the that, but that's not a likely additional failure mode, but it could save a few pounds of weight. My concern would be all the plumbing and electrical complexities using the plans fuel selector along with micro switches and mechanical cutoff valves down stream. It's so many valves and pathways. I think your system shows ingenuity, with great workmanship. I'm building my strakes now, and have mapped several systems over the years leading up to this point. Always designing it from the KISS principal. Now that I'm finally forced to make a decision, I've given up on the plans valve. But this is not the forum to build my system in your comments. Maybe some day at Rough River, Oshkosh, or SnF we could have a beverage and talk for hours about fuel systems. Cheers

[@grandenauto3214]

@@Verb130 I’ve been working with automobiles for years and have changed out many fuel pumps.... and 95% of the time the fuel is as clean as you can have. The 5% are guys who get gas from unknown or unwise sources. When I build I’m going to design a fuel system with that in mind.... pumps fail because pumps fail not because of bad fuel.

[@metalzhenry]

So if you engage the second pump utilizing the boost button then move the selector valve, then disengage the boost button do you still get the rpm drop?

[@GregoryACross]

That's a promising idea! I'll have to try it. It makes sense. The valve only determines where the excess pumped fuel goes, so the turning off of one pump and turning on the other one would seem to be the cause of the momentary pressure drop and the rpm drop. By starting the other pump first, that should alleviate the problem.

Hi Greg, did you have any difficulty with mounting that engine on a Cozy? Does an engine mount and FWF come with the engine?

[@GregoryACross]

Sean, the engine comes with the mount points that are intended to be welded onto a mount appropriate to the aircraft you are installing your engine on. Since the Cozy is not a kit, i.e. it's scratch built from plans, there is no mount provided with the engine. However, it does come with all the accessories you would normally have to buy separately. UL Power here in the U.S. will build you a custom mount on request. You would want to talk to UL Power service rep. Ray Lawrence at Kaolin Aviation in Georgia about it: [phone].

[@dan-phokathedewman4696]

What is the Progress at the moment?

[@GregoryACross]

I'm currently working on finishing the exterior. Lots of filling, contouring and sanding, before it can be painted. It's slow work.