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Fuel system design

xblueh2o

Well Known Member
I am a few weeks away from beginning the build up of the plumbing portion of my fuel system. I have been running through past posts and build logs trying to learn as much as I can and found lots of interesting data and ideas but a lot of the relevant posts I see are several years old. Looking for more recent data. I plan on running an injected motor and I am looking at a setup that does not have a return line to avoid the weight and complexity.

Tell me about how you set up your aircraft. What/whose parts did you use?
What did you like or dislike about them? Would you do it again?

I saw some people putting filters in the wing root. On the one hand it seems a good idea since you would not be spilling fuel on the cockpit floor during servicing. On the other hand, that seems like an awfully cramped area to be working. Thoughts?
 
With filters in the wing roots you need to drain the tanks to clean the filter. The stock system works well and is simple.
 
With filters in the wing roots you need to drain the tanks to clean the filter.

Nah, if you're quick about it and have some plastic plugs handy, you don't spill much. I just completed my first annual and removed/cleaned my filters in the wing roots. They had a little bit of "fur" in them but nothing significant. Glad I have the filters there so that stuff doesn't go through my selector valve and electric pump. It's a little cramped, but in my opinion way easier than laying down on your belly in the foot space to remove/replace a filter installed in the cabin.

There are many thousands of RVs flying without filters in the roots. Both ways can work.
 
Hi Sam

Here is a suggested layout. Not saying there are not easier /cheaper / better ways of doing it.

Tanks to Andair Fuel Valve (rather than Vans) as per plans.

Then Andair Gascolator. In an RV-8 put it under the inboard edge of the left "mid cabin cover". It is also a fuel filter, and suggest you plug the drain hole since it is in cockpit. It now takes ~5mins to clean filter, and no need to disturb metal pipework.

Andair Fuel Pump - lightweight, only has 2 connections (in and out) - install in RV-8 plans location.

Consider using plastic fuel type piping for vent lines. It will then take you about 15mins to fabricate and install both vent lines, not 1-2 days!

If you want to do extended inverted flight, suggest 1 Flop Tube (only) - most people do Left.

Any qu's on above do ask...
 
The best idea I've seen for a fuel system 'mod' came from a plastic pusher driver who's worked in failure mode analysis. He suggests using an automotive style in-tank 'sock' type filter instead of a regular in-line pre filter. If you haven't seen one, it's the orange rectangle in this link:
http://www.ebay.com/itm/360843503639?_trksid=p2060353.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
There's a plastic 'scaffold' inside the mesh to keep it open. The automotive style filters tend to be self cleaning, due to fuel sloshing over them constantly, and are much less likely to clog. I saw this after I'd closed my tanks, but I will probably go back and add them to my pickup lines in the tanks before I fly.

You do know not to put the super-fine filter before the fuel pump, right?

And not to start another nosewheel/tailwheel style debate, but if you have a micron-level filter in the system, and the tank quickdrains are the lowest points in the fuel system, do you need a gascolator?

Charlie
 
When talking about fuel system mods, you need to remember a few things. First - the majority of fatalities in Phase 1 testing due to mechancial issues are caused by engine stoppage - and most of those are caused by failure to get fuel to the engine. Second - a century of aircraft design has shown that the simplest fuel system is generally the most reliable in getting fuel to the engine. Third - most designers have extremely simple fuel system designs in their airplanes, not becasue they are cheap or non-creative - but becasue they work.

Many of the folks that crashed becasue of fuel starvation or delivery issues thought that they had invented a better mousetrap. Before setting off to do something different, examine your goals - if your goal is to pioneer a new method of fuel delivery, and you are willing to accept the risks, then proceed (carefully). If your goal is to have a proven, reliable method of delivering fuel to your engine so that it keeps running - why not use what has worked for thousands and thousands of builders (and not just RV's) over the years?

Just a thought.....
 
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Agreed.
What I want is simple, safe, airworthy and easy to service/maintain.
Those are my design criteria.
 
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