Fuel System Questions

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Includes: Highlander, Escapade, Summit and SuperSTOL.

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Re: Fuel System Questions

Postby SheepdogRD » Thu Jan 02, 2014 12:03 pm

Okay, as long as we're on the topic of fuel systems . . . I'm wondering about fuel valves.

We have a valve on the main fuel line to the engine. If we have an engine fire, we can shut off fuel flow to the engine compartment.

But, if we have a return line that goes from the engine compartment to the top of the header tank, and if we assume that the header tank is full, then -- in the event of a fire -- couldn't that return line allow fuel to flow to the fire? If so, shouldn't we have a shutoff on the return line, as well?
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Re: Fuel System Questions

Postby kenryan » Thu Jan 02, 2014 12:34 pm

I'm not positive about this, but I believe the wing tanks feed only from the rear. So, in the event of low fuel and a steep enough descent, the wing tank outlets would become unported and once the fuel in the lines were to be consumed the engine would stop. The header tank would extend the time before the engine quits. Another reason for the header tank could be to meet the Rotax requirement of having a return line. It's easier to run it to the header tank than to a wing tank, particularly with a folding wing.

With regard to the question of fuel running from the top of the header to the engine compartment, a check valve should be installed to prevent flow in that direction.
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Re: Fuel System Questions

Postby SheepdogRD » Thu Jan 02, 2014 12:50 pm

kenryan wrote:With regard to the question of fuel running from the top of the header to the engine compartment, a check valve should be installed to prevent flow in that direction.

Thanks, Ken. I'll add that to the plan.
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Re: Fuel System Questions

Postby User GDS » Thu Jan 02, 2014 3:44 pm

On the Rotax there is a restricting orifice in the fitting that connects to the return line. It is designed so that the path of least resistance for fuel is to the carburetors, very little fuel goes through the return line. (particularly when the system is being fed only by gravity, in other words, fuel pump off) If there were a fire I think that would be a pretty small source of fuel.
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Re: Fuel System Questions

Postby 957DK » Tue Jan 07, 2014 6:07 pm

Thanks everyone!

I'm installing a Facet fuel pump, 3/8" aluminum fuel lines, 1/4" return line and aeroquip flexible hoses at the tanks. That should take care of the fuel system.

Anyone have any suggestions as to what I should agonize over next?

Thanks again,
Dan
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Re: Fuel System Questions

Postby danerazz » Tue Jan 07, 2014 10:44 pm

Electrical system?
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Re: Fuel System Questions

Postby aircraftspecialty » Wed Jan 15, 2014 12:40 am

If anyone is interested in a Rotax 912 conversion to all Conductive Teflon fuel hoses without a 5 year hose replacement, we would be happy to discuss some of the options that are available. We have recently completed a complete retrofit package for the Rotax 912 engine that can be adapted to any aircraft with this engine.

Have a great day,
Steve
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As builders, we understand the importance of quality work and impeccable customer service. We offer Custom Hoses, Instrument Panels, CNC parts and tools for experimental aircraft.
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Re: Fuel System Questions

Postby User GDS » Sun Mar 30, 2014 10:47 am

I like my auxiliary fuel pump. Sound is not too great on this video but listen carefully around 20 seconds. Hot day and I got minor vapor lock that cleared as soon as I flipped the switch.

http://vimeo.com/90458487

In 130 hours this is the only time I've had this problem.
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