Fuel Line Routing

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Fuel Line Routing

Postby jjacky » Thu Aug 15, 2019 10:26 am

Woke up last night worrying about how I routed the fuel lines on the Highlander. The worry is... if a slug of water gets in a dip in the fuel line will the hydro-static pressure of the fuel shove it to the gascolator. I routed my fuel lines under the floor and seats. Now I'm thinking running them down the rudder cable fair-leads would be a better solution...what did you all do?
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Re: Fuel Line Routing

Postby Tralika » Thu Aug 15, 2019 12:48 pm

Along the bottom stringer under the seats.
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Re: Fuel Line Routing

Postby BucF16 » Thu Aug 15, 2019 12:51 pm

same
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Re: Fuel Line Routing

Postby SheepdogRD » Thu Aug 15, 2019 9:55 pm

Tralika wrote:Along the bottom stringer under the seats.

Same here.
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Re: Fuel Line Routing

Postby alan » Fri Aug 16, 2019 8:38 am

Ditto.
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Re: Fuel Line Routing

Postby jjacky » Fri Aug 16, 2019 11:15 am

Fantastic, now I can sleep again. Just a caveat, a friend of mine (a fuel systems engineer) warned me to watch out for freezing temps
and frozen water slugs but, if you're conscientious about your fuel management, this should not be a problem.
Thanks All!
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Re: Fuel Line Routing

Postby FredHoffman » Sat Aug 17, 2019 4:22 pm

I made sure the lines ran in a descent (in 3 point attitude ) from the tank to a sump drain under my seat and from there in an ascent to firewall. If the fuel lines go lower than your header tank sump drain water can collect in that fuel line which is now the lowest point. Ethanol fuel can suspend a significant amount of water and can precipitate out as the temperature changes. It could collect in that lower line and stay there until say something like a very nose low high power setting while (buzzing your friends) sucks the water into the engine !
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Re: Fuel Line Routing

Postby SheepdogRD » Mon Aug 19, 2019 5:25 pm

FredHoffman wrote:I made sure the lines ran in a descent (in 3 point attitude ) from the tank to a sump drain under my seat and from there in an ascent to firewall. If the fuel lines go lower than your header tank sump drain water can collect in that fuel line which is now the lowest point. Ethanol fuel can suspend a significant amount of water and can precipitate out as the temperature changes. It could collect in that lower line and stay there until say something like a very nose low high power setting while (buzzing your friends) sucks the water into the engine !

A couple of years ago, I was at the Plane Fun Fly-In in Brasstown, NC (https://www.planefunaircraft.com). Co-host Vic Payne pointed out the same thing: that the header tank is not the lowest point in the fuel system. In testing, they used clear fuel lines in the cockpit, and they saw water collect in the line between the header and the fuel valve.

Vic showed me a Highlander with a fuel system that resolves that problem, and I took some pictures. This system has the fuel line from the header angling down along the fuselage side panel to the fuselage tube that crosses behind the seats.

1.jpg
(viewed from the left side)

It turns toward the center of the aircraft to the inboard right seat rail...

2.jpg
(viewed from the left side)

...and then turns forward to a gascolator mounted on the seat rail. This is the low point of the system.

3.jpg
(looking down from the right side)

Then the line angles up to the fuel valve. From the valve, it angles up across the right side of the control tunnel.

4.jpg
(looking down from the right side)

At the forward doorpost, it goes up along the angled tube in the cowl side panel, and then to the engine.

5.jpg
(viewed from the left side)

Vic said the advantage to the system is that the gascolator is at the lowest point in the system in both tail down and tail up configurations, so water that gets past the header tank naturally goes to the gascolator.

When I learned about this, my system was already plumbed below the floor in aluminum tubing, and my inside panels were covered. I filed the information in notes for the next build.
Richard Holtz
Highlander N570L -- Ms. Tonka -- in gestation

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Re: Fuel Line Routing

Postby jjacky » Mon Aug 19, 2019 6:16 pm

Guys thanks a-bunch for the info and great pictures. My fabric person is hot to trot so I'm not going to redo the whole fuel system but, like you Dog, I'll keep this on file for the next build and I'm going to install a couple of sumps per yer suggestion Fred. Now I just gotta find a couple of simple sumps.
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Re: Fuel Line Routing

Postby FredHoffman » Mon Aug 19, 2019 9:10 pm

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Re: Fuel Line Routing

Postby danerazz » Mon Aug 19, 2019 11:32 pm

My biggest takeaway here is your seatbelts are attached to the rails.
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Re: Fuel Line Routing

Postby SheepdogRD » Tue Aug 20, 2019 3:14 pm

danerazz wrote:My biggest takeaway here is your seatbelts are attached to the rails.

Interesting observation. Let's append that discussion to the Lap Belt Attach Points thread you started http://www.wingsforum.com/viewtopic.php?f=218&t=23964. I'll put a transition post there.
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