Fuel Lines

[mchesney]

I have a 9A and I'm working on the fuel lines from the valve to the wings. The plans show the lines going through the bottom grommets but when trying that route the gear weldment obstructed the grommet opening on the brackets that hold the covers in place. I opted to use the top grommets which are larger but the route seems much easier. Is this Kosher? Also, I had to make a pretty sharp bend to line up to the fuel valve and I ended up with a very slight flattening of the line. Not enough to affect flow or rigidity (I'm assuming) but ever so slight...is this acceptable? Thanks all!!

[Greg Arehart]

Mike,

I'm also putting in the fuel lines. I first did so a couple of weeks ago, hand bending the tubing through the gear leg mounts. I have ultimately decided to pull these tubes, and replace (I prefer to replace them rather than try to rebend - try bending these Al tubes back and forth a couple times and watch them crack!) them, routing the line in front of the gear leg mounts rather than through them. Main reasons are 1) access, in case I ever have to replace them (hope not) and 2) less chance of rubbing a hole in them against the gear leg mount (I think I could deal with a hole in the vent line, brake line or some other part, but not a fuel line!). I also plan to go to my Lowes aircraft section and purchase some plastic tubing (3/8 inch ID, about $ 0.16/foot) which I will split and wrap around the fuel line anywhere it goes near a potential wear spot, also to minimize the possibility of a rubbed hole. The plastic should show wear spots before it wears through to the Al; I plan on including visual inspection in my list of regular inspection stuff.

Your original query was about flattening of the tube - unless you bent it pretty sharp and/or flat, it should not be a fluid flow problem.

greg

[craigvince]

Another option would be to contact Bonaco; Talk to Brett there. They now make flexible fuel lines (made from stainless braided teflon with a clear chafe coating) to go from the sidewall to the center fuel valve for the 7As and 9As. I spent several hours trying to bend mine like you guys did, and if these new fuel lines had been available, it could have saved me a lot of cussing!

[mchesney]

I like the idea of the SS lines! Do you just run them straight out the rubber grommet to the wing?

[ksouthar]

After struggling for days trying to put the fuel line in one piece winding through the gear leg and over and up to the selector valve, I changed the approach and installed it in two pieces with a union at the rib closest to the valve. Took me a couple of hours to complete the installation in that manner after struggling for days trying to do it in one piece!

A week later, I saw a post here where someone else had done exactly the same thing (they also posted pictures). Lighter and less expensive than SS lines...

Keith
N355RV
Flying!

[MTBehnke]

I used Bret Smith's suggestion to keep the gear mounts loose until the fuel lines are run - worked great.

[rv9builder]

Originally Posted by ksouthar

After struggling for days trying to put the fuel line in one piece winding through the gear leg and over and up to the selector valve, I changed the approach and installed it in two pieces with a union at the rib closest to the valve.

A guy in my EAA chapter used two pieces and a union for the fuel lines in his 9A. The plane flies just fine.

I installed my fuel lines by keeping the gear mounts loose. It worked OK, but I still wouldn't say it was easy. I decided to use two pieces and a union for my brake lines and that went pretty smoothly. I just hope the extra fittings don't leak.

[N941WR]

Originally Posted by mchesney

I have a 9A and I'm working on the fuel lines from the valve to the wings. The plans show the lines going through the bottom grommets but when trying that route the gear weldment obstructed the grommet opening on the brackets that hold the covers in place. I opted to use the top grommets which are larger but the route seems much easier. Is this Kosher? ...

It is only Kosher if you don't run any wires under it. Should you have a leak, the fuel could drip on the wires and that may not be a good thing.

Any Tech Advisor worth his salt would ask you to move the fuel lines to the bottom holes.

[alpinelakespilot2000]

Originally Posted by mchesney

Also, I had to make a pretty sharp bend to line up to the fuel valve and I ended up with a very slight flattening of the line. Not enough to affect flow or rigidity (I'm assuming) but ever so slight...is this acceptable?

Check AC43.13 or Standard Aircraft Handbook. I think the rule (going from memory) is that the flat part of your bend must be 75-80% of the normal diameter of the tubing. If you've bent it thinner than that it probably needs to be replaced. Those lines are a bear, even for taildraggers, so hang in there. Hope this helps.

[Rivethead]

Here's s a page I wrote awhile ago to help out. This would be documenting the second time I ran my fuel lines on the same project.

http://www.rvforge7.com/pg3.htm