Fuel System Routing

Now that I had all the parts I needed, it was time to begin routing the fuel system through the center fuselage. I am deviating from the TAF instructions, the following is a summary of the changes:

  • Relocating the fuel valve body to slightly below and behind the dash, remotely controlled from the dash
  • Relocating the fuel filters to the wings
  • Running 3/8″ OD aluminum tubing , 3003-O “Versatube” instead of rubber hoses
  • Running 3/8″ OD tubing for both supply and return lines (instead of 8mm and 6mm ID rubber tubing, respectively)
  • Terminating the tubing at the firewall with bulkhead fittings
  • Terminating the tubing at the wing connection point with inline union fittings
Fuel System Block Diagram

Although the aluminum tubing I bought (3003-0 “Versatube”) is hand-bendable, I chose to use a bending tool to control the radius of the bends without compromising the shape of the tube. Not having any instructions, it took quite a bit of time to measure out the overall length of the tube as well as the location and degree of each bend. After that, it took additional time to cut the tubes, deburr and clean the ends, then use a flaring tool to form the flared ends. In total, I spent about 30 hours doing this design mod, but I’m pretty pleased with how it came out. You can watch the three YouTube videos to get a better look at the details and see the process along the way. I also have a bunch of pictures below showing more details.

First I needed to temporarily place the dash in place, so that I could design a bracket to secure the duplex fuel valve
Fuel valve bracket designed in Fusion 360 using the Sheet Metal toolbox. I printed this drawing 1:1 scale, so that I could tape this template right to a sheet of metal to cut it out and form the shape
Cutting out the bracket using hand shears, drill, and hole-cutting bit on a drill press
Bracket angles formed with a press brake
Initial mounting of the fuel selector valve and bracket, to aid with measurements for the tubing
Extension bar and universal joint to connect the fuel valve to the selector panel on the dash
Initial forming of the left and right side tubes complete
AN-style connectors at the wing attachment point; each is also held in place with a cushion clamp attached to the small bracket I fabricated

In order to route the tubes over to the wings without having a break in the lines, unfortunately I had to uninstall the joystick assemblies. These were a bit of a pain to install, so I loathed having to do this! I also had to remove small gussets at the aft end of the center tunnel, shown at the left side in the next picture. These were also a bit difficult to remove due to tight access, and the fact that I had to drill out a rivnut in addition to rivets. While painful, this allowed me to run the fuel lines continuous from the wing connection up to the selector valve.

Routing in front of the wing spar carry-through

Initially I routed the supply and return lines to the firewall as per the kit manual – which has them cross diagonally above the copilot footwell – but I didn’t like the possibility of the tubes getting bumped into (for example, in turbulence), so instead I re-routed the tubes continuing forward through the center tunnel and then turning over to the connection points on the firewall

Initial routing to the firewall, right above the copilot footwell
Revised lines up to the firewall
Revised routing, now stays clear of footwell area

The tubes are all labeled either “FUEL” or “RETURN” with direction arrows. In addition, each tube pair is tied together to form an assembly; to do this, I cut a short piece of 3/8″ ID vinyl tubing, split it open, wrapped it over one or both of the aluminum tubes, then put a zip tie around the set. This keeps the tubes neat and stable, while also preventing the tubes from banging into each other under vibration. A few cushion clamps along the routing paths ensure the tube assemblies stay in place.

How the tube pairs are held together with short pieces of vinyl tube and zip tie


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.