9.7.0 Fuel System Plumbing

You’ve already seen this photo in Section 9.4.5. In this section the lines of interest are the two lower feed lines coming from each fuel tank. As mentioned in the sidebar on the right, I modified the system a bit to include maintenance shutoff valves for each tank. Those are the items with the yellow handles. They are not remotely controllable - there really is no need for that. But if I ever need to do any maintenance on the sump tank or on a fuel tank. I can use these shutoff valves to eliminate having to drain out all of the fuel. During normal operations, these valves will be tie wrapped open so that vibration doesn’t accidentally close them.

You’ll also notice that the two fuel lines bend down at a slight angle. Fuel from the tank into the sump tank is gravity fed so we can’t have any high points in those lines. All of the other lines that you see in the photo are vent lines.

Wings - Fuel System - Fuel Lines

Completed fuel and vent lines in the back of the fuselage.

In the photo below, the sump tank has been removed for the installation of the main feed line to the engine. Fuel from the sump tank is pulled out by the engine’s fuel pump, so gravity isn’t as much of a concern here. I’m also using a larger diameter line here - 1/2” (the feeds from each tank into the sump are 3/8”) - since the 300 hp engine I plan to install needs that extra capacity. I also added a standoff and clamp for the line to keep it from vibrating.

Wings - Fuel System - Fuel Lines 1

I also needed to make a support for the main fuel line from the sump tank to the engine. This will have an even larger fuel shutoff valve that will also be controllable by the pilot should the fuel need to be shut off to the engine due to a fire or whatever.

The sump tank is now reinstalled in the aft end of the fuselage. I’ve also added the shutoff valve in the photo along with the control cable. Eventually a fuel line gets added here that feeds the engine. I had to modify the valve slightly to work with the control cable. The handle came with one of those yellow plastic covers which I cut off. I then drilled a hole in the handle to accommodate the drilled bolt that I’m using to capture the cable. I actually had to drill out the diameter of drilled bolt’s hole a bit so that the control cable can pass through. I’m using a couple of nuts to clamp the cable in place. Eventually I’ll bend the cable around the bolt so that if the nut comes off the cable stays attached. The bolt itself is not tightly attached to the handle. It needs to rotate in the hole when the cable is activated. There’s a specced radius that the control cable can accomodate so I drilled that hole at that location so that the valve handle can rotate the full 90 degrees. It’s working perfectly!

Fuselage - Emergency Fuel System Cutoff

Emergency fuel shutoff valve with control cable attached.

Here’s the cockpit end of the control cable. It sits along the outside wall of the fuselage. I purchased this cable from McMaster-Carr. It even came with that nice, b right red handle (even though the catalog showed a black handle!) I created a hard point for the homemade brackets used to hold the assembly (see below) along with a bracket to support the cable before it bends and enters the conduit I ran to hold the cable in place from the front to the back of the fuselage. (The conduit is a piece of 1/2” PVC pipe that I hot glued along the floor and up against the fiberglass conduit used to hold the battery cables. The carpeting will cover up this conduit.)

Because this cable doesn’t come with a locking mechanism I decided to make my own. It’s just a simple piece of aluminum, painted red, with some foam stuck on the back to press on the red knob. It’s simple and it works! Because I painted the brackets I put some blue tape on them to protect them from getting scratched.

Fuselage - Emergency Fuel System Cutoff 1

Finished and installed control cable, stop bracket and support bracket for the emergency fuel cutoff system.

The main bracket is just a piece of 1/8” thick aluminum (2” wide) that I bent at a 90 degree angle. I epoxied that directly to the wall of the fuselage and covered it with 2 BID to keep it secure. The bracket that holds the red stop is shown in the photo below. Again, it’s pretty simple but it works. This bracket is held in place with the nuts the hold the cable in place. The two screws sticking out are used to level the bracket on the main bracket.

Fuselage - Emergency Fuel System Cutoff 2

Painting the emergency fuel shutoff stop bracket.

The photo below shows the assembled sub-bracket.

Fuselage - Emergency Fuel System Cutoff 3

Completed emergency fuel system shutoff stop bracket before installation.

Once the engine is installed I’ll be adding more plumbing. 

ui© John Trautschold 2018