So here comes a box with a fuel pump and filter some check valves and some Aluminum tubing to connect them. This particular kit comes to me from Air Flow Performance via Van's Web Store. The basic idea here is to filter the fuel coming in from the tanks and provide a backup means to pump fuel to the engine. The back up in this case is an electric fuel pump that augments the mechanical fuel pump which is attached to, and driven by, the engine. The electric fuel pump is designed to be switched only during critical phases of flight. What is a critical phase? Well, that would be a flight regime where fuel starvation of the engine could present a life threatening condition. Just after take off, for example, when the aircraft is not yet high enough to glide to a safe landing. Think of the auxiliary fuel pump as a $700 insurance policy against the mechanical fuel pump failing and wrecking your day.
The fuel pump kit from Van's also includes a base plate to mount the pump and a fuel filter. In addition there are anodized fittings to connect the pump to the check valve and sufficient aluminum tubing and fittings to complete their interconnections. At first glance, the plumbing looks to be quite complicated, but after thoroughly studying the supplied instructions and drawings I would say the it is only 'very' complicated.
Out of the box and on to the base plate.
I really enjoy the bending of the aluminum tubing. I don't know why. The first step is to cut the tubing to length and square the cut end. I like to run the end past the Scotch-Brite wheel to smooth the edges before go on to the flaring of the ends.
It's really important to remember to put the B-Nut and sleeve on before flaring the end. I really can't stress this enough. Also one needs to pay attention to the direction of the nut and sleeve before the flare goes on.
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Here's the first bend complete.
And here we are about half way through with the plumbing. Note the addition of the TEE which will connect to the Andair fuel selector valve.
This is the fuel selector valve without the handle connected. It doesn't really look like much, but it has two very important jobs: To relieve excess wallet pressure which it does with breath taking efficiency, and to select from which tank the fuel will come.
And mounted on the pump assembly.
Here it is in the plane with the left and right fuel lines run.
Is that a rats nest or what? It's a bit too modernist for most of the rats I know. Perhaps some German rats would like it -- I don't know.
Here is some more showing the routing of the fuel lines coming in from the tanks.
And then the line exits the fuselage in the wing root. The left side is long because it still needs to go through the forward wing attach bracket at left and then turn toward the wing near the leading edge.
The fun is not yet over as I still have the fuel tank vents to route. These are 1/4" soft aluminum tubing and are quite easily bent. One can manage most of the bends without the tubing bender. The vent comes into the fuselage at fuel tank level and travels up to the main longeron and then back down to the floor. The rise in elevation, I suppose, is to prevent the vent from draining the fuel tank. Not a bad design feature for the cost of 4 feet of tubing. Here is the vent entering at the wing root.
Going up, turn, and back down again.
At the floor, the vents terminate at fittings which protrude into the air stream. These AN-4 fittings have been cut at 45 degrees and the threads sanded off. Then a small piece of screen is glued to the face with Pro-Seal. After the Pro-Seal cures, the edges and screen will be cleaned up and the fittings will be installed on the ends of the vent tubing facing forward -- into the airstream.
By orienting the vent this way, the tank is slightly pressurized by high speed air entering the vent. This may help to feed fuel, but more importantly, a vacuum is not created at the vent opening which could suck fuel overboard.
Installed vent facing forward illustrating the 45 degree cut.
That's about it for the auxiliary fuel pump and fuel line routing.
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