AFP Fuel pump assembly

We started with fuel system installation. As many builders have reported, getting the fuel lines in once the gear leg weldments are in place is a major PITA on the -A models... Anyway, we prefer to leave the weldments nicely fitted in place and do it the hard way *G*

Since we're building a full fuel return system, there need to be 2 holes instead of one everywhere. Hence we tried to go with smaller grommets...

This did not work out, not enough play to fit the fuel line... We're now going to order some more grommets as per Van's plans and then try it again. On this picture you can see the close quarters you have to work in. This is another one of these jobs where 2 hands just won't do it, make sure you have plenty manpower available to pull, push and bend...

So we let the fuel lines rest till we get some of the additional parts from spruce. Continued on the Airflow Performance fuel pump assembly. The kit only contains the fuel filter (yellow cylinder) and the pump package (not on this pic), everything else we had to design and order on our own. We decided to mount the filter with 2 MS21919-WDG26 and the pump with 2 MS211919-WDG28 (largest that spruce carries) clamps respectively.
We decided to mount the whole package on a common base, so it will be easier to service eventually.
The mount for the fuel selector is custom as well, 4 spacers made from 2024T3 ALUM TUBE 3/8X.065 and 4 AN3-31A bolts.

The yellow texture is anti-slip mat, intended to keep the bottom of the fuel selector from damaging the base plate. Also note that the fuel filter bolts are held by 2 nutplates, as the fuel filter is the only part requiring regular maintenance, it will be possible to remove without taking the whole assembly out of the airplane.

Also made a small bracket holding the connections going forward to the firewall.

Another common experience for builders is that it takes a bit of practice to learn how to cut, bend and flare tubing... Make sure you order some extra tube... We redid several lines, just to get a better fit. Also even when working carefully, you'll damage lines by trying to bend too tightly, forgetting a sleeve before flaring, scratching the outside with the bending tools etc...

Anyway, we had ordered a 50ft coil of 3/8" tubing from spruce at little cost which allows us some play. With only the tubing provided in the kit, you would have to get everything right at the first attempt.

The package is slowly coming together. By the way, the piano hinges on the sides will be used to mount a cover later on.

Bernie's brother Adrian, was on visit and we put in a great building session.

Although we had purchased some extra 180° bending tools, our experience so far is that the triple header 90° bending tool that Avery and others carry will do everything you need. Also two 90° bends are by far better than a single 180°...

We initially tried to hand-form some lines but later found that it's better to try even the slightest bend with the tool. Turns out better and no problems for fitting the sleeves on the ends for example.

The work of art from a single afternoon.

Integrating the supply side with the return line makes it look much more complex than it actually is.

And some right angle views. The side facing the spar.

Left side with the fuel filter.

Front. Note that there will be another check valve in the return line at the firewall. This prevents reverse fuel flow from the pump package to firewall forward.

Top down.

And an illustrated view.

UPDATE: We will have to rework the fuel pump pack! In a thread over at Airflow Performance came up with the info, that there is a small orifice in the pressure relief valve, to relieve pressure even without an overpressure condition. This was not documented anywhere. What this means with the current setup is, that with the engine fuel pump "sucking" there is a chance of air entering the supply side from the return line via the pressure relief valve. Now, the pressure relief must again be plumbed right back to the inlet side of the pump giving a "short circuit".


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