Reworking Fuel Pump Package

Completed some more minor things on the fuselage. One was to install the AHRS box in the back of the fuselage. Also the idea was to keep it simple, just in case we decide on another EFIS last minute or the separate box becomes obsolete.

The AHRS needs to be aligned precisely in all 3 axis. This required a small bracket on the bulkhead slightly offset from the centerline and a small spacer for the forward mounting hole. We figured the box is quite sturdy and has a strong baseplate, so no special mounting plate appears to be required. If needed we can always add later, the same goes for another rib or a fourth mounting point. Fortunately the area is quite accessible through the baggage compartment.

A couple of screws with nutplates mounted to the base will do.

Nice extension for the toolbits that we got in OSH put to good use.

And the empty box temporarily installed.

Now onto the fuel pump package. Maybe you've followed the story. We had the fuel pump package done (Airflow Performance electrical boost pump for fuel injection) with the pressure relief valve plumbed into the return line. Now in a thread at provided info that there is a tiny pinhole in the pressure relief valve to relief again pressure from that valve when the system is unpowered. Now this had the potential to suck air from the return line into the supply side of things through that pinhole. Not good.

Essentially this came down to moving a tee fitting from the return line to the supply line. In the end we re-did all pipes as this had a major influence on layout and fittings.

Adrian's got it figured out pretty well by now... The second time around, everything just falls in place a lot quicker and prettier as well.

One connection after the other is being bent.

And tattaaa, the end result. Alex' comment was that it looked like the 3d pipes screensaver in Windows XP ;-)

The return line is no longer shaped like a loop, but an omega.

Also the lines are supported by soft pvc tube velcro strips.

The design was again focused on a compact package, and easy maintenance of the fuel filter.

Trying to prevent a siphon effect, we installed the fuel filter on a riser.

Looking forward to final installation and leak testing ;-)

The center console/cover is the only thing now remaining to be done, besides the electrical wiring.

It will yet come apart, so it's not torqued yet.

The fuel filter riser is made from some stock aluminum profile.

The front connections, left supply for the engine, right return to the tanks.


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