RV-8F

N772RW

Building, testing and operating an experimental aircraft

The Tao of Tube: Andair Fuel System

28 Jul 2013

With the fuselage now flipped right-side-up, Dad and I got busy installing some critical fuel system components in the cockpit. We decided to deviate a bit from Van’s stock fuel selector, filter, and pump, and (like many other RV builders) we elected to go with the wonderfully-designed Andair components.

Fuselage Canoe Fuselage “Canoe”

Here’s what we got:

Mounting the Fuel Selector

To hold the new fuel selector in place, Dad fabricated a bulletproof new bracket from 0.125” aluminum which is designed to locate the Andair selector in roughly the same place as the stock Van’s unit. We wanted to have as few tube bends as possible, and avoid the “spaghetti” look of some of the setups we’ve seen.

Andair Fuel Selector Bracket Andair Fuel Selector Bracket

In the stock position, the Andair outlet port is essentially in line with the pre-drilled gear tower pass-through hole, and it’s also a very pilot-friendly position – easily accessible from the front seat without leaning forward, but yet still tucked away behind the bulkhead enough to avoid inadvertent operation.

We ended up having to make a few modifications to Dad’s original bracket in order to keep the red Andair valve selector actuator from rubbing against the cover plate, which caused the locking pin to pop out of its detents too easily. I think the Andair instructions say that you only have about 0.25” to work with in terms of panel thickness, so we had to shave a little thickness off of our 0.125” sheet.

Fuel Pump and Filter

We really wanted the cleanest and simplest installation we could get, avoiding as many U-turns and bends as possible. We used the Andair RV-7 installation instructions as a template for our own, making the necessary modifications to the design to accommodate the gear tower location and the E.I. Red Cube transducer.

Andair Fuel Pump Plumbed Andair Fuel Pump Plumbed

I fabricated a mounting bracket for the fuel pump out of 1.5” aluminum angle to raise the pump and filter assembly up to the height of the gear tower outlet hole.

Mounting the Red Cube

Do a quick web search on where and how to install this transducer, and you will get just about every conceivable opinion and jury-rigged setup under the sun. The FT-60 instructions state that “if the aircraft has a fuel pump(s), the flow transducer MUST be installed downstream of the last fuel pump.” This seems to suggest that it needs to be mounted in the engine compartment, after the engine-driven pump.

E.I. FT-60 Red Cube Installed E.I. FT-60 Red Cube Installed

We decided to locate the Red Cube inside the cockpit, immediately after the fuel valve, before the filter and pump. This seemed a convenient and elegant location, and we found several builders who have had luck with this setup, including Mel Asberry in his RV-6, and Danny King in his RV-8, “Beautiful Doll”:

The Doll’s fuel system is very simple. Tanks to fuel valve to fuel transducer to electric boost pump to filter to 90deg firewall fitting, 303 hose to the engine driven fuel pump, 303 hose to the Bendix throttle unit and 303 hose to the fuel distributor. Two hundred and twenty six hours later all is well with the fuel system.

In our installation, the Red Cube is mounted securely to a bracket, it’s not subject to excessive vibration, it requires no protection from heat, and the adjacent fuel lines and fittings are easy to inspect. If its location causes fuel cavitation resulting in “jumpy” readings, we’ll either live with it or re-evaluate. If it becomes a safety risk, we’ll simply move it. But so far I think the pros outweigh the cons.

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