> I want a minimum-management on-off fuel supply. For my L235 w/ IO320, I'm
> now running the fuel line from each wing tank through a  filter on each
> Facet pump, then from each pump -- both into an open Tee, up to the header
> tank -- Control of the Facet wingtank pumps' is on-off with an optical
> level-sensor in the header,  to break or complete the plus-circuit 12VDC
> to each/both tanks' power-on/off switches.

I think the PPAv XFR Fuel Pump Controller ($190) is what you're looking for.
http://www.ppavionics.com/XFR.htm
The full manual is at...
http://www.ppavionics.com/PDFFiles/JKManualRevG011805.pdf

The controller has manual on/off, or timed transfer modes. When combined
with their optical level sensors in the header
http://www.ppavionics.com/FSD.htm (another $190) it can automatically
switch on the two Facet pumps. Fuel is transferred until the upper sensor
is wet, or until the wing tank sucks air.

> How can power to the L and R wing tank
> Facet pumps automatically switch off when the wing tanks are dry?   

Interesting question. The folks at Pillar Point Avionics tell me that their circuit monitors the current draw of the Facet pumps. When the pumps run
dry, their resonant frequency decreases. The controller senses the frequency
change and shuts off the pump.

> Would it hurt the Facets to run if one runs dry before the other? (No
> check valves; Flow is one-way through the pumps).

I have run my pump dry and it didn't fail. It makes such a racket, though,
that I woudn't want to leave it on. I would guess that the pump stays cooler
when it can pass its heat on to the fuel.

Note that there are (at least) three general types of Facet pumps.
The "interupter" pumps are cylindrical and don't usually end up in
experimental aircraft.
The blocky ones come in two general types.
p/n 40171 has an integral valve that is CLOSED when the pump is off.
http://www.ppavionics.com/FuelPump.htm

The more usual Facet pumps are models 40105, 40106, or 40108. They allow
fuel to flow through the pump when they are not powered. These are the ones
usually used in a 235/320/360.

I have not yet installed the Pillar Point fuel controller, but have looked it
over closely and it appears to be well designed and engineered. I'm planning
to install it soon.

-bob

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