Thanks everybody for their input. This is why I love the Rotary Forum. There
are so many different guys with a wide variety of expertise, that there will
always be someone with firsthand practical experience to give their opinion.
Because I don't fly that often, I tend to think what works well for a car
will automaticaly work on an aircraft.

Attached is try nr two. I want to have a system that is simple, inexpensive
and requires minimum input from the pilot.

This is essentially an electrical controlled system (In my trade). I'm
thinking of having a centre console mounted rotary switch with left, right
and off positions. In the left and right positions it will switch on the
relevant Facet pump and open the relevant return line solenoid. A mechanical
overide will be incorporated to prevent me from switching it Off by
accident. My thinking on the centre solenoid, forward of the HP pumps, is to
have it open for both left and right positions but closed in the Off
position. This is to cut off all fuel in case of an engine fire.

The left and right HP pumps will be controlled by two switches on the panel
so that either one or both can be switched on as required.

I'm planning to build an electronic timer to give me a visual
indication,flashing LED, of approx. 20 minutes to remind me to switch
between tanks.

I have a few qustions though:

1. Will the HP pump ensure that the facet pump does not pump fuel overboard
through the vents. I'm thinking to maybe wire it up in such a way that the
Hp pump is switched on before the Facet pump goes on. Or would I need a
mechanical way, needle and seat or float valve to control it?

2. Can I use car airconditioning solenoids for the fuel?

3. Are there any restrictions on the size of the surge tank? Can I use it to
increase fuel tank capacity?

4. Are the fuel supply and return lines the right size?

Pierre


I think you should return all fuel to the sump tank. No return solenoids required.
A float valve is a good idea. The facet pumps are used to feed carbs with
float valves. T the Facet pumps together before feeding the sump. Check them
for one way valves. If they don't have them get some.

Here is your 2nd drawing modified to my suggestions.

Questions:

2. I don't know.

3. Other than weight and balance no. Yes it can be used to increase fuel
    capacity.

4. 3/8th are fine for everything. Vents can be 1/4 inch.

A sight gage on the sump tank is a good idea if it is mounted high.

Paul Lamar

Thanks again. I'll use your system. I might just replace the remaining
solenoid cut-off valve with a manual ball valve. Less to go wrong.

Pierre

A good float valve is essential as 5 psi fuel pressure can blow up
a large sump tank. Another trick is use a pressure switch in the
sump tank to turn the facet pumps off when the tank is full.
Just make sure there is an over ride switch in case the pressure
switch works.

Paul Lamar