Charlie,
I
transferred fuel to a T in the return line from the
regulator. The regulator return was connected to the side
branch of the T. I suspect that the back pressure from this
connection adversely affected the flow rate from the Facet
pump. A separate line to the main tank or a different
connection arrangement at the T might have been better. The
high pressure pump had a higher and predictable flow rate.
While
returning the fuel to only the main tank would work, it
seems to leave the possibility for a couple of undesirable
situations.
One
would be in the event that the supply from the main tank
were compromised, fuel would have to be drawn from the aux
tank while the returned fuel would accumulate in the main
tank where it would be inaccessible and possibly vented.
A
second possibility would be to draw fuel from the aux tank
and return it to an operational but full main tank where it
would be vented. I’m sure you would not do this. Me?...
I’m not so sure.
Steve
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On Behalf Of Charlie
England
Sent: Thursday, February 24, 2011 4:18 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Fwd: Fuel injector pump
cooling??
Ouch; I hadn't thought about that. But I
suspect that even a low pressure pump would damage the tank if
the vent is blocked. Thanks for the data point on the fact
that a high pressure pump can be used effectively as a
transfer pump.
Were you using a separate port on the main tank for your
transfer point? My tentative plan is to T into either the
regulator return, or (assuming an effective back/anti-siphon
setup), into the main supply between tank & engine pump.
Obviously, the anti-siphon feature would need to be bullet
proof to tap the supply line.
One option I've considered is to use the fuel selector
'normally', but have all regulator bypass return to a single
'main' tank. This arrangement is actually used in some
certified planes with injected Continentals, but I'm leery of
having my primary engine pump run dry for even a very short
interval as I empty an aux tank. I suppose that with that
arrangement, it would only run dry for a couple of seconds (
:-> ), so maybe it would work out fine. Any thoughts?
Charlie