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I've settled on a design that uses a positive cut-off transfer pump to pull from an AUX to a MAIN tank. An emergency crossover valve will allow access to the AUX tank fuel in case of a transfer pump failure. Two 2-psi pumps, after the gascolator, in parallel and with back-flow prevention provide redundancy to push the fuel through individual filters and up to the top of the firewall, where a Holley float bowl will meter the fuel and provide a reservoir for the head pressure and smooth flow needed to by the AeroVee carb. I'm still analyzing it, but I think it is a really simple and safe design.
It's not a rotary, but as always the open, non-theocratic helpfulness of this group is simply amazing compared to just about every other discussion group I've ever been a part of. I'll have a safer airplane, because of the discussions I have here.
On Tuesday, November 4, 2014 6:05 AM, Mark McClure
<flyrotary@lancaironline.net> wrote:
I'm a huge fan of the transfer pump method. But I think this would depend on your tank setup. For me building a Glasair I have a single wing tank and a header tank. The header is a perfect reserve fuel tank. One hours worth of flying. Easy plumbing dumps that into the main and you are off. (Gravity or xfer pump)
As for a T valve for low wing aircraft. I have flown behind a turbine low wing with a T. Fuel splits were not that common as long as the aircraft was flown in balance. And if you wanted to pull from one vs the other to get rid of an unbalance you just let ball go out.
Mark McClure
On 10/31/2014 8:09 AM, Ernest Christley
wrote:
>But...Didn't you mention 6psi fuel pressure?
If that's correct, then why have a return line at
all? If it's a carb engine,
>just use Facet 'solid state' (interrupter
style) pumps. No return line needed.
Good point, Charlie, but the engine came with one of
those AeroVee carbs on it. It's basically a throttle
body with a drip feed for fuel. It gets upset with more
that 2psi of pressure, and there are very few regulators
that are accurate down that low. They're basically
designed to be gravity fed, and the 601XL doesn't have a
header tank.
I'm now seriously considering the transfer pump
configuration. Now that I've been reminded, I remember
that Tracy has been flying with that setup for years.
I've got to think about it more.
But what can you use for a bypass style regulator that's accurate at
2 psi, anyway?
Facet makes cube ('solid state') pumps rated as low as 2.0 psi max.
Here's a list; the window scrolls for more models.
http://www.facet-purolator.com/cube-fuel-pumps.php
That page mentions 'optional check valve' (CV) but doesn't explain
the PSO column. That's basically a 'positive shutoff' or anti-siphon
that prevents fuel from flowing through the pump if it's not
running. Whether you want that depends on how you plumb the
installation. 2 in parallel, you could potentially eliminate valves.
2 in series, twice the pressure but no flow unless both are running.
The .pdf link in the page has a better description.
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