Sender: <marv@lancaironline.net> (Marvin Kaye)
To: lml@lancaironline.net
Date: Sat, 10 Jan 2004 17:27:36 -0500
Message-ID: <redirect-2926906@logan.com>
Reply-To: "Dan Schaefer" <dfs155@earthlink.net>
From: "Dan Schaefer" <dfs155@earthlink.net>
Subject: Pillar Point Fuel Sensor
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Regarding Rob Wolf's question about air in the fuel lines, etc.

Rob, the one thing you can take to the bank as regards to fuel systems in
our experimentals is that there are probably no two alike so, in my opinion,
just about all advice will be airplane specific. When I built my 235, back
in Lancair's prehistory (began in '86, flew in '93 - obviously, there were
no quick-build kits back then) there was some direction for the fuel system
in the manuals, but not much. As a result, you'll likely get as many answers
to your questions as there are LNC2's out there.

Here's one more: I used the fuel selector valve supplied with the early kits
(selects either wing tank) connected to each wing directly, followed by two
facet pumps in series feeding a single line to the header. I originally had
just one pump but had an early failure so I installed the second one
(figured that if I had to carry two I might as well just put them in series,
since they have a pump-thru feature - if one fails, I can still get at the
fuel in both wings). My reasoning for locating them after the selector valve
was that I didn't want a single pump failure to not allow me to get at all
the wing fuel.

From the selector valve to the first pump, I installed a length of
transparent tubing that is looped up the side of the instrument panel
center, higher than the fuel level in the wings (so a tubing failure
wouldn't allow flow from the wings to the cockpit) in clear view of the
pilot. When a wing tank goes dry, the pump sucks air and the tubing shows a
lot of air bubbles, indicating the tank is empty.

I know you asked about whether there would ever be air downstream of the
Facet pump and my system shows the pump intake line, so this doesn't
properly answer you question. My guess is that since the pump doesn't pump
air, once a bubble gets into the pump, it's not likely to be forced into the
output. But you definitely will get some air bubbles on the inlet side while
the pickup is still being sloshed with fuel, since I see it everytime I run
a wing tank empty.

Dan Schaefer
N235SP