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Hi Colyn,
So far I have no indication that I get air in the fuel system. Even if I
run the tank dry - the engine runs smooth until it stops and then I
switch tanks immediately (low boost on before and I wait pretty much on
the fuel starvation with my hand close to the fuel selector) and the
engine keeps running fine.
The only time I had fuel starvation with enough fuel was when I was
flying with crossed controls (I think it's called a skid) for a longer
period of time with the ball probably way out of center (my instructor
made me do this) - I switched tanks and I needed the high boost to make
it come alive again. Also on take-off when I am completely topped off
and my ball gets out of center I can see fuel coming out the vent line
off my left wing on the wing tip (not the winglets) - it seems like when
the ball is out of center that the fuel gets driven into the wing tips
away from the fuelage
The T fitting behind the fuel selector: I don't have my hydraulic print
handy but I am pretty certain that it is the feed line for either gear
in or out (it comes from the vale gets split between front and main
gears behind the fuel selector and probably gets split again in the gear
box for left and right. There are more lines in this channel - the left
and right main brake is also hard piped in there) - if you have any
concern with that T fitting let me know and I dig out my hydraulic chart
(I think I remember that I changed the hydraulics slightly to make my
installation a little cleaner)
Ralf -----Original Message-----
From: Colyn Case [mailto:colyncase@earthlink.net] Sent: Tuesday, January 29, 2013 10:53 AM
To: lml@lancaironline.net
Subject: Re: [LML] Re: Question about Dukes Fuel Pumps - Fuel selector
leak
Ralf,
I can't come up with a risk for fuel transfer other than that it's going
to make your inflight fuel calcs a little off.
However, there's a big risk if any air is getting into the valve. We
had some issues with that some years back. Does anyone recall the
details?
b.t.w. - what are those lines teed off to the left side behind the fuel
selector?
Colyn
On Jan 28, 2013, at 3:24 PM, <bronnenmeier@GROBSYSTEMS.COM>
<bronnenmeier@GROBSYSTEMS.COM> wrote:
George,
It's been a while and I don't have the schematics here right now. But I
am pretty certain that there is a return from the fuel pump. It would be
the middle line on the left side. The other two on the left side is the
nose gear hydraulics.
The blue fat line on the right side is the fuel feed line.
Question for the group: is it a problem it the fuel selector is leaking
a little internally. My wing tanks are "talking" to each other. If I
run one tank completely dry and the other tank is half full about 1/2
gal of fuel is moving from the full to the empty tank in about 24 hrs. I
noticed it when I run one tank dry and let the plane sit for a week or
so - it is just a habit that when I run low on fuel that I rather have
all my fuel in on tank (and plan my turns accordingly) instead of having
two almost empty tanks. I do not have any stains or fuel smell around
the fuel selector.
Ralf
-----Original Message-----
From: George Wehrung [mailto:gw5@me.com]
Sent: Sunday, January 27, 2013 1:30 PM
To: lml@lancaironline.net
Subject: Question about Dukes Fuel Pumps
All,
A couple of questions about Dukes electric boost pumps. If the engine
driven fuel pump fails, can the Dukes electric boost pump, in the low
flow mode supply enough fuel to keep the IO-550 running, at what I would
guess a lower power setting to find a place to land?
I have noticed that some installations have both a prime button and have
a separate high flow mode incorporated into a a HIGH-OFF-LOW rocker
switch. My airplane only has a LOW-OFF selection for the boost pump in
addition to the push to engage Prime mode, which I have learned is the
High Flow mode for the boost pump. It does not seem to make sense that if one lost the engine driven fuel
pump that you would have to hold the prime button in order to have High
Flow mode from the electric boost pump to keep the engine running. Or,
should my airplane have the HIGH-OFF-LOW boost pump rocker switch
installed?
There doesn't seem to be any spec sheets available on the flow volume in
the High and Low modes of the Dukes Electric Boost pump.
Lastly, from what I have learned in the build manual that there must be
an internal bypass in the engine driven fuel pump if it fails? The
plumbing seems to be as follows: Fuel tank, fuel tank selector valve,
electric boost pump, firewall, gascolator, engine driven boost pump, and
then fuel distributor, and then injectors. I know there is a return line
from the engine driven boost pump back to the fuel selector valve. Thanks for the help
George
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