Hi,
Attached is my idea of a simple fuel system for my Vision low wing
aircraft.
Will this work or am I overlooking something?
Regards,
Pierre Swanepoel
Not a bad idea. Looks like it is worth a try. Monitor the tank
quantities when testing to see what happens. I assume there is a bit
of dihedral in the wings.
Paul Lamar
Pierre,
What would happen if someone closed the shut-off valve while the pumps
were
running?
Mark S.
Good point Mark. Probably best to forget the valve and turn off the pumps.
Paul Lamar
Classic teaching is that you don't run low-wing aircraft on "both" tanks.
Can't remember the exact reason. Maybe too easy to pick up air from the
dry(er) tank? But certified low wings always have a valve that
definitively
selects which tank is in use and there is no tank equalization by gravity.
That lesson was probably learned the hard way..
FWIW, I also think that you will find that you prefer to have better
control of where the fuel is for a lot of reasons. I have one wing that is
a little heavy, but I solve the issue by keeping a little more fuel in the
tank on the other side. I also prefer to 'stack' my fuel into one tank at
the end of a long cross country. You get the picture.
--
David Leonard
Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net <
http://n4vy.rotaryroster.net/
http://RotaryRoster.net <
http://rotaryroster.net/
Pierre, I was looking at your fuel system schematic. I wouldn't have
the manual shutoff as shown. This valve (solenoid operated) would be better
placed after the fuel rail to hold pressure on the fuel rail. It would be
wired with the ignition on to close. If you get air in the system opening
the valve would flush the air back to the tanks. If your pumps are gear
pumps with constant flow then there needs to be a return from the regulator
to tanks. If you run both tanks for takeoff and initial climb you could use
a tee from the regulator return to two tanks but the flow will not be evenly
devided. I was called in to sort out a hydraulic pump system with four
150HP dual gear pumps with separate relief, unloader, and proportional
directional valves. All four ran a single hi- speed cylinder (60 ft in 2.5
sec) The problem was reduced cylinder speed and the individual tanks
overflowing everywhere. There was 6 inches of saturated saw dust on the
floor. By reading motor amps on all motors simutainously after I overhauled
the 16 vickers operators and adjusting the pump units to the same load the
speed and control was fine but the overflow problem persisted. There was a
1-1/2" balance line between the tanks. This was working at atmospheric
pressure (14.7psi) and the return was at the filter backpressure of 40psi. I
increased the balance pipe diameter to 4" and it worked as intended, however
the oil level in the four sight guages never matched. For your system It
appears the pressureXarea or the balance tube needs to be equal or greater
than that of the return.
As an addition I would have a fuel pressure sensor before the regulator
to compare pump output pressures of the two pumps running individually to
detect pump or filter problems during runup before takeoff. The intank
flters seem likely to be infrequently changed due to the inconvienance
factor. It might be allright with welded aluminum tanks but with the recent
epoxy degredation problems due to the "govmunt fuel improvements" I wouldn't
have in tank filters with composite tanks.
george grimes
"This valve (solenoid operated) would be better
placed after the fuel rail to hold pressure on the fuel rail."
That is normally achieved with the pressure regulator after the fuel rail.
Paul Lamar