Interesting discussion on fuel return and battery placement and to
review long ago topics.
The return line was plumbed to the bottom because it was easy and it
works. All points are valid that have been made.
914 Engines require no orifice and must have little restriction or poor
performance will result.
912/Jabiru normally aspirated engines so equipped with returns must use
the recommended restrictor by that engine manufacturer and hose size.
Return fuel back to the tank to the top requires more plumbing and is
perfectly fine provided the fuel size and fitting size is maintained.
Slightly more head pressure is required on the return but in my opinion
is minor as the pressure would be similar when the tank is full and a
normal return fitted. As a technique, plumb a 5/16 fitting into the
cobra neck for the return or use the same fitting as on the long ranger
tank for the return interface. Then buy a pump for your long ranger
tank and figure out something else for its plumbing and the tank vent.
Nothing comes easy on a modification.
Battery location in the trigear with most configurations follows from my
shops construction logs:
912 with fixed prop any panel put the battery on the passenger footwell.
912S same as above.
912S with Airmaster or equivalent prop, move the battery to the baggage
floor behind the flap tube.
914 with Airmaster or equivalent prop, move the battery to the baggage
floor behind the flap tube.
Jabiru 3300 may be put on the footwell, or the baggage bay floor with
fixed prop and VFR panel.
Mono wheel configurations 912, 912S or Jabiru 3300 are same as above but
the CG will tend to be about 1/2 to one inch forward of ideal of 60
inches empty.
For the 914/Airmaster with IFR panel, and autopilot, the battery must be
installed near the mass balance support bracket. If installed in the
baggage bay normally a 5 pound weight attached to the tail spring bolt
attach point or similar is going to be required. Otherwise mount the
battery to the tail spring.
We use the Odessy PC680 as our standard battery as it is reliable and
reasonably light (15 pounds). We use the metal battery box supplied as
an option. This is based on price, availability options such as the
metal battery box premade, and US lack of restrictions.
Attach to the fuselage floor using a wood or metal floor fitted to the
inside the battery box and attach with AN #10 tapered screws of your
choice to a floor mounting plate. The flange on the bottom of the
battery box can be used to screw through but I find a 1/8 ply with glass
faces as a floor to be more expedient. Battery hold downs are simple
aluminum angles riveted to the box, then nut plates are installed for
the battery hold down bolts. Secure a flat bar across the battery to
the metal battery box angles with appropriate #10 hardware to suite.
The mount to the floor is via a glassed (4 layers) in wood plate, flox
and foam. Nut plates are installed beneath the wood so as to be aligned
with the wood floor in the battery box.
If there is a question of CG in the Mono, I make another mount near the
mass balance guide post identical to the one in the baggage bay floor.
Do the weight and balance, and if necessary move the battery if required
the extra few feet.
I use #4 cable and attach studs to the vertical ply mount for the
positive and negative terminals. This makes battery attachment a single
cable affair instead of a mass of junkie wires all attached to the
battery for whatever you forgot, external electrical plugs, charging
jacks, or future electrical upgrades requiring direct battery access.
To move the battery, just make a new pair of wire attach cables to suit
the new battery location. Affix the cables securely to the floor.
Great advice from you all.
Regards,
Bud Yerly
Tech Support
----- Original Message -----
From: Remi Guerner<mailto:air.guerner@orange.fr>
To: europa-list@matronics.com<mailto:europa-list@matronics.com>
Sent: Sunday, April 29, 2012 7:16 AM
Subject: Europa-List: Re: Fuel Return Line
<air.guerner@orange.fr<mailto:air.guerner@orange.fr>>
It is always instructive to have look at what is done on type
certificated aircraft. Attached pages from the Diampnd Katana show the
aircraft fuel system. As you can see: the return line goes to the top of
the fuel tank, which is located behind the seat, as in the Europa. There
was a one way valve in the return line of the first 90 production
aircraft. Then the one way valve was removed on subsequent production
aircraft and a Service Bulletin was issued to allow the retrofit of this
modification, probably for a good reason.
Another thing is the diameter of the restrictor. The diameter of the
restrictor supplied with the kit by Europa is .75 mm while ROTAX
specifies .35 mm in their 912 series Installation Manual. I believe .35
is appropriate whenever the return line goes to the top of the tank and
the bigger diameter is necessary in the Europa configuration due to
somme back pressure caused by the line returning to the bottom of the
tank.
Remi Guerner
F-PGKL
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