All,
Gary asked "I wonder why the coupe tends to lose fuel this way".
(siphoning)
There are a variety of fuel systems "out there", and therefore more
than a few
reasons for such fuel loss.
Prewar 65HP coupes had a five gallon fuselage tank and one 9-gallon
wing tank.
It was on the right side, opposite the pilot's weight. Both were of
ternplate.
Excess fuel transferred by the fuel pump returned from the fuselage
tank via an
overflow line to the wing tank until all wing tank fuel was consumed.
Postwar 75HP 415-Cs added another 9-gallon ternplate wing tank. A
crossover
line connected the two wing tanks and the fuel transfer pump drew from
a tee in
the crossover line nearer to the right tank. The main tanks fuel gauge
was in
the right tank.
The present Ercoupe Parts Manual ignores the fact that Ercoupes through
Serial
No. 812 required wing tanks, part number 48028L & R, allowing steel
main gear
legs to attach to the front of the main wing spar. Ercoupes from
Serial No. 813
to 2622 could be altered to take the later aluminum wing tanks per
Ercoupe
Service Memorandum No. 31, item #5, and ESM 39.
The Service Manual says 5 gal. fuselage tanks of stainless steel were
installed
commencing with Serial No. 2469. At some point replacement wing tanks
were
fabricated of stainless steel, but identical to and interchangeable
with tern ones.
Aluminum tanks were installed commenting with Serial No. 2623 and the
overflow line from the new 6-gallon fuselage tank now went to the left
wing tank,
per ESM 31, Item 17. This information conflicts with ESM No. 42, Fig.
1, which
shows the overflow going to a tee in the line connecting the main tanks
near the
left one for Serial Nos. 2623 through 3220. The fuel system schematic
for
Ercoupes "3468 & Subsequent" in ESM No. 43 and in the Ercoupe parts
Manual do
NOT agree. Ercoupes with fuselage tank overflow going to a single wing
tank require VENTED caps.
I believe the one in ESM No. 43 to be correct, and the one on p. 28 of
the Parts
Manual, Fig. 20, to be incorrectly identified, and actually applicable
to Serial Nos.
4424 & up (and those 100+ 415-Cs that ERCO modified in the field to
become 415-CDs). This is the fuel system shown in Flight Manual for
the 415-D
(and subsequent CD, E and G Models) with the fuselage tank overflow
splitting
into separate overflow lines to each wing tank. Any Ercoupe (Forney,
Alon,
M10) with this system was originally intended to have UNVENTED wing
tank caps.
If an Ercoupe (et al) with UNVENTED wing caps is venting wing tank fuel
in flight
the cap/gasket/flange is not sealing correctly. If one with VENTED
caps is venting
wing tank fuel, I would suspect (1) the cap/gasket/flange is not
sealing correctly,
(2) the 1/16" hole in the fuel transfer pump discharge fitting is too
big (or not so
restricted), (3) one of the wing tank cap vents is obstructed (or
somehow
different in size from the other or (4) the cap has been put on
backward (Serial
Nos. 2623 and earlier only).
Serials prior to 3468 had a smaller single overflow line, and there
could be some
initial conditions of flow with full wing tanks that returning fuel to
one main tank
is unable to "balance" via the crossover line between the main tanks
(perhaps a
partial obstruction or dirty finger strainer). There are relatively
FEW Ercoupes
that experience other than momentary "siphoning" if the above
suggestions are
diligently applied.
It was always my personal practice to fill the fuselage tank first,
then the wing
tank that did NOT receive overflow, and finally the one that did...each
within 1/2"
or so of the cap seat.
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2009)
--
On Aug 6, 2009, at 13:58, Hartmut Beil wrote:
Maybe the line itself is the restrictor.
In any event, the tanks slowly level out when being filled.
Like I said, what do I know.
Hartmut
To: [email protected]
From: [email protected]
Date: Thu, 6 Aug 2009 12:26:32 +0000
Subject: [ercoupe-tech] Re: how full of fuel
Thats the first I have heard of a restrictor in the line between the
tanks????
Kevin1
--- In [email protected], Hartmut Beil <hb...@...> wrote:
>
> "I wonder why the coupe tends to lose fuel this way"
>
> The Ercoupe fuel system takes the fuel from the interconnected two
main tanks, pumps it in the nose- or header tank and from there all
fuel in excess of the engine need flows over to the left wing tank (in
most cases).
>
> The left wing tank is connected to the right one and here the fuel
starts its journey again.
>
> The problem is that the pump takes fuel from both interconnected
tanks but the overflow goes into one of the main tanks only.
>
> The fuel does not even out between both main tanks, due to a
restrictor fitting in the connecting line.
>
> So if you don't leave a small buffer for the fuel , it has to
overflow.
>
> Later style fuel systems tried to correct the overflow issue by
proving an header tank overflow into both main tanks, I have such
system in my plane.
>
> It works , but only on level ground or in-flight. When my coupe is
slightly tilted, the fuel again flows only into one wing tank and the
fuel sprays out of that tank.
>
> The fuel system in a cessna does not have these problems, since
their tanks are all above the engine, all are gravity feeding the
engine and the whole business of pumping fuel through a system might
not be an issue there.
>
> But what do I know.
>
> Hartmut
>
>
>
> To: [email protected]
> From: alfen...@...
> Date: Wed, 5 Aug 2009 19:28:56 -0700
> Subject: [ercoupe-tech] how full of fuel
>
> I have the 46 coupe 415-C. I also have the 7.5 gal tanks, instead of
9 like most of you do. My question is, how full to fill the tanks. I
have heard that up to the brim, and I will lose fuel to siphoning. I
never had this problem in my 172, and I wonder why the coupe tends to
lose fuel this way. I am now putting too little fuel in, and just want
to know a good ballpark average the rest of you men/women use. Thanks
for reading this.
> Gary
