p = 0.434 h SG
where
p = pressure (psi)
h = head (ft)
SG = specific gravity
The specific gravity of gasoline ranges from 0.68 to 0.74 depending on the
blend.
So using this for 39" of head, or 3.2',
p = 0.434 * 3.2 * 0.71
p = 0.986048
Mike
----- Original Message -----
From: "Ted Waltman" <ted@vafm.org>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 10:27 AM
Subject: RE: [rebel-builders] Subaru - redundancy?
How do you know that 39" of head pressure = 1 psi fuel pressure? I assume
since fuel/liquid is not compressible that the size fuel line has no
effect.
Ted
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Richard Wampach
Sent: Monday, November 02, 2009 12:09 PM
To: rebel-builders@dcsol.com
Subject: RE: [rebel-builders] Subaru - redundancy?
Perhaps it is worth reading and appreciating some of the FAR's covering
design of an airplane. The FAA in their infinite wisdom, advises if you
need an engine fuel pump, you need a back up system also. This has helped
a
number of times to keep an engine running when it would have quit for lack
of fuel. It is not always practical to pull over to the side of the
freeway
with an airplane.
Yes I have an engine driven fuel pump on my Lycoming, and a back up
electric
pump going in my Moose. Even though it probably would keep on running if
the engine pump failed, the fuel level in the carburetor would be lower
with
only gravity feed (39" head pressure equals 1 Lb of fuel pressure), the
float is adjusted to work with about 5 PSI. The engine would run lean.
So please follow the guide lines for the system you are using and have a
back up...
Dick Wampach SR-108 N331RW
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Wayne
G. O'Shea
Sent: Monday, November 02, 2009 9:55 AM
To: Murphy Rebel Builders List
Subject: [rebel-builders] Subaru - redundancy?
Ken and others...
I have a Rebel in the hangar right now that is running a Crossflow Subaru.
Considering you have to be running an electric fuel pump to keep these
things airborne... does yours have, or what are your thoughts on:
dual batteries and a 1/2/both marine style switch (or dual battery
masters)
or similar??.. and an isolator for dual battery charging.
Thanks,
Wayne
PS (yes I'm a Lycoming boy !)
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