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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[rebel-builders] Subaru - redundancy?
-
Bob Palmer
[rebel-builders] Subaru - redundancy?
Wayne,
I have dual electronic ignition. Same problem so I will have a backup
battery. So far the plan is to allow it to run off a power board that
has an automatic battery backup circuit but I am uncomfortable with that
because of the possibility of a failure of the circuit board. The
current draw is low enough that it could be switched but I want it
low tech enough that the switch is going to work. Marine switches I have
seen are heavy and clunky. I had considered making my own knife switch
however I am still looking for ideas.
Bob 773E
G. O'Shea wrote:
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I have dual electronic ignition. Same problem so I will have a backup
battery. So far the plan is to allow it to run off a power board that
has an automatic battery backup circuit but I am uncomfortable with that
because of the possibility of a failure of the circuit board. The
current draw is low enough that it could be switched but I want it
low tech enough that the switch is going to work. Marine switches I have
seen are heavy and clunky. I had considered making my own knife switch
however I am still looking for ideas.
Bob 773E
G. O'Shea wrote:
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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Wayne G. O'Shea
[rebel-builders] Subaru - redundancy?
I know what it says in the design stuff Dick and it was me that questioned
the owner as to why only one battery in the bird.... just wondering how guys
have tackled it to date in the real world.
Customer brought this in after buying it this summer and said to go thru it
with a fine tooth comb and do what ever it needs. He has two fuel pump..
both electric so maintaining fuel flow redundancy is covered.. SORT OF !
They are on the same two way switch.. up is pump 1.. down is pump 2.. so IF
the switched failed.....
..and more importantly if the battery dies.. doesn't matter which way he
flips that switch !
----- Original Message -----
From: "Richard Wampach" <rwampach@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 2:09 PM
Subject: RE: [rebel-builders] Subaru - redundancy?
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the owner as to why only one battery in the bird.... just wondering how guys
have tackled it to date in the real world.
Customer brought this in after buying it this summer and said to go thru it
with a fine tooth comb and do what ever it needs. He has two fuel pump..
both electric so maintaining fuel flow redundancy is covered.. SORT OF !
They are on the same two way switch.. up is pump 1.. down is pump 2.. so IF
the switched failed.....
..and more importantly if the battery dies.. doesn't matter which way he
flips that switch !
----- Original Message -----
From: "Richard Wampach" <rwampach@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 2:09 PM
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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Joe Ronco
[rebel-builders] Subaru - redundancy?
TED: To convert head in Ft to pressure in PSI use the following formula:
Head = Pressure x 2.31 or Pressure = Head x Specific Gravity
Specific Gravity 2.31
With 100LL having an SG of 0.68-0.74, say 0.71 then pressure for 39" of head
= 3.25 Ft is
P = (3.25 x 0.71)/ 2.31 = 1 PSI.
Hope this helps.
Joe
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ted
Waltman
Sent: Monday, November 02, 2009 12:27 PM
To: rebel-builders@dcsol.com
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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Head = Pressure x 2.31 or Pressure = Head x Specific Gravity
Specific Gravity 2.31
With 100LL having an SG of 0.68-0.74, say 0.71 then pressure for 39" of head
= 3.25 Ft is
P = (3.25 x 0.71)/ 2.31 = 1 PSI.
Hope this helps.
Joe
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ted
Waltman
Sent: Monday, November 02, 2009 12:27 PM
To: rebel-builders@dcsol.com
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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-
Ron Shannon
[rebel-builders] Subaru - redundancy?
This can be (should be) a complex topic. There are numerous issues and
options that should be understood, including possible multiple alternator
setups, control (switching), monitoring, supply (bus) structures,
appropriate hardware, and of course, all the potential failure modes that go
with those choices, among other things. IMHO, the issues cannot be
adequately covered on a mailing list.
Anyone designing this or any other electrical system should refer to
http://aeroelectric.com, the site run by long time aviation electrical
system engineer Bob Nuckolls. There you can get his essential book
(AeroElectric Connection) for little (hard copy) or nothing (free download)
which covers most aspects of aviation electrical systems, including dozens
of suggested full system schematics, including dual electronic ignition
systems. They are very well thought out, tried and tested. The schematics
are also available for direct download by themselves.
Bob's designs and notes are an essential starting point for any experimental
aircraft builder. You may choose to do something different, but if so, you
should at least understand _why_ you've chosen to leave something out, or
put something else in, i.e., why your solution is better.
Ron
254R
On Mon, Nov 2, 2009 at 11:47 AM, Bob Palmer <rtpalmer@shaw.ca> wrote:
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options that should be understood, including possible multiple alternator
setups, control (switching), monitoring, supply (bus) structures,
appropriate hardware, and of course, all the potential failure modes that go
with those choices, among other things. IMHO, the issues cannot be
adequately covered on a mailing list.
Anyone designing this or any other electrical system should refer to
http://aeroelectric.com, the site run by long time aviation electrical
system engineer Bob Nuckolls. There you can get his essential book
(AeroElectric Connection) for little (hard copy) or nothing (free download)
which covers most aspects of aviation electrical systems, including dozens
of suggested full system schematics, including dual electronic ignition
systems. They are very well thought out, tried and tested. The schematics
are also available for direct download by themselves.
Bob's designs and notes are an essential starting point for any experimental
aircraft builder. You may choose to do something different, but if so, you
should at least understand _why_ you've chosen to leave something out, or
put something else in, i.e., why your solution is better.
Ron
254R
On Mon, Nov 2, 2009 at 11:47 AM, Bob Palmer <rtpalmer@shaw.ca> wrote:
Wayne,
I have dual electronic ignition. Same problem so I will have a backup
battery. So far the plan is to allow it to run off a power board that
has an automatic battery backup circuit but I am uncomfortable with that
because of the possibility of a failure of the circuit board. The
current draw is low enough that it could be switched but I want it
low tech enough that the switch is going to work. Marine switches I have
seen are heavy and clunky. I had considered making my own knife switch
however I am still looking for ideas.
Bob 773E
G. O'Shea wrote:Subaru.Ken and others...
I have a Rebel in the hangar right now that is running a Crossflowmasters)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 batteryor similar??.. and an isolator for dual battery charging.
Thanks,
Wayne
PS (yes I'm a Lycoming boy !)
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Schmucker, Del
[rebel-builders] Subaru - redundancy?
Wayne:
I have Subaru in my Rebel. I have one battery, 2 ignitions, 2 fuel pumps. Each ignition and each fuel pump is on a separate circuit with its own switch. I have one alternator, and one battery in theory each could fail stimulatingly but his is hardly likely. In our "on the road" vehicles we rarely see both of these fail at the same time. Usually the alternator goes and sometime later the battery goes dead. I made sure that my battery is large enough to run my ignitions and fuel pumps for 45 minutes to one hour after the alternator fails. Yes it "might" be more advantageous to have 2 batteries, 2 buses, 2 alternators, 2 ignitions, 2 fuel pumps, 2 engines, 2 props, etc etc.......... but somewhere we have to be realistic and also weigh the risks.
Thank you,
I have Subaru in my Rebel. I have one battery, 2 ignitions, 2 fuel pumps. Each ignition and each fuel pump is on a separate circuit with its own switch. I have one alternator, and one battery in theory each could fail stimulatingly but his is hardly likely. In our "on the road" vehicles we rarely see both of these fail at the same time. Usually the alternator goes and sometime later the battery goes dead. I made sure that my battery is large enough to run my ignitions and fuel pumps for 45 minutes to one hour after the alternator fails. Yes it "might" be more advantageous to have 2 batteries, 2 buses, 2 alternators, 2 ignitions, 2 fuel pumps, 2 engines, 2 props, etc etc.......... but somewhere we have to be realistic and also weigh the risks.
Thank you,
-
Richard Wampach
[rebel-builders] Subaru - redundancy?
IT is something I remember from my decays in A/P school in the mid 60's.
Static pressure is no problem, if the flow is hi and the line size is too
small yes a problem. 3/8" line for 10 gal should not present a problem. I
am using 1/2" to the firewall.
Dick
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ted
Waltman
Sent: Monday, November 02, 2009 11:27 AM
To: rebel-builders@dcsol.com
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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Static pressure is no problem, if the flow is hi and the line size is too
small yes a problem. 3/8" line for 10 gal should not present a problem. I
am using 1/2" to the firewall.
Dick
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ted
Waltman
Sent: Monday, November 02, 2009 11:27 AM
To: rebel-builders@dcsol.com
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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Richard Wampach
[rebel-builders] Subaru - redundancy?
Well if nothing else we have stirred up a good interest in safety of design
and redundancy of systems. I must admit over kill does add weight and
expense and room for more failures, but lessens the chance of an unscheduled
landing...And under designing raises those chances. So! Pick the worst
case scenario and design around it.
Keep building and flying,
Dick
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Schmucker, Del
Wayne:
I have Subaru in my Rebel. I have one battery, 2 ignitions, 2 fuel pumps.
Each ignition and each fuel pump is on a separate circuit with its own
switch. I have one alternator, and one battery in theory each could fail
stimulatingly but his is hardly likely. In our "on the road" vehicles we
rarely see both of these fail at the same time. Usually the alternator goes
and sometime later the battery goes dead. I made sure that my battery is
large enough to run my ignitions and fuel pumps for 45 minutes to one hour
after the alternator fails. Yes it "might" be more advantageous to have 2
batteries, 2 buses, 2 alternators, 2 ignitions, 2 fuel pumps, 2 engines, 2
props, etc etc.......... but somewhere we have to be realistic and also
weigh the risks.
Thank you,
and redundancy of systems. I must admit over kill does add weight and
expense and room for more failures, but lessens the chance of an unscheduled
landing...And under designing raises those chances. So! Pick the worst
case scenario and design around it.
Keep building and flying,
Dick
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Schmucker, Del
Wayne:
I have Subaru in my Rebel. I have one battery, 2 ignitions, 2 fuel pumps.
Each ignition and each fuel pump is on a separate circuit with its own
switch. I have one alternator, and one battery in theory each could fail
stimulatingly but his is hardly likely. In our "on the road" vehicles we
rarely see both of these fail at the same time. Usually the alternator goes
and sometime later the battery goes dead. I made sure that my battery is
large enough to run my ignitions and fuel pumps for 45 minutes to one hour
after the alternator fails. Yes it "might" be more advantageous to have 2
batteries, 2 buses, 2 alternators, 2 ignitions, 2 fuel pumps, 2 engines, 2
props, etc etc.......... but somewhere we have to be realistic and also
weigh the risks.
Thank you,
-
Mike Davis
[rebel-builders] Subaru - redundancy?
As I am still leaning towards a V8 installation, with electronic fuel
injection and ignition, I have often considered using a RAT, or Ram Air
Turbine for the backup. There are some small and lightweight units on the
market, and unlike batteries, they'll keep producing power as long as you're
still moving through the air.
I didn't spend to much time looking for a link just now, but here's a unit
that's only 24 lbs... I know I've seen smaller.
http://www.ghetzleraeropower.com/lowspeed.htm
Mike
----- Original Message -----
From: "Richard Wampach" <rwampach@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 12:31 PM
Subject: RE: [rebel-builders] Subaru - redundancy?
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injection and ignition, I have often considered using a RAT, or Ram Air
Turbine for the backup. There are some small and lightweight units on the
market, and unlike batteries, they'll keep producing power as long as you're
still moving through the air.
I didn't spend to much time looking for a link just now, but here's a unit
that's only 24 lbs... I know I've seen smaller.
http://www.ghetzleraeropower.com/lowspeed.htm
Mike
----- Original Message -----
From: "Richard Wampach" <rwampach@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 12:31 PM
Subject: RE: [rebel-builders] Subaru - redundancy?
Well if nothing else we have stirred up a good interest in safety of
design
and redundancy of systems. I must admit over kill does add weight and
expense and room for more failures, but lessens the chance of an
unscheduled
landing...And under designing raises those chances. So! Pick the worst
case scenario and design around it.
Keep building and flying,
Dick
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Schmucker, Del
Wayne:
I have Subaru in my Rebel. I have one battery, 2 ignitions, 2 fuel pumps.
Each ignition and each fuel pump is on a separate circuit with its own
switch. I have one alternator, and one battery in theory each could fail
stimulatingly but his is hardly likely. In our "on the road" vehicles we
rarely see both of these fail at the same time. Usually the alternator
goes
and sometime later the battery goes dead. I made sure that my battery is
large enough to run my ignitions and fuel pumps for 45 minutes to one hour
after the alternator fails. Yes it "might" be more advantageous to have
2
batteries, 2 buses, 2 alternators, 2 ignitions, 2 fuel pumps, 2 engines, 2
props, etc etc.......... but somewhere we have to be realistic and also
weigh the risks.
Thank you,
Del Schmucker
---Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Wayne
G. O'Shea
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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Ron Stahla
[rebel-builders] Subaru - redundancy?
Anyone looking for SUBARU ENGINE IN THE NEBRASKA AREA I HAVE ONE THAT I AM NOT GOING TO USE AND WOULD SELL.
RON STAHLA
_________________________________________________________________
Windows 7: It works the way you want.
http://www.microsoft.com/Windows/window ... en2:112009
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RON STAHLA
From: mike.davis@dcsol.com
To: rebel-builders@dcsol.com
Subject: Re: [rebel-builders] Subaru - redundancy?
Date: Mon, 2 Nov 2009 12:56:20 -0900
As I am still leaning towards a V8 installation, with electronic fuel
injection and ignition, I have often considered using a RAT, or Ram Air
Turbine for the backup. There are some small and lightweight units on the
market, and unlike batteries, they'll keep producing power as long as you're
still moving through the air.
I didn't spend to much time looking for a link just now, but here's a unit
that's only 24 lbs... I know I've seen smaller.
http://www.ghetzleraeropower.com/lowspeed.htm
Mike
----- Original Message -----
From: "Richard Wampach" <rwampach@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 12:31 PM
Subject: RE: [rebel-builders] Subaru - redundancy?
Well if nothing else we have stirred up a good interest in safety of
design
and redundancy of systems. I must admit over kill does add weight and
expense and room for more failures, but lessens the chance of an
unscheduled
landing...And under designing raises those chances. So! Pick the worst
case scenario and design around it.
Keep building and flying,
Dick
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Schmucker, Del
Wayne:
I have Subaru in my Rebel. I have one battery, 2 ignitions, 2 fuel pumps.
Each ignition and each fuel pump is on a separate circuit with its own
switch. I have one alternator, and one battery in theory each could fail
stimulatingly but his is hardly likely. In our "on the road" vehicles we
rarely see both of these fail at the same time. Usually the alternator
goes
and sometime later the battery goes dead. I made sure that my battery is
large enough to run my ignitions and fuel pumps for 45 minutes to one hour
after the alternator fails. Yes it "might" be more advantageous to have
2
batteries, 2 buses, 2 alternators, 2 ignitions, 2 fuel pumps, 2 engines, 2
props, etc etc.......... but somewhere we have to be realistic and also
weigh the risks.
Thank you,
Del Schmucker
---Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of
Wayne
G. O'Shea
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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_________________________________________________________________
Windows 7: It works the way you want.
http://www.microsoft.com/Windows/window ... en2:112009
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Bob Palmer
[rebel-builders] Subaru - redundancy?
Del,
Wouldn't some types of battery failures result in an alternator failure?
I'm not sure about that. What I suggest is that you look carefully at
each system requirement and decide if there is a reasonable solution
that would provide redundancy. For instance, if two electric fuel pumps
are desired then two power sources are required. That doesn't mean that
they both have to be batteries or that they have to be the same size.
Just don't have one power system dependent on the other or you may not
have the redundancy you thought you had. That is why I don't want all of
my power going through one board.
Bob 773E
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Wouldn't some types of battery failures result in an alternator failure?
I'm not sure about that. What I suggest is that you look carefully at
each system requirement and decide if there is a reasonable solution
that would provide redundancy. For instance, if two electric fuel pumps
are desired then two power sources are required. That doesn't mean that
they both have to be batteries or that they have to be the same size.
Just don't have one power system dependent on the other or you may not
have the redundancy you thought you had. That is why I don't want all of
my power going through one board.
Bob 773E
Wayne:
I have Subaru in my Rebel. I have one battery, 2 ignitions, 2 fuel pumps. Each ignition and each fuel pump is on a separate circuit with its own switch. I have one alternator, and one battery in theory each could fail stimulatingly but his is hardly likely. In our "on the road" vehicles we rarely see both of these fail at the same time. Usually the alternator goes and sometime later the battery goes dead. I made sure that my battery is large enough to run my ignitions and fuel pumps for 45 minutes to one hour after the alternator fails. Yes it "might" be more advantageous to have 2 batteries, 2 buses, 2 alternators, 2 ignitions, 2 fuel pumps, 2 engines, 2 props, etc etc.......... but somewhere we have to be realistic and also weigh the risks.
Thank you,
Del Schmucker
Information Systems Manager
Keewatin-Patricia District School Board
807-223-5311 ext. 254
807-938-5554 Cell
807-223-4703 Fax
del.schmucker@kpdsb.on.ca
www.kpdsb.on.ca
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Wayne G. O'Shea
Sent: Monday, November 02, 2009 11:55 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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Ted Waltman
[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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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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Ken
[rebel-builders] Subaru - redundancy?
1. Most important item in an electrically dependent engined airplane by
an order of magnitude (and highly recommended for any aircraft) is
independent notification of alternator failure. ie an immediate
unmistakable notification of voltage dropping below about 12.8 volts.
The alternator light is unreliable and next to useless for this as many
guys who have deadsticked will attest. Something like an EIS (big
flashing light and beeping in headset) is great or a separate little
circuit can do it. Some GPS units can be set up to do it.
2. The rest is icing on the cake as long as the battery is occasionally
tested for capacity or replaced every 2 years so you know it will run
the engine for the planned time.
3. Absolutely recommend independent electrical circuits to two fuel
pumps with no common failure points. For those not familiar, these pumps
supply pressure regulated fuel at 36 psi above manifold pressure for
most MPFI soobs. I let the computer control one pump through it's main
relay as per the automobile. It will shut down if the engine stops. The
second pump is manually controlled from a battery bus circuit on my
bird. No electrical circuits to the engine should go through a battery
contactor. (Perhaps acceptable if there is a second automatic or always
on supply.) Some guys will use a manual battery switch instead of a
contactor but most just use a direct wire and fuse off the battery. An
ATO fuse block from Princess Auto is very handy for this.
4. AGM batteries (essentially all non liquid filled batteries) are so
reliable that you can't build much of a case that two are more reliable
than one so there is no real harm in using one large one instead of two
smaller ones. But two smaller ones do allow you to swap one out on
regular intervals if you don't test capacity. There are several easy
ways to test capacity though.
5. The only real risk of one failure taking down an alternator AND a
battery is a shorted alternator that draws several hundred amps FROM the
battery. That is why we put a circuit breaker or fuse of some kind in
the B lead from the alternator which solves that scenario and prevents
melting the B lead wire.
6. Most guys that get into the diode feed circuits (or battery
isolators) are kidding themselves about the benefits but there are some
cases where it makes sense.
That's the basics learned from many years of watching incidents as I see
it. Oh yes and I might as well add that anyone (likely including this
aircraft owner and all firewall forward package customers) who is not
interested in doing the homework will indeed usually be better off with
a Lycosaur ;)
Ken
Wayne G. O'Shea wrote:
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an order of magnitude (and highly recommended for any aircraft) is
independent notification of alternator failure. ie an immediate
unmistakable notification of voltage dropping below about 12.8 volts.
The alternator light is unreliable and next to useless for this as many
guys who have deadsticked will attest. Something like an EIS (big
flashing light and beeping in headset) is great or a separate little
circuit can do it. Some GPS units can be set up to do it.
2. The rest is icing on the cake as long as the battery is occasionally
tested for capacity or replaced every 2 years so you know it will run
the engine for the planned time.
3. Absolutely recommend independent electrical circuits to two fuel
pumps with no common failure points. For those not familiar, these pumps
supply pressure regulated fuel at 36 psi above manifold pressure for
most MPFI soobs. I let the computer control one pump through it's main
relay as per the automobile. It will shut down if the engine stops. The
second pump is manually controlled from a battery bus circuit on my
bird. No electrical circuits to the engine should go through a battery
contactor. (Perhaps acceptable if there is a second automatic or always
on supply.) Some guys will use a manual battery switch instead of a
contactor but most just use a direct wire and fuse off the battery. An
ATO fuse block from Princess Auto is very handy for this.
4. AGM batteries (essentially all non liquid filled batteries) are so
reliable that you can't build much of a case that two are more reliable
than one so there is no real harm in using one large one instead of two
smaller ones. But two smaller ones do allow you to swap one out on
regular intervals if you don't test capacity. There are several easy
ways to test capacity though.
5. The only real risk of one failure taking down an alternator AND a
battery is a shorted alternator that draws several hundred amps FROM the
battery. That is why we put a circuit breaker or fuse of some kind in
the B lead from the alternator which solves that scenario and prevents
melting the B lead wire.
6. Most guys that get into the diode feed circuits (or battery
isolators) are kidding themselves about the benefits but there are some
cases where it makes sense.
That's the basics learned from many years of watching incidents as I see
it. Oh yes and I might as well add that anyone (likely including this
aircraft owner and all firewall forward package customers) who is not
interested in doing the homework will indeed usually be better off with
a Lycosaur ;)
Ken
Wayne G. O'Shea wrote:
I know what it says in the design stuff Dick and it was me that questioned
the owner as to why only one battery in the bird.... just wondering how guys
have tackled it to date in the real world.
Customer brought this in after buying it this summer and said to go thru it
with a fine tooth comb and do what ever it needs. He has two fuel pump..
both electric so maintaining fuel flow redundancy is covered.. SORT OF !
They are on the same two way switch.. up is pump 1.. down is pump 2.. so IF
the switched failed.....
..and more importantly if the battery dies.. doesn't matter which way he
flips that switch !
----- Original Message -----
From: "Richard Wampach" <rwampach@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 2:09 PM
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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Wayne G. O'Shea
[rebel-builders] Subaru - redundancy?
Thanks Ken !! What I'm looking for.
My first caution on this birds install is a single double rocker (pump 1 /
pump 2) switch with off in the center. Second thing that stands out for me
is a normal Cessna style master switch that pulls in a contactor. This one
is for accessories etc as best I can see and then the key switch for the
"car" engine.. first detent I hear it pull in another contactor and up comes
the voltage guage and engine instruments.
The last one of these that I had in the hangar... that I ripped the Subaru
off of and installed Walters old O-320 FWF onto.... had a drag cars bumper
style battery switch. Manual throw on/off. I'm gonna have to hunt down what
runs what in this thing and get rid of the electrically engaged solenoid...
that's a given.
The dash has a really bright red light and another yellow... not sure their
function and will check with the owner (and call the original builder if
need be).
THANKS again,
Wayne
----- Original Message -----
From: "Ken" <klehman@albedo.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 8:51 PM
Subject: Re: [rebel-builders] Subaru - redundancy?
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My first caution on this birds install is a single double rocker (pump 1 /
pump 2) switch with off in the center. Second thing that stands out for me
is a normal Cessna style master switch that pulls in a contactor. This one
is for accessories etc as best I can see and then the key switch for the
"car" engine.. first detent I hear it pull in another contactor and up comes
the voltage guage and engine instruments.
The last one of these that I had in the hangar... that I ripped the Subaru
off of and installed Walters old O-320 FWF onto.... had a drag cars bumper
style battery switch. Manual throw on/off. I'm gonna have to hunt down what
runs what in this thing and get rid of the electrically engaged solenoid...
that's a given.
The dash has a really bright red light and another yellow... not sure their
function and will check with the owner (and call the original builder if
need be).
THANKS again,
Wayne
----- Original Message -----
From: "Ken" <klehman@albedo.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 8:51 PM
Subject: Re: [rebel-builders] Subaru - redundancy?
1. Most important item in an electrically dependent engined airplane by
an order of magnitude (and highly recommended for any aircraft) is
independent notification of alternator failure. ie an immediate
unmistakable notification of voltage dropping below about 12.8 volts.
The alternator light is unreliable and next to useless for this as many
guys who have deadsticked will attest. Something like an EIS (big
flashing light and beeping in headset) is great or a separate little
circuit can do it. Some GPS units can be set up to do it.
2. The rest is icing on the cake as long as the battery is occasionally
tested for capacity or replaced every 2 years so you know it will run
the engine for the planned time.
3. Absolutely recommend independent electrical circuits to two fuel
pumps with no common failure points. For those not familiar, these pumps
supply pressure regulated fuel at 36 psi above manifold pressure for
most MPFI soobs. I let the computer control one pump through it's main
relay as per the automobile. It will shut down if the engine stops. The
second pump is manually controlled from a battery bus circuit on my
bird. No electrical circuits to the engine should go through a battery
contactor. (Perhaps acceptable if there is a second automatic or always
on supply.) Some guys will use a manual battery switch instead of a
contactor but most just use a direct wire and fuse off the battery. An
ATO fuse block from Princess Auto is very handy for this.
4. AGM batteries (essentially all non liquid filled batteries) are so
reliable that you can't build much of a case that two are more reliable
than one so there is no real harm in using one large one instead of two
smaller ones. But two smaller ones do allow you to swap one out on
regular intervals if you don't test capacity. There are several easy
ways to test capacity though.
5. The only real risk of one failure taking down an alternator AND a
battery is a shorted alternator that draws several hundred amps FROM the
battery. That is why we put a circuit breaker or fuse of some kind in
the B lead from the alternator which solves that scenario and prevents
melting the B lead wire.
6. Most guys that get into the diode feed circuits (or battery
isolators) are kidding themselves about the benefits but there are some
cases where it makes sense.
That's the basics learned from many years of watching incidents as I see
it. Oh yes and I might as well add that anyone (likely including this
aircraft owner and all firewall forward package customers) who is not
interested in doing the homework will indeed usually be better off with
a Lycosaur ;)
Ken
Wayne G. O'Shea wrote:I know what it says in the design stuff Dick and it was me that
questioned
the owner as to why only one battery in the bird.... just wondering how
guys
have tackled it to date in the real world.
Customer brought this in after buying it this summer and said to go thru
it
with a fine tooth comb and do what ever it needs. He has two fuel pump..
both electric so maintaining fuel flow redundancy is covered.. SORT OF !
They are on the same two way switch.. up is pump 1.. down is pump 2.. so
IF
the switched failed.....
..and more importantly if the battery dies.. doesn't matter which way he
flips that switch !
----- Original Message -----
From: "Richard Wampach" <rwampach@comcast.net>
To: <rebel-builders@dcsol.com>
Sent: Monday, November 02, 2009 2:09 PM
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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ray.mason
[rebel-builders] Subaru - redundancy?
My subie powered rebel initially came with one high pressure pump. After the
HP pump in my daughters car failed and having a problem with air getting into
my line I redesigned my fuel system for two pumps on separate switches and
made sure they were below the header tank. I only have one battery, an
odyssey. I can't remember ever hearing of a battery just dying so IMO one is
enough. My pumps will not provide enough pressure when the voltage drops
to below 10V. I have had a Alt wiring failure and noticed the flag on my elec
gyro came down, so that is an additional warning you can use and make sure
you land before the voltage gets to low.
On 11/2/2009 4:51 PM, klehman@albedo.net wrote to rebel-builders:
-> 1. Most important item in an electrically dependent engined airplane by
-> an order of magnitude (and highly recommended for any aircraft) is
-> independent notification of alternator failure. ie an immediate
-> unmistakable notification of voltage dropping below about 12.8 volts.
-> The alternator light is unreliable and next to useless for this as many
-> guys who have deadsticked will attest. Something like an EIS (big
-> flashing light and beeping in headset) is great or a separate little
-> circuit can do it. Some GPS units can be set up to do it.
->
-> 2. The rest is icing on the cake as long as the battery is occasionally
-> tested for capacity or replaced every 2 years so you know it will run
-> the engine for the planned time.
->
-> 3. Absolutely recommend independent electrical circuits to two fuel
-> pumps with no common failure points. For those not familiar, these pumps
-> supply pressure regulated fuel at 36 psi above manifold pressure for
-> most MPFI soobs. I let the computer control one pump through it's main
-> relay as per the automobile. It will shut down if the engine stops. The
-> second pump is manually controlled from a battery bus circuit on my
-> bird. No electrical circuits to the engine should go through a battery
-> contactor. (Perhaps acceptable if there is a second automatic or always
-> on supply.) Some guys will use a manual battery switch instead of a
-> contactor but most just use a direct wire and fuse off the battery. An
-> ATO fuse block from Princess Auto is very handy for this.
->
-> 4. AGM batteries (essentially all non liquid filled batteries) are so
-> reliable that you can't build much of a case that two are more reliable
-> than one so there is no real harm in using one large one instead of two
-> smaller ones. But two smaller ones do allow you to swap one out on
-> regular intervals if you don't test capacity. There are several easy
-> ways to test capacity though.
->
-> 5. The only real risk of one failure taking down an alternator AND a
-> battery is a shorted alternator that draws several hundred amps FROM the
-> battery. That is why we put a circuit breaker or fuse of some kind in
-> the B lead from the alternator which solves that scenario and prevents
-> melting the B lead wire.
->
-> 6. Most guys that get into the diode feed circuits (or battery
-> isolators) are kidding themselves about the benefits but there are some
-> cases where it makes sense.
->
-> That's the basics learned from many years of watching incidents as I see
-> it. Oh yes and I might as well add that anyone (likely including this
-> aircraft owner and all firewall forward package customers) who is not
-> interested in doing the homework will indeed usually be better off with
-> a Lycosaur ;)
->
-> Ken
->
-> Wayne G. O'Shea wrote:
-> > I know what it says in the design stuff Dick and it was me that
questioned
-> > the owner as to why only one battery in the bird.... just wondering how
guys
-> > have tackled it to date in the real world.
-> >
-> > Customer brought this in after buying it this summer and said to go thru
it
-> > with a fine tooth comb and do what ever it needs. He has two fuel
pump..
-> > both electric so maintaining fuel flow redundancy is covered.. SORT OF !
-> > They are on the same two way switch.. up is pump 1.. down is pump 2..
so IF
-> > the switched failed.....
-> >
-> > ..and more importantly if the battery dies.. doesn't matter which way he
-> > flips that switch !
-> >
-> > ----- Original Message -----
-> > From: "Richard Wampach" <rwampach@comcast.net>
-> > To: <rebel-builders@dcsol.com>
-> > Sent: Monday, November 02, 2009 2:09 PM
-> > 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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HP pump in my daughters car failed and having a problem with air getting into
my line I redesigned my fuel system for two pumps on separate switches and
made sure they were below the header tank. I only have one battery, an
odyssey. I can't remember ever hearing of a battery just dying so IMO one is
enough. My pumps will not provide enough pressure when the voltage drops
to below 10V. I have had a Alt wiring failure and noticed the flag on my elec
gyro came down, so that is an additional warning you can use and make sure
you land before the voltage gets to low.
On 11/2/2009 4:51 PM, klehman@albedo.net wrote to rebel-builders:
-> 1. Most important item in an electrically dependent engined airplane by
-> an order of magnitude (and highly recommended for any aircraft) is
-> independent notification of alternator failure. ie an immediate
-> unmistakable notification of voltage dropping below about 12.8 volts.
-> The alternator light is unreliable and next to useless for this as many
-> guys who have deadsticked will attest. Something like an EIS (big
-> flashing light and beeping in headset) is great or a separate little
-> circuit can do it. Some GPS units can be set up to do it.
->
-> 2. The rest is icing on the cake as long as the battery is occasionally
-> tested for capacity or replaced every 2 years so you know it will run
-> the engine for the planned time.
->
-> 3. Absolutely recommend independent electrical circuits to two fuel
-> pumps with no common failure points. For those not familiar, these pumps
-> supply pressure regulated fuel at 36 psi above manifold pressure for
-> most MPFI soobs. I let the computer control one pump through it's main
-> relay as per the automobile. It will shut down if the engine stops. The
-> second pump is manually controlled from a battery bus circuit on my
-> bird. No electrical circuits to the engine should go through a battery
-> contactor. (Perhaps acceptable if there is a second automatic or always
-> on supply.) Some guys will use a manual battery switch instead of a
-> contactor but most just use a direct wire and fuse off the battery. An
-> ATO fuse block from Princess Auto is very handy for this.
->
-> 4. AGM batteries (essentially all non liquid filled batteries) are so
-> reliable that you can't build much of a case that two are more reliable
-> than one so there is no real harm in using one large one instead of two
-> smaller ones. But two smaller ones do allow you to swap one out on
-> regular intervals if you don't test capacity. There are several easy
-> ways to test capacity though.
->
-> 5. The only real risk of one failure taking down an alternator AND a
-> battery is a shorted alternator that draws several hundred amps FROM the
-> battery. That is why we put a circuit breaker or fuse of some kind in
-> the B lead from the alternator which solves that scenario and prevents
-> melting the B lead wire.
->
-> 6. Most guys that get into the diode feed circuits (or battery
-> isolators) are kidding themselves about the benefits but there are some
-> cases where it makes sense.
->
-> That's the basics learned from many years of watching incidents as I see
-> it. Oh yes and I might as well add that anyone (likely including this
-> aircraft owner and all firewall forward package customers) who is not
-> interested in doing the homework will indeed usually be better off with
-> a Lycosaur ;)
->
-> Ken
->
-> Wayne G. O'Shea wrote:
-> > I know what it says in the design stuff Dick and it was me that
questioned
-> > the owner as to why only one battery in the bird.... just wondering how
guys
-> > have tackled it to date in the real world.
-> >
-> > Customer brought this in after buying it this summer and said to go thru
it
-> > with a fine tooth comb and do what ever it needs. He has two fuel
pump..
-> > both electric so maintaining fuel flow redundancy is covered.. SORT OF !
-> > They are on the same two way switch.. up is pump 1.. down is pump 2..
so IF
-> > the switched failed.....
-> >
-> > ..and more importantly if the battery dies.. doesn't matter which way he
-> > flips that switch !
-> >
-> > ----- Original Message -----
-> > From: "Richard Wampach" <rwampach@comcast.net>
-> > To: <rebel-builders@dcsol.com>
-> > Sent: Monday, November 02, 2009 2:09 PM
-> > 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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