Today's Message Index:
----------------------
1. 12:21 AM - Re: Lithium batteries redux (mmayfield)
2. 08:16 AM - Re: Redundant Fuel pump wiring, 914 Rotax (Yahoo hasbroucka)
3. 09:33 AM - Re: Redundant Fuel pump wiring, 914 Rotax (Robert L. Nuckolls, III)
4. 10:37 AM - Re: Redundant Fuel pump wiring, 914 Rotax (Yahoo hasbroucka)
5. 12:34 PM - Z-13 and Dead Battery (h&jeuropa)
6. 04:01 PM - Re: Z-13 and Dead Battery (Robert L. Nuckolls, III)
7. 04:16 PM - Re: Redundant Fuel pump wiring, 914 Rotax (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Lithium batteries redux |
I have to sympathise with Bob's views here.
Lithium-chemistry based batteries hold a lot of promise for aircraft power sources,
but there are clearly issues to be resolved, not least of which is the possibility
of a battery fire. I know the problems will eventually be solved, but
until that time, I have to question whether the risk is worth taking.
There's a limit to how far I'm willing to push the "experimental" aspect!
--------
Mike
Your political opinions are noted. And ignored.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=392692#392692
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Redundant Fuel pump wiring, 914 Rotax |
Thanks for previous input
I have considered the info provided as well as studied all of the Rotax
914
documents, and find the following for consideration.
I am using only the 914 internal Stator and a single battery.
Rotax suggests that the 914 being dependant on electric fuel delivery:
1) Have the 22,000uf/25v capacitor mounted near the V-reg.
2) Have the primary pump connected directly off of the B+ line at
the
capacitor, with 5A slow-blow breaker protection.
3) Breaking the B+ line for charging control and OV protection
(instead of breaking a field wire).
Rotax claims that the capacitor will allow the internal alternator to
run
without battery connection, and prevent damage to the fuel pump, Stator
and
V-reg, while providing a completely independent source of power to the
main
fuel pump (2nd pump wired off the battery).
In studying Z-16, it looks to me that moving and sizing the 'Alt. OV
Disconnect relay' to the B+ would be the only change, and everything
else
will work fine.
To my thinking:
a) This truly does eliminate all common points of failure for the
two
pumps.
b) The 22A Max stator output, makes this a reasonably small relay.
c) This configuration provides the same level of OV protection to
the
rest of the electrical system.
d) If I can use a self-reset breaker at the large capacitor to
protect
the fuel pump wiring, then there is no way for the pilot to accidentally
(or
intentionally) kill power to the main fuel pump. (I think this is a good
thing?)
The logic is that even in an OV situation, the main fuel pump keeps
running;
at least till it is killed by the OV. Where having only one battery, a
battery connection failure could kill both fuel pumps in any other
wiring
method.
My list of questions are:
1) Are there any dangers, or omissions to the above concept?
2) Is it acceptable to use an automatic reset breaker in a
location
that is only ground serviceable? If yes, what would be considered
equivalent
to a "slow blow 5a fuse" as indicated in the Rotax manual? Listed pump
running load is 1.7A.
3) What would be the correct relay to use to break the B+ line?
Rotax
recommends the B+ be protected by a "slow blow 25A fuse", though I
propose
to use a fuse-able link here, at the starter relay terminal, to protect
the
B+ wire from battery output; as in Z-16.
Alan , HasbrouckA@yahoo.com
SeaRey Amphibian, framework and hull assembled (not covered). Working on
VFR
avionics and wiring (Dynon Skyview full suite). Top Priority is keep it
light, and place weight forward!
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L.
Nuckolls, III
Sent: Monday, January 07, 2013 2:01 PM
Subject: RE: AeroElectric-List: Redundant Fuel pump wiring
At 10:42 AM 1/7/2013, you wrote:
Bob, Care to describe what you are thinking. What advantage is there to
having one on the Main Bus?
Independent power paths with no common failure
points.
Bob . . .
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Redundant Fuel pump wiring, 914 Rotax |
>
>1) Are there any dangers, or omissions to the above concept?
I think you're getting wrapped around the multiple
failures axle . . .
The properly maintained battery is your most
reliable source of energy on the airplane.
Having one pump tied to the battery and
a second pump tied anywhere else drives
probability for loss of fuel pressure
into the very tiny numbers.
>2) Is it acceptable to use an automatic reset breaker in a
>location that is only ground serviceable? If yes, what would be
>considered equivalent to a "slow blow 5a fuse" as indicated in the
>Rotax manual? Listed pump running load is 1.7A.
>3) What would be the correct relay to use to break the B+
>line? Rotax recommends the B+ be protected by a "slow blow 25A
>fuse", though I propose to use a fuse-able link here, at the starter
>relay terminal, to protect the B+ wire from battery output; as in Z-16.
What you're struggling with is the stirring
of multiple recipes into the same dish.
The trick is to assess each recipe separately
and deduce effects of all possible SINGLE failures
and evaluate whether or not a plan-b exists
for mitigating that failure. See chapter 17 of
the 'Connection.
Whether you use z-16, the rotax manual, or something
else as the starting point doesn't matter. But
as soon as you begin cherry picking features from
one system and folding into another system raises
risks of generating new situations that the original
designers should have already covered.
Assume Z-16: Primary pump fed directly from battery.
Secondary pump from main bus.
Question: Deduce and articulate any single failure that
will deprive the engine of fuel.
If such a condition exists, then Z-16 needs to be
fixed.
Bob . . .
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Redundant Fuel pump wiring, 914 Rotax |
What happens if there is a failure at (or very near) the battery (hot or
ground) making an open circuit. This disconnect from the alternator
seems
likely to trip the crowbar, thus eliminating the charging circuit too,
drops
the battery and charging contactors open with no means to re-energize
the OV
relay.
I believe that I now have an engine that will gladly continue to run,
but
will not have fuel feed?
Alan , HasbrouckA@yahoo.com
SeaRey Amphibian, framework and hull assembled (not covered). Working on
VFR
avionics and wiring (Dynon Skyview full suite). Top Priority is keep it
light, and place weight forward!
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Robert L.
Nuckolls, III
Sent: Sunday, January 20, 2013 12:32 PM
Subject: RE: AeroElectric-List: Redundant Fuel pump wiring, 914 Rotax
1) Are there any dangers, or omissions to the above concept?
I think you're getting wrapped around the multiple
failures axle . . .
The properly maintained battery is your most
reliable source of energy on the airplane.
Having one pump tied to the battery and
a second pump tied anywhere else drives
probability for loss of fuel pressure
into the very tiny numbers.
2) Is it acceptable to use an automatic reset breaker in a
location
that is only ground serviceable? If yes, what would be considered
equivalent
to a "slow blow 5a fuse" as indicated in the Rotax manual? Listed pump
running load is 1.7A.
3) What would be the correct relay to use to break the B+ line?
Rotax
recommends the B+ be protected by a "slow blow 25A fuse", though I
propose
to use a fuse-able link here, at the starter relay terminal, to protect
the
B+ wire from battery output; as in Z-16.
What you're struggling with is the stirring
of multiple recipes into the same dish.
The trick is to assess each recipe separately
and deduce effects of all possible SINGLE failures
and evaluate whether or not a plan-b exists
for mitigating that failure. See chapter 17 of
the 'Connection.
Whether you use z-16, the Rotax manual, or something
else as the starting point doesn't matter. But
as soon as you begin cherry picking features from
one system and folding into another system raises
risks of generating new situations that the original
designers should have already covered.
Assume Z-16: Primary pump fed directly from battery.
Secondary pump from main bus.
Question: Deduce and articulate any single failure that
will deprive the engine of fuel.
If such a condition exists, then Z-16 needs to be
fixed.
Bob . . .
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Z-13 and Dead Battery |
I'm wondering what happens with a dynamo electrical system like Z-13 if the battery
is totally dead and the main alternator is also not functional. The engine
can be started by hand propping which will enable the dynamo with its self
excitation circuit. When you turn on the AUX ALT the dynamo will be connected
to the dead battery, the battery bus and endurance bus.
Will the battery represent a huge load to the dynamo, draw a lot of amperage and
drop the system voltage making avionics etc malfunction?
Or since you are on the ground anyway must you charge the battery to some extent
with a charger before hand propping and continuing?
Thanks
Jim Butcher
helping with Tailwind
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=392754#392754
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Z-13 and Dead Battery |
At 02:31 PM 1/20/2013, you wrote:
>
>I'm wondering what happens with a dynamo electrical system like Z-13
>if the battery is totally dead and the main alternator is also not
>functional. The engine can be started by hand propping which will
>enable the dynamo with its self excitation circuit. When you turn
>on the AUX ALT the dynamo will be connected to the dead battery, the
>battery bus and endurance bus.
>
>Will the battery represent a huge load to the dynamo, draw a lot of
>amperage and drop the system voltage making avionics etc malfunction?
Depends. If the battery was dead, Dead, DEAD like the
master switch was left on for a month, then in all likelihood
the battery is kaput. An SD-8 doesn't deliver significant
current at ramp idle or taxi speeds, it's unlikely that
you're going to hurt the SD-8. It might bring the battery
up enough (8 volts or more) to close the battery contactor
whereupon the main alternator would come up and do a much
more robust job of charging the battery.
>Or since you are on the ground anyway must you charge the battery to
>some extent with a charger before hand propping and continuing?
Depends. If you're a day-vfr airplane and just wanting
to get the airplane home, then hand propping . . . letting
the main alternator bring the battery up will get you home.
But ANY time the battery suffers a total discharge it should
be recharged and cap checked on the ground to make sure it
meets your design goals for minimum battery performance. In
any case, with a battery taking heavy recharge currents from
the engine driven power sources, I would not turn on much
in the way of electro-whizzies until the low volts warning
light has been out for 5-10 minutes. If the ship's voltmeter
says anything over 11 volts, electro-whizzies should work as
advertised, but leaving the ground without assurances that
the battery is taking on a charge is good pilotage.
Bob . . .
>Thanks
>
>Jim Butcher
>helping with Tailwind
>
>
>Read this topic online here:
>
>http://forums.matronics.com/viewtopic.php?p=392754#392754
>
>
>-----
>No virus found in this message.
>Checked by AVG - www.avg.com
Bob . . .
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Redundant Fuel pump wiring, 914 Rotax |
At 12:36 PM 1/20/2013, you wrote:
>What happens if there is a failure at (or very near) the battery
>(hot or ground) making an open circuit.
Those kinds of failures are generally pretty much
in the 'never happens' category. In other words,
those wires, terminals, components and craftsmanship
for installation is so robust by design that they're
treated much like wing struts and prop bolts . . . not
part of a failure mode effects analysis.
> This disconnect from the alternator seems likely to trip the
> crowbar, thus eliminating the charging circuit too, drops the
> battery and charging contactors open with no means to re-energize the OV relay.
Don't know why. If the Rotax alternator is suppose to
run well sans battery, I don't know why it would produce
an ov event because the battery became disconnected.
That's an experiment you can run. In fact, if any of
your plan-b mitigations are predicated on a disconnected
battery then you ought to test it.
>
>I believe that I now have an engine that will gladly continue to
>run, but will not have fuel feed?
What's your proposed battery configuration?
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|