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stevei(at)carey.asn.au
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 Posted: Sun Feb 28, 2010 7:55 pm Post subject: Questions |
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Hi Bob and all
I'm building a Glasair Super II RG powered by a Mazda Renesis Rotary using Tracy Crook's EC2 (injection and ignition) and EM3 (Engine monitoring) and using standard starter and a small 40amp modern auto. So fully reliant on 14v source power.
I have a Radio and embedded systems background so I'm not completely ignorant of electrons.
I'm familiar with your Z-19 and have some general questions in order to weigh risks.
My questions are:
1. What are the failure modes of Aircraft Batteries?
2. What are the failure modes of auto starter motors?
3. What are the failure modes of auto alternators?
I hope these questions are firstly reasonable and not naive and can be answered.
Many thanks for having already benefited from this list.
Steve Izett
Perth Western Australia
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nuckolls.bob(at)aeroelect
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| Posted: Mon Mar 01, 2010 4:39 pm Post subject: Questions |
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At 09:35 PM 2/28/2010, you wrote:
| Quote: | Hi Bob and all
I’m building a Glasair Super II RG powered by a Mazda Renesis Rotary using Tracy Crook’s EC2 (injection and ignition) and EM3 (Engine monitoring) and using standard starter and a small 40amp modern auto. So fully reliant on 14v source power.
I have a Radio and embedded systems background so I’m not completely ignorant of electrons.
I’m familiar with your Z-19 and have some general questions in order to weigh risks.
My questions are: - What are the failure modes of Aircraft Batteries?
- What are the failure modes of auto starter motors?
- What are the failure modes of auto alternators?
I hope these questions are firstly reasonable and not naive and can be answered. |
Probably not. The failure modes are legion. To "weigh" risks
you need failure rates to factor into a fault-tree
having calculable probabilities that will drive your
decision making processes.
In FAA parlance, one failure per million flight hours
doesn't need back up, and things that cannot be backed
up (wings falling off) need calculated rates on the
order of one per billion flight hours. The point is
that were anyone on the List willing to give you the
20 page data-dump that your question seems to seek,
you would be no closer to making rational build/buy
decisions.
It's far easier to simply ASSUME those things ARE
going to break in the time that you own the airplane.
Assuming that one of them DOES cease to be flight-worthy,
what are your plans for dealing with it in a graceful
manner. This is called failure tolerant design that
forces you to think about how you put things together.
You're further encouraged to understand and PLAN for how
you'll do without them.
The nice thing about this mode of thought relieves
you of the need to seek and purchase mil-spec, space-rated,
supper parts and HOPE they never fail. You can
buy parts from the hardware store with confidence that
any failure is not going to ruin your day.
See chapter 17 in the 'Connection.
Bob . . . [quote][b]
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stevei(at)carey.asn.au
Guest
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| Posted: Tue Mar 02, 2010 10:57 pm Post subject: Questions |
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Thanks Bob
I get the freedom that “expecting things to break” brings. That is very helpful, so thanks.
We all must make a call between no backup and the backup of the backup to the Nth order.
Many years ago I was a tech working on the Perth Airport ILS system.
All I can remember is that it was the arbiter that decided which system was functioning correctly and which was failing, was most often the part that failed and took the ILS system offline!
What level of redundancy does one go to before the backups defeat the original purpose and intent.
I suppose where I am still pondering is, given your systems make sense for aircraft batteries, alternator/generators and starters (I understand to be technologically challenged – but may be miss informed), how would they change (if any) given modern alternators, starters etc? (My question predicates (foolishly) that all modern equipment is equal in reliability!!!???)
Perhaps, even if the mean time between failures has quadrupled in modern equipment the risks still demand your backup systems.
Again, thanks for the help on the journey and the decision making that lies at every turn.
Cheers
Steve Izett
On 2/03/10 8:35 AM, "Robert L. Nuckolls, III" <[url=nuckolls.bob(at)aeroelectric.com]nuckolls.bob(at)aeroelectric.com[/url]> wrote:
[quote]At 09:35 PM 2/28/2010, you wrote:
| Quote: | Hi Bob and all
I‚m building a Glasair Super II RG powered by a Mazda Renesis Rotary using Tracy Crook‚s EC2 (injection and ignition) and EM3 (Engine monitoring) and using standard starter and a small 40amp modern auto. So fully reliant on 14v source power.
I have a Radio and embedded systems background so I‚m not completely ignorant of electrons.
I‚m familiar with your Z-19 and have some general questions in order to weigh risks.
My questions are:
- What are the failure modes of Aircraft Batteries?
- What are the failure modes of auto starter motors?
- What are the failure modes of auto alternators?
I hope these questions are firstly reasonable and not naive and can be answered.
|
Probably not. The failure modes are legion. To "weigh" risks
you need failure rates to factor into a fault-tree
having calculable probabilities that will drive your
decision making processes.
In FAA parlance, one failure per million flight hours
doesn't need back up, and things that cannot be backed
up (wings falling off) need calculated rates on the
order of one per billion flight hours. The point is
that were anyone on the List willing to give you the
20 page data-dump that your question seems to seek,
you would be no closer to making rational build/buy
decisions.
It's far easier to simply ASSUME those things ARE
going to break in the time that you own the airplane.
Assuming that one of them DOES cease to be flight-worthy,
what are your plans for dealing with it in a graceful
manner. This is called failure tolerant design that
forces you to think about how you put things together.
You're further encouraged to understand and PLAN for how
you'll do without them.
The nice thing about this mode of thought relieves
you of the need to seek and purchase mil-spec, space-rated,
supper parts and HOPE they never fail. You can
buy parts from the hardware store with confidence that
any failure is not going to ruin your day.
See chapter 17 in the 'Connection.
Bob . . .
[b]
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Wed Mar 03, 2010 7:08 am Post subject: Questions |
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At 12:42 AM 3/3/2010, you wrote:
Thanks Bob
I get the freedom that "expecting things to
break" brings. That is very helpful, so thanks.
We all must make a call between no backup and the
backup of the backup to the Nth order.
Many years ago I was a tech working on the Perth Airport ILS system.
All I can remember is that it was the arbiter
that decided which system was functioning
correctly and which was failing, was most often
the part that failed and took the ILS system offline!
What level of redundancy does one go to before
the backups defeat the original purpose and intent.
Yeah. I had an opportunity to craft and install the
cockpit mounted controller for a series of explosively
deployed recovery parachutes in flight test aircraft.
In fact, I'm presently tasked with doing the 4th
such installation for Hawker-Beech.
The design I replaced was horribly complex made so
by some desire to monitor all features of a redundant
and sometimes quad redundant system. Failures were
displayed on an LCD screen. Over a year into the design,
the system could not be made to work because of the
monitoring system kept raising alarms . . . and the
control system ultimately glitched one night and
launched the 'chute in the hangar.
The guys in the Targets group got together and built
one in two weeks.
http://aeroelectric.com/Pictures/Misc/Recovery_Parachute_Controller.jpg
Simple array of relays, solid state sequencer, failure
tolerant, preflight testable, very low comparative
parts count. A little brother to that controller
is on my bench right now awaiting a modern AC mains
powered battery maintainer. A review of the service
history of past installations revealed a lot of replaced
batteries. Seems the crews were pulling the breaker
from ship's DC power when the system was being
"disabled". Then when needed next time, the internal
battery wasn't fully charged.
I'm building a battery maintainer into the controller
with a placard that it be plugged in at least 1 hour
in the 48 hours preceding a flight where the
parachute will be armed.
I suppose where I am still pondering is, given
your systems make sense for aircraft batteries,
alternator/generators and starters (I understand
to be technologically challenged – but may be
miss informed), how would they change (if any)
given modern alternators, starters etc? (My
question predicates (foolishly) that all modern
equipment is equal in reliability!!!???)
It's an absolute fact that modern vehicular DC
power components of all stripes are longer lived
and more robust than their ancestors. So yes,
one can comfortably state that reliability of
components has increased . . . in virtually
all technologies and brands.
Perhaps, even if the mean time between failures
has quadrupled in modern equipment the risks still demand your backup systems.
Absolutely.
It's been my observation that the vast majority
of electrical systems unhappiness in OBAM aircraft
(and a substantial number of TC aircraft) DOES
NOT originate in ABILITY OF ANY PART TO DO ITS JOB.
Most problems arise from mis-application of parts and
poor process. Of course, all parts have service
lives and will ultimately cease to function.
From a systems perspective, reliability arguments
that focus on parts are academic and non-productive.
Resolution of such arguments depends heavily on statistical
data derived from laboratory tests that may or may
not accurately mimic service conditions. This is
ESPECIALLY true when service conditions are defined
by the knowledge, resources and skill sets of
the designer/installer.
That's why I started focusing on SYSTEM reliability
through failure mode effects analysis and designs
tolerant of failures. Once this relatively simple skill
was mastered, it mattered little where one
purchases parts. We're now free to concentrate
on the weakest links the OBAM aircraft fabrication
chain . . . knowledge, resources and skill set
of the builder. This is one area where process
trumps science every day.
Again, thanks for the help on the journey and the
decision making that lies at every turn.
My pleasure sir . . .
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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stevei(at)carey.asn.au
Guest
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| Posted: Wed Mar 03, 2010 7:25 am Post subject: Questions |
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Once again, thanks Bob, these fundamentals will steer the required decisions in the right direction.
Steve Izett
Perth WA
On 3/03/10 11:07 PM, "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:
At 12:42 AM 3/3/2010, you wrote:
Thanks Bob
I get the freedom that "expecting things to
break" brings. That is very helpful, so thanks.
We all must make a call between no backup and the
backup of the backup to the Nth order.
Many years ago I was a tech working on the Perth Airport ILS system.
All I can remember is that it was the arbiter
that decided which system was functioning
correctly and which was failing, was most often
the part that failed and took the ILS system offline!
What level of redundancy does one go to before
the backups defeat the original purpose and intent.
Yeah. I had an opportunity to craft and install the
cockpit mounted controller for a series of explosively
deployed recovery parachutes in flight test aircraft.
In fact, I'm presently tasked with doing the 4th
such installation for Hawker-Beech.
The design I replaced was horribly complex made so
by some desire to monitor all features of a redundant
and sometimes quad redundant system. Failures were
displayed on an LCD screen. Over a year into the design,
the system could not be made to work because of the
monitoring system kept raising alarms . . . and the
control system ultimately glitched one night and
launched the 'chute in the hangar.
The guys in the Targets group got together and built
one in two weeks.
http://aeroelectric.com/Pictures/Misc/Recovery_Parachute_Controller.jpg
Simple array of relays, solid state sequencer, failure
tolerant, preflight testable, very low comparative
parts count. A little brother to that controller
is on my bench right now awaiting a modern AC mains
powered battery maintainer. A review of the service
history of past installations revealed a lot of replaced
batteries. Seems the crews were pulling the breaker
from ship's DC power when the system was being
"disabled". Then when needed next time, the internal
battery wasn't fully charged.
I'm building a battery maintainer into the controller
with a placard that it be plugged in at least 1 hour
in the 48 hours preceding a flight where the
parachute will be armed.
I suppose where I am still pondering is, given
your systems make sense for aircraft batteries,
alternator/generators and starters (I understand
to be technologically challenged - but may be
miss informed), how would they change (if any)
given modern alternators, starters etc? (My
question predicates (foolishly) that all modern
equipment is equal in reliability!!!???)
It's an absolute fact that modern vehicular DC
power components of all stripes are longer lived
and more robust than their ancestors. So yes,
one can comfortably state that reliability of
components has increased . . . in virtually
all technologies and brands.
Perhaps, even if the mean time between failures
has quadrupled in modern equipment the risks still demand your backup systems.
Absolutely.
It's been my observation that the vast majority
of electrical systems unhappiness in OBAM aircraft
(and a substantial number of TC aircraft) DOES
NOT originate in ABILITY OF ANY PART TO DO ITS JOB.
Most problems arise from mis-application of parts and
poor process. Of course, all parts have service
lives and will ultimately cease to function.
From a systems perspective, reliability arguments
that focus on parts are academic and non-productive.
Resolution of such arguments depends heavily on statistical
data derived from laboratory tests that may or may
not accurately mimic service conditions. This is
ESPECIALLY true when service conditions are defined
by the knowledge, resources and skill sets of
the designer/installer.
That's why I started focusing on SYSTEM reliability
through failure mode effects analysis and designs
tolerant of failures. Once this relatively simple skill
was mastered, it mattered little where one
purchases parts. We're now free to concentrate
on the weakest links the OBAM aircraft fabrication
chain . . . knowledge, resources and skill set
of the builder. This is one area where process
trumps science every day.
Again, thanks for the help on the journey and the
decision making that lies at every turn.
My pleasure sir . . .
Bob . . .
--
This message was scanned by ESVA and is believed to be clean.
________________________________
The contents of this email are confidential and intended only for the named recipients of this e-mail. If you have received this e-mail in error, you are hereby notified that any use, reproduction, disclosure or distribution or the information contained in this e-mail is prohibited. Please notify the sender immediately and then delete/destroy the e-mail and any printed copies. All liability for viruses is excluded to the fullest extent of the law
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
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