Today's Message Index:
----------------------
1. 06:12 AM - Re: BASIC DUAL INDEPENDENT POWER SUPPLY (Ken)
2. 07:21 AM - Re: BASIC DUAL INDEPENDENT POWER SUPPLY (Robert L. Nuckolls, III)
3. 08:48 AM - Broken Battery (Charles Brame)
4. 11:28 AM - Belden Triax vs. Coax rg58 (Dave S)
5. 12:04 PM - Re: BASIC DUAL INDEPENDENT POWER SUPPLY (Ernest Christley)
6. 12:12 PM - Re: Belden Triax vs. Coax rg58 (Ron Quillin)
7. 01:11 PM - Re: Belden Triax vs. Coax rg58 (Matt Prather)
8. 02:50 PM - Re: BASIC DUAL INDEPENDENT POWER SUPPLY (Peter Harris)
9. 04:23 PM - Odessesy Bats (Chuck Jensen)
10. 04:51 PM - Re: Odessesy Bats (Robert L. Nuckolls, III)
11. 05:00 PM - Re: Wiring integrity!!! (Frank Stringham)
12. 05:02 PM - Re: Low Voltage Light Flashing (Duane Bentley)
13. 05:08 PM - Re: Odessesy Bats (Chuck Jensen)
14. 06:27 PM - Switch confusion (Christopher Barber)
15. 07:11 PM - Re: BASIC DUAL INDEPENDENT POWER SUPPLY (Robert L. Nuckolls, III)
16. 07:36 PM - Re: Two Txrs on one antenna (Todd Heffley)
17. 07:56 PM - Re: Odessesy Bats (Mike)
18. 09:06 PM - Re: Switch confusion (Peter Harris)
19. 09:32 PM - Re: BASIC DUAL INDEPENDENT POWER SUPPLY (Peter Harris)
20. 10:50 PM - Re: Wiring integrity!!! (Robert L. Nuckolls, III)
Message 1
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Subject: | Re: BASIC DUAL INDEPENDENT POWER SUPPLY |
With my belt drive dynamo I feel that the regulator is not really a weak
point in the system compared to the belt, bearings, wiring, etc.
However with a Jabiru that has I think a direct drive dynamo, would
there be any value in having a second regulator that could be manually
connected to the battery or the e-bus?
Regulator failures do seem to happen much more often than dynamo
failures. Personally I'd be content with Z-21 as it is probably more
reliable than his EFI system, but Peter seems reluctant to just rely on
battery power for extended endurance after an alternator failure. A
second regulator is light and wouldn't necesarilly need OV protection if
switched in manually. However it would only cater to a regulator problem
and wouldn't help if the dynamo quit...
I should find note 25 for Z-21 as well. I semi followed the discussion
on self excitation a few months ago but it is not obvious to me how the
two resistors and diode achieve self excitation when I look at Z-21 now.
Ken
Robert L. Nuckolls, III wrote:
> <nuckollsr@cox.net>
>
> At 07:13 AM 5/5/2007 +1000, you wrote:
>
>> <peterjfharris@bigpond.com>
>>
>> Bob,
>> The EFI including pump, ECU and injectors together with his main bus
>> radio
>> and instruments is using 4A according to advice from the guy who
>> engineered
>> this simple single body TBI system. (I don't have a figure for the
>> separate
>> ebus draw for the EFI so you would need to discount for radio and
>> instruments)I could also run the electronic ignition module and ignition
>> coil for additional ebus current I guessed 4A but it would probably
>> be less.
>> I am using a Bosch HE coil.
>> Alternative landing sites are up to 1hr apart. The endurance is 41/2HRS.
>> Thanks
>> Peter
>
>
> So how much batter-only endurance are you designing for? What
> plans are you making for preventative maintenance to make
> sure that design goals slip for lack of due diligence in
> maintenance?
>
> Assuming you're considering a battery capacity on the order
> of the popular 3 x 6 x 7 inch form-factor, a 4A load on a
> new battery will give you just over two hours of operation
> assuming that nothing in your system gives up above 10.5
> volts. See:
>
> http://www.aeroelectric.com/Pictures/Curves/17AH_Capcity_vs_Load.gif
>
> Here we see that a 17 ah battery will carry 4A for about 3 hours.
>
> http://www.aeroelectric.com/Pictures/Curves/28AH_12V_Capacity_vs_Load.gif
>
> To go out for duration of fuel aboard, you'll need to upsize to
> the 28 ah critter for an increase to something on the order of
> 360 minutes or 6 hours.
>
> It's my recommendation that you consider z21 posted at:
>
> http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z21A.pdf
>
> Stuff needed to keep the engine running should run from
> the battery bus and be switched by their own power switches
> SEPARATE from DC power management for the rest of the airplane.
> You don't need the diodes. A battery does not fail in a manner
> that takes the rest of the system down. Tying the alternator
> directly to the battery al-la Z13/8 lets you load-shed the
> main bus plus contactor and run only battery bus + ebus loads.
> Even the e-bus can be shed if desired.
>
> I presume you're planning on carrying flight-bag backups
> for the panel mounted hardware like
>
> http://www.aeroelectric.com/Pictures/Misc/Failure_Tolerance.pdf
>
> This architecture meets the design goals of dual supplies
> for keeping the engine lit up.
>
> Bob . . .
>
Message 2
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Subject: | Re: BASIC DUAL INDEPENDENT POWER SUPPLY |
At 09:05 AM 5/8/2007 -0400, you wrote:
>
>With my belt drive dynamo I feel that the regulator is not really a weak
>point in the system compared to the belt, bearings, wiring, etc.
Certainly things that move, flex, need lubrication, and vibrate
are victims of certain kinds of stresses and have obvious
limitations to service life.
Things that don't move and need grease are not immune from
their own stresses which can have an effect on service life
too. Just because it's "solid state" doesn't mean that it's
automatically more likely to outlive any other component
of the system.
>However with a Jabiru that has I think a direct drive dynamo, would there
>be any value in having a second regulator that could be manually connected
>to the battery or the e-bus?
The key term here is "value". Indeed, a calculation of
cost-of-ownership along with a probability study for
any particular failure offers the math and statistics
junkie an opportunity for a couple-hundred hour high.
Adding another regulator increased parts count not only
by doubling the number of regulators but adds a switch
to select between them which has its own unique failure
modes.
>Regulator failures do seem to happen much more often than dynamo failures.
. . . an anecdotal observation that may be true but to
simply add-another-regulator may not be the optimal
solution. WHY does the regulator fail? If it had a better
heat sink, would it last longer? If it were redesigned
slightly, would it last longer? Until one knows root cause
of a failure, the only "remedy" is to play swap-tronics . . .
add-a-spare, change brands, etc. It may be comforting
from the neophyte's perspective but in fact could have
no useful effect on probability of avoiding a sweaty
experience while airborne.
> Personally I'd be content with Z-21 as it is probably more reliable than
> his EFI system, but Peter seems reluctant to just rely on battery power
> for extended endurance after an alternator failure.
I don't read that into his words. His question was
to identify a methodology for crafting "dual, independent
power supply". His original notion was that diodes were
necessary to acquire independence . . . which is not
the case. Moving the alternator feed from bus to battery
side of the contactor covers the issues for a failed
battery contactor.
> A second regulator is light and wouldn't necesarilly need OV protection
> if switched in manually. However it would only cater to a regulator
> problem and wouldn't help if the dynamo quit...
The dynamo is wire wound around a stack of laminations
with no moving parts. If these things quit, then it's
because a wire broke. That's an exceedingly rare event
unworthy of worry.
>I should find note 25 for Z-21 as well. I semi followed the discussion on
>self excitation a few months ago but it is not obvious to me how the two
>resistors and diode achieve self excitation when I look at Z-21 now.
It' provides a high source impedance "leakage" around
SCR's internal to the regulator such that the rectifier/
regulator is never completely shut down. This causes
output from a dynamo to keep a low voltage charge on the
output filter capacitor sufficiently elevated to keep
the regulator's control circuits from shutting down.
Note 25 is a general note for Appendix Z found on page
Z-11 of
http://aeroelectric.com/articles/Rev11/AppZ_R11J.pdf
The foundation for this exchange rests solidly on
the notion that a WELL MAINTAINED battery is the most
reliable source of energy aboard the aircraft. Of course
one strives to reduce likelihood of charging system
failure . . . but this is ALWAYS best achieved by
increasing service life of the existing components
as opposed to increasing numbers of components.
Bob . . .
Message 3
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Bob,
Where can I get info on how to do a Cap-Check? What equipment is
required?
I realize this is pretty basic stuff, but I am clueless.
Charlie Brame
RV-6A N11CB
San Antonio
> Cap-check is a capacity test. Something that everyone
> who depends on the battery for alternator out, e-bus
> support should do. The battery will get replaced before
> it fails to crank the engine any more.
>
>
> Bob . . .
>
Message 4
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Subject: | Belden Triax vs. Coax rg58 |
Glasair sells and installs Belden 9222 triax for the tail com antenna and
for the wing tip nav antenna. Everyone says rg400 is preferred over rg58,
but is the triax a step up from the regular rg58 coax? The triax is
installed now for the #1 com tail antenna and nav antenna, but I bought more
Belden 9222 triax for transponder, 2nd com, and marker antenna runs, should
I scrap it and install rg 400?
Thanks,
Dave Shiffer
Message 5
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Subject: | Re: BASIC DUAL INDEPENDENT POWER SUPPLY |
> However with a Jabiru that has I think a direct drive dynamo, would
> there be any value in having a second regulator that could be manually
> connected to the battery or the e-bus?
Sometimes redundancy means two pieces of hardware dying at the same
time. I installed two hard drives in a RAID configuration on my
computer for the sake of redundancy. I found a good deal on 7200RPM IBM
drives, so I bought a couple. Ran great for years. Fast and reliable.
Then both drives crapped out (technical term) within hours of one
another. I lost nearly everything. I noticed the problems with one
drive, and the other died before I could finish a backup. The serial
numbers were within about 4 units of one another. They lived in the
same environment, and fed off the same power supply.
Message 6
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Subject: | Re: Belden Triax vs. Coax rg58 |
At 11:24 5/8/2007, you wrote:
>Glasair sells and installs Belden 9222 triax for the tail com
>antenna and for the wing tip nav antenna. Everyone says rg400 is
>preferred over rg58, but is the triax a step up from the regular
>rg58 coax? The triax is installed now for the #1 com tail antenna
>and nav antenna, but I bought more Belden 9222 triax for
>transponder, 2nd com, and marker antenna runs, should I scrap it and
>install rg 400?
>
>Thanks,
>
>Dave Shiffer
Belden 9222 is double shielded coax. Tinned copper conductors and
PVC outer jacket
RG-400 is double shielded coax. Silver plated copper conductors with
FEP Teflon outer jacket.
The RG is MIL-17 rated, the 9222 is not.
We used RG-400 doing a refurb of a certified A/C, and pulled out all
the old PVC cable we could find.
Ron Q.
Message 7
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Subject: | Re: Belden Triax vs. Coax rg58 |
I don't think any of these cable types will perform appreciably different
for small airplane applications. While the RG400 is more tolerant of high
temps, I don't think that's relevent for avionics signaling. The RG400 is
supposed to be a bit more flexible than RG58, and since 9222 is triax, I
might guess that it's less flexible than RG58.
The RF performance of RG58 varies depending which part num you buy. Some
of the "Low Loss" cable show somewhat better numbers, particularly at
transponder freq. Even so, for the cable run lengths and considering the
power output of a healthy transponder, it's not an issue.
In any case, if you already have equipment installed using 9222, I'd leave
it, and if you have the cable and tools to use it for the rest of the
airplane, fine. But, I wouldn't go out and buy tools for installing it.
The connectors I saw for 9222 look bulky. Might be a hassle in a cramped
space.
BTW, Belden lists 9222 as a type of RG58 even though it's triax.
BTW2, The RG400 I saw has a double layer braid shield, but since it
doesn't have a dielectric between the layers, it's not triax.
Regards,
Matt-
> Glasair sells and installs Belden 9222 triax for the tail com antenna and
> for the wing tip nav antenna. Everyone says rg400 is preferred over rg58,
> but is the triax a step up from the regular rg58 coax? The triax is
> installed now for the #1 com tail antenna and nav antenna, but I bought
> more
> Belden 9222 triax for transponder, 2nd com, and marker antenna runs,
> should
> I scrap it and install rg 400?
>
> Thanks,
>
> Dave Shiffer
>
>
Message 8
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Subject: | BASIC DUAL INDEPENDENT POWER SUPPLY |
Bob the true practical value of Z-21 is still sinking in and I have been
researching batteries. The experienced advice that I am getting down here is
not for Odyssey incidentally because of variable quality and that ties in
with a recent post. Sometimes I think that we get suspect product down here
because we are a long way from the big market. I have been shown an
HGL35-12. I was definitely interested in Ken's original suggestion to
consider dual regulators because I had never seen the idea before. I had a
regulator failure years ago and with the unprotected Quickie circuit and a
Revmaster PM installation with no warning on a 900 NM trip. The battery was
almost boiling when I arrived after the second leg of the trip. Scary. No
concern for that issue with any of your circuits but it is still in my mind
that the regulator is the weakest link in the power supply and may be a
candidate for a properly designed duplication?
Peter
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Wednesday, 9 May 2007 1:16 AM
Subject: Re: AeroElectric-List: BASIC DUAL INDEPENDENT POWER SUPPLY
<nuckollsr@cox.net>
At 09:05 AM 5/8/2007 -0400, you wrote:
>
>With my belt drive dynamo I feel that the regulator is not really a weak
>point in the system compared to the belt, bearings, wiring, etc.
Certainly things that move, flex, need lubrication, and vibrate
are victims of certain kinds of stresses and have obvious
limitations to service life.
Things that don't move and need grease are not immune from
their own stresses which can have an effect on service life
too. Just because it's "solid state" doesn't mean that it's
automatically more likely to outlive any other component
of the system.
>However with a Jabiru that has I think a direct drive dynamo, would there
>be any value in having a second regulator that could be manually connected
>to the battery or the e-bus?
The key term here is "value". Indeed, a calculation of
cost-of-ownership along with a probability study for
any particular failure offers the math and statistics
junkie an opportunity for a couple-hundred hour high.
Adding another regulator increased parts count not only
by doubling the number of regulators but adds a switch
to select between them which has its own unique failure
modes.
>Regulator failures do seem to happen much more often than dynamo failures.
. . . an anecdotal observation that may be true but to
simply add-another-regulator may not be the optimal
solution. WHY does the regulator fail? If it had a better
heat sink, would it last longer? If it were redesigned
slightly, would it last longer? Until one knows root cause
of a failure, the only "remedy" is to play swap-tronics . . .
add-a-spare, change brands, etc. It may be comforting
from the neophyte's perspective but in fact could have
no useful effect on probability of avoiding a sweaty
experience while airborne.
> Personally I'd be content with Z-21 as it is probably more reliable than
> his EFI system, but Peter seems reluctant to just rely on battery power
> for extended endurance after an alternator failure.
I don't read that into his words. His question was
to identify a methodology for crafting "dual, independent
power supply". His original notion was that diodes were
necessary to acquire independence . . . which is not
the case. Moving the alternator feed from bus to battery
side of the contactor covers the issues for a failed
battery contactor.
> A second regulator is light and wouldn't necesarilly need OV protection
> if switched in manually. However it would only cater to a regulator
> problem and wouldn't help if the dynamo quit...
The dynamo is wire wound around a stack of laminations
with no moving parts. If these things quit, then it's
because a wire broke. That's an exceedingly rare event
unworthy of worry.
>I should find note 25 for Z-21 as well. I semi followed the discussion on
>self excitation a few months ago but it is not obvious to me how the two
>resistors and diode achieve self excitation when I look at Z-21 now.
It' provides a high source impedance "leakage" around
SCR's internal to the regulator such that the rectifier/
regulator is never completely shut down. This causes
output from a dynamo to keep a low voltage charge on the
output filter capacitor sufficiently elevated to keep
the regulator's control circuits from shutting down.
Note 25 is a general note for Appendix Z found on page
Z-11 of
http://aeroelectric.com/articles/Rev11/AppZ_R11J.pdf
The foundation for this exchange rests solidly on
the notion that a WELL MAINTAINED battery is the most
reliable source of energy aboard the aircraft. Of course
one strives to reduce likelihood of charging system
failure . . . but this is ALWAYS best achieved by
increasing service life of the existing components
as opposed to increasing numbers of components.
Bob . . .
Message 9
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Is the Odessesy PC 680 sufficient to spin an IO 540 (BNC starter)?
Chuck Jensen
Message 10
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Subject: | Re: Odessesy Bats |
At 07:20 PM 5/8/2007 -0400, you wrote:
>Is the Odessesy PC 680 sufficient to spin an IO 540 (BNC starter)?
>
>Chuck Jensen
Absolutely. It's a rare VSLA battery in the
17-20 ah class that won't.
I've run tests on 10 a.h. batteries that would
crank a competition IO-360 engine for 5 or more
hard starting cycles (10+ blades).
When they won't it's often traced to other losses
in the system such as too small cranking wires
and/or drops across contactors.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 11
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Subject: | Re: ectric-List:Wiring integrity!!! |
A Cessna 210 on a flight from San Antonio to Seattle when his distress call
said smoke in the cabin. The sad out come was the pilot lost control and
crashed near Springville, Utah.
Now i know that there are other causes of smoke but it raised my concern of
eletrical fires.
I am wiring my plane according Z-13/8. Now the question: What are the usual
failure points that cause electrical fires? in aircraft wiring systems?
I know this is pretty open ended and I must also admit that I haven't done
a search yet so if you want to with hold until I have done my home work
that is fine but if you have some pearls of wisdom .......please
help!!!!!!!!!!!!!!
Frank @ SGU RV7A "NDY" Panel / electrical.....
_________________________________________________________________
More photos, more messages, more storageget 2GB with Windows Live Hotmail.
Message 12
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Subject: | RE: Low Voltage Light Flashing |
Situation corrected.
I contacted B&C this morning and talked to Tim Hedding. He didn't think
either the alternator or regulator were defective and sent me to the
troubleshooting guide for the LR3C. Working through the steps under the
panel, I traced it down to a blown fuse in the power line to the alt.
field, (pin 6) of the regulator. I had put in a 5 amp fuse instead of a
breaker and missed this fuse in my check last night. Before installing
another one, I ohmed the 2-10 battery/alternator switch but found no
shorts. The rest of the troubleshoot guide was followed and all checked
out. I restarted the plane and the system charges correctly.
I call Tim back and said I couldn't find the short but would replace the
switch as a precaution. Tim suggested it was unlikely to be a switch
problem and that I may have had a temporary over voltage, which blew the
5 amp fuse and shut the alternator down. He suggested I put in a
circuit breaker and check for conditions that may have caused the event,
which I will do.
Duane Bentley
RV6 N515DB
255 hrs.
Message 13
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I hadn't had a problem with the PC 680 yet but I'm replacing a FLA
battery with the 680 and it always takes one aback to see the difference
in size (not that size matters, mind you), so I expect it'll be good to
go.
Chuck Jensen
Robert L. Nuckolls, III
>Is the Odessesy PC 680 sufficient to spin an IO 540 (BNC starter)?
>
>Chuck Jensen
Absolutely. It's a rare VSLA battery in the
17-20 ah class that won't.
I've run tests on 10 a.h. batteries that would
crank a competition IO-360 engine for 5 or more
hard starting cycles (10+ blades).
When they won't it's often traced to other losses
in the system such as too small cranking wires
and/or drops across contactors.
Bob . . .
----------------------------------------
( IF one aspires to be "world class", )
( what ever you do must be exercised )
( EVERY day . . . )
( R. L. Nuckolls III )
----------------------------------------
Message 14
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Subject: | Switch confusion |
Maybe I read it and now am forgetting (and now can't find it), but on
the Z-14 drawings the two contactor switches that are called out are
three position switches. Why? What are the middle positions suppossed
to be used for? What position should be used during flight? I got my
Z-14 layout cranking my engine today (my 46th birthday <g> ) and I was
tickled to have my Wankle rotary churning over effortlessly (just
cranking, not yet ready for starting). However, in my use, swithing the
switches all the way up seemed to be what activated the contactors
allowing the cranking. Insight to what may be obvious is appreciated.
TIA.
All the best,
Chris
Message 15
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Subject: | BASIC DUAL INDEPENDENT POWER SUPPLY |
At 07:47 AM 5/9/2007 +1000, you wrote:
><peterjfharris@bigpond.com>
>
>Bob the true practical value of Z-21 is still sinking in and I have been
>researching batteries. The experienced advice that I am getting down here is
>not for Odyssey incidentally because of variable quality and that ties in
>with a recent post. Sometimes I think that we get suspect product down here
>because we are a long way from the big market. I have been shown an
>HGL35-12. I was definitely interested in Ken's original suggestion to
>consider dual regulators because I had never seen the idea before. I had a
>regulator failure years ago and with the unprotected Quickie circuit and a
>Revmaster PM installation with no warning on a 900 NM trip. The battery was
>almost boiling when I arrived after the second leg of the trip. Scary. No
>concern for that issue with any of your circuits but it is still in my mind
>that the regulator is the weakest link in the power supply and may be a
>candidate for a properly designed duplication?
The "no sweat" electrical system is one that can tolerate any
single failure. You experienced what appears to be a runaway
that ran unabated. This produced a second failure which, if
allowed to run longer, might have smoked lots of stuff.
One can stack redundancy on top of redundancy but in every
case you first need to do drill:
How can this part fail?
Is it preflight detectable? If so, is it on my
preflight check list to look?
How will I know that it failed while in flight?
If failure occurs in flight, is it useful for
comfortable termination of flight?
If so, what's the plan-b for replacing its
usefulness?
Finally, the most effective failure mitigation
plans include a preventative maintenance program
that tracks time in service and/or present
degradation of performance so that a replacement
is made long before failure.
A "Plan-B" for a failed part is best crafted from
completely different parts and architecture. For
example, hand-helds in the flight bag are totally
independent of panel mounted hardware and (assuming
batteries have been maintained) can be counted
on to function when needed.
So, if you've done the homework and preventative
maintenance that insures sweat-free termination
of flight in spite of a failed regulator then
adding a second, switched regulator is not the
minimum parts count nor totally independent scenario
for plan-b.
For example, the Cessna Skymaster and Beech Barons
had single regulators driving both alternators in
parallel. Someone thought that "twin engine reliability"
could be maintained by providing a second regulator that
could be switched in to replace a failed main regulator.
But suppose a short on the field circuit takes out
one regulator. Switching in the standby regulator
produces TWO failed regulators.
If it were my airplane, Z-21 would be the way to
go. If the engine were fitted with dual ECFI systems
like the Subaru conversions featured in Z-19, then
a second battery provides total separation of power
sources for dual engine electronics. Given that your
engine is fitted with a single system, then there
ARE single points of failure that are not going to
go away no matter how many power sources you carry.
Hence, I'd be more interested in believing that the
ECFI had the reliability of propeller bolts than with
stacking on more power sources.
Bob . . .
Message 16
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Subject: | Re: Two Txrs on one antenna |
I support Jet aircraft with these coax relays.
They are often the source of intermittant problems.
the worst are coax relays that split two transponders to one blade antenna.
Higher Frequncy IMHO.
My experince leads me to think two working antennas are more valuable
than one antenna and one unreliable relay.
My opinion is colored by maintenance experience, not building experience.
Todd
Message 17
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I crank a Cont. IO-550 with 10:1 pistons with a PC 680. One year and
counting and so far and no problems..
Mike Larkin
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Chuck
Jensen
Sent: Tuesday, May 08, 2007 4:21 PM
Subject: AeroElectric-List: Odessesy Bats
Is the Odessesy PC 680 sufficient to spin an IO 540 (BNC starter)?
Chuck Jensen
"http://www.matronics.com/Navigator?AeroElectric-List"http://www.matroni
cs.com/Navigator?AeroElectric-List
"http://forums.matronics.com"http://forums.matronics.com
--
11:52 AM
--
11:52 AM
Message 18
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Subject: | Switch confusion |
Chris off topic . Which Wankel are you using. I ran the Norton 95HP rotary
for 3 years.
Peter
_____
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of
Christopher Barber
Sent: Wednesday, 9 May 2007 11:26 AM
Subject: AeroElectric-List: Switch confusion
Maybe I read it and now am forgetting (and now can't find it), but on the
Z-14 drawings the two contactor switches that are called out are three
position switches. Why? What are the middle positions suppossed to be used
for? What position should be used during flight? I got my Z-14 layout
cranking my engine today (my 46th birthday <g> ) and I was tickled to have
my Wankle rotary churning over effortlessly (just cranking, not yet ready
for starting). However, in my use, swithing the switches all the way up
seemed to be what activated the contactors allowing the cranking. Insight
to what may be obvious is appreciated. TIA.
All the best,
Chris
Message 19
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Subject: | BASIC DUAL INDEPENDENT POWER SUPPLY |
Thanks Bob I am going down that path. And you make a good point about the
reliability of the ECU.
Peter
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Robert L.
Nuckolls, III
Sent: Wednesday, 9 May 2007 1:11 PM
Subject: RE: AeroElectric-List: BASIC DUAL INDEPENDENT POWER SUPPLY
<nuckollsr@cox.net>
At 07:47 AM 5/9/2007 +1000, you wrote:
><peterjfharris@bigpond.com>
>
>Bob the true practical value of Z-21 is still sinking in and I have been
>researching batteries. The experienced advice that I am getting down here
is
>not for Odyssey incidentally because of variable quality and that ties in
>with a recent post. Sometimes I think that we get suspect product down here
>because we are a long way from the big market. I have been shown an
>HGL35-12. I was definitely interested in Ken's original suggestion to
>consider dual regulators because I had never seen the idea before. I had a
>regulator failure years ago and with the unprotected Quickie circuit and a
>Revmaster PM installation with no warning on a 900 NM trip. The battery was
>almost boiling when I arrived after the second leg of the trip. Scary. No
>concern for that issue with any of your circuits but it is still in my mind
>that the regulator is the weakest link in the power supply and may be a
>candidate for a properly designed duplication?
The "no sweat" electrical system is one that can tolerate any
single failure. You experienced what appears to be a runaway
that ran unabated. This produced a second failure which, if
allowed to run longer, might have smoked lots of stuff.
One can stack redundancy on top of redundancy but in every
case you first need to do drill:
How can this part fail?
Is it preflight detectable? If so, is it on my
preflight check list to look?
How will I know that it failed while in flight?
If failure occurs in flight, is it useful for
comfortable termination of flight?
If so, what's the plan-b for replacing its
usefulness?
Finally, the most effective failure mitigation
plans include a preventative maintenance program
that tracks time in service and/or present
degradation of performance so that a replacement
is made long before failure.
A "Plan-B" for a failed part is best crafted from
completely different parts and architecture. For
example, hand-helds in the flight bag are totally
independent of panel mounted hardware and (assuming
batteries have been maintained) can be counted
on to function when needed.
So, if you've done the homework and preventative
maintenance that insures sweat-free termination
of flight in spite of a failed regulator then
adding a second, switched regulator is not the
minimum parts count nor totally independent scenario
for plan-b.
For example, the Cessna Skymaster and Beech Barons
had single regulators driving both alternators in
parallel. Someone thought that "twin engine reliability"
could be maintained by providing a second regulator that
could be switched in to replace a failed main regulator.
But suppose a short on the field circuit takes out
one regulator. Switching in the standby regulator
produces TWO failed regulators.
If it were my airplane, Z-21 would be the way to
go. If the engine were fitted with dual ECFI systems
like the Subaru conversions featured in Z-19, then
a second battery provides total separation of power
sources for dual engine electronics. Given that your
engine is fitted with a single system, then there
ARE single points of failure that are not going to
go away no matter how many power sources you carry.
Hence, I'd be more interested in believing that the
ECFI had the reliability of propeller bolts than with
stacking on more power sources.
Bob . . .
Message 20
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Subject: | Re: ectric-List:Wiring integrity!!! |
At 05:57 PM 5/8/2007 -0600, you wrote:
><fstringham@hotmail.com>
>
>A Cessna 210 on a flight from San Antonio to Seattle when his distress
>call said smoke in the cabin. The sad out come was the pilot lost control
>and crashed near Springville, Utah.
>
>Now i know that there are other causes of smoke but it raised my concern
>of eletrical fires.
>
>I am wiring my plane according Z-13/8. Now the question: What are the
>usual failure points that cause electrical fires? in aircraft wiring systems?
This is one of the really BIG problems with 99% of the
stories cited with tid-bits of anecdotal info. I've worked
accidents with smoke in cabin from blower motors, gas-fired
heaters, smoking components within a radio, and a fire
in a junction box precipitated by out-of-sequence switching
of batteries in a 24-48v cranking system on an MU-2. In
every case, pilots got the airplane on the ground but in
the MU-2 a post-landing fire trashed the interior (although
a technician who worked for me years later in the video
business worked on the restoration of the same airplane!).
In the few cases where I've been privy to the initial
failure of a major system component where the pilots lost
control and died, none of them involved smoke in the
cabin and all scenarios stretched a pilot beyond his
ability to cope with the situation. One was a dual
alternator failure on a big piston twin where both
alternators had been overhauled by the same shop who
rewound stators and failed to powder coat the stacks
or install slot liners. The two alternators were overhauled
several hundred hours apart from each other but failed
within minutes of each other on the same flight . . . in
icing IMC.
When queried as to how many accidents had been investigated
at Beech/RAC/Hawker-Beech wherein an electrical system failure
was an initiating or participating event, not one of the
gray beards in the department could cite a case. In
one case, a soft-fault came close to causing an accident.
A C-90 on short final to Clovis NM about 1990 was
suddenly stricken with complete disconnect of control in pitch.
Elevator forces in wheel went to zero. The pilots did a go around
and managed to land safely with power and pitch trim.
A teardown revealed a mis-positioned wire bundle under the
floorboards where a 40A protected wire for co-pilot's windshield
heat had had been rubbing against the elevator cable for some
period of time.
No smoke, no fire, no flickers in the electrical system, no
trips of the 40A breaker. Over the pre-failure interval,
megajoules of energy were released in the erosion of steel
wires (the copper wire was in pretty good shape . . . this
demonstrates why layers of copper are included in the design
of safes . . . nearly impossible to penetrate with a cutting
torch).
>I know this is pretty open ended and I must also admit that I haven't
>done a search yet so if you want to with hold until I have done my home
>work that is fine but if you have some pearls of wisdom .......please
>help!!!!!!!!!!!!!!
The best thing I can offer is do a good job installing
your equipment. Be ready to shut EVERYTHING but the engine
off should you experience a smoke event. But know too that
likelihood of an electrical system generated smoke event
causing a bad day in the cockpit is exceedingly remote. If you
do get a smoke event, keeping your cool is more important
than self recriminations for not having anticipated the
event or loosing sleep over trying to anticipate it now.
I wouldn't worry about it.
Bob . . .
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