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gkrysztopik(at)satx.rr.co
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 Posted: Sun Apr 16, 2006 12:29 pm Post subject: oh no! OV again |
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I recently had what I suspect is a regulator failure with an EA-81 and
Suzuki Samuri alternator. I'm not quite sure exactly what happened but many
many thanks to Bob and the list for helping out when I was wiring my plane
four or five years ago. My backup battery and backup ignition saved me and
got me to the nearest airport (twice).
I have a glass VFR panel but didn't want the complexity and weight of a
bigger aux bus. My simple little 5AH aux battery is only wired to the
backup ignition, second electric fuel pump, and tiny LCD voltmeter. It's
just enough to keep the engine running while I get my handheld radio out
(with VOR for backup nav). I wired it thru a completely different area of
the panel and firewall for complete redundancy. It is connected to the main
bus via a diode for charging. I check every preflight that the backup
battery and ignition are working. That's the good part - it worked as
intended.
I was a long time reader on the list but went thru three big moves over the
last couple years and I wasn't able to keep up with all my lists and missed
a large part of the Paul vs Bob OV discussion as well as anything that took
place since. I'm not sure whether to retain my OV module and solenoid but
I'll be reading up on things. One of my mistakes was to have a partial OV
circuit and the other was not to have sufficient and active engine
monitoring. I'm here to learn so feel free to point out any other mistakes
that we can learn from.
- OV circuit problem last year - I noticed my battery was run down because
the alternator was not charging it. I found that the alternator contactor
was not closing (used in OV circuit for internally regulated alternators per
aeroelectric schematic). I attributed the failure to a poor mounting
location - I tried to keep it simple so I put it right between the alt and
starter which was on the subaru cylinder head where there were spare
mounting holes already tapped in the head. I'm guessing excessive heat and
vibration caused the failure. I bypassed the contactor but left the OV
module in there intending to relocate the contactor. I should have
disconnected the circuit - either all in or all out.
- gnd strap problem last fall - while starting the plane, the power
fluctuated then dropped out. I traced it to a loose ground strap. Funny, I
made all my big cables per Bob's 12 ga wire wedge solder method and all held
up great. For some reason I wanted a nice braided steel ground strap so I
bought two custom length from an aircraft place for battery to firewall and
engine block to firewall. These are the ones that failed - the crimp was
loose and the strap pulled right out. Lesson - make redundant ground
straps. Another lesson - I gently tug on all bat and gnd straps preflight
but the two gnd straps were neatly tie wrapped together so when I checked
them, the good one was supporting the bad one. That's both good and bad I
guess. I mention this because the incident blew some fuses and must have
sent some spikes thru the system, possibly reducing the life of the
regulator?
- in-flight failure #1 - the other week on the way to SNF, radio blinks,
popping in headset, then panel goes black and engine gets quiet. Backup
switch on, engine comes back up and land at nearest. Probe around and find
battery contactor chattering, not able to keep bat and alt on main bus.
Probe around engine and panel for a couple hours, everything else looks ok
except alt OV breaker was popped (missed hint?). I assumed the main bus
disconnect sent a spike thru the system and popped the breaker. I had a
contactor fail before, made sense so I called around for one. No luck, so I
move cables to one side of contactor to bypass. Only one hour flight to SNF
so I'll find one there. Very long runup, everything looks good - off I go.
- in-flight failure #2 - 15 minutes into flight, radio starts blinking and I
start cursing. I notice aux bat volts fluctuating between 15.x and 16.x
(this is after diode drop from main bus). This is normally at 13.8 volts.
Aha! The regulator is bad! Everything goes out again. "golly, gosh darn
it" (ya right) Backup switch on, engine comes on again (whew!). Land at
nearest. Bad place to land but that's another story. I pull the alt and
get a ride to town. I went to an auto parts store and they tested it. It
failed on the tester "when the switch was on alternator but passed when it
was set to generator". They had no idea what that meant but it sounded like
a bad regulator to me. They didn't have a Suzuki Samuri alternator in stock
but said a guy up the road fixes them. Off to the guy up the road and he
tested it. "Nothing wrong with this alternator" he said. I asked to keep
testing, and he got it really hot under full load and it still worked.
Maybe under vibration or higher rpm? Dunno. Went to another auto parts
store and they ordered one - "be here in two hours". They tested it and it
passed on a third type of test stand, this one fully automated. I wanted
new anyway.
Got the new alt, went back and installed it, but the battery wouldn't come
up after charging so it was toast. I found the same size and replaced it.
I also removed the overvoltage circuit and removed a diode to ground on the
field line from the contactor. It's normally not good to make more than one
change at a time but I wanted to remove all in doubt and try to recreate the
problem later at home. I ran it up for a long time not feeling good that I
didn't understand exactly what happened or find and fix a hard failure.
Told the tower that I was going to keep climbing and circling for a while,
and everything seemed ok.
Made it Lakeland (after doing several laps around Lake Parker #$%(at)&
!),
couldn't find a contactor and never found anything else wrong. So it made
it to my new home after another 10 hours as-is. Everything seems fine with
the new alt, new bat and contactor bypassed (I already ordered a new master
contactor).
- is it likely for the regulator to go bad but test ok?
- would the regulator shut itself down? (someone said they do that)
- would the OV ciruit have pulled the "field" line down and caused screwy
operation because the OV contactor was not there?
- would an overvoltage toast the master contactor?
- the first main bus failure makes sense if the master contactor removed all
power, but the second time they were hard wired (stupid, yes). Would the OV
toast an RG battery that quick? Battery goes high temp and shorts?
- do I replace the OV circuit and contactor? I had about 150 hours on it
with no problems using the OV circuit.
Happy to share my stupidity so nobody else does that, and highly recommend
simple redundant circuits that will get you home. Also happy to provide
real-world data for discussion here. In my feeble defense, this
cross-country move came up quickly with a fixed timeframe so I scrambled to
clean up details on the plane but didn't get to replacing or removing OV
stuff. The plane flew great from RI to FL after 10 hours and when it failed
I was 1000 miles from anyone I knew. If I was near home I don't think I
would have continued until it was 100% but I'm also not sure that I would
have found anything more than I did. I saved the old alt so I can try to
get it to fail (Bob - you want it?). It would be nice to know what happened
and improve my design. I'm 90% done with a homemade engine monitor. I have
three hall-effect current sensors in place and audio warning with data
recording. Would have been nice but I still have 90% to go on it. I think
I'll sell that project and buy a new one soon.
Gary Krysztopik
Pelican/Stratus - 175 hours
San Antonio, TX
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nuckollsr(at)cox.net
Guest
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| Posted: Mon Apr 17, 2006 5:43 am Post subject: oh no! OV again |
|
|
At 03:25 PM 4/16/2006 -0500, you wrote:
| Quote: |
I recently had what I suspect is a regulator failure with an EA-81 and
Suzuki Samuri alternator. I'm not quite sure exactly what happened but many
many thanks to Bob and the list for helping out when I was wiring my plane
four or five years ago. My backup battery and backup ignition saved me and
got me to the nearest airport (twice).
I have a glass VFR panel but didn't want the complexity and weight of a
bigger aux bus. My simple little 5AH aux battery is only wired to the
backup ignition, second electric fuel pump, and tiny LCD voltmeter. It's
just enough to keep the engine running while I get my handheld radio out
(with VOR for backup nav). I wired it thru a completely different area of
the panel and firewall for complete redundancy. It is connected to the main
bus via a diode for charging. I check every preflight that the backup
battery and ignition are working. That's the good part - it worked as
intended.
|
| Quote: | I was a long time reader on the list but went thru three big moves over the
last couple years and I wasn't able to keep up with all my lists and missed
a large part of the Paul vs Bob OV discussion as well as anything that took
place since. I'm not sure whether to retain my OV module and solenoid but
I'll be reading up on things. One of my mistakes was to have a partial OV
circuit and the other was not to have sufficient and active engine
monitoring. I'm here to learn so feel free to point out any other mistakes
that we can learn from.
|
The figure Z-24 ov system is not inherently evil. It does offer
risks to the alternator's regulator IF the system is turned OFF
while the alternator is under load. On the other hand, the system
has performed as intended and taken runaway alternators off line
on several occasions reported to us. There's a replacement for
Z-24 in the design phases and some testing has been done which sent
us back to the drawing board. But it's a low priority concern. If
you have Z-24 in place, just operate it as you would any other
airplane and it will be fine in interim.
| Quote: | - OV circuit problem last year - I noticed my battery was run down because
the alternator was not charging it. I found that the alternator contactor
was not closing (used in OV circuit for internally regulated alternators per
aeroelectric schematic). I attributed the failure to a poor mounting
location - I tried to keep it simple so I put it right between the alt and
starter which was on the subaru cylinder head where there were spare
mounting holes already tapped in the head. I'm guessing excessive heat and
vibration caused the failure. I bypassed the contactor but left the OV
module in there intending to relocate the contactor. I should have
disconnected the circuit - either all in or all out.
|
I think your analysis has merit. The contactor would not live
happily mounted on the engine.
| Quote: | - gnd strap problem last fall - while starting the plane, the power
fluctuated then dropped out. I traced it to a loose ground strap. Funny, I
made all my big cables per Bob's 12 ga wire wedge solder method and all held
up great. For some reason I wanted a nice braided steel ground strap so I
bought two custom length from an aircraft place for battery to firewall and
engine block to firewall. These are the ones that failed - the crimp was
loose and the strap pulled right out. Lesson - make redundant ground
straps.
|
Or solder with confidence in your skill and powers of observation
to know that the join integrity is good . . .
| Quote: | Another lesson - I gently tug on all bat and gnd straps preflight
but the two gnd straps were neatly tie wrapped together so when I checked
them, the good one was supporting the bad one. That's both good and bad I
guess. I mention this because the incident blew some fuses and must have
sent some spikes thru the system, possibly reducing the life of the
regulator?
|
It's anybody's guess. Normally I would not expect the condition
you describe to chip away at the service life of a regulator.
| Quote: | - in-flight failure #1 - the other week on the way to SNF, radio blinks,
popping in headset, then panel goes black and engine gets quiet. Backup
switch on, engine comes back up and land at nearest. Probe around and find
battery contactor chattering, not able to keep bat and alt on main bus.
Probe around engine and panel for a couple hours, everything else looks ok
except alt OV breaker was popped (missed hint?). I assumed the main bus
disconnect sent a spike thru the system and popped the breaker. I had a
contactor fail before, made sense so I called around for one. No luck, so I
move cables to one side of contactor to bypass. Only one hour flight to SNF
so I'll find one there. Very long runup, everything looks good - off I go.
- in-flight failure #2 - 15 minutes into flight, radio starts blinking and I
start cursing. I notice aux bat volts fluctuating between 15.x and 16.x
(this is after diode drop from main bus). This is normally at 13.8 volts.
Aha! The regulator is bad! Everything goes out again. "golly, gosh darn
it" (ya right) Backup switch on, engine comes on again (whew!). Land at
nearest. Bad place to land but that's another story. I pull the alt and
get a ride to town. I went to an auto parts store and they tested it. It
failed on the tester "when the switch was on alternator but passed when it
was set to generator". They had no idea what that meant but it sounded like
a bad regulator to me. They didn't have a Suzuki Samuri alternator in stock
but said a guy up the road fixes them. Off to the guy up the road and he
tested it. "Nothing wrong with this alternator" he said. I asked to keep
testing, and he got it really hot under full load and it still worked.
Maybe under vibration or higher rpm? Dunno. Went to another auto parts
store and they ordered one - "be here in two hours". They tested it and it
passed on a third type of test stand, this one fully automated. I wanted
new anyway.
|
This is not an unusual story. It's not uncommon for folks who
sell and even overhaul things to know exactly HOW the product
OR their test equipment works. They provide a very useful function
with their ability to fix common ailments (one doesn't have too
many choices as to repairable items in alternators) but in spite
of their extensive knowledge, it's not uncommon to find that
they understand little about the alternator and even less about
any unique features of your application.
| Quote: | Got the new alt, went back and installed it, but the battery wouldn't come
up after charging so it was toast. I found the same size and replaced it.
I also removed the overvoltage circuit and removed a diode to ground on the
field line from the contactor. It's normally not good to make more than one
change at a time but I wanted to remove all in doubt and try to recreate the
problem later at home. I ran it up for a long time not feeling good that I
didn't understand exactly what happened or find and fix a hard failure.
Told the tower that I was going to keep climbing and circling for a while,
and everything seemed ok.
Made it Lakeland (after doing several laps around Lake Parker #$%(at)&
!),
couldn't find a contactor and never found anything else wrong. So it made
it to my new home after another 10 hours as-is. Everything seems fine with
the new alt, new bat and contactor bypassed (I already ordered a new master
contactor).
- is it likely for the regulator to go bad but test ok?
- would the regulator shut itself down? (someone said they do that)
- would the OV ciruit have pulled the "field" line down and caused screwy
operation because the OV contactor was not there?
- would an overvoltage toast the master contactor?
- the first main bus failure makes sense if the master contactor removed all
power, but the second time they were hard wired (stupid, yes). Would the OV
toast an RG battery that quick?
|
Yes. See:
http://www.aeroelectric.com/Pictures/Battery/Odyssey_OV/
| Quote: | Battery goes high temp and shorts?
|
Shorts under normal operating conditions are rare in RG batteries.
The failure mode that precipitated shorts in flooded batteries does
not exist for RG batteries. However, under duress, all bets are off.
Here a real $high$ battery that shorted internally and caught fire
internally:
http://www.aeroelectric.com/Pictures/Battery/Internal_Fire
. . in this case, all damage was contained within the battery
except for a tiny hole in the case. We're not sure what precipitated
the event. Too much damage to burned cell to deduce and the other
cells did not show signs of overcharge. We're thinking this was
a one-of, exceedingly rare event . . . but who knows? We may get
a surprise one day.
| Quote: | - do I replace the OV circuit and contactor? I had about 150 hours on it
with no problems using the OV circuit.
|
I'd recommend you leave it in but move the hardware off the engine.
Had it been in place and functioning you should never have seen
the high voltage readings you cited. The ov event should have
be corralled in milliseconds after onset. Now, having the
Z-24 contactor open COULD be antagonistic to your alternator's
regulator . . . but since it has already wandered off into
the weeds, you might as well put it out of it's misery and
save the rest of the airplane.
At first blush, it sounds as if you might have multiple issues
of craftsmanship in installation and wiring of components. It's
a certainty that 'loose' connections in a system under load can
mimic the load-dump stresses known to be antagonistic to alternator
regulators.
| Quote: | Happy to share my stupidity so nobody else does that, and highly recommend
simple redundant circuits that will get you home. Also happy to provide
real-world data for discussion here. In my feeble defense, this
cross-country move came up quickly with a fixed timeframe so I scrambled to
clean up details on the plane but didn't get to replacing or removing OV
stuff. The plane flew great from RI to FL after 10 hours and when it failed
I was 1000 miles from anyone I knew. If I was near home I don't think I
would have continued until it was 100% but I'm also not sure that I would
have found anything more than I did. I saved the old alt so I can try to
get it to fail (Bob - you want it?).
|
Sure. I have access to an automotive guy who knows a great deal
and wants to understand as much as he can about what he knows.
We'd be pleased to take a look at it with due diligence to
understanding and respect for the repeatable experiment.
| Quote: | It would be nice to know what happened
and improve my design. I'm 90% done with a homemade engine monitor. I have
three hall-effect current sensors in place and audio warning with data
recording. Would have been nice but I still have 90% to go on it. I think
I'll sell that project and buy a new one soon.
|
| Quote: | Gary Krysztopik
Pelican/Stratus - 175 hours
San Antonio, TX
|
You're not real far from Wichita. It might be useful for you
to fly up some weekend and we could help you comb over the system
for any potential 'gotchas' that might still be lurking. It's
exceedingly difficult to pinpoint root cause purely from
un-quantified observations. Do you have a schematic of your
system you could send?
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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