Today's Message Index:
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1. 08:43 AM - Re: OV push to test button, is there a hack for SB1B (Robert L. Nuckolls, III)
2. 01:35 PM - Re: OV push to test button, is there a hack for SB1B (Robert L. Nuckolls, III)
3. 03:06 PM - Re: OV push to test button, is there a hack for SB1B (Ken Ryan)
4. 04:42 PM - Re: OV push to test button, is there a hack for SB1B (Robert L. Nuckolls, III)
5. 05:03 PM - OV module testing (Correction) (Robert L. Nuckolls, III)
6. 06:22 PM - Re: DC clamp meter (blues750)
7. 06:41 PM - Re: Re: DC clamp meter (Gilles Thesee)
Message 1
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| Subject: | Re: OV push to test button, is there a hack for SB1B |
At 08:07 PM 5/5/2020, you wrote:
><john_s_bright@yahoo.com>
>
>Hi Bob,
>
>Seems like a nice feature that SB1B has an annunciatior light that it has
>come online but unlike LR3C there is not an OV PTT... is there a way to
>hack into SB1B for an OV PTT button?
That feature was included in the first iterations
of the LR series regulators but never 'implemented'
in the installation instructions. I seem to recall
the recommendation was that it be manually checked
at intervals . . . like oil changes or annuals.
The ov protection system in all B&C (and AEC)
products are 'passive monitors'. They experience
miniscul operational stresses. Hence, under mil-hndbk-217
reliability studies, the device suffers no practical
service life limits.
It was decided that periodic ptt or 'live'
verification of functionality was more than
sufficient for continued airworthiness. If
you never tested the thing, you risk for
failure to perform is exceedingly low.
Bob . . .
Message 2
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| Subject: | Re: OV push to test button, is there a hack for |
SB1B
> If you never tested the thing, you risk for
> failure to perform is exceedingly low.
A follow up: I've worked on dozens of
TC aircraft. I forget how many products
I've designed and qualified into OV
management systems. Not one has ever
included or required a press-to-test
feature.
The very first OV management module I designed
went into the single engine Cessnas back
in the 70's. This was a three-wire potted
assembly that was ultimately manufactured
by the tens of thousands. Worked good, lasted
a long time.
Bob . . .
Message 3
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| Subject: | Re: OV push to test button, is there a hack for SB1B |
Bob, you say "they worked good and lasted a long time." What was the
eventual failure mode? How did one know when they did fail?
On Wed, May 6, 2020 at 12:42 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> If you never tested the thing, you risk for
> failure to perform is exceedingly low.
>
>
> A follow up: I've worked on dozens of
> TC aircraft. I forget how many products
> I've designed and qualified into OV
> management systems. Not one has ever
> included or required a press-to-test
> feature.
>
> The very first OV management module I designed
> went into the single engine Cessnas back
> in the 70's. This was a three-wire potted
> assembly that was ultimately manufactured
> by the tens of thousands. Worked good, lasted
> a long time.
>
>
> Bob . . .
>
Message 4
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| Subject: | Re: OV push to test button, is there a hack for SB1B |
At 05:00 PM 5/6/2020, you wrote:
>Bob, you say "they worked good and lasted a long time." What was the
>eventual failure mode? How did one know when they did fail?
Good question. I know there were spares
stocked and shipped over the years but
I'm not privy to the failure modes.
I do know that they were vulnerable
to shorts on the output lead which
would cause them to open up.
Did a quick search on
cessna single engine over voltage
Didn't find any postings on failures
Did find this service bulletin from
1972 that added an external capacitor
to preclude nuisance trips.
https://tinyurl.com/ybojxucx
That was the first ov protection system
ever installed on the Pawnee Plant
Cessnas. The term "over voltage"
was not a well quantified event
in terms of cause, effect and timing.
The protocol then was to shut down
'quickly' i.e. in 50 to 100 mS after
detection of a condition. The
circuitry was a bit sensitive to
otherwise normal transients on the bus.
Nowadays, the static trip points are
generally lower (16v) which must
sustain for 500 milliseconds or so.
If the transient ends before time-out,
the timer resets.
This protocol is still well inside
qualification test limits (20v for 1
second; 40v for 100 mS) and virtually
trip-free.
I was well out of the loop on that
line of aircraft after about 1975
so I have no first-hand knowledge
of any failure modes.
Installation instructions for the CBOVM
module I used to sell describes
a recommended yearly test for functionality.
https://tinyurl.com/ybojxucx
Bob . . .
Message 5
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| Subject: | OV module testing (Correction) |
> Installation instructions for the CBOVM
> module I used to sell describes
> a recommended yearly test for functionality.
LINK CORRECTION
> https://tinyurl.com/joeopsn
Bob . . .
Message 6
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| Subject: | Re: DC clamp meter |
Bob, I cannot imagine how to go about doing the voltmeter method with an electrical
dependent engine running...hence my plan...
Once batteries are charged my normal inflight electrical load is approx 20 amps
when not using pitot heat. This is consistent with my predicted load analysis.
I have a dual ECU electrically dependent engine which requires approx 13 amps
to keep me flying (derived from the engine manufacturer's chart). By shutting
down one ECU and a few other items I can safely continue flight and recover
to an airfield or suitable airstrip (day VMC) with about the same electrical
load of 13 amps.
My plan was to test each battery separately with a 15 amp load (hence the need
for a DC clamp meter) and see how long I got energy from the battery before the
voltages dropped off below 10V (ECU/engine quitting time) or the EarthX BMS
shuts down due to over discharge. As I've already got a few flying seasons on
the batteries, I can only compare my discharge amp-hrs to the battery specs and
then use the 80% factor for battery changeout.
Does this sound like a reasonable way to do a meaningful capacity check? It does
to me, but what the heck may I be missing? Seems like the hardest thing to
do will be rigging up the resistive dummy load (open for ideas) so I can consistently
do the load test per battery year to year.
Thanks again for the insight and ideas!!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496241#496241
Message 7
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| Subject: | Re: DC clamp meter |
Le 07/05/2020 03:17, blues750 a crit:
>
> Bob, I cannot imagine how to go about doing the voltmeter method with an electrical
dependent engine running...hence my plan...
>
> Once batteries are charged my normal inflight electrical load is approx 20 amps
when not using pitot heat. This is consistent with my predicted load analysis.
I have a dual ECU electrically dependent engine which requires approx 13 amps
to keep me flying (derived from the engine manufacturer's chart).
Performing actual voltage and current measurements at cruise power would
be interesting.
It can safely be done on the ground.
FWIW,
--
Best regards,
Gilles
http://contrails.free.fr
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