Today's Message Index:
----------------------
1. 03:48 AM - The value of FMEA (Robert L. Nuckolls, III)
2. 04:54 AM - Re: Re: Too many Circuit breakers.... (Robert L. Nuckolls, III)
3. 06:37 AM - Re: Re: Too many Circuit breakers.... (Charlie England)
4. 09:00 AM - Re: Re: Too many Circuit breakers.... (Robert L. Nuckolls, III)
5. 10:49 AM - Re: The value of FMEA (user9253)
6. 11:08 AM - Re: Re: Too many Circuit breakers.... (Robert L. Nuckolls, III)
7. 11:11 AM - Re: Re: Too many Circuit breakers.... (Robert L. Nuckolls, III)
8. 11:20 AM - Re: Re: The value of FMEA (Robert L. Nuckolls, III)
9. 12:45 PM - Re: Re: Too many Circuit breakers.... (Charlie England)
10. 02:00 PM - Re: Re: Too many Circuit breakers.... (Sebastien S)
11. 04:56 PM - Re: Re: Too many Circuit breakers.... (Charlie England)
Message 1
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| Subject: | The value of FMEA |
I'll encourage everyone to view this video on youtube.
It's an excellent demonstration of competent flight testing
but a sobering example of hazards to accomplish
a competent FMEA.
Electrical system details are offered at about 44
minutes into the video.
https://youtu.be/4PHTVTw_Y2A
Failure of the engine in this story reminds me of
the LancAir IVP accident where ignition system
was designed to fail.
We don't have enough wiring detail to do an
after action debrief on this incident but I
hope it's strong incentive to get our homework
done before we take the active.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 2
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| Subject: | Re: Too many Circuit breakers.... |
At 02:54 PM 5/7/2022, you wrote:
>
>Alright - looks like I might have some breakers to sell.
>What's an ideal fuse block model for the ATC fuses. Any good brand
>or model suggested? I'm scared of some of the stuff I see.
>
>
>nuckolls.bob(at)aeroelect wrote:
> >
> >
> >
> > > The only thing on that list that I'd put on a breaker is the
> alternator field supply.
> >
> > But even this is not necessary if you have something
> > other than crowbar ov management.
> >
>
>Do I read this as: Since I've got the LR3D I don't need a breaker
>for the alternator even though BandC calls for one? Just put a fuse
>where they call for breakers?
NO! The B&C products FEATURE crowbar ov
management . . . a system that expects
to open the alternator field feeder
during an ov condition. That protection
CAN be a fuse but then you have no
convenient way to reset in case of a rare
but not zero probability of a nuisance
trip.
This is why you see a breaker in the field
supply feeder in all of the z-figures
when a B&C alternator controller -OR-
crowbar ov module is incorporated. This
is recommended whether or not you choose
to use fuse blocks.
>My ignitions - 2 Lightspeeds - What's the best protection for the
>wires running from the panel to the back seat? I still need switches
>to turn them on or off, might I be better off with a W31 Breaker
>switch and that be it, or is the complexity of the W31 a risk? Part
>of me would like to be able to reset it if the engine goes quiet and
>I'm out of other options. Though 2 dying at once seems highly improbable.
You have pretty much answered your own
question. Review architecture and series
of events that ended up trashing a nice
LanceAir IVP a few years ago.
http://aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/
My post of last night suggests reviewing
an accident that was probably a result
of poor electrical system architecture.
Being able to reset blown protection in flight
is WAayyy down on the list of priorities
for pilots. Electro-whizzies go belly-up
for many MORE reasons than a fault that opens
a breaker. When a breaker does open, it indicates
(1) a DESIGN problem (see youtube narrative on
P51 replica crash) or (2) something is broke (and
resetting the breaker is not going to fix it).
Judicious exercise of failure mode effects analysis
leads to failure tolerant selection of appliances
and architecture powering those appliances thus
mitigating design issues. This leaves only
a gross overload events for which a re-setable
feeder protection is of no value.
Besides, if something stops working in flight,
one is well advised to get on the ground before
trading your pilot's hat for a mechanic's hat.
>Radio Master (Currently a W31 breaker switch) - people seem to be
>moving away from avionics masters - is that really the best case these days?
I was at Cessna circa 1965 when the avionics
master was conceived . . . for the wrong reasons.
Nonetheless, the concept flourished in virtually
all GA aircraft in spite of no demonstrable risks
to avionics and in spite of environmental qualification
testing requiring that avionics be immune to
normal and expected electrical stresses in
the ship's power generation system.
>Let the Garmin and Avidyne stuff suffer the brown-out during start
>and reboot? Or go around twisting knobs off and on? I'd like to be
>able to get rid of as much load during start. Normally, only things
>I have is LED Nav lights and the engine monitor. (Engine monitor
>only needs ~4 volts to run)
Load shedding for the purposes of relieving
stress on battery during start is a thing of
yesteryear. A panel full of radios in a 1965
C172 was a significant load on a soggy
battery suffering the abuse of starter motor
adapted from farm tractors.
Today's avionics draw a small fraction of that
energy. Batteries are more robust. Starters
get the fan fired up much faster. Load shedding
for start assist is an idea that has pretty
much evaporated.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 3
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| Subject: | Re: Too many Circuit breakers.... |
snipped
> Let the Garmin and Avidyne stuff suffer the brown-out during start and
> reboot? Or go around twisting knobs off and on? I'd like to be able to get
> rid of as much load during start. Normally, only things I have is LED Nav
> lights and the engine monitor. (Engine monitor only needs ~4 volts to run)
>
>
> Load shedding for the purposes of relieving
> stress on battery during start is a thing of
> yesteryear. A panel full of radios in a 1965
> C172 was a significant load on a soggy
> battery suffering the abuse of starter motor
> adapted from farm tractors.
>
> Today's avionics draw a small fraction of that
> energy. Batteries are more robust. Starters
> get the fan fired up much faster. Load shedding
> for start assist is an idea that has pretty
> much evaporated.
>
> Bob . . .
>
These days, with EFIS equipment, it's more about inconvenience than load
shedding. Some EFIS products take 2-3 minutes to boot and
self-calibrate, and I've seen them 'lock up' during engine start. If they
reboot due to brownout at engine start, that 3 minutes feels like half the
planned flight time. ;-) If they lock up, then you typically have to power
down the whole panel to get them to restart.
Message 4
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| Subject: | Re: Too many Circuit breakers.... |
>Because the Avidyne IFD has dual power inputs that are diode or'd,
>I'll feed one side from the Avionics and the other from the
>Essential bus. Other items don't so I'll put two schottky diodes in
>to prevent backfeeding.
Are you exploiting any of the z-figures? Two
diodes should never be needed.
It would be exceedingly useful if you would sketch
your distribution plan and share it on the
List. It's that ol' "Picture worth 10,000
words thingy".
> Or, what 20A schottky diode is recommended that can support my
> whole essential bus? Can't see where I can buy the AEC9001-1.
Essential or endurance bus? And do you KNOW
what the total load on that bus is?
The 9001 was discontinued because it was a bad
idea. Over the years we got wrapped tightly around
the 'save energy' axle . . . and Schottky
diodes planted the seed of some poor decisions.
For the past 25 years or so, I've showcased
the bridge rectifier assembly as a ready-off-the-
shelf solution to diode isolation in our
distribution systems. Inexpensive, dozens
of sources, easy wiring (fast-ons), easy
mounting (one screw in the middle), zero
risk for shorting (no insulators required).
Down side? A few tenths of a volt greater
voltage drop. Okay, what are the OBSERVABLE
benefits for eliminating that extra drop?
ZERO
So what is the return on investment for fiddling
with that gold-plated solution to lowering
voltage drop? I suggest its on a par with
going lithium just to save weight. There are
no benefits to either (1) saving of a few tenths
of a volt -or- (2) a few pounds in an airplane.
Both are more expensive and fussier to
implement/maintain with performance improvements
difficult to measure and impossible to demonstrate.
>One ignition will have a 3 position switch - middle position will go
>to a small standby
>battery for power in case the world is coming undone.
Do you not plan to maintain the ship's battery
in an airworthy condition? I.e. periodic cap-checks
to maintain design goals? If not, then what is
your game plan for maintaining a SECOND battery
in an airworthy condition?
Over the years, we've studied the occasional dark-n-stormy-
night narrative from one of aviation journals. A common
characteristic of those stories is that they seldom,
if ever, describe shortcomings in either selection of
hardware or preventative maintenance that would have
kept that event from occurring. They ALWAYS conjure
up a litany of advice and cautions for how to deal
with that situation should it happen AGAIN to you!
Failure tolerant design and maintenance strives to
prevent any failure from becoming a dark-n-stormy
night story over beers . . . or an obituary.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 5
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| Subject: | Re: The value of FMEA |
If the accident aircraft had been wired per Z-101, the engine would not have quit
and electrical power to the main
power bus would not have been lost. Of course the plane still would have crashed
because the landing gear failed.
If the 30 amp circuit breaker had not been installed to protect the main power
bus, then the main power
bus would not have lost electrical power. A fuselink would have been a better
choice than a circuit breaker.
Most small planes do not have any short circuit protection for the main bus other
than the battery contactor.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=506706#506706
Message 6
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| Subject: | Re: Too many Circuit breakers.... |
>
>
>These days, with EFIS equipment, it's more about
>inconvenience than load shedding. Some EFIS
>products take 2-3 minutes to boot and
>self-calibrate,=C2 and I've seen them 'lock up'
>during engine start. If they reboot due to
>brownout at engine start, that 3 minutes feels
>like half the planned flight time. ;-)=C2 If they
>lock up, then you typically have to power down
>the whole panel to get them to restart.=C2
Brown-out mitigation is indicated for sure
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 7
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| Subject: | Re: Too many Circuit breakers.... |
>These days, with EFIS equipment, it's more about
>inconvenience than load shedding. Some EFIS
>products take 2-3 minutes to boot and
>self-calibrate,=C2 and I've seen them 'lock up'
>during engine start. If they reboot due to
>brownout at engine start, that 3 minutes feels
>like half the planned flight time. ;-)=C2 If they
>lock up, then you typically have to power down
>the whole panel to get them to restart.=C2
If I were qualifying an electro-whizzy for TC
aircraft, DO160 power input tests have to demonstrate
timely fault free recovery under various
power input conditions. I would not be able to
put such devices on a TC aircraft.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 8
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| Subject: | Re: The value of FMEA |
At 12:46 PM 5/9/2022, you wrote:
>
>If the accident aircraft had been wired per Z-101, the engine would
>not have quit and electrical power to the main
>power bus would not have been lost. Of course the plane still would
>have crashed because the landing gear failed.
>If the 30 amp circuit breaker had not been installed to protect the
>main power bus, then the main power
>bus would not have lost electrical power. A fuselink would have
>been a better choice than a circuit breaker.
>Most small planes do not have any short circuit protection for the
>main bus other than the battery contactor.
Precisely. Any circuit protection upstream of
dedicated feeder protection should have been
ROBUST . . . like a current limiter. It would
be interesting to see the gear control/annunciation
logic. I think I would have preferred to shut the
pump off based on pressure . . . not limit switches.
I would power the hydraulic system thru a current
limiter at the battery contactor. Engine
critical devices need their own, dedicated
bus structure with SHORT access to the
well maintained battery.
Do I recall that he experienced engine stoppage
earlier in the flight as well?
Having a properly responding engine might
have mitigated the outcome if he had
more options for energy management during
approach/touchdown . . . but yeah
that gear collapse was a game changer.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 9
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| Subject: | Re: Too many Circuit breakers.... |
On Mon, May 9, 2022 at 2:29 PM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> These days, with EFIS equipment, it's more about inconvenience than load
> shedding. Some EFIS products take 2-3 minutes to boot and self-calibrate,
=C3=82
> and I've seen them 'lock up' during engine start. If they reboot due to
> brownout at engine start, that 3 minutes feels like half the planned flig
ht
> time. ;-)=C3=82 If they lock up, then you typically have to power down t
he
> whole panel to get them to restart.=C3=82
>
>
> If I were qualifying an electro-whizzy for TC
> aircraft, DO160 power input tests have to demonstrate
> timely fault free recovery under various
> power input conditions. I would not be able to
> put such devices on a TC aircraft.
>
>
> I'll bet you couldn't sell a $100,000 certified EFIS array for $5,000 (or
under $2K on the used market, either. ;-)
I doubt that any of the newer exp models have the same 'lockup' issues, but
it can happen with some of the near-prehistoric ones (pre-turn of the
century). But once up and running, they're about as solid as the $100,000
certified models.
Many homebuilt a/c could never pass FAA certification either, but they
perform their missions better than any certified a/c. We play the cards
we're dealt (or can afford to purchase).
Charlie
Message 10
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| Subject: | Re: Too many Circuit breakers.... |
One of the rockets I fly has a current production GRT which has to be left o
ff for engine start or it goes dark and locks up. Once the engine starts we q
uickly turn it on and check that the red idiot light is out. If it=99s
not then we don=99t know what the problem is but since oil pressure i
s a possibility I would just shut it down. Not ideal.
> On May 9, 2022, at 13:46, Charlie England <ceengland7@gmail.com> wrote:
>
> =EF=BB
>
>
>> On Mon, May 9, 2022 at 2:29 PM Robert L. Nuckolls, III <nuckolls.bob@aero
electric.com> wrote:
>>> These days, with EFIS equipment, it's more about inconvenience than load
shedding. Some EFIS products take 2-3 minutes to boot and self-calibrate,=C3
=82 and I've seen them 'lock up' during engine start. If they reboot due to b
rownout at engine start, that 3 minutes feels like half the planned flight t
ime. ;-)=C3=82 If they lock up, then you typically have to power down the w
hole panel to get them to restart.=C3=82
>>
>> If I were qualifying an electro-whizzy for TC
>> aircraft, DO160 power input tests have to demonstrate
>> timely fault free recovery under various
>> power input conditions. I would not be able to
>> put such devices on a TC aircraft.
>>
>>
> I'll bet you couldn't sell a $100,000 certified EFIS array for $5,000 (or u
nder $2K on the used market, either. ;-)
>
> I doubt that any of the newer exp models have the same 'lockup' issues, bu
t it can happen with some of the near-prehistoric ones (pre-turn of the cent
ury). But once up and running, they're about as solid as the $100,000 certif
ied models.
>
> Many homebuilt a/c could never pass FAA certification either, but they per
form their missions better than any certified a/c. We play the cards we're d
ealt (or can afford to purchase).
>
> Charlie
>
Message 11
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| Subject: | Re: Too many Circuit breakers.... |
snipped
> Charlie, What's your brown-out booster look like?
>
> Getting real close! Thanks!
>
> Andy
Sorry for the delay in answering this. There are lots of options out
there. I picked one that had both a low enough input voltage, and plenty
of 'headroom' on the higher voltage end, simply for better survivability.
This is the one I used (with a few spares for future projects):
https://smile.amazon.com/gp/product/B07XG323G8/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I set it up on the bench with an adjustable bench supply to maintain
around 11V with an 8V supply voltage (the little blue block with a slot
head screw is the adjustment). The old GRT EFIS had multiple
diode-isolated power inputs, so I simply tapped the EFIS' primary power
wire & ground to power the boost converter, and fed the converter's
output to one of the spare power inputs on the EFIS. They're pretty
small (~1" x 2.5") so I just drilled some ventilation holes in a plastic
prescription bottle & used it for a case. the whole affair was basically
just a bulge in the harness going to the EFIS.
On the particular units I received, the output ground is common to the
input ground, so I only needed one output connection to the EFIS. Note
that some boost converters may actually isolate the grounds, so you need
to check for that, and also check to be sure that tying them together
(via the ground in the plane and the EFIS) won't be an issue for the
converter.
Also note that this particular unit is limited to 3 amps. It will
probably handle most single EFIS units, but I wouldn't think powering
more than one with it would be a good idea. On the other hand, you do
get extras for other stuff. ;-)
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