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nuckolls.bob(at)aeroelect
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 Posted: Sat Jan 11, 2014 7:13 am Post subject: Z-12 Essential Bus Questions |
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At 04:24 PM 1/10/2014, you wrote:
| Quote: | Hello Bob N and anyone else with thoughts on this,
We’re working to implement your Z-12 power
grid/distribution architecture (Prime Alt,
Standby Alt, Single Battery, E-Bus) in our
Lancair Legacy. I’m struggling a bit with
whether or not to have an Essential Bus. I
don’t see it as saving that much time if the
alternators go down to load shed with one switch
vs. just powering down some boxes one by one. I
see the main advantage of the Essential Bus is
having a way to get power to critical
boxes/functions even if the two alternators and the battery contactor fails.
What’s complicating my thinking on this
architecture is my desire for an Avionics
Bus. If I remember right, you’re not a fan of
Avionics Buses. My reasoning for one is that we
have an EFIS system with no dedicated engine
instruments. So, for engine start we’ll have
the minimum EFIS components on to monitor the
engine health and not expose any other avionics
to the engine start voltage drop and potential
unnecessary power cycling. One key box I’d like
to protect, as an example, is the $15,000 Garmin
GTN 750 – of course there are others...
So then when I think about what needs to be on
the E-Bus, a bunch of avionics seems to belong
there – which would expose them to the risk of
the engine start power cycling… It seems like
I’d need an E-Bus off the Main Bus and the Avionics Bus…?
When I consider the low probability of both
alternators and the battery contactor going down
at the same time, I wonder if it’s worth the complication.
Would appreciate anyone’s thoughts on
this. Below is an excerpt from power grid hybrid schematic.
Thanks,
Valin Thorn
Lancair Legacy Project
Boulder, Colorado
|
You've expressed concerns for "unnecessary power cycling", "voltage drops",
etc. Is it written anywhere that such stresses are to be avoided . . .
particularly by the folks who manufactured and qualified the hardware?
After all, they KNEW it was intended for use in an airplane. They
were obligated to test to all the nasties that DO-160 would throw
at it. If there were things that you should avoid . . . or adopt as
specialized operating practice for their device . . . it seems that
such words would be included in the installation or operating literature.
I am not a fan of avionics busses because they were ill-conceived
in the first place and are certainly unnecessary given the rigorous
testing required to get a device onto a TC airplane.
The Essential Bus is really an ENDURANCE bus . . . and yes,
very unlikely to be needed to back up dual alternator failures.
But it DOES offer a way to power up a minimal suite of electro-whizzies
during pre-flight to get the ATIS and clearance delivery. Some people
put a "clearance delivery" switch feature in the power to the comm
radio for this purpose . . . but as long as you're going to add one
more switch, it might just as well be the E-Bus Alt Feed switch.
I would encourage you to produce drawings not unlike those found
in the back of the service manuals for a Beech, Cessna, Piper
or those found on the aeroelectric.com website. Wirebook schematics are
a language intended to convey meaning . . . you've spent a significant
amount of time and effort to produce the pictograms . . . and while
they are accurate, they are the linguistic equivalent of ebonics
or some other variant of the spoken word.
The schematic processes cited above will convey the meat of your
meaning in a heartbeat. The pictograms take some study and
might give some folks pause to wonder if they should bother.
Bob . . .
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Valin
Joined: 13 Apr 2010
Posts: 31
Location: Colorado
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| Posted: Sat Jan 11, 2014 9:40 am Post subject: Z-12 Essential Bus Questions |
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|
Thanks Bob. I read your recent, excellent article on DO-160 testing. With EAB airplanes, can we count on all the devices installed having seen the same testing? I’m planning on a bunch of Garmin’s experimental avionics offerings and I’m not sure those boxes see the same testing as their certified hardware. I’ve Googled it a few times but can’t find anything. I need to ask Garmin’s Team X about it. So that’s why I’m a bit shy to risk putting all the avionics through engine start power cycling.
Good point about the every flight usefulness of at least getting a radio up without bring all your avionics up – so yes, why not add a few other essentials and provide a path around the battery contactor as well...
Sorry about my “pictogram schematics” sometimes requiring more study than a basic schematic. The power grid is a bad example of the benefits in my wiring drawings. I have about 10 drawing layers covering the various systems where the wiring schematic is laid out in a kind of topology of the airplane – a top down view of the airplane in cartoon form. It helps me visualize where components and wires need to be within the airplane and where connectors might be most useful. On these drawings are also included the basic wiring schematic and other key info related to that system like pin outs for connectors, part numbers, etc.. The power grid example in my email was an excerpt from its overall page and didn’t include the ancillary stuff. Working them up helps me get my novice head around the problems involved and collect a lot of key related data in one place.
Thanks again Bob and everyone for your help.
Valin
--
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Mauledriver(at)nc.rr.com
Guest
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| Posted: Sat Jan 11, 2014 9:49 am Post subject: Z-12 Essential Bus Questions |
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On 1/11/2014 10:12 AM, Robert L. Nuckolls, III wrote:
| Quote: |
<nuckolls.bob(at)aeroelectric.com>
At 04:24 PM 1/10/2014, you wrote:
> Hello Bob N and anyone else with thoughts on this,
>
> We’re working to implement your Z-12 power grid/distribution
> architecture (Prime Alt, Standby Alt, Single Battery, E-Bus) in our
> Lancair Legacy. I’m struggling a bit with whether or not to have an
> Essential Bus. I don’t see it as saving that much time if the
> alternators go down to load shed with one switch vs. just powering
> down some boxes one by one. I see the main advantage of the Essential
> Bus is having a way to get power to critical boxes/functions even if
> the two alternators and the battery contactor fails.
>
> What’s complicating my thinking on this architecture is my desire for
> an Avionics Bus. If I remember right, you’re not a fan of Avionics
> Buses. My reasoning for one is that we have an EFIS system with no
> dedicated engine instruments. So, for engine start we’ll have the
> minimum EFIS components on to monitor the engine health and not
> expose any other avionics to the engine start voltage drop and
> potential unnecessary power cycling. One key box I’d like to protect,
> as an example, is the $15,000 Garmin GTN 750 – of course there are
> others...
>
> So then when I think about what needs to be on the E-Bus, a bunch of
> avionics seems to belong there – which would expose them to the risk
> of the engine start power cycling… It seems like I’d need an E-Bus
> off the Main Bus and the Avionics Bus…?
>
> When I consider the low probability of both alternators and the
> battery contactor going down at the same time, I wonder if it’s worth
> the complication.
>
> Would appreciate anyone’s thoughts on this. Below is an excerpt from
> power grid hybrid schematic.
>
> Thanks,
>
> Valin Thorn
> Lancair Legacy Project
> Boulder, Colorado
Valiln, I had some similar concerns with my RV10 panel. I built a Z-14
|
(dual batt, dual alt, dual bus - diagram attached) with an avionics
panel containing a full complement of electro whiz-bangs. I had no
avionics bus or additional power switching for any devices that did not
include such a switch. Of note, I have 3 GRT/HX EFISs that power up with
the master switch.
| Quote: |
You've expressed concerns for "unnecessary power cycling", "voltage
drops",
etc. Is it written anywhere that such stresses are to be avoided . . .
particularly by the folks who manufactured and qualified the hardware?
GRT does not document any concerns about "unnecessary power cycling" or
|
"voltage drops". However, in conversations with GRT I was warned that
interruption of the EFIS boot procedure may result in problems. Nothing
definitive beyond that. However, before hearing this, I did expose the 3
units to a number of interrupted boot sequences. And I did have to
return the unit that experienced most of the interrupts for service
during this period though no connection with the interrupts was
necessarily made. (I'd add that I am many software updates past this
experience and any boot/power issues may have been addressed.)
| Quote: |
After all, they KNEW it was intended for use in an airplane. They
were obligated to test to all the nasties that DO-160 would throw
at it. If there were things that you should avoid . . . or adopt as
specialized operating practice for their device . . . it seems that
such words would be included in the installation or operating literature.
Agreed. The procedure I adopted was to insure that the 15sec+ boot
|
procedure on all 3 units be complete before engine start. Seems obvious
since a display is required for engine parameter display but early on I
did expose 1 unit to cycling during the start because 1 unit would
always lag behind the other 2 due to configuration differences... and I
was unnecessarily impatient.
My EFIS units were still occasionally being cycled during engine start
due to some issues unrelated to the discussion here (thanks to Bob and
GRT for working these thru with me). During the course of getting these
issues under control, I added a TCW Technologies Intelligent Power
Stabilizer (IPS) to my installation. It was connected to some unused
backup power inputs on the EFIS units. Now, no matter how much I 'abuse'
my system, I can rely on my EFIS units to stay up during engine start.
What do I mean by 'abuse'? Running the EFIS units and some other
avionics for an extended period on battery power only and then
attempting a start of a cold engine, on a cold day, and perhaps
forgetting to tie the buses and their batteries together for the start.
At this point I think the IPS is unneeded, but for a period of time, it
stopped some inadvertent power cycling of the units. You might consider
one of these units for your installation to ease your concerns. I know
that some Garmin units have backup power inputs in which case the
addition of an IPS is similar to simply adding a backup battery that you
never need to charge. It will also work with units that only have a
single power input.
| Quote: |
I am not a fan of avionics busses because they were ill-conceived
in the first place and are certainly unnecessary given the rigorous
testing required to get a device onto a TC airplane.
The Essential Bus is really an ENDURANCE bus . . . and yes,
very unlikely to be needed to back up dual alternator failures.
But it DOES offer a way to power up a minimal suite of electro-whizzies
during pre-flight to get the ATIS and clearance delivery. Some people
put a "clearance delivery" switch feature in the power to the comm
radio for this purpose . . . but as long as you're going to add one
more switch, it might just as well be the E-Bus Alt Feed switch.
I would encourage you to produce drawings not unlike those found
in the back of the service manuals for a Beech, Cessna, Piper
or those found on the aeroelectric.com website. Wirebook schematics are
a language intended to convey meaning . . . you've spent a significant
amount of time and effort to produce the pictograms . . . and while
they are accurate, they are the linguistic equivalent of ebonics
or some other variant of the spoken word.
This electrically challenged builder found the drawings clear and easy
|
to read.... but then I'm probably fluent in ebonics.
| Quote: | The schematic processes cited above will convey the meat of your
meaning in a heartbeat. The pictograms take some study and
might give some folks pause to wonder if they should bother.
Bob . . .
-----
No virus found in this message.
Checked by AVG - www.avg.com
|
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Mon Jan 13, 2014 6:37 am Post subject: Z-12 Essential Bus Questions |
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|
At 11:39 AM 1/11/2014, you wrote:
Thanks Bob. I read your recent, excellent
article on DO-160 testing. With EAB airplanes,
can we count on all the devices installed having
seen the same testing? I’m planning on a bunch
of Garmin’s experimental avionics offerings and
I’m not sure those boxes see the same testing as
their certified hardware. I’ve Googled it a few
times but can’t find anything. I need to ask
Garmin’s Team X about it. So that’s why I’m a
bit shy to risk putting all the avionics through engine start power cycling.
DO-160 isn't something that people shy away from
to be complied with only when mandated by the
customer . . . or the government.
It's design guidance that says, "If you want your
product to perform as advertised in the proposed
application (in this case, airplanes) then expect
to experience the following kinds of stresses.
The prudent designer of electro-whizzies for
any market has an intense interest in KNOWING
the nature source and magnitude of upsetting
stresses to their product . . . putting
an admonition into the operating manual to
"turn off during engine cranking" is a sad
anomaly that grew out of a knee-jerk reaction
to a spate of failures in solid state avionics
about 50 years ago. It went uncorrected for
decades after the lights of understanding came
on.
Garmin, nor anyone else I know, has a dual-path
development philosophy that says, "Do all the
good testing on products for TC aircraft and
we can let the OBAM market slide."
Good point about the every flight usefulness of
at least getting a radio up without bring all
your avionics up – so yes, why not add a few
other essentials and provide a path around the battery contactor as well...
Sorry about my “pictogram schematics” sometimes
requiring more study than a basic schematic. The
power grid is a bad example of the benefits in my
wiring drawings. I have about 10 drawing layers
covering the various systems where the wiring
schematic is laid out in a kind of topology of
the airplane – a top down view of the airplane in
cartoon form. It helps me visualize where
components and wires need to be within the
airplane and where connectors might be most
useful. On these drawings are also included the
basic wiring schematic and other key info related
to that system like pin outs for connectors, part
numbers, etc.. The power grid example in my
email was an excerpt from its overall page and
didn’t include the ancillary stuff. Working them
up helps me get my novice head around the
problems involved and collect a lot of key related data in one place.
Understand. It's a powerful visualization tool for
assisting in your understanding and planning. But
its a variant on the language common to the
vast majority of practitioners which impedes
the rapid and accurate transfer of functional
understanding to others.
Bob . . .
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nuckolls.bob(at)aeroelect
Guest
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| Posted: Thu Jan 16, 2014 3:11 pm Post subject: Z-12 Essential Bus Questions |
|
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At 11:39 AM 1/11/2014, you wrote:
| Quote: | Thanks Bob. I read your recent, excellent article on DO-160
testing. With EAB airplanes, can we count on all the devices
installed having seen the same testing? I'm planning on a bunch of
Garmin's experimental avionics offerings and I'm not sure those
boxes see the same testing as their certified hardware. I've
Googled it a few times but can't find anything. I need to ask
Garmin's Team X about it. So that's why I'm a bit shy to risk
putting all the avionics through engine start power cycling.
|
Garmin doesn't have a dual-path set of products.
Everything they build for the panel has roots
in TC aircraft. DO-160 has become the 'design
bible' for any/all devices attached to a vehicular
DC power system. Except for issues of lightning
strike, gizmos that go into cars and trucks are
just as vulnerable to 'gremlins' as the
stuff that goes onto airplanes.
Garmin's "experimental specific" products are
essentially identical to their TC counterparts.
Bob . . .
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