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nuckolls.bob(at)aeroelect
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 Posted: Tue Mar 31, 2020 6:50 pm Post subject: Z11 "Generic Electrical system" with Dual Electron |
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At 08:52 PM 3/31/2020, you wrote:
| Quote: | | Quote: | | The Z11 digram titled “Generic Light Aircraft Electrical Systemâ€Âť is my favorite. |
e.
| Quote: | But the Dual Electronic Ignition needs are special. I called Surefly and they
agreed that prudence demands I install a dedicated battery for each ignition module. |
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Absolutely not recommended. All due respect to
Surefly, they are not systems integrators nor
should they attempt to become so without adding
a butt-load of tribal knowledge in the aircraft
arts. They have reason to worry, 'deprive our
pride and joy product(s) of energy and your
engine stops'. It is sufficient to make that
assertion and leave it at that.
Your task then is to PROVIDE failure-tolerant
power sources to critical equipment such that
no single failure puts the airframe (and by
extension it's occupants) at risk.
| Quote: | | Quote: | Further guidance from the Ignition Supplier
-Use a hefty diode to the Aux Batt to reliably protect it from back feeding
-Monitor the Voltage to the Aux Batt.
-Size of Aux Battery can be small, just so its duration exceeds the fuel duration. 8 amp hour?
Some here might be interested in electrical needs of a single ignition module.
-Required Voltage = 8-30V
-Amp draw = 0.7A +/- 0.2A at 2700 RPM
-Permanently connect Power to the + Batt terminal OR the Master Solenoid battery + input.
-Use 14AWG and a 10A fuse or CB.
-When the Ignition is placed in Standby mode (turned off) by grounding the P-lead, it draws less than 1ma. |
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Good data . . . EXACTLY what is their DUTY
to supply such that good decisions can be
made by the systems integration individual
(or team) to provide an FMEA friendly
architecture and operating philosophy
that (1) minimizes risk and (2) minimizes
cost of ownership. Adding backup batteries
NEVER reduces cost. Further, if a backup
battery is really necessary, then there's
strong probability that something is
seriously wrong with the basic architecture.
The premise behind this idea is that airplanes
have a family of devices presenting various levels
of criticality for comfortable termination
of flight. So you have dual electronic
ignition? Fine . . . are you comfortable
launching into the blue not having offered
the rest of your electro-whizzies the same
courtesies as your ignition systems? If not,
the does it not stand to reason that if
the rest of your 'critical' systems are
happy, so too will be your ignition systems?
The optimal answer is 'fix the architecture'
and leave the batteries on the dealer's shelves.
| Quote: | | Quote: | So, I'm proposing a Z11 system with one ignition wired directly to a normal size Main Battery, and the second ignition wired directly to a small single purpose Aux Battery.
Although Bob’s Book has a Dual Batt diagram, In the spirit of simplicity I didn't use a solenoid for the Aux Battery, I protect the aux battery with a diode, and I will monitor the voltage of the Aux battery. |
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| Quote: |
What are your thoughts? |
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Have you considered the fledgling architecture posted
here on the list a few weeks back . . . See
https://tinyurl.com/qnzenca
Here we've shown an 'engine bus' that enjoys
dual feedpaths such that no single failure
of power generation/storage sources will
bring down that bus.
If that assertion is in error, let's deduce
root cause and fix it. I'm not suggesting
that a 'standby battery' would never be
the elegant mitigation of an identified
failure mode . . . but that is the key
word . . . IDENTIFIED.
Perhaps it is your project that offers a
pathway to illuminating a condition that
begs 'fixing'.
There's a particular project manager at
Hawker-Beech who still figures in my
dreams wherein I can see him peering at
me over his reading glasses and asserting:
"Nuckolls, CONVINCE me that this system's
certification fortunes hinge on the addition
of a (stick your favorite band-aid in here)."
Let's do our homework and see if we can
figure out how to make your project fly
comfortably on one, judiciously maintained
battery . . . just has hundreds of thousands
of airplanes have flown for over a century.
Bob . . .
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bcone1381
Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan
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| Posted: Wed Apr 01, 2020 8:20 am Post subject: Re: Z11 |
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| Quote: | Your task then is to PROVIDE failure-tolerant
power sources to critical equipment such that
no single failure puts the airframe (and by
extension it's occupants) at risk.
.....The premise behind this idea is that airplanes
have a family of devices presenting various levels
of criticality for comfortable termination
of flight. So you have dual electronic
ignition? Fine . . . are you comfortable
launching into the blue not having offered
the rest of your electro-whizzies the same
courtesies as your ignition systems? If not,
the does it not stand to reason that if
the rest of your 'critical' systems are
happy, so too will be your ignition systems?
The optimal answer is 'fix the architecture'
and leave the batteries on the dealer's shelves. |
The Ignition is the critical item. I am comfortable loosing power to all the electronics other than the ignition, therefore the electrical system architecture is being designed to accommodate it.
Kind of......I considered the diagram but not the architecture. Dual alternators, brownout bus, it seemed complex for my application. My perception is electrical demands for EFI are large compared with my choice of ignition at 1.4A total. Since both ignitions tied to a single battery was not failure tolerant , the SureFly small second battery (12V 8Ahr is $50) seemed simple.
| Quote: | Let's do our homework and see if we can
figure out how to make your project fly
comfortably on one, judiciously maintained
battery . . . just has hundreds of thousands
of airplanes have flown for over a century.
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So lets reconsider that as archetecure and see what we come up with.
I have integrated the Architecture into my diagram, and removed the Aux Battery. The load on the Engine bus will be less than 5A so I will use a switch instead of a solenoid. I removed the Battery Bus to avoid a human error that might deplete the battery out in the bush.
If the power supply from the ALT side of the master solenoid fails, the engine dies until the switch is flipped by reliable human action. Not ideal. A diode to replace the switch eliminates human failure.
The next step I see is to remove the engine bus, bolt both power wires to the Battery side of the master solenoid. Now I am chasing my tail back to where I was. But lets say I did that. If the Solenoid fails open, then the engine is battery powered while the rest of the ship is powered by the alternator.
I think you already discussed months ago, but it looks to me like the Engine Bus duplicates the Essential bus.
How am I doing?
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Brooks Cone
Bearhawk Patrol Kit Build |
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user9253
Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan
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| Posted: Wed Apr 01, 2020 9:39 am Post subject: Re: Z11 |
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Why put a switch in series with the E-Bus diode?
I suggest that switch be eliminated. If it is not installed, it can not fail.
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I suggest that a double pole switch be used for the engine bus switch.
The second half of that switch can enable the engine start circuit.
Properly wired, the engine bus switch must be on in order to start the engine.
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Joe Gores |
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user9253
Joined: 28 Mar 2008
Posts: 1908
Location: Riley TWP Michigan
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| Posted: Wed Apr 01, 2020 3:09 pm Post subject: Re: Z11 |
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Bob, In figure Z-01, Should the brownout bus fuse be increased in size from 10 amps to 30 amps?
Since that fuse is in series with other fuses, we wouldn't want a short circuit to blow two fuses.
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Joe Gores |
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bcone1381
Joined: 25 Apr 2017
Posts: 42
Location: Southeast Michigan
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| Posted: Thu Apr 02, 2020 8:19 am Post subject: Re: Z11 |
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| Quote: | Why put a switch in series with the E-Bus diode?
I suggest that switch be eliminated. If it is not installed, it can not fail. |
Merely Personal preference.....I like an avionics switch. The avionics will be on the essential bus.
In Bob's book he says that an avionics switch is a single point failure for every item on the avionics bus. Bob's fundamentals of aircraft design fixes that with a diode. If I place on the Essential Bus all the Avionics, my preference for an avionics switch is satisfied and no longer a single point failure because it has a secondary path from the battery.
The Switch and the Diode are used between the main and essential buses to avoid the main bus from ever drawing power through the essential bus.
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Brooks Cone
Bearhawk Patrol Kit Build |
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eschlanser
Joined: 08 Apr 2010
Posts: 60
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| Posted: Fri Apr 03, 2020 7:55 am Post subject: Re: Z11 |
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Bob or anyone, can someone please point me to the messages about the Z01 architecture “posted here on the list a few weeks back”? I must have missed it and have searched but cannot find them. Thanks in advance,
Eric
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