Today's Message Index:
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1. 03:29 PM - Re: Is an ATC/ATO Fuse Block a Realistic Single Pt. of Failure (markfw)
2. 04:07 PM - Re: Proposed Z-14 implementation (Robert L. Nuckolls, III)
3. 07:13 PM - Battery Voltage Under Load, no Charger (farmrjohn)
Message 1
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| Subject: | Re: Is an ATC/ATO Fuse Block a Realistic Single Pt. |
of Failure
Bob,
You are right I should have called it my e-bus.
I have actually merged my endurance bus and e-bus. I had extra slots in my fuse
block after wiring the EFI fuses. With the new low-power electronics my "other
instruments" power draw in endurance mode is only 1.9 amps of the total 9.15
amps power draw, so I think I can afford the power draw and it is simpler.
Those instruments are (currently):
GRT EIS
B & C Warning LED
Trim servo
COM1 - MGL V6 Radio
Sandia Mode "C" Transponder - STX165R
uAvionix - SKYFYX GPS
Bose Headphones (2)
uAvionics ADS In/Out - EchoUAT
MGL ASV-1 (ASI, VSI, Alt Combo) & Altitude encoder
EFI Monitor Gauge
With this setup I am visible to, and can talk to, the world, I still have traffic,
weather, etc on a tablet on battery, and I can monitor my engine and the EFI.
With my dual battery, 24 amp hour reserve I should have a safe, low stress flight
for at least 2 hours in an ALT OUT situation. I am day, VFR so I am comfortable
with this. I have been trying to follow your flight planning advice, and
I thank you for it.
I am working on my FMEA.
Mark
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494440#494440
Message 2
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| Subject: | Re: Proposed Z-14 implementation |
At 02:33 PM 1/23/2020, you wrote:
><john_s_bright@yahoo.com>
>
>Thanks Bob,
>
>I do understand, as importantly shown in the N811HB accident
>investigation, that failures that have no effect on the current
>flight should be detected before the next flight! Those unfamiliar
>with N811HB may well learn more than one lesson at
>http://www.aeroelectric.com/Reference_Docs/Accidents/N811HB_Feb2008_LA-IVp/
This is an example of a system that was DESIGNED
to fail. The builder attended one of my seminars
out in Eugene OR some years earlier. Had the book.
Was assisted by a degreed engineer neighbor.
The same neighbor adapted Z-14 as a recommended
architecture for a high performance airplane
carrying a full-up compliment of Garmin glass . . .
but then ignored the advice offered by his
own recommendations by bringing BOTH ignitions
to a common bus with a poorly crafted constellation
of protective devices.
The whole point of the Z14 philosophy is
independent redundancy . . . but lost in
this airplane by adding a feature that negated
that philosophy in a catastrophic way. The
feature? A dual diode feed common bus for
both ignitions.
If they had simply subscribed to this List
and run the ideas past the members, the error
would have most certainly been avoided with advice
from numerous members.
>I am planning an O-360 with dual SDS ignition and injection. Part of
>my approach is to develop a detailed schematic of what it takes to
>keep the engine running, have a radio, and have a "six pack" of
>instruments long enough to make an alternate airport with the main
>contactors open (Z-14 derivative). I plan an engine bus with dual
>feeds, one from each battery via Schottky diodes; loss of one feed
>is preflight detectable using EFIS voltmeters.
Why dual feed bus? Run half the engine
goodies from one battery bus, the rest
from the opposite battery bus.
These busses are already QUAD feed.
either bus has the opportunity to power
up from a total of 4 sources. No single
failure will deprive BOTH busses of
a robust energy source.
>I do a wire by wire failure analysis that informs the preflight checklist:
>Assume only one failure per flight.
>What are the effects of a wire shorted or open?
Wires, bus bars and most power distribution
components are considered to be exceedingly
low failure rate . . . those kinds of things
are generally never a part of the system
reliability study.
>Does the failure affect safety? If so, can the safety effect be designed out?
>How will the failure be discovered before the next flight?
This is important for failures that may not be
obvious in flight . . . for example a light
bulb in a warning system, exterior lamps,
back up pumps for the engine driven mechanical
pump, etc. One might suffer a failure that
would go unnoticed unless explored as part
of a pre-flight process.
>If the failure affects flight safety, can something be done about it?
Have an alternative . . . i.e. plan-B . . .
a way to do without that accessory.
>How will the crew know what to do? Can they do it immediately by
>simple predetermined actions?
You betcha . . . that's what the FEMA and architecture
refinement is all about. The design goal is to be able
to tolerate failure of any LRU (line replaceable unit)
with the least possible work load on crew. Z-14, for all
it's robustness, only has three switches to fiddle with.
They have NO potential for pilot-induced hazard. I.e.
no mis-positioning of switches creates immediate
hazard.
>In case of electrical fire can the battery contactor(s) be opened
>without affecting flight safety?
Generally yes . . . I've initiated and/or completed
numerous flights in the "J-3" mode . . . ZERO
electrics. With engine feeds as recommended
above, you can shut down all DC power
management switches without affecting
engine ops.
>Some failures not detectable by preflight checks are added to annual
>inspection:
There should be no useful/critical accessory that is not
at least pre-flight testable . . . otherwise,
why carry it around?
>A fat wire short to sheetmetal that clears itself.
>Redundant grounds for both the computer and the injector driver
>sections of the ECUs. (Loss of computer ground sends injectors and
>coils 100% duty cycle.)
>Redundant grounds to voltage regulators.
>
>Some check done twice yearly:
>Ship's batteries and EFIS backup batteries capacity checks.
>Primary and aux alternator crowbar test.
You've got an excellent start on the
task . . . let's keep talking.
Bob . . .
Message 3
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| Subject: | Battery Voltage Under Load, no Charger |
My search skills are not the best. I've found that a 12 volt battery should indicate
12.8 volts on its own. What voltage should it indicate if it has loads
applied to it, i.e. checking out electrical components without the engine running
or a charger/external power applied?
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=494442#494442
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