Today's Message Index:
----------------------
0. 04:08 AM - PLEASE READ - Matronics Email List 2018 Fund Raiser During November! (Matt Dralle)
1. 03:18 AM - Re: Question on Grounding (user9253)
2. 06:43 AM - IVO Prop current limiter (Bob Verwey)
3. 06:47 AM - Re: Re: Question on Grounding (FLYaDIVE)
4. 07:20 AM - Re: E-Bus Fuse Size (Robert L. Nuckolls, III)
5. 07:34 AM - Re: IVO Prop current limiter (Robert L. Nuckolls, III)
6. 10:09 AM - Re: E-Bus Fuse Size (user9253)
7. 12:44 PM - Re: Re: Question on Grounding (John Morgensen)
8. 06:53 PM - Re: Question on Grounding (Rocketman1988)
9. 06:53 PM - Re: Re: E-Bus Fuse Size (Robert L. Nuckolls, III)
10. 06:55 PM - Re: Re: E-Bus Fuse Size (Rick Beebe)
11. 08:12 PM - Re: E-Bus Fuse Size (user9253)
12. 08:24 PM - Re: Re: E-Bus Fuse Size (Robert L. Nuckolls, III)
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| Subject: | PLEASE READ - Matronics Email List 2018 Fund Raiser |
During November!
Dear Listers,
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Matronics Email List Administrator
RV-4/RV-6/RV-8 Builder/Rebuilder/Pilot
Message 1
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| Subject: | Re: Question on Grounding |
> Are you on DRUGS!
Violation of "AeroElectric-List Usage Guidelines"
- Feel free to disagree with other viewpoints, BUT keep your tone
polite and respectful. Don't make snide comments, personally attack
other listers, or take the moral high ground on an obviously
controversial issue. This will only cause a pointless debate that
will hurt feelings, waste bandwidth and resolve nothing.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484142#484142
Message 2
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| Subject: | IVO Prop current limiter |
Guys how difficult would it be to have an adjustment for the current trip
setpoint? I'm thinking of this as a good option for a hydraulic pump
application on an aircraft, it makes sense because of the versatility and
lightness.
Best...
Bob Verwey
082 331 2727
On Mon, 29 May 2017 at 18:04, Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 11:06 PM 5/27/2017, you wrote:
>
> with the engine off, the prop and circuit behaved normally. With the
> engine running, the prop current is shut down almost immediately, though a
> small bit of pitch change does occur prior to cut-off.
>
> --------
> Doug
>
>
> Could this have something to do with the higher system voltage when the
> engine is running?
>
>
> possibly . . . but I think not. The
> current limiter is configured to 'latch'
> into an OFF state approx 200 mS after
> a current limit on the order of 9A is
> achieved.
>
> The 'latch' is subject to premature triggering
> if subjected to noise which I suspect is coming
> from the ship's alternator.
>
>
> [image: Emacs!]
>
>
> Doug,
>
> Try tacking this combination of components onto
> your assembly. The experiment is to see if adding
> a smoothing capacitor to the circuit's power
> source will sufficiently attenuate the antagonistic
> energies. The 100 uF cap is the 'smoother' while
> the 10 ohm resistor mitigates inrush currents impressed
> on the circuit when the directional control switch
> closes . . .
>
>
> Bob . . .
>
Message 3
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| Subject: | Re: Question on Grounding |
Will do Joe,
Sorry and thank you.
Barry
On Thu, Nov 1, 2018 at 6:23 AM user9253 <fransew@gmail.com> wrote:
>
>
> > Are you on DRUGS!
>
> Violation of "AeroElectric-List Usage Guidelines"
> - Feel free to disagree with other viewpoints, BUT keep your tone
> polite and respectful. Don't make snide comments, personally attack
> other listers, or take the moral high ground on an obviously
> controversial issue. This will only cause a pointless debate that
> will hurt feelings, waste bandwidth and resolve nothing.
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=484142#484142
>
>
Message 4
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| Subject: | Re: E-Bus Fuse Size |
At 07:35 PM 10/31/2018, you wrote:
>
>A pilot recently experienced an instrument panel blackout at night.
What was the failure that took down his main
bus?
> When he turned on the E-Bus switch, the panel briefly came back
> on, but soon went black again. Luckily the weather was good and he
> landed safely. You can read about it here.
>http://www.vansairforce.com/community/showthread.php?t=165520
>The E-Bus was protected by 15 amp fuses. Evidently the second and
>third owners of the aircraft connected more loads to the E-Ebus,
>eventually overloading it.
Yup . . . ignorance is your worst enemy . . .
sometimes the foundation for fatal mistakes.
>If two fuses are connected in series, even if one is bigger, either
>one or both could blow in case of hard ground fault.
> Should the E-Bus have main fuses?
>If so, then how much larger should the main fuse be than a branch
>circuit fuse?
The z-figures are too often treated as "the
way to set up my airplane" . . . they are
ARCHITECTURE drawings that consider options
for minimizing risk under various failure modes.
The values for wire and fuses are exemplar,
not necessarily applicable to any one builder's
project.
The very FIRST step in planning the ship's
final configuration is to do a LOAD ANALYSIS.
It's real simple. The web-page at
https://tinyurl.com/9rt6ymn
offers two type of tools. One based on paper-
pencil-pink-pearl technology. The other uses
Excel. Either method gets the job done. I prefer
the paper/pencil approach . . . it fits in the
3-ring binder of shop notes.
There is a form that can be downloaded from
http://www.aeroelectric.com/PPS/Load_Analysis/Blank_Form.pdf
You need one page for EACH bus in the aircraft.
Just how many busses is driven by choice of
architecture. Devices fed by those busses
is driven by your "plan-b" analysis for dealing
with single failures of any electro-whizzie.
The sums of running loads for each bus are
critical to calculating ship's endurance mode
loads and sizing the battery to meet endurance
mode design goals.
These pages do another good thing. They
are the INDEX for a page-per-system wire book.
Each fuse/breaker on a bus gets sized, paired with
appropriate wire and tagged as to what page
that system's wiring details will be found.
Once the e-bus running loads are established,
ONLY THEN does one have sufficient information to
size the normal and alternate feed protection.
One COULD take the uber-conservative approach
and wire these paths with say 10AWG wire protected
with MAX40 fuses . . . or you can use data
described in the load-analysis to size the
wire/protection with at least 100% headroom
based on running loads.
Those are BUS feeders and need to be ROBUST with
respect to total running loads on the bus. The
original e-busses had typical running loads on
the order of 3-4 amps. But as endurance mode
support (SD-8 etc) got bigger, the constellation
of e-bus hardware went up too.
Had the original builder of this aircraft provided
such information with the sale of his project,
the future owners would at least possess information
necessary for well crafted modifications to
their aircraft. I've done my share of
b*#$$n and m(#$&g about the uber-regulated
TC aircraft environment but the hat-dance-
of-paperwork associated with this topic
in TC aircraft has solid foundation.
When modifying the airplane, tho shalt
not mess with the aerodynamics, bust
the edges of the envelope for weight/
balance. You will validate structural integrity
of the installed device -AND- it's
attach points. Lastly . . . revisit
the electrical load analysis for validation
of performance and FMEA.
I'm pleased that this incident didn't have
a sad outcome. It's a good thing that we
learn from his experience.
Feel free to cross post this narrative
to the Van's support forums.
Bob . . .
Message 5
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| Subject: | Re: IVO Prop current limiter |
At 08:41 AM 11/1/2018, you wrote:
>Guys how difficult would it be to have an adjustment for the current
>trip setpoint? I'm thinking of this as a good option for a hydraulic
>pump application on an aircraft, it makes sense because of the
>versatility and lightness.
The IVO controller is nothing more than
an electronic circuit breaker with tightly
calibrated trip current and trip delay.
This product was made practical by design
choices of the IVO prop drive mechanism.
It is difficult if not impossible to fit
the pitch actuator with limit switches.
The original designers elected to size
motor torque, gearbox robustness and
mechanical limit stops such that no
mechanical damage is incurred by allowing
the mechanism to routinely visit hard
stops at the end of travel.
Many actuators I've worked with are not
so robust . . . repeated encounters with
hard stops severely limits service life
or poses risk of damage.
The IVO actuator's circuit breaker proved
to be both electrical fault protection
-AND- an indicator for having reached end
of travel. Like crowbar ov protection, the
prop pitch breaker simply pops when the
system reaches mechanical limits.
The IVO controller was simply an extension
of this design philosophy to make the end-of-
travel-trip both self resetting -AND-
event annunciating. Hence it is more a
controller than circuit breaker.
Unlike the IVO prop, the hydraulic pump does
not routinely trip the feeder protection.
Bob . . .
Message 6
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| Subject: | Re: E-Bus Fuse Size |
> What was the failure that took down his main bus?
Bob, thanks for your reply.
Sorry that I did not explain the failure well. It was not the main power bus that
lost power. It was the E-Bus. The E-bus was wired per AeroElectric diagrams
with two power inputs, one from the main bus and one from the battery. Both
inputs had 15 amp fuses. The fuses blew because of builder error: too heavy
of a load.
When two fuses are in series, what should the fuse ampacity ratio be to be sure
that only the smaller fuse blows and not both? 2 to 1, or 5 to 1, or 10 to 1,
or what?
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484227#484227
Message 7
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| Subject: | Re: Question on Grounding |
Thank you, Joe.
On 11/1/2018 3:17 AM, user9253 wrote:
>
>
>> Are you on DRUGS!
> Violation of "AeroElectric-List Usage Guidelines"
> - Feel free to disagree with other viewpoints, BUT keep your tone
> polite and respectful. Don't make snide comments, personally attack
> other listers, or take the moral high ground on an obviously
> controversial issue. This will only cause a pointless debate that
> will hurt feelings, waste bandwidth and resolve nothing.
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=484142#484142
>
>
Message 8
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| Subject: | Re: Question on Grounding |
Sorry I asked...
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484233#484233
Message 9
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| Subject: | Re: E-Bus Fuse Size |
At 12:09 PM 11/1/2018, you wrote:
>
>
> > What was the failure that took down his main bus?
>
>Bob, thanks for your reply.
>Sorry that I did not explain the failure well. It was not the main
>power bus that lost power. It was the E-Bus. The E-bus was wired
>per AeroElectric diagrams with two power inputs, one from the main
>bus and one from the battery. Both inputs had 15 amp fuses. The
>fuses blew because of builder error: too heavy of a load.
>When two fuses are in series, what should the fuse ampacity ratio be
>to be sure that only the smaller fuse blows and not both? 2 to 1,
>or 5 to 1, or 10 to 1, or what?
>
>--------
>Joe Gores
Joe, the complete answer will take a bit . . . but
I'll get to it. In the mean time, I've been massaging
the history of the e-bus. It is clear that the
spirit, design goals and intent for e-bus configuration
have evolved several generations over the past 30 years.
I'm considering an update to the idea that removes
all risks for not having considered the pesky details
of fuse physics. Let's graduate the e-bus up
to the same design philosophy as bus structures
in most other aircraft.
http://www.aeroelectric.com/PPS/Adobe_Architecture_Pdfs/Z36P1.pdf
The design cited above would support all practical
e-bus loads from a LongEz to any heavy-hauler in the
OBAM aviation world. While beefier than the Long-Ez
needs, weight penalty is small and besides, its
all in the nose where the canard pushers need
the ballast anyhow.
The bus is still crew controlled for crash safety
and protected by a current limiter that meets the
spirit and intent of protection for bus feeders
while being totally immune to nuisance tripping
by the opening of any subordinate protection.
Next pass through the z-figures will show this
configuration.
Comments welcome . . .
Bob . . .
Message 10
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| Subject: | Re: E-Bus Fuse Size |
If two fuses are really in series I would think the smaller one would
almost always blow first and then the second wouldn't have power on it
any more. In this incident, the fuses were really in parallel and he
actively switched from the main feed to the alt feed. Since the load was
still higher than 15 amps the second one blew as well. Had he turned
some things off before switching he probably would have been just fine.
A realization he has come to, btw. Along with the realization that he
really needs to decipher the wiring and re-assign devices to the
appropriate buss.
--Rick
On 11/1/2018 1:09 PM, user9253 wrote:
>
>
>> What was the failure that took down his main bus?
> Bob, thanks for your reply.
> Sorry that I did not explain the failure well. It was not the main power bus
that lost power. It was the E-Bus. The E-bus was wired per AeroElectric diagrams
with two power inputs, one from the main bus and one from the battery.
Both inputs had 15 amp fuses. The fuses blew because of builder error: too heavy
of a load.
> When two fuses are in series, what should the fuse ampacity ratio be to be sure
that only the smaller fuse blows and not both? 2 to 1, or 5 to 1, or 10 to
1, or what?
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=484227#484227
>
>
Message 11
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| Subject: | Re: E-Bus Fuse Size |
What I meant by being in series are the input fuse to the E-bus and one of the
E-Bus loads. My concern is what will happen in case a load circuit shorts to
ground. For a fraction of a second, the current arcing across a fuse will exceed
the fuse value. That high arcing current could be enough to blow an upstream
fuse, even if that upstream fuse has a higher current rating. Ever notice
that circuit breakers in a home service entrance panel are labeled "10K Amps"
even though the breaker size is 15 or 20 amps? The reason is that when the circuit
breaker trips with a dead short, the current arcing across the opening
contacts is only limited by the power company's ability to provide it. Thus the
circuit breaker is capable of withstanding very high arcing current up to 10K
amps for a fraction of a second without blowing itself apart.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=484236#484236
Message 12
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| Subject: | Re: E-Bus Fuse Size |
At 12:09 PM 11/1/2018, you wrote:
>
>
> > What was the failure that took down his main bus?
>
>Bob, thanks for your reply.
>Sorry that I did not explain the failure well. It was not the main
>power bus that lost power. It was the E-Bus. The E-bus was wired
>per AeroElectric diagrams with two power inputs, one from the main
>bus and one from the battery. Both inputs had 15 amp fuses.
The normal feed path normally doesn't
have circuit protection. The e-bus and
main bus should be located adjacent to
each other and tied together through
the back-feed prevention diode with
SHORT leads as shown in Z-13/8. Loss
of bus due loss of feeder should never have
occurred.
The only time we need protection in the
alternate path is when the alternate feed
path control is a panel mounted switch.
Wire in the alternate feed path is relatively
small but protected with fuse that's pretty
stiff compared to the RUNNING loads on
the bus. I've shown 15A in most of the
drawings but upsized to 30A in Z02.
For the incident in question, any weakness
in the feeder protection should have been
rooted out with flight testing . . . an
activity that is MANDATED for one-off
mods in TC aircraft.
When you have an alternate feed path
relay, that path becomes a crew-controlled
inter-bus feeder. With the relay located
at the battery the feeder can be made cold
for crash safety, then we can upsize both
the feeder and it's protection.
> The fuses blew because of builder error: too heavy of a load.
>When two fuses are in series, what should the fuse ampacity ratio be
>to be sure that only the smaller fuse blows and not both? 2 to 1,
>or 5 to 1, or 10 to 1, or what?
It's a bit more complicated than that. Fuses,
indeed ALL thermally actuated protective
devices, have an actuation time constant that
varies inversely as the square of current.
This is a rough figure of merit that lets
you compare fuses of the same 'rating' but
of different design philosophy. For example,
a 5A "slow blow' fuse has a higher fusing
constant than its 'fast blow' cousin of the
same 5A rating.
As a general rule we don't operate thermal
devices at more than 75% of their rating
so that pre-heating of the thermal element
is minimized. A thermal device may stay
closed at 80% of rating but since it's already
warmed up, response interval to a step rise
in current is much faster.
In the case of a fuse protected feeder to
an e-bus, normal e-bus loads WILL induce
some heating in the feeder protection thus
pushing the fusing response down the curve.
As I suggested earlier, operating with a
bus feeder fuse 2x the normal running loads
is probably sufficient but protecting with
an extra robust (3x) or LONG time constant
device (like a current limiter) is certainly
an option.
The short answer to your question is:
The ability of upstream protection
to hold against a downstream fault cleared
by lighter protection is a function of
fusing-time depression induced by pre-heating
due to normal running loads. You can
size by rules of thumb but VERIFY with
operational testing.
It was a failure to operationally test combined
with poorly thought out modifications to
recommended architecture that brought
down a nearly new LA4 and got some people
hurt.
See:
http://www.aeroelectric.com/Reference_Docs/Accidents/N811HB/02_N11HB_Configuration.wmv
http://www.aeroelectric.com/Reference_Docs/Accidents/N811HB/01_Fuse%20vs%20Breaker.wmv
Bob . . .
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