Today's Message Index:
----------------------
1. 10:09 AM - Re: OVM14 MkIII, rev P3 (Robert L. Nuckolls, III)
2. 11:46 AM - Re: OVM14 MkIII, rev P3 (user9253)
3. 01:35 PM - Re: OVM14 MkIII, rev P3 (Eric Page)
4. 01:58 PM - Re: Official AeroElectric-List Usage Guidelines (John Bright)
5. 02:31 PM - Re: Official AeroElectric-List Usage Guidelines (Jeff Holdridge)
6. 02:49 PM - Re: Re: OVM14 MkIII, rev P3 (Robert L. Nuckolls, III)
7. 07:26 PM - Re: PVC Conduit in Certificated Aircraft (Alec Myers)
8. 07:28 PM - Re: PVC Conduit in Certificated Aircraft (Alec Myers)
9. 10:02 PM - Re: Re: OVM14 MkIII, rev P1 (Robert L. Nuckolls, III)
10. 10:34 PM - Re: PVC Conduit in Certificated Aircraft (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: OVM14 MkIII, rev P3 |
At 01:42 PM 10/1/2023, you wrote:
>
>Bob, I can't argue with your logic. However, airplanes are toys for many of
>us. And builders like to equip their toys with more toys. Take for instance
>the VP-X Electronic Circuit Breaker System. It has lots of nice
>features. But a
>builder could install fuses for much less money than the sales tax
>on the VP-X.
>Even so, many builders elect to install the VP-X because they want the
>extra features. It is the same with the over-voltage module. Some pilots
>want the extra feature of an over-voltage indicator light. Others
>might elect
>to not install the light or reset button.
No argument there my friend. Certainly everyone here on
the list is encouraged to fabricate the airplane
of their dreams.
I hope that what I bring to the List is several
decades of experience in keep it simple, light
as possible, low cost as possible, absolute
conformance to a well stated design goal,
more than passing homage to lessons learned
and human factors.
Yeah . . . the VPX system is a good case study.
I'm recalling conversations with pilots while
working the GP180 project at Lear. Over lunch
one day, we were discussing the features of
the latest EFIS/Navigation system being
integrating into the proposed new airplane.
One fellow opined that he was really pleased
with some of our proposals, "Yeah, all that
stuff gives us something to pass the time
during hours of watching the ground
crawl slowly below."
I was tempted to suggest a pocket video game
but I kept my mouth shut.
I may come off as curmudgeonly in these
discussions. For every one participating
there are 10x present and future readers
perhaps not so confident/capable of sorting
out the issues. Some of these readers might
be better served by crafting an airplane
that behaves very much like their grandpa's
C170. Not trying to be a hard-ass . . . just
encouraging everyone to achieve personal
goals with a foundation of understanding.
Speaking of the test switch 'option', I
have incorporated it onto the ECB as a
maintenance aid. Latest iteration of the
schematic attached. Also did a real estate
survey. I think I can get this critter
assembled and packaged it only 1/4" longer
than the legacy design. Further, it has
retained the simple, two wire integration
feature of the older offerings. One can
ignore the switch and have it work just
like the first few hundred examples did.
Opps, already spotted a 'bug'. R10 calculated
value is 56.2K
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 2
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| Subject: | Re: OVM14 MkIII, rev P3 |
Suggestion: Instead of having a wire or wires exiting the over-voltage module
for an external switch, use an internal solid state switch that is magnetically
operated. These devices are small like a transistor and go by various names:
digital magnetoresistive sensors, Unipolar Hall-effect sensor ICs, unipolar
switches, Hall effect IC, Hall switch. Some of these devices require either a
north or south magnetic pole. Others are bipolar. They cost from less than a
dollar on up. For the annual OVM test, a magnet is held near a certain spot
on the OVM. The OVM could be mounted on one side of aluminum skin and
the magnet held on the other side. No external wires or switch required
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511540#511540
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| Subject: | Re: OVM14 MkIII, rev P3 |
Bob, did my questions about your Rev P1 schematic slip by unnoticed? See the second post in this thread: http://forums.matronics.com/viewtopic.php?t=16781079
My 2nd question is resolved by Rev P3 but I'm still curious about questions 1,
3 and 4.
Please ignore my last question, below the dashes. I found the answer.
-Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511541#511541
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| Subject: | Re: Official AeroElectric-List Usage Guidelines |
Thanks Matt... question... any way to get my account fixed so I can post on
the Aeroelectric List website?
Thanks,
John Bright
Newport News, VA
cell: 757-812-1909
john_s_bright@outlook.com
________________________________
From: owner-aeroelectric-list-server@matronics.com <owner-aeroelectric-list
-server@matronics.com> on behalf of Matt Dralle <dralle@matronics.com>
Sent: Monday, October 2, 2023 02:00
Subject: AeroElectric-List: Official AeroElectric-List Usage Guidelines
Dear Listers,
Please read over the AeroElectric-List Usage Guidelines below. The complet
e
AeroElectric-List FAQ including these Usage Guidelines can be found at the
following URL:
http://www.matronics.com/FAQs/AeroElectric-List.FAQ.html
Thank you,
Matt Dralle
Matronics Email List Administrator
***************************************************************************
***
AeroElectric-List Usage Guidelines
***************************************************************************
***
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You are encouraged to read it carefully, and to abide by the rules therein.
Failure to use the AeroElectric-List in the manner described below may resu
lt
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The purpose of the AeroElectric-List is to provide a forum of discussion fo
r
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| Subject: | Re: Official AeroElectric-List Usage Guidelines |
Same here.=C2- Can't log into my newly approved account.
Sent from Yahoo Mail on Android
On Mon, Oct 2, 2023 at 3:09 PM, John Bright<john_s_bright@outlook.com> wr
ote: Thanks Matt... question... any way to get my account fixed so I can
post on the Aeroelectric List website?
Thanks,
John Bright
Newport News, VA
cell: 757-812-1909
john_s_bright@outlook.com
From: owner-aeroelectric-list-server@matronics.com <owner-aeroelectric-list
-server@matronics.com> on behalf of Matt Dralle <dralle@matronics.com>
Sent: Monday, October 2, 2023 02:00
Subject: AeroElectric-List: Official AeroElectric-List Usage Guidelines=C2
om>
Dear Listers,
=C2-
Please read over the AeroElectric-List Usage Guidelines below.=C2- The co
mplete
AeroElectric-List FAQ including these Usage Guidelines can be found at the
following URL:
=C2-
=C2-=C2- http://www.matronics.com/FAQs/AeroElectric-List.FAQ.html
=C2-
Thank you,
=C2-
Matt Dralle
Matronics Email List Administrator
=C2-
=C2-
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st.
You are encouraged to read it carefully, and to abide by the rules therein.
Failure to use the AeroElectric-List in the manner described below may resu
lt
in the removal of the subscribers from the List.
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The purpose of the AeroElectric-List is to provide a forum of discussion fo
r
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are to serve as an information resource to its members; to deliver
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s
requires the participation and cooperation of each and every member of
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:
=C2-- Please keep all posts related to the List at some level.=C2- Do n
ot submit
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ill be
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ric-List Email Forum -
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Message 6
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| Subject: | Re: OVM14 MkIII, rev P3 |
At 01:46 PM 10/2/2023, you wrote:
>
>Suggestion: Instead of having a wire or wires exiting the over-voltage module
>for an external switch, use an internal solid state switch that is
>magnetically
>operated.
<snip>
> No external wires or switch required
Hadn't considered that but it could probably
work. Perhaps a reed switch. They'll operate
on either magnetic polarity.
Opted for the dip-switch. Gold, low-level
contacts, environmentally robust. No external
'tools' needed.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 7
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| Subject: | Re: PVC Conduit in Certificated Aircraft |
I have a small certified aircraft with PVC tubes. I just read the 3000 hour inspection
checklist that requires them to be inspected. Theres a cable conduit under
the cabin floor that Im pretty sure is PVC, although Im not sure if thats
one that needs inspecting. Some of the control surfaces have PVC tubes in.
Searching through the maintenance manual, I see that the entire structure of the
aircraft is described variously as "GRP skins [AND] a rigid PVC foam core, and
theres a lot of rigid PVC foam too.
On Oct 1, 2023, at 12:37, Jeff Luckey <jluckey@pacbell.net> wrote:
Bob and others,
I want to summarize ...
Bob - I understand, agree with, and appreciate your cogent and concise explanation
of the rules. Right on the money, as usual.
However, as far as anyone who responded knows, there is no FAR or other regulation
that would prohibit the use of a PVC conduit in a Certificated airframe.
If an A&P/IA completes a 337 and gets it approved by their local FSDO, a piece
of PVC could be used in a Certificated airplane. It is really up to the FSDO
and the relationship that A&P has with them. I understand that the approval process
might be challenging, but there is no reg that prohibits the use of PVC
as a conduit.
Over the past few years, I have come to discover that what is dis-allowed by one
FSDO might be approved by another. I was surprised to find out just how capricious
and inconsistent the application of the rules is from district to district
across the country.
For the record, I am not considering using PVC for a conduit in a Certificated
or Experimental aircraft. Based on my understanding of the toxic properties of
PVC, I would not consider it. I had overheard a conversation with an IA who
suggested using a piece of PVC in the tail of an Experimental and he went on
to say that "he had done it in a Cessna". And I thought that was odd and I also
thought: "I wouldn't let this guy work on MY airplane".
-Jeff
On Saturday, September 30, 2023 at 06:37:37 PM PDT, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
wrote:
At 11:57 AM 9/30/2023, you wrote:
> Does anyone know if PVC can be used for a wiring conduit in Certificated aircraft?
A TC aircraft left the factory configured
per approved drawings. Substituting any
part not on that drawing requires an
approval via one-time field approval (Form 337)
or an STC.
I can't imagine any licensed technician
attempting to 'sell' such a deviation
to the local FSDO.
What kind of 'mod' are we talking about?
If the wires were not part of the original
TC then one is advised to rely on
legacy practices when submitting a Form 337.
To be sure, PVC plumbing would not fall in that category.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 8
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| Subject: | Re: PVC Conduit in Certificated Aircraft |
Sorry - that should say a lot of rigid PVC honeycomb too.
On Oct 2, 2023, at 22:25, Alec Myers <alec@alecmyers.com> wrote:
I have a small certified aircraft with PVC tubes. I just read the 3000 hour inspection
checklist that requires them to be inspected. Theres a cable conduit under
the cabin floor that Im pretty sure is PVC, although Im not sure if thats
one that needs inspecting. Some of the control surfaces have PVC tubes in.
Searching through the maintenance manual, I see that the entire structure of the
aircraft is described variously as "GRP skins [AND] a rigid PVC foam core, and
theres a lot of rigid PVC foam too.
On Oct 1, 2023, at 12:37, Jeff Luckey <jluckey@pacbell.net> wrote:
Bob and others,
I want to summarize ...
Bob - I understand, agree with, and appreciate your cogent and concise explanation
of the rules. Right on the money, as usual.
However, as far as anyone who responded knows, there is no FAR or other regulation
that would prohibit the use of a PVC conduit in a Certificated airframe.
If an A&P/IA completes a 337 and gets it approved by their local FSDO, a piece
of PVC could be used in a Certificated airplane. It is really up to the FSDO
and the relationship that A&P has with them. I understand that the approval process
might be challenging, but there is no reg that prohibits the use of PVC
as a conduit.
Over the past few years, I have come to discover that what is dis-allowed by one
FSDO might be approved by another. I was surprised to find out just how capricious
and inconsistent the application of the rules is from district to district
across the country.
For the record, I am not considering using PVC for a conduit in a Certificated
or Experimental aircraft. Based on my understanding of the toxic properties of
PVC, I would not consider it. I had overheard a conversation with an IA who
suggested using a piece of PVC in the tail of an Experimental and he went on
to say that "he had done it in a Cessna". And I thought that was odd and I also
thought: "I wouldn't let this guy work on MY airplane".
-Jeff
On Saturday, September 30, 2023 at 06:37:37 PM PDT, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
wrote:
At 11:57 AM 9/30/2023, you wrote:
> Does anyone know if PVC can be used for a wiring conduit in Certificated aircraft?
A TC aircraft left the factory configured
per approved drawings. Substituting any
part not on that drawing requires an
approval via one-time field approval (Form 337)
or an STC.
I can't imagine any licensed technician
attempting to 'sell' such a deviation
to the local FSDO.
What kind of 'mod' are we talking about?
If the wires were not part of the original
TC then one is advised to rely on
legacy practices when submitting a Form 337.
To be sure, PVC plumbing would not fall in that category.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
Message 9
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| Subject: | Re: OVM14 MkIII, rev P1 |
Eric: My 2nd question is resolved by Rev P3 but
I'm still curious about questions 1, 3 and 4.
Ach!!! Sorry 'bout that!
At 02:50 PM 9/22/2023, you wrote:
>
>A few things that I noticed...
>
>1. Absolute maximum cathode-to-anode voltage on
>the LM431 is 37V (see TI and onsemi
>datasheets). A significant OV event could
>exceed that limit until the crowbar brings bus
>voltage under control. This might not be an
>issue with a lead-acid battery, but the OV
>behavior of the BMS in lithium batteries is
>unknown. If a lithium BMS disconnects pronto,
>bus voltage could rise farther and more quickly than with lead-acid on the
job.
>
>Q: Should there be a 33V Zener in parallel to protect the LM431?
The LM431 IS a zener. It's biased up thru
392 ohm R1. So the 10V Vcc rail is rigid.
If anything is at-risk from a bus voltage
excursion, it's probably R1.
>-----
>
>2. The recommended maximum voltage on LM293
>inputs is Vcc minus 2V (see table 6.2 in the TI
>datasheet). In this case Vcc is 8V, so the max input voltage is 6V.
>- The 7V reference exceeds 6V on the inverting inputs of both comparators.
>- Any bus voltage >13.64V will exceed 6V on the non-inverting input of
U16A.
>- Timing capacitor C11 on the non-inverting input of U16B will charge to
8V.
Yeah, raised Vcc to 10V. Changed trip reference to 2.5V.
The Non inverting input to U16B will not exceed 8V 'cause
that's where the SCR trips.
>Q: Should the comparator reference be adjusted
>downward (perhaps delete R4, adjust R3/R5, and
>use the LM431's 2.5V reference for the comparators)?
Yup.
>Q: Should the non-inverting inputs be protected with 5.1V Zeners?
Nope . . .
>-----
>
>3. In recent discussion of the OVM task you
>mentioned your intent to make the trip delay
>500mS +/- 50mS. This schematic provides ~200mS.
>
>Q: Have you reconsidered the 500mS trip delay?
Not necessarily. Legacy OVM management devices were oblivious
to the 20V for 1 second qualification requirements under DO160.
Powers that be were fond of the 50mS value for step response from
14.2 to 20V. I think I mentioned having offered a very
similar configuration and running the delay out further.
Early days solid-state latches for OV management were plagued
with nuisance trips very short, low energy noises on the
bus that would do a dv/dt trigger of the scr. Ultimately
managed with the 0.1 uF cap right across the SCR combined
with low value resistor gate to cathode (which drives
up required trigger current).
This design now ties the gate to ground through the open
collector output of U11B. I'm anticipating dv/dt issues
to be irrelevant.
AS to selection of time delay certainly much longer than
50mS and much smaller than 1 second. 500mS seems like a
happy medium but given the self-resetting nature of the
comparator/timer, 200mS is probably comfortable too. Either
value honors design guidance of DO160/Mil-Std-704
The current proposal offers a way to select ov trip,
maintenance trip and trip delay values with a simple
adjustment of resistors.
>-----
>
>4. Schematic Note 1 contemplates a crowbar
>current of 100-200A DC for 25mS. The BT139-600E
>SCR datasheet shows a peak non-repetitive
>on-state current of 155A, but that specification
>assumes an initial junction temperature of
>25degC (unlikely under an engine cowling), a
>pulse duration =89=A420mS and a full-sine-wave AC pulse, not DC.
Those have been proven conservative . . . especially
in later years of SCR offerings. Beech had a qualification
requirement to effect 50 shutdowns in a row, each
about 2 seconds apart, with the 51st still in spec.
That protocol arose from the fact that the weakest
link in contemporary ov RELAY designs was relay
CONTACTS failing to break the inductively stabilized
ARC. Powers that be assumed that no airplane would
every experience 50 OV events, hence the BIG HAMMER
test.
It was during development of the prototype Beech Lightning
(single engine turboprop) that not a single OV relay
in Beech inventory would pass the test including those
we sold at Electo-Mech. When Jack Thurman called
to tell me the sad story, I told him I'd be in his
office in an hour.
I modified one of our stock regulator/ov relay
products to a CrowbarSCR configuration and took
it out to try on the bench test. When Jack hit
the OV initiate button, he thought something was
broke. No squawks from the alternator, no great flashing
of panel lights. The chart recorder showed a rather
un-impressive rise to 32 volts whereupon the system
was quietly shut down.
"Yeah says Jack, will it do it 50 times?"
"You bet says I".
The previously stressed devices was a relay trying
to break an inductively driven ARC. Now, major stress
was on a circuit breaker qualified for thousands of
operations doing the job it was designed for . . .
clear a faulted feeder.
Had the Lightning project continued to production,
I have no doubt that the crowbar ov management system
would see it's first application in a TC aircraft.
Unfortunately, volume production of crowbar ov
management had to wait until it appeared in the
B&C LR series regulators which eventually made
it onto TC aircraft. Lamar, PlanePower and others
picked up on the idea . . . tens of thousands of crowbar
ov sytems are flying today.
Indeed, the 50x tests were no problem. Only time
we lost SCRs was when someone tried to crowbar
a fatter breaker . . . or one with a particularly
long operate time. Typically, our favorite style
of miniature breaker opens in 25mS or less.
>Q: Can the BT139-600E handle this crowbar
>task? If not, could you swap U16B's inputs and
>interpose a P-FET to trigger a beefier SCR?
Don't think this will be necessary. All of our OVM-14
versions used SCR's with rather benign single cycle
ratings. But just for grins and in honor of Jack Thurman's
skeptical testing protocols, I'll do the 50x test at 100A.
I'll go rescue my environmental chamber from a
lab in Wichita so I can test it at temperature . . .
say -20 to +150F.
Bob . . .
////
(o o)
===========o00o=(_)=o00o=======
=
< Go ahead, make my day . . . >
< show me where I'm wrong. >
========================
========
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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| Subject: | Re: PVC Conduit in Certificated Aircraft |
>Bob and others,
>
>I want to summarize ...
>
>Bob - I understand, agree with, and appreciate your cogent and
>concise explanation of the rules. Right on the money, as usual.
>
>However, as far as anyone who responded knows, there is no FAR or
>other regulation that would prohibit the use of a PVC conduit in a
>Certificated airframe.
Didn't say there was . . . only that deviations
from the airplane's type certification is
to be discouraged without overriding approval
lest lightning from on high come down and smite thee.
Now, if some manufacture has achieved certification
with ANY particular material, then that TC
becomes "approved data" but only for that particular
application. PVC approved in one place doesn't say
okay to use anywhere.
>If an A&P/IA completes a 337 and gets it approved by their
>local FSDO, a piece of PVC could be used in a Certificated
>airplane. It is really up to the FSDO and the relationship
>that A&P has with them. I understand that the approval
>process might be challenging, but there is no reg that
>prohibits the use of PVC as a conduit.
I recall rules that speak to flammability of any
material used on the airframe. The topic got really
hot after Swissair 111 suffered some soft fault ignition
of insulation in the overhead. Something about
flaming drips, self extinguishing times, fumes, proximity
to critical systems, etc.
Yup, here 'tis:
https://www.faa.gov/documentlibrary/media/advisory_circular/ac%2023-2a.pdf
>Over the past few years, I have come to discover that what is
>dis-allowed by one FSDO might be approved by another. I
>was surprised to find out just how capricious and inconsistent
>the application of the rules is from district to district across the country.
You got that right! In years past seekers of royal
permission would FSDO Shop . . . Back then Ft. Worth
and Seattle were popular shops. Last I heard,
the practice was halted with a directive, "Tho
shalt seek blessings only from thy local FSDO."
I think the Teterboro office got miffed 'cause
nobody ever asked them for permission/guidance . . .
wonder why.
>I had overheard a conversation with an IA who suggested using a
>piece of PVC in the tail of an Experimental and he went on to
>say that "he had done it in a Cessna". And I thought
>that was odd and I also thought: "I wouldn't let this guy work on MY
>airplane".
I wonder if he jumped the hoops for paperwork.
There's nothing inherently hazardous for incorporation
of PVC . . . depends on application and exacerbation
of risk. But the absolutely minimal risk solutions
call for consideration of better materials
first. I suspect PVC conduit in the tailcone is not
a significant elevation of risk.
Bob . . .
////
(o o)
===========o00o=(_)=o00o========
< Go ahead, make my day . . . >
< show me where I'm wrong. >
================================
In the interest of creative evolution
of the-best-we-know-how-to-do based
on physics and good practice.
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