Today's Message Index:
----------------------
1. 01:42 AM - Re: PVC Conduit in Certificated Aircraft (Bill Settle)
2. 03:35 AM - Re: PVC Conduit in Certificated Aircraft (Alec Myers)
3. 03:39 AM - Re: PVC Conduit in Certificated Aircraft (Alec Myers)
4. 01:39 PM - Re: OVM14 MkIII, rev P1 (Eric Page)
5. 05:27 PM - Theory of Operation; goezintas & goezouttas (Ken Wilkerson)
6. 05:58 PM - Re: OVM14 MkIII, rev P1 (user9253)
7. 07:02 PM - Re: OVM14 MkIII, rev P1 (Eric Page)
8. 07:04 PM - Re: PVC Conduit in Certificated Aircraft (Robert L. Nuckolls, III)
Message 1
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| Subject: | PVC Conduit in Certificated Aircraft |
What is the aircraft?
Thanks,
Bill
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com <owner-aeroelectric-list-server@matronics.com>
On Behalf Of Alec Myers
Sent: Monday, October 2, 2023 10:27 PM
Subject: Re: AeroElectric-List: 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 2
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| Subject: | Re: PVC Conduit in Certificated Aircraft |
Bob,
That link is to a document describing flammability tests. It doesnt have any advice
as to where flammable (or other) materials can be used.
There is in it a list of regulatory references (on page 7) that apply to individual
parts of the aircraft, but they are very very specific. It may have been
extended since 2007 when that AC was issued.
Looking through the FAR sections listed there that appear to apply to cables and
accessories, the only relevant stipulation is this one:
23.1365(b) Any equipment that is associated with any electrical cable installation
and that would overheat in the event of circuit overload or fault must be
flame resistant. That equipment and the electrical cables must not emit dangerous
quantities of toxic fumes.
If a circuit is protected, does it still count as something that would overheat
in the event of overload or fault?
On Oct 3, 2023, at 01:34, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
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.
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
Message 3
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| Subject: | Re: PVC Conduit in Certificated Aircraft |
Its a Grob G115
On Oct 3, 2023, at 04:41, Bill Settle <billsettle@bellsouth.net> wrote:
What is the aircraft?
Thanks,
Bill
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com <owner-aeroelectric-list-server@matronics.com>
On Behalf Of Alec Myers
Sent: Monday, October 2, 2023 10:27 PM
Subject: Re: AeroElectric-List: 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 4
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| Subject: | Re: OVM14 MkIII, rev P1 |
Wow! Thanks, Bob. That was WAY more than I expected. Sometimes
I feel like I should be making student loan payments for what I learn
on this forum.
nuckolls.bob(at)aeroelect wrote:
> 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.
Ugh. That's pretty obvious when I read it and look at the schematic again.
More learning...
> The Non inverting input to U16B will not exceed 8V 'cause that's where
> the SCR trips.
After reading the datasheet again, I can see that protecting the non-inverting
inputs is a non-issue. The Vcc-2V figure is an operating recommendation; the
absolute maximum is 38V. In the case of your P3 schematic, it would take 247V
on the bus to exceed that limit on U16A!
> 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.
Got it. Exact delay value is unimportant, as long as it responds fast enough to
protect and slow enough to avoid nuisance trips.
> ...the weakest link in contemporary ov RELAY designs was relay CONTACTS
> failing to break the inductively stabilized ARC.
OK, here's where I have another question. My application for OV protection is on
a Rotax 912iS, which has a built-in 450W 3-phase PM stator. Since I can't corral
a stator by blowing a breaker, I'm adapting your design to drive relays.
I've chosen an automotive relay with integral coil-suppression diode and contacts
rated for 75VDC at 40A:
https://www.digikey.com/short/n8qhp98t
Do you think that relay is likely to have any trouble breaking each leg of the
Rotax stator feed? I'm guessing not since it's an AC circuit, but guessing has
a poor track record...
-Eric
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511551#511551
Message 5
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| Subject: | Theory of Operation; goezintas & goezouttas |
An acquaintance is trying to interface a Dynon H34 with a KN53. It looks to me
like the Dynon H34 does not have an internal VOR/LOC converter. Trying to explain
to my friend that hed need something like a KN72 to make it work.
Can anyone point me to a theory of operation that describes the required inputs/outputs
for VOR/LOC/GS receiver, VOR/LOC converter and CDI?
Thanks!
Message 6
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| Subject: | Re: OVM14 MkIII, rev P1 |
Eric, be sure to clearly mark the positive relay coil terminal so that you don't
mistake the same mistake that I made. The Rotax 912iS fuse box also has
relays with internal diodes. If I remember correctly, those relay coils have
higher coil resistance. Might be 110 ohms.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511553#511553
Message 7
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| Subject: | Re: OVM14 MkIII, rev P1 |
That's very good advice, Joe. Screw it up and I'll have a crowbar whether I want
one or not!
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=511554#511554
Message 8
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| Subject: | Re: PVC Conduit in Certificated Aircraft |
>
>Looking through the FAR sections listed there that appear to apply
>to cables and accessories, the only relevant stipulation is this one:
>
>23.1365(b) Any equipment that is associated with any electrical
>cable installation and that would overheat in the event of circuit
>overload or fault must be flame resistant. That equipment and the
>electrical cables must not emit dangerous quantities of toxic fumes.
>
>
>If a circuit is protected, does it still count as something that
>would overheat in the event of overload or fault?
One would think. I've heard opinions from more than
one 'knowing' source. One agreed with that assertion.
The other did not . . . everything on the
ship's TC was originally assessed for fire risks.
Anything new is subject to the same assessment.
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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