Today's Message Index:
----------------------
1. 07:40 AM - The joys of a Z-14 during an charging system failure (Bill Watson)
2. 10:09 AM - Re: Grounding to tube frame structures (jrevens)
3. 10:34 AM - Re: Re: Grounding to tube frame structures (Art Zemon)
4. 11:03 AM - Re: Re: Grounding to tube frame structures (Charlie England)
5. 11:50 AM - Re: Grounding to tube frame structures (jrevens)
6. 12:38 PM - Re: Re: Grounding to tube frame structures (Charlie England)
7. 03:18 PM - Re: Re: Grounding to tube frame structures (Robert L. Nuckolls, III)
Message 1
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | The joys of a Z-14 during an charging system failure |
Having just passed 1100 hours on my RV-10, I experienced my 2nd LR3C
voltage regulator failure. Like the first, this turned out to be a
non-event despite some difficulty in problem determination.
I installed a Z-14 dual bus, dual alternator, dual battery electrical
system. Specifically a B&C L-40, a B&C SD-20, (2) Odyssey PC680s, and
(2) LR3c B&C regulators. Dual mags but an electrically hungry panel
with (3) GRT EFISs and the rest of the usual kitchen sink.
The charging system failure occurred during cruise in the normal
configuration; i.e. with both buses running independently and not
linked. I first noticed the voltage slowly drop on bus1. I switched
the cross-link on and off a few times and observed the voltage climb
each time suggesting something on bus1 had failed but bus2 was running fine.
Soon the low voltage light lit so I simply switched the cross link on
and completed the 2 hour leg.
Upon landing and suspecting an LR3c failure, I ran through the problem
determination procedure per B&C. Problem was it all checked out so I
call them and they said it was probably a failed alternator. I sent it
in, they checked it out, the 1100 hour L-40 was just fine so they sent
it back for the cost of postage. I reinstalled it, reset the belt
tension and took a test flight.
All was well on the test flight so a week later I went on a 3 leg
journey to DC, Pgh and return. No problems on the first 2 legs but on
the third leg, bus 1 was out again. It was a non-event relative to
finishing the 1.5 hour leg.
I re-ran the regulator's PD procedure and step 4 failed (no voltage
drop for those following along). Since I had a previously repaired one
on the shelf, I simply swapped it out and was off and flying again.
Findings:
- The LR3c can 'soft-fail' and can be suspect even if PD checks out.
- The 20amp backup alternator is capable of running my full daytime
cruising load including battery charging. It only comes up short at low
RPMs during ground ops.
- The 40amp main alternator is enough for my fully loaded RV10 and will
keep things running and charging even during low RPM ground ops (I
already knew this).
- The Z-14 provides a great deal of 'dispatch reliability'. I can
finish out a trip and get home safely in most instances even with a
failed regulator or alternator. I feel confident enough to take off
with one side failed if need be, an example being on trips to the
Bahamas as long as battery life will carry me to an airport even with a
2nd charging system failure.
- Don't mount the LR3c on the back of the firewall up under the RV10
panel where it is so *^*&^I%%$$#GD hard to get at for adjustment or
replacement.
Bill "experiencing the joys of ongoing OBAM aircraft maintenance" Watson
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 2
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Grounding to tube frame structures |
This is not exactly on topic, but I would like to get Bob's take on it. In a recent
online forum, the writer posted the following in regards to the "forest
of tabs" grounding structure -
> Avionics Ground BusAll other aircraft systems should be grounded through the
avionics ground bus. This can be a "field of tabs" bus or simply a copper strip
to accept ground wires from each of the systems. The avionics ground bus should
not be grounded directly to the airframe. It should be locally isolated from
the airframe with appropriate mounting. An 8 ga. wire should connect the avionics
bus to the firewall pass-through bolt to complete the ground path.
It seems a little silly to insulate the forest of tabs from the airframe and then
connect it to the airframe with a wire to the pass through bolt. I'm also
wondering about bringing all other aircraft system grounds to the "Avionics" buss.
This was supposedly from an article in Kitplanes magazine.
--------
John Evens
Thorp T-18 N71JE (sold)
Kitfox SS7 N27JE (built & flying)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=488746#488746
Attachments:
http://forums.matronics.com//files/final_ground_system_113.jpg
Message 3
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Grounding to tube frame structures |
I have two forests of tabs, one on each side of the firewall. There is a
hefty bolt, 5/16 if I remember correctly but maybe 1/4, that physically
supports the two electrically connects them to the firewall. It's a metal
airplane.
One additional note: I had enough tabs in the forest inside the cabin that
I did not bother with a seperate avionics ground bus. If I run out of tabs,
I will add an avionics ground bus connected to one of the tabs.
-- Art Z.
On Mon, Apr 15, 2019 at 12:24 PM jrevens <jrevens@comcast.net> wrote:
>
> This is not exactly on topic, but I would like to get Bob's take on it.
> In a recent online forum, the writer posted the following in regards to t
he
> "forest of tabs" grounding structure -
>
>
> > Avionics Ground Bus=94All other aircraft systems should be ground
ed
> through the avionics ground bus. This can be a "field of tabs" bus or
> simply a copper strip to accept ground wires from each of the systems. Th
e
> avionics ground bus should not be grounded directly to the airframe. It
> should be locally isolated from the airframe with appropriate mounting. A
n
> 8 ga. wire should connect the avionics bus to the firewall pass-through
> bolt to complete the ground path.
>
--
https://CheerfulCurmudgeon.com/
*"Love wins. Love always wins." Morrie Schwartz*
Message 4
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Grounding to tube frame structures |
On 4/15/2019 12:09 PM, jrevens wrote:
>
> This is not exactly on topic, but I would like to get Bob's take on it. In a
recent online forum, the writer posted the following in regards to the "forest
of tabs" grounding structure -
>
>
>> Avionics Ground BusAll other aircraft systems should be grounded through the
avionics ground bus. This can be a "field of tabs" bus or simply a copper strip
to accept ground wires from each of the systems. The avionics ground bus should
not be grounded directly to the airframe. It should be locally isolated from
the airframe with appropriate mounting. An 8 ga. wire should connect the avionics
bus to the firewall pass-through bolt to complete the ground path.
>
> It seems a little silly to insulate the forest of tabs from the airframe and
then connect it to the airframe with a wire to the pass through bolt. I'm also
wondering about bringing all other aircraft system grounds to the "Avionics"
buss. This was supposedly from an article in Kitplanes magazine.
>
> --------
> John Evens
> Thorp T-18 N71JE (sold)
> Kitfox SS7 N27JE (built & flying)
>
>
I think the logic is that if the avionics ground bus is remote from the
main ground bus at the firewall, keeping it isolated and running its own
ground wire to the firewall serves the same purpose as the firewall
mounted bus: to prevent ground 'loops' (noise in the ground path showing
up in undesired locations).
Charlie
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 5
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Grounding to tube frame structures |
ceengland7(at)gmail.com wrote:
> On 4/15/2019 12:09 PM, jrevens wrote:
>
> >
> >
> > This is not exactly on topic, but I would like to get Bob's take on it. In
a recent online forum, the writer posted the following in regards to the "forest
of tabs" grounding structure -
> >
> >
> > > Avionics Ground BusAll other aircraft systems should be grounded through
the avionics ground bus. This can be a "field of tabs" bus or simply a copper
strip to accept ground wires from each of the systems. The avionics ground bus
should not be grounded directly to the airframe. It should be locally isolated
from the airframe with appropriate mounting. An 8 ga. wire should connect the
avionics bus to the firewall pass-through bolt to complete the ground path.
> >
> > It seems a little silly to insulate the forest of tabs from the airframe and
then connect it to the airframe with a wire to the pass through bolt. I'm
also wondering about bringing all other aircraft system grounds to the "Avionics"
buss. This was supposedly from an article in Kitplanes magazine.
> >
> > --------
> > John Evens
> > Thorp T-18 N71JE (sold)
> > Kitfox SS7 N27JE (built & flying)
> >
> >
> > I think the logic is that if the avionics ground bus is remote from the
> >
>
> main ground bus at the firewall, keeping it isolated and running its own
> ground wire to the firewall serves the same purpose as the firewall
> mounted bus: to prevent ground 'loops' (noise in the ground path showing
> up in undesired locations).
>
> Charlie
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
Agreed, Charlie. I just couldn't see why you would want to insulate the forest
of tabs from the firewall, as shown in the drawing. The direct connection to
the carry through bolt and the firewall seems simpler and smarter. The author
seems to imply that the forest of tabs must be insulated from the airframe,
when the wire connecting it to the bolt connects it to the airframe anyway. I
guess I just don't see the reasoning for "isolating" the bus when it is also connected
with a conductor to the airframe.
--------
John Evens
Thorp T-18 N71JE (sold)
Kitfox SS7 N27JE (built & flying)
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=488751#488751
Message 6
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Grounding to tube frame structures |
On Mon, Apr 15, 2019 at 1:55 PM jrevens <jrevens@comcast.net> wrote:
>
>
> ceengland7(at)gmail.com wrote:
> > On 4/15/2019 12:09 PM, jrevens wrote:
> >
> > >
> > >
> > > This is not exactly on topic, but I would like to get Bob's take on
> it. In a recent online forum, the writer posted the following in regards
> to the "forest of tabs" grounding structure -
> > >
> > >
> > > > Avionics Ground Bus=94All other aircraft systems should be gr
ounded
> through the avionics ground bus. This can be a "field of tabs" bus or
> simply a copper strip to accept ground wires from each of the systems. Th
e
> avionics ground bus should not be grounded directly to the airframe. It
> should be locally isolated from the airframe with appropriate mounting. A
n
> 8 ga. wire should connect the avionics bus to the firewall pass-through
> bolt to complete the ground path.
> > >
> > > It seems a little silly to insulate the forest of tabs from the
> airframe and then connect it to the airframe with a wire to the pass
> through bolt. I'm also wondering about bringing all other aircraft syste
m
> grounds to the "Avionics" buss. This was supposedly from an article in
> Kitplanes magazine.
> > >
> > > --------
> > > John Evens
> > > Thorp T-18 N71JE (sold)
> > > Kitfox SS7 N27JE (built & flying)
> > >
> > >
> > > I think the logic is that if the avionics ground bus is remote from
> the
> > >
> >
> > main ground bus at the firewall, keeping it isolated and running its ow
n
> > ground wire to the firewall serves the same purpose as the firewall
> > mounted bus: to prevent ground 'loops' (noise in the ground path showin
g
> > up in undesired locations).
> >
> > Charlie
> >
> > ---
> > This email has been checked for viruses by Avast antivirus software.
> > https://www.avast.com/antivirus
>
>
> Agreed, Charlie. I just couldn't see why you would want to insulate the
> forest of tabs from the firewall, as shown in the drawing. The direct
> connection to the carry through bolt and the firewall seems simpler and
> smarter. The author seems to imply that the forest of tabs must be
> insulated from the airframe, when the wire connecting it to the bolt
> connects it to the airframe anyway. I guess I just don't see the reasonin
g
> for "isolating" the bus when it is also connected with a conductor to the
> airframe.
>
> --------
> John Evens
> Thorp T-18 N71JE (sold)
> Kitfox SS7 N27JE (built & flying)
>
>
Ah; didn't even see his pic when I posted. You're right; absolutely no
reason to isolate the firewall mounted FOT.
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_c
ampaign=sig-email&utm_content=webmail&utm_term=icon>
Virus-free.
www.avast.com
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_c
ampaign=sig-email&utm_content=webmail&utm_term=link>
<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>
Message 7
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Grounding to tube frame structures |
>
> > > > Avionics Ground Bus=94All other aircraft
> systems should be grounded through the avionics
> ground bus. This can be a "field of tabs" bus
> or simply a copper strip to accept ground wires
> from each of the systems. The avionics ground
> bus should not be grounded directly to the
> airframe. It should be locally isolated from
> the airframe with appropriate mounting. An 8
> ga. wire should connect the avionics bus to the
> firewall pass-through bolt to complete the ground path.
> I think the logic is that if the avionics ground bus is remote from the
> > main ground bus at the firewall, keeping it isolated and running its own
> > ground wire to the firewall serves the same purpose as the firewall
> > mounted bus: to prevent ground 'loops' (noise in the ground path showing
> > up in undesired locations).
Correct. See various examples in
Figure Z-15 https://tinyurl.com/5wxzn7
The 'avionics bus' is a CENTRAL grounding
point located in closest practical proximity
to potential noise VICTIMS(generally all
panel mounted). This ground point may well
be electrically common to the airframe . . .
this would be true if your airplane is all
metal and the panel structure gets 'hooked
up electrically' to the rest of the airplane.
The magic things about an avionics bus:
(1) central location to potential VICTIMS
(2) single point for grounding all components
in constellation of potential VICTIMS.
(3) this ground is NOT SHARED with any potential
ANTAGONIST (all those other things scattered
around the airplane).
If the airplane is composite, then you'll need
to extend the avionics ground down to the firewall
ground point with either a relatively robust
bond wire (8awg is a bit overkill 12AWG is
probably fine for modern suite of solid-state
avionics).
The avionics ground bus generally has lots
of small wires none of which carries big
currents. A product like this
https://tinyurl.com/y44yngbm
is much easier to mount in close proximity
to the panel mounted electro-whizzies.
For potential antagonists, grounding
to the AIRFRAME can be managed with
a product like this:
https://tinyurl.com/y4gvepup
But there's nothing magic about
bringing all your airframe grounds
to a single point. If you have an
all-metal airplane, remote grounding
of things like landing lights, strobe
supplies, landing gear motors, batteries
etc is quite practical.
Insulating your ground system from the
airframe is not recommended and has
no demonstrable value. However, running
all airframe grounds to the firewall thru-
stud bus is not a 'bad' thing to do either.
Bob . . .
Other Matronics Email List Services
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|