Today's Message Index:
----------------------
1. 05:08 AM - Magnetos connection to ground (Carlos Trigo)
2. 05:45 AM - Re: Magnetos connection to ground (Charlie England)
3. 07:58 AM - Avionics Master (Robert L. Nuckolls, III)
4. 10:04 AM - Re: Magnetos connection to ground (Charlie England)
5. 10:33 AM - Re: Magnetos connection to ground (Robert L. Nuckolls, III)
6. 11:25 AM - Re: Magnetos connection to ground (David Lloyd)
7. 02:53 PM - Re: Magnetos connection to ground (Stuart Hutchison)
Message 1
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Subject: | Magnetos connection to ground |
Guys
Which is the best practice to connect the Magnetos Ground terminals to the Firewall
Ground "forest"?
Is it recommended to wire Left and Right magnetos with separate wires, or can they
be connected to each other and then to the Ground forest?
And how about the wires to be used, should they be shielded or unshielded? Which
gauge?
One more question: for the connections from the ignition switch to both magnetos,
I am using shielded wires, so should the shields be connected on both sides
(like it is recommended in Tony Bingelis' books), or only on one side?
In this last case, the shield should be connected in the magneto side, so is it
good to connect the shield to the Ground terminal of the magneto?
Thanks in advance
Carlos
Message 2
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Subject: | Re: Magnetos connection to ground |
On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo <trigo@mail.telepac.pt> wrote:
> trigo@mail.telepac.pt>
>
> Guys
>
> Which is the best practice to connect the Magnetos Ground terminals to the
> Firewall Ground "forest"?
> Is it recommended to wire Left and Right magnetos with separate wires, or
> can they be connected to each other and then to the Ground forest?
>
> And how about the wires to be used, should they be shielded or unshielded?
> Which gauge?
>
> One more question: for the connections from the ignition switch to both
> magnetos, I am using shielded wires, so should the shields be connected on
> both sides (like it is recommended in Tony Bingelis' books), or only on one
> side?
> In this last case, the shield should be connected in the magneto side, so
> is it good to connect the shield to the Ground terminal of the magneto?
>
> Thanks in advance
> Carlos
Hi Carlos,
You don't need to carry the mag ground to the firewall. The wire from the
mag to the switch should be a shielded wire, with the center conductor tied
to the 'P' lead terminal and the shield tied to the mag's case, using any
convenient screw on the case. The mag's case is electrically bonded to the
engine, and the engine has a ground to the firewall/battery negative. The
other end of the wire should have the center (P-lead) tied to one of the
terminals on your switch, and the shield tied to the other terminal (or the
ground terminal, if you're using a key type switch). No need to ground it
locally near the switch, and I don't do it, since there's the potential of
injecting mag noise into your other electronics. Grounding it locally gives
the noise you're trying to shield an additional path to follow, which may
be around/through other electronics. Grounding it locally can also mask a
failed shield connection, because the P lead would still be shorted to
ground even with the shield broken. The hazard of this is when you (or
worse, someone else) is doing maintenance. If you have a broken shield &
don't know it, everything will appear to be normal until someone is doing
maintenance & removes a ground wire for electrical safety. If this
ungrounds the engine from the rest of the airframe, the mag is now 'hot',
even with the mag switch 'off'.
The shielded P-lead has a dual purpose. While the engine is operating, the
shield is grounded only at the mag and functions purely as a shield, to
limit the radiated noise from the mag. When you turn off the mag, you're
actually closing the switch contacts, and the shield serves as the ground
return to short out mag's primary coil.
Charlie
Message 3
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>Comments/Questions: Bob ... I took our seminar many years ago and
>you suggested not to use an Avionics Master .. that you can just
>turn on each component etc. So that's what i did .. and it's worked
>just fine. However, I'm now redesigning my panel with remote mount
>avionics .. COMM, TRANSPONDER, AUDIO PANEL etc. Now I'm curious how
>I should protect these during start up? Should I now plan for a
>MASTER or do I have to use individual switches for each component?
>
>Thank you for your expertise!
>
>Regards,
>
>Dave
The avionics master switch was borne of an idea not
grounded in physics. I was at Cessna in the 60's when,
for reasons we didn't understand, radios were being
killed in brand new airplanes by the dozens. Adding
the AV Master did indeed 'help' but for reasons we
did not know.
Check out the writings on my website concerning
the AV Master.
http://tinyurl.com/mr2jk8g
If you ever get to OSH, it would be interesting
to stop by the booths of the manufacturer of ANY
solid state device be it radio, instrument, system
controller, etc. and inquire as to their recommendations
for 'protecting their product from the effects of
engine cranking'.
If any one of them says that an AV Master is recommended,
I'd like to hear about it. Since the universal adoption
of DO-160 protocols about 50 years ago, risks to electronics
from startup transients (or other any well understood
transients) has gone to zero.
Turns out that the 'radio killer' in the 1960's Cessnas
was soggy batteries combined with poor design rules
for the radio's newly minted solid state power supplies.
That combination of shortfalls was easily and has been
eliminated.
Bob . . .
Message 4
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Subject: | Re: Magnetos connection to ground |
On Sat, Dec 3, 2016 at 7:44 AM, Charlie England <ceengland7@gmail.com>
wrote:
>
>
> On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo <trigo@mail.telepac.pt>
> wrote:
>
>> trigo@mail.telepac.pt>
>>
>> Guys
>>
>> Which is the best practice to connect the Magnetos Ground terminals to
>> the Firewall Ground "forest"?
>> Is it recommended to wire Left and Right magnetos with separate wires, or
>> can they be connected to each other and then to the Ground forest?
>>
>> And how about the wires to be used, should they be shielded or
>> unshielded? Which gauge?
>>
>> One more question: for the connections from the ignition switch to both
>> magnetos, I am using shielded wires, so should the shields be connected on
>> both sides (like it is recommended in Tony Bingelis' books), or only on one
>> side?
>> In this last case, the shield should be connected in the magneto side, so
>> is it good to connect the shield to the Ground terminal of the magneto?
>>
>> Thanks in advance
>> Carlos
>
> Hi Carlos,
>
> You don't need to carry the mag ground to the firewall. The wire from the
> mag to the switch should be a shielded wire, with the center conductor tied
> to the 'P' lead terminal and the shield tied to the mag's case, using any
> convenient screw on the case. The mag's case is electrically bonded to the
> engine, and the engine has a ground to the firewall/battery negative. The
> other end of the wire should have the center (P-lead) tied to one of the
> terminals on your switch, and the shield tied to the other terminal (or the
> ground terminal, if you're using a key type switch). No need to ground it
> locally near the switch, and I don't do it, since there's the potential of
> injecting mag noise into your other electronics. Grounding it locally gives
> the noise you're trying to shield an additional path to follow, which may
> be around/through other electronics. Grounding it locally can also mask a
> failed shield connection, because the P lead would still be shorted to
> ground even with the shield broken. The hazard of this is when you (or
> worse, someone else) is doing maintenance. If you have a broken shield &
> don't know it, everything will appear to be normal until someone is doing
> maintenance & removes a ground wire for electrical safety. If this
> ungrounds the engine from the rest of the airframe, the mag is now 'hot',
> even with the mag switch 'off'.
>
> The shielded P-lead has a dual purpose. While the engine is operating, the
> shield is grounded only at the mag and functions purely as a shield, to
> limit the radiated noise from the mag. When you turn off the mag, you're
> actually closing the switch contacts, and the shield serves as the ground
> return to short out mag's primary coil.
>
> Charlie
>
> Forgot to add, each mag should be a separate entity, with its own shielded
P-lead. The only thing that should be common is (potentially) the grounding
(shutdown) terminal(s) in the switch, if you're using a key-switch type
control for the mags. If you're using toggles, then nothing would be common
between the mags' wiring.
Message 5
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Subject: | Re: Magnetos connection to ground |
At 07:04 AM 12/3/2016, you wrote:
>
>Guys
>
>Which is the best practice to connect the Magnetos Ground terminals
>to the Firewall Ground "forest"?
>Is it recommended to wire Left and Right magnetos with separate
>wires, or can they be connected to each other and then to the Ground forest?
>
>And how about the wires to be used, should they be shielded or
>unshielded? Which gauge?
They can be any size . . . but 20AWG or larger is
sort of standard practice for mechanical robustness.
Some OEM TC airplane guys don't use anything smaller
than 20AWG under the cowl.
>One more question: for the connections from the ignition switch to
>both magnetos, I am using shielded wires, so should the shields be
>connected on both sides (like it is recommended in Tony Bingelis'
>books), or only on one side?
>In this last case, the shield should be connected in the magneto
>side, so is it good to connect the shield to the Ground terminal of
>the magneto?
Here is the recommended configuration for managing
p-leads.
Emacs!
This connection philosophy offers greatest noise
control and eliminates any potential for burning
the p-leads with starter current in the event that
the crankcase bonding jumper is disconnected (don't
laugh . . . I've seen it happen twice).
Bob . . .
Message 6
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Subject: | Re: Magnetos connection to ground |
A comment about the P-lead mounting.
That wire connection at the mag is subject to a lot of vibration and turbul
ence.
Secure the P-lead as if a room full of kindergarten kids are going to use i
t as a tug of rope game.
We all know the danger of a disconnected P-lead leaving the mag hot and rea
dy to fire a plug if the prop is moved.
---------------------------------------------------------------------------
-----
----- Original Message -----
From: Charlie England
To: aeroelectric-list@matronics.com
Sent: Saturday, December 03, 2016 10:03 AM
Subject: Re: AeroElectric-List: Magnetos connection to ground
On Sat, Dec 3, 2016 at 7:44 AM, Charlie England <ceengland7@gmail.com> wr
ote:
On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo <trigo@mail.telepac.pt> wr
ote:
epac.pt>
Guys
Which is the best practice to connect the Magnetos Ground terminals t
o the Firewall Ground "forest"?
Is it recommended to wire Left and Right magnetos with separate wires
, or can they be connected to each other and then to the Ground forest?
And how about the wires to be used, should they be shielded or unshie
lded? Which gauge?
One more question: for the connections from the ignition switch to bo
th magnetos, I am using shielded wires, so should the shields be connected
on both sides (like it is recommended in Tony Bingelis' books), or only on
one side?
In this last case, the shield should be connected in the magneto side
, so is it good to connect the shield to the Ground terminal of the magneto
?
Thanks in advance
Carlos
Hi Carlos,
You don't need to carry the mag ground to the firewall. The wire from t
he mag to the switch should be a shielded wire, with the center conductor t
ied to the 'P' lead terminal and the shield tied to the mag's case, using a
ny convenient screw on the case. The mag's case is electrically bonded to t
he engine, and the engine has a ground to the firewall/battery negative. Th
e other end of the wire should have the center (P-lead) tied to one of the
terminals on your switch, and the shield tied to the other terminal (or the
ground terminal, if you're using a key type switch). No need to ground it
locally near the switch, and I don't do it, since there's the potential of
injecting mag noise into your other electronics. Grounding it locally gives
the noise you're trying to shield an additional path to follow, which may
be around/through other electronics. Grounding it locally can also mask a f
ailed shield connection, because the P lead would still be shorted to groun
d even with the shield broken. The hazard of this is when you (or worse, so
meone else) is doing maintenance. If you have a broken shield & don't know
it, everything will appear to be normal until someone is doing maintenance
& removes a ground wire for electrical safety. If this ungrounds the engine
from the rest of the airframe, the mag is now 'hot', even with the mag swi
tch 'off'.
The shielded P-lead has a dual purpose. While the engine is operating,
the shield is grounded only at the mag and functions purely as a shield, to
limit the radiated noise from the mag. When you turn off the mag, you're a
ctually closing the switch contacts, and the shield serves as the ground re
turn to short out mag's primary coil.
Charlie
Forgot to add, each mag should be a separate entity, with its own shielde
d P-lead. The only thing that should be common is (potentially) the groundi
ng (shutdown) terminal(s) in the switch, if you're using a key-switch type
control for the mags. If you're using toggles, then nothing would be common
between the mags' wiring.
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
Message 7
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Subject: | Re: Magnetos connection to ground |
Yes, dangers such as this recent example . that caught the
pilot by surprise because the switches were left on .
https://youtu.be/XFqDZagVeJU <https://youtu.be/XFqDZagVeJU>
> On 4 Dec. 2016, at 06:23, David Lloyd <skywagon@charter.net> wrote:
>
> A comment about the P-lead mounting.
>
> That wire connection at the mag is subject to a lot of vibration and
turbulence.
> Secure the P-lead as if a room full of kindergarten kids are going to
use it as a tug of rope game.
> We all know the danger of a disconnected P-lead leaving the mag hot
and ready to fire a plug if the prop is moved.
>
>> ----- Original Message -----
>> From: Charlie England <mailto:ceengland7@gmail.com>
>> To: aeroelectric-list@matronics.com
<mailto:aeroelectric-list@matronics.com>
>> Sent: Saturday, December 03, 2016 10:03 AM
>> Subject: Re: AeroElectric-List: Magnetos connection to ground
>>
>>
>>
>> On Sat, Dec 3, 2016 at 7:44 AM, Charlie England <ceengland7@gmail.com
<mailto:ceengland7@gmail.com>> wrote:
>>>
>>>
>>> On Sat, Dec 3, 2016 at 7:04 AM, Carlos Trigo <trigo@mail.telepac.pt
<mailto:trigo@mail.telepac.pt>> wrote:
<trigo@mail.telepac.pt <mailto:trigo@mail.telepac.pt>>
>>>>
>>>> Guys
>>>>
>>>> Which is the best practice to connect the Magnetos Ground terminals
to the Firewall Ground "forest"?
>>>> Is it recommended to wire Left and Right magnetos with separate
wires, or can they be connected to each other and then to the Ground
forest?
>>>>
>>>> And how about the wires to be used, should they be shielded or
unshielded? Which gauge?
>>>>
>>>> One more question: for the connections from the ignition switch to
both magnetos, I am using shielded wires, so should the shields be
connected on both sides (like it is recommended in Tony Bingelis'
books), or only on one side?
>>>> In this last case, the shield should be connected in the magneto
side, so is it good to connect the shield to the Ground terminal of the
magneto?
>>>>
>>>> Thanks in advance
>>>> Carlos
>>> Hi Carlos,
>>>
>>> You don't need to carry the mag ground to the firewall. The wire
from the mag to the switch should be a shielded wire, with the center
conductor tied to the 'P' lead terminal and the shield tied to the mag's
case, using any convenient screw on the case. The mag's case is
electrically bonded to the engine, and the engine has a ground to the
firewall/battery negative. The other end of the wire should have the
center (P-lead) tied to one of the terminals on your switch, and the
shield tied to the other terminal (or the ground terminal, if you're
using a key type switch). No need to ground it locally near the switch,
and I don't do it, since there's the potential of injecting mag noise
into your other electronics. Grounding it locally gives the noise you're
trying to shield an additional path to follow, which may be
around/through other electronics. Grounding it locally can also mask a
failed shield connection, because the P lead would still be shorted to
ground even with the shield broken. The hazard of this is when you (or
worse, someone else) is doing maintenance. If you have a broken shield &
don't know it, everything will appear to be normal until someone is
doing maintenance & removes a ground wire for electrical safety. If this
ungrounds the engine from the rest of the airframe, the mag is now
'hot', even with the mag switch 'off'.
>>>
>>> The shielded P-lead has a dual purpose. While the engine is
operating, the shield is grounded only at the mag and functions purely
as a shield, to limit the radiated noise from the mag. When you turn off
the mag, you're actually closing the switch contacts, and the shield
serves as the ground return to short out mag's primary coil.
>>>
>>> Charlie
>>>
>> Forgot to add, each mag should be a separate entity, with its own
shielded P-lead. The only thing that should be common is (potentially)
the grounding (shutdown) terminal(s) in the switch, if you're using a
key-switch type control for the mags. If you're using toggles, then
nothing would be common between the mags' wiring.
>
>
> <https://www.avast.com/antivirus>
> This email has been checked for viruses by Avast antivirus software.
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