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Question: can these wires be put in one wire bundle?

 
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nuckolls.bob(at)aeroelect
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PostPosted: Sun Oct 07, 2018 9:52 am    Post subject: Question: can these wires be put in one wire bundle? Reply with quote

At 08:44 AM 10/7/2018, you wrote:
Quote:
Oh, Marcel:

Some other tricks I do:
1 - I use Black and Red wire for primary B+ voltages.
2 - I twist the B+ wires - about 4 to 6 twists per inch. This helps in keeping noise out of the system.

Noise from where to where?

Quote:
3 - Use shielded cables for Audio lines.
4 - Audio lines are Grounded ONLY at the source - Example: At the radio and at the intercom.

Treat shields per manufacturer's installation instructions.
Shields are sometimes part of the energy management.

Quote:
5 - If you have two set of similar wires - Example: A RS232 from one Nav/Comm and another Nav/Comm keep them apart and/or use shielded wires.

There is no reason for doing this. If we attempted
to keep everythting separated behind the panel
of a King Air, it would look like a spider-web
as opposed to an organized, mechanically
secure installtion.

Quote:
Side note: I have installed 4 sets of Garmin G5's. NOISE is a huge issue with them. I use Toroids on the B+ hot wires, wrap them well, the more wraps the better and ONLY on the B+ Positive wire.

Noise from where to where? What is the nature
of the noise? Are these not a DO160
qualified system? Is the G5 the victim or
the antagonist?


Bob . . .


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nuckolls.bob(at)aeroelect
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PostPosted: Sun Oct 07, 2018 12:43 pm    Post subject: Question: can these wires be put in one wire bundle? Reply with quote

Quote:
Quote:
Some other tricks I do:
1 - I use Black and Red wire for primary B+ voltages.
2 - I twist the B+ wires - about 4 to 6 twists per inch. This helps in keeping noise out of the system.

Noise from where to where?

Barry - When I know where the noise is coming from I attack the noise. In the meantime I do what I can to prevent the noise from attacking
the system.


Quote:
Barry - There sure is! You do what you can where you can to keep the noise down OR you are forced to live with it.

You speak of 'the noise' . . . never met a
noise problem I couldn't whip . . . albeit
some were pretty bizarre. But in decades
of helping push certified iron down the
production line, not once have I encountered
a noise issue that was cured or would have
be prevented by:

Adding inductors to power lines of
a properly qualified appliance, twisting
any pairs of wires together, adding shielding
above or beyond that specified by the
manufacturer of the system or adding/increasing
separation of coaxes from other wires in
the airframe.

Quote:
Barry - Spider Web. They are very organized. It's the Rat's Nest I despise.
You keep separated what you can. You use shielded wire where you can.
You of course do not have to go weird in your actions.
But, the issue becomes a problem AFTER the wiring is complete and THEN you
find you have noise. Then you scramble with capacitors, coils and filter
networks - Maybe or Maybe not being able to solve the problem ONLY to
find proper wiring would have eliminated the noise.

I have never encountered a case of 'improper wiring'.
If moving a wire or adding an heretofore unspecified
shield, then there's something seriously wrong with
the selection of hardware.

I prefer to identify the victim, point of entry for
noise into that system. Identify the noise source.
Identify the propagation pathway. Then craft a
'fire-break' in that pathway to reduce interference
to acceptable levels.

Quote:
Why scramble for a band-aid instead of eliminating the problem?

But Barry,

Quote:
Quote:
Side note: I have installed 4 sets of Garmin G5's.
NOISE is a huge issue with them. I use Toroids on the B+ hot
wires, wrap them well, the more wraps the better and ONLY on the
B+ Positive wire.

Noise from where to where? What is the nature
of the noise? Are these not a DO160
qualified system?

Barry - I do not know! They are a Garmin system (LCD Attitude Indicator, ASI,
VSI, HSI and they interface to Panel Mounted GPS & A/P) pretty much an all glass panel.

https://www.garmin.com/en-US/blog/aviation/announcement-g5-electronic-flight-instrument-as-dghsi-in-certificated-aircraft/
Okay, if these are going into TC ships, then they must
have been vetted for EMC.

If they succumb to some stimulus in an existing airframe,
the stimulus has to be much larger and/or of a nature
not anticipated by the folks who craft certification protocols.

If a filter was found necessary to protect
functionality of the Garmin system, how do you know
that the same antagonist isn't deleterious to other
systems? What was the core material used and number of
turns. What was the value of inductance added with
this filter (speaks to the spectrum of noise for which
his would be an effective filter). Are you sure that
the core 'packed with as many turns as possible' was
not saturated with the DC current flow through its
winding?

Quote:

Is the G5 the victim or
the antagonist?

Barry - It is the VICTIM, as the G5 has a Noise Testing program built into them.
The big issue of noise, is because it has a remote mounted Magnetometer.


What does the G5 installation manual say about noise?
Remote magnetometers have been around for nearly a century
and yes, need to be thoughtfully installed
to avoid interference to its accuracy . . . but adding
inductance to the power supply line for an input qualified
to Mil-STD-704 stimulus would not be one of the factory
recommended fixes.


Bob . . .


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PostPosted: Mon Oct 08, 2018 8:47 am    Post subject: Question: can these wires be put in one wire bundle? Reply with quote

Quote:

There is another issue that has snuck its head into our 'modern' aviation world. Things Change - Way Back in Bob N.'s day of King Air and simple bundles of wires with ALL cables bundled together is No Longer. We have new items entering the market place every day and many produce noise. We have to do what ever we can to reduce and eliminate all sorts of noise. Here on this list we spoke about the modern noise from LED's. It's not going away.


Barry, your talking about hardware that would
not be allowed onto a production airplane . . .
twisting power wires never helped any
noise issue. It has mitigated a magnetic
interference situation with windshield mounted
compasses . . . twisting the wires (or using
a shielded wire for outbound and return) on
the light bulb reduced heading errors from that
source to zero.

I have designed, built, qualified and integrated dozens
of appliances onto type certificated airplanes
with the notion that EVERY qualified device should
live happily with all other qualified devices
with NO special attention on the part of the
installer/system integrator with respect to noise.

Installation instructions were expected to include
special considerations with respect to environment,
orientation, mechanical mounting, etc. But special
considerations with respect to noise would be
hard to sell to the ACO.

One of the last noise issues I worked at Beech was
a newly qualified cabin HVAC system wherein the
rear mounted blower hosed the ADF.
Ran the blower in our lab and found it to be
exceedingly noisy.

This device was recently 'qualified' by a lab in
Dallas. I drove down and visited the lab. Looked
a their test set up and talked with the test technician.
Looked at his test data plot. "Wow", says he, "this
the the quietest motor I've ever tested". To be sure
the plots didn't rise off the receiver's noise floor!

We poked around the EMC test cell and found that the
coax through the wall to their conducted noise
transformer had been disconnected . . .

Fortunately, there were only about a dozen products
they had erroneously holy watered in that test
cell . . easy to spot in the test data. The
test technician wasn't experienced enough to know that
the noise was never zero. It just had to be below
a pass/fail line.

We had a dozen systems in the field. Modifying
the blower would call for re-qualification. Made
a midnight run to Captor Corporation where
a fellow gray-beard and I crafted a filter-connector
to go on the end of the harness that mated with the
blower.

I had worked with this fellow for decades on
a host of filter designs but this was the
first time we met face to face and hammered
out a solution together. He was semi-retired
and I was getting close . . . it was a
great experience.

[img]cid:.0[/img]

Had to do this kind of thing on another airplane
where vintage starter-generator controllers (never
qualified to modern design philosophies) needed
a bunch of capacitors installed under the
connector back shell.

[img]cid:.1[/img]

These noise problems were the result of poorly
designed and/or qualified devices. The fact
that they were fielded made it necessary to
craft 'band aids' to bring them into compliance.

But these are very rare circumstances. The
noises from products you allude to would
not be mitigated by line twisting or repositioning
of wires. Adding some filtering might do
the job . . . we've done that on several
devices discussed here on the List.

Yes, many of my anecdotes have some age on
them . . . been doing this for a long time.
But the SCIENCE hasn't materially changed in
my lifetime.

And by the way, production airplanes are generally
wired with white wire.


Bob . . .


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