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Avionics Installation stanards


milotron

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This might be a bit of an open ended question and may be a little OCD, but it is about installation of replacement avionics.

What are the standards or normal expectations when installing, say, a GPS/NAV/COM to replace an existing NAV/COM? Would it be to replace all wiring harness that this device interfaces with; butt splice or extend existing wiring to suit the new equipment; terminate existing wiring to new connector pins or....?  It seems that a lot of replacement avionics take the same signals/inputs/outputs and simply need to have these conductors landed on the new proprietary connector assembly.  Obviously there are other performance constraints requiring wire replacement ( coax, etc comes to mind )

What is the standard practice for this?

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Many go the cheapest route, re-using as many wires as possible...

ultra cheap, includes abandoning un-used wires in place.

People looking for problem free and noise free installations use all new wires in their installation.  And they remove all the old stuff to preserve UL.

In some cases...  like replacing one radio with a similar like Avidyne for an old Garmin or a BK KT74 in place of an old BK 76A, only a few wires are added or replaced for the new functionality....

Does that answer the question?

Best regards,

-a-

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Thanks. Sort of... I would have thought that there would be some standard or expectation of conformance on behalf of the installer as everything else seems to be quite regulated. i suppose that so long as what was done meets whatever level of acceptance the the A/P deems acceptable, then it is airworthy. Beyond that so long as it performs and meets the checkout items from them manufacturer, I guess that is all that is required.

I know behind the panel of my K there are sedimentary levels of quality and attention to detail. Sadly is gets worse with the newer work. All of the old Loran wiring is still in place, plus it looks like the older equipment also used Cannon plugs for easier swapping of equipment, while the newer stuff seems hardwired direct to the connectors on the back of the unit.

I am an electrical engineer so am a little sensitive to this stuff. I know what I see done in aircraft I would never accept on the systems or equipment I work on, and they can't fall out of the sky!

Have a look at wiring on a sailboat or luxury power boat these ays. It makes those backyard car stereo installations look good.

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You will probably like working with your installer and discussing the details...  many MS people have skills to do this job really well.  By working with a mechanic or an electronics pro, you get to do the work, and they sign the log book.

As for removing the old stuff...  use caution, it is easy to accidently stress some of the other things you want to keep working.

Best regards,

-a-

 

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My installer insisted on replacing much of the wiring anyway, including antenna and it's wiring for new gps, they said it prevents problems down the road.

But I was replacing almost the entire right side, if only replacing a com,nav unit not sure they would have been more surgical.

This is what my boat looks like (the white loose wires are mine):

b121779256edb6db8a544ef6e48fc0a9.jpg

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Nice. Better than most I have seen here.

I have been discussing some future installs with my AME and he is willing to inspect, sign off and do the revised weight/balance, etc. I suspect I may go this route even though it would likely cost a bit for some specialized crimper dies, etc.

it is a little frustrating as am in a position where I should be paying people to do this work, but after seeing what most installers and techs seems to think is acceptable, means that I usually have to go back in and clean it up to my standards.  I can't hire people to work on my house for the same reason...

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Panel wiring is one part technical and another part artwork.

when you open an electrical panel and everything is organized and cut to perfect lengths and go around corners in perfect 90° bends, everything is labeled including the wires... it is a thing of beauty...

This comes from selling industrial machinery for a shop that had an artist/electrician building control panels.  Every cut-out was perfectly placed to match the drawing that was perfectly laid out.  Customer tours included looking at stainless steel panels, inside and out.

If you ever have to work on a panel in the field doing maintenance, you immediately appreciate a panel that was built right verses the one that was built for the lowest cost...

Best regards,

-a-

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2 hours ago, milotron said:

This might be a bit of an open ended question and may be a little OCD, but it is about installation of replacement avionics.

What are the standards or normal expectations when installing, say, a GPS/NAV/COM to replace an existing NAV/COM? Would it be to replace all wiring harness that this device interfaces with; butt splice or extend existing wiring to suit the new equipment; terminate existing wiring to new connector pins or....?  It seems that a lot of replacement avionics take the same signals/inputs/outputs and simply need to have these conductors landed on the new proprietary connector assembly.  Obviously there are other performance constraints requiring wire replacement ( coax, etc comes to mind )

What is the standard practice for this?

A good avionics shop should know.  On my panel upgrade all old wiring was removed and replaced.  This is the hardware in the back of my plane and how a good avionics shop's work should look like.

Avionics Rack for N9148W.jpg

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AC 43.13 ch 11 will answer some of your questions. In some instances it is perfectly acceptable to replace the pins and connectors on the end of the harness with the ones for the new radio. 

In other cases there may be some problems with this. 

Old systems used airframe ground for return. Newer stuff provides its own low path for the return which is not the same ground.

Old wires are often very stiff and difficult to work with depending on age. 

A lot of the older stuff was wired with larger wire and you will not be able to get it into the new high density connectors on the new stuff. 

 

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Moonys from the factory (at least in 1975) are not done proper.   There is a mass of wires that run along the firewall.  Not separated into bundles by class and stuff.  Each wire is labeled.  Probably the best way to install things would be to unpin the cannon plugs or make up new cannon plugs so there would be no splices.   I guess the uninsulated voltage dropping resistor on the eyeball light in the roof would be the best example of  how things were done back then.

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Other things like using unshielded wire for the strobes and grounding the power supplies to the outboard wing.  Then often intercom grounds are terminated near the jack instead of a center point ground then you have all kinds of strobe noise in the headset. 

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  • 2 weeks later...

For reference  I sometimes refer to Stien Air's   web site   not so much for 'how to cable striping technique'   but to keep a consistent  and standard practice   from a reputable outfit.

sometimes to get parts  and other accessories.

http://www.steinair.com/documents-and-support/videos/ 

http://aeroelectric.com/Photos_Figures.html

 

James '67C

Edited by jamesm
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On 2/19/2017 at 2:53 PM, donkaye said:

A good avionics shop should know.  On my panel upgrade all old wiring was removed and replaced.  This is the hardware in the back of my plane and how a good avionics shop's work should look like.

Avionics Rack for N9148W.jpg

Your brake reservoir looks a little low in that picture Don!

Oops, looking a little closer, I see you have the line protected with spiral wrap.

Edited by Greg_D
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