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Dear Homebuilt Electronics Manufacturers...

BuckWynd

Well Known Member
Time for a bit of a rant. Over the past two weeks, I have experienced TWO separate failures of what I consider to be inappropriate electrical connectors. One of them resulted in a loss of power to the affected unit. One was caught before it could cause any issues. On top of this, I have received several reports from acquaintances over the past few years of similar issues.

All of them are related to what I call "non aerospace-grade" wire connectors in a couple of common, apparently-accepted formats, and they are in many of our electronic units. (And yes, all of these installations were installed in accordance with the manufacturer's instructions and good building practices.)

For several reasons, I will not discuss any aviation manufacturer names on this thread, and I think we should leave that out of the discussion. I just want to point out what I think are connectors that should NOT be in electronics that are subject to vibration levels like that of a light airplane.

The photos below show the types of connectors I'm referring to. (These are not mine.) Both types require you to merely strip the wire and insert it into a recess. After that, the method of securing it is either 1). push the wire until it "locks" in place, or b). tighten a set-screw or plate onto the bare wire, flattening it down. The white one is called a "press-fit connector" or a "press connector," and the green one is called either a "pluggable terminal block," Euroblock, or Phoenix connector.

In my opinion, these are wonderful methods to secure your stereo speaker wires or your electronic hobby power supply cables, but they are alarmingly unsecure, subject to failure, and totally unsuitable for use in any aerospace vehicle except maybe a hobby drone.

Bare wires tightened under a screw? Or worse, pushing a bare wire into a hole and hoping it stays there? Why, oh why, are we so accepting of this kind of nonsense in our airplanes? I spent over $700 on some really nice wire crimping tools of various kinds for my airplane project. I don't want some kind of half-baked hobby connectors on my critical flight gear. Give me a ring terminal ANY day. I am now to the point where I will never buy an aviation product, no matter how awesome it is, if it requires me to use a Euro connector.

I've never had a Molex, CPC, D-sub, PIDG Ring/Spade, Deutsch, Seal-All, or other normal connector simply disconnect or fall apart under normal conditions. So manufacturers, please stop using unsuitable, cheesy connectors in your aviation products!

And don't get me started on those tiny 26 AWG wires coming out of that certain brand of trim servo!

Is it just me? Sigh...


i-kGWSf38-L.jpg


i-WpmNq7T-L.jpg


i-qHQP282-L.jpg
 
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Ok...I get what you're saying, and if I'd experienced a failure due to substandard design, I'd be annoyed as well.

But...the picture you have above is of a popular brand of LED landing light that we all know and love. Was that your failure? If so, it seems like complaining here isn't doing nearly as much good as reaching out the the manufacturer. He's a good guy with great customer service. If you legit have a problem he'll take care of you.

p.s. I hate the idea that the screw type connector is used on p-mags, but I'm going with two anyway, since people don't seem to be having much of a problem with them.
 
Connectors

One SHOULD be using crimp ferrules on those type connectors, not just putting bare wires into them. They are cheap and secure and have a plastic lead-in that prevents the cut end of the insulation from being a stress point.
Ed
 
Ok...I get what you're saying, and if I'd experienced a failure due to substandard design, I'd be annoyed as well.

But...the picture you have above is of a popular brand of LED landing light that we all know and love. Was that your failure? If so, it seems like complaining here isn't doing nearly as much good as reaching out the the manufacturer. He's a good guy with great customer service. If you legit have a problem he'll take care of you.

p.s. I hate the idea that the screw type connector is used on p-mags, but I'm going with two anyway, since people don't seem to be having much of a problem with them.

To the OP:

On the wig wag module - If you didn't like it, why didn't you just de-solder the connector and solder in wires with the connector you like? In my experience, these problems can be resolved by various wire restraining methods. I agree that screw down type connectors are not the best method for use with vibration, but I don't understand why you didn't take measures (i.e. restraining wires so that don't vibrate at teh connection and can't pull out) during installation to minimize risk.

I had something similar on the B&C regulator and the wiring bundle is fully restrained close to that device to minimize any potential issues.

Larry
 
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One SHOULD be using crimp ferrules on those type connectors, not just putting bare wires into them. They are cheap and secure and have a plastic lead-in that prevents the cut end of the insulation from being a stress point.
Ed

That's a good idea, Ed -- perhaps the manufacturers of these devices should include them with their products, or at least mention them in the instructions. But they don't. In fact, they specifically say to insert bare wires into the connectors.
 
I agree that screw down type connectors are not the best method for use with vibration

You mean like electronic ignition modules and magnetos mounted directly on an engine? I agree completely!
 
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You mean like electronic ignition modules and magnetos mounted directly on an engine? I agree completely!
And yet... You don't hear of a lot of failures of those. Despite being on an engine.

The green Phoenix connectors (screw down type) are essentially crimp terminals, with the crimp being provided by a screw. Adequate torque on the screw = adequate crimp and adequate locking to prevent loosening under vibration.
 
The fact is, these green Euro connectors are used in our aviation products because they are easy to install on a circuit board, they're cheap, and they're available. But just because we are used to seeing them does not make them suitable for our applications.

Once again, my posting here is not a request for these manufacturers to fix any issues I've had, but for designers to think long and hard before they design aviation products with the first components that come along.

It's also a reminder for builders to be VERY cautious when selecting products to put in their airplanes.
 
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Did you provide any support for the wires close to the connectors? Or are the connectors themselves taking the load of supporting the wires?
 
Did you provide any support for the wires close to the connectors? Or are the connectors themselves taking the load of supporting the wires?

Hi Mike,

Yes the wires were supported as well as they could be, mechanically. The fact is, you simply can't indefinitely vibrate a bare wire conductor that's mashed underneath a screw mounted directly to an aircraft engine, and have it last forever. I am thinking about adding some non-conducting "goop" type sealant over the connector to further stabilize the last inch of wire where it goes in.
 
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One SHOULD be using crimp ferrules on those type connectors, not just putting bare wires into them. They are cheap and secure and have a plastic lead-in that prevents the cut end of the insulation from being a stress point.
Ed

I'm shamelessly hijacking this, but what sort of ferrule are you talking about? I agree with the OP that these are less than ideal, and would happily upgrade the end if I could find something reasonable to use.
 
Ferrules

I'm shamelessly hijacking this, but what sort of ferrule are you talking about? I agree with the OP that these are less than ideal, and would happily upgrade the end if I could find something reasonable to use.
If you have difficulty with the linkl go to Amazon and search for Wire Ferrules. They are used almost exclusively in Europe for exactly this reason.
Ed

I use a kit like this:
https://www.amazon.com/s?k=wire+fer...rrule,aps,1261&ref=nb_sb_ss_midas-iss-sm_2_12

Ed
 
In my humble opinion, adding a crimped on ferrule simply adds another potential failure point and it is my understanding that the green style terminal strip is intended for use with stranded wire, not a solid pin.

A small service loop and strain relief very close to the connection is the ticket here.

At annual, check the tightness of the screws and condition of the wires. Since you have the service loop, you will be able to cut off the 1/4 inch of smashed wire, re-strip and reconnect if needed.

Bevan


If you have difficulty with the linkl go to Amazon and search for Wire Ferrules. They are used almost exclusively in Europe for exactly this reason.
Ed

I use a kit like this:
https://www.amazon.com/s?k=wire+fer...rrule,aps,1261&ref=nb_sb_ss_midas-iss-sm_2_12

Ed
 
Molex is the scourge of a wiring system, they have no excuse for existing. Radio Shack featured them, what more can you say?
 
$400-$500

Molex / AMP connectors are kind of the GA standard. The problem is getting the correct crimpers which cost $400-$500. The $30 crimpers worked ok, but The single action, ratcheting crimpers that are specific to the gauge of wire/pin/plug made me laugh the first time I used them. There's nothing better.

I've seen bad Molex connections on components that cost $800,000 that were done with the wrong crimper in the part 135 realm. When I called the company and spoke with their DER about the bad crimps, he was unaware of the FAA requirement to use ratcheting crimpers designed for the specific connector.

The pictures in the first post are really sad - I wouldn't have that on my lawnmower.
 
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Molex

I've used Molex connectors for some 30 years and never had a failure, but I solider every wire to the Molex pin after I crimp it. It's a pain but it works.
 
I've used Molex connectors for some 30 years and never had a failure, but I solider every wire to the Molex pin after I crimp it. It's a pain but it works.

Just curious what's the scope of your maintenance activities, a couple aircraft or hundreds? I do agree that if you take extra care with them it helps, but it's still a 2 cent connector prone to failure.
 
Connectors

Just curious what's the scope of your maintenance activities, a couple aircraft or hundreds? I do agree that if you take extra care with them it helps, but it's still a 2 cent connector prone to failure.

So Walt....what are your connectors of choice?
 
When we built the Cozy MKIV, Blue Mountain was first in the game with an electronic CB power distribution module board. It had a 1/4-20 lug for the power in and those green Phoenix connectors on the board for circuit connections. In addition to a couple of the circuit breaker self destructing, those Phoenix connectors were an early source of electrical gremlins with the clamp down screws vibrating loose even when torqued way down. We solved the problem by using a dab of blue Loctite on the clamp screw threads. Even the nut on the 1/4-20 lug bolt would come loose with a lock washer. We used the green wicking Loctite on that. I don't like using Loctite on electrical connections but in this case we ran out of ideas. I think those screws that have a key cut in them with the plastic(?) insert for locking the screw in would help. This image is an example I am thinking about:
 

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Hi Buck

The choice of connectors for my products has always been a considered one, and every one of them has compromises.
Price was not the first priority.

For your WigWag Module, the spring grip connector chosen was selected for its wire retaining capabilities, its lack of screws, ease of use, 16 amps current capability, and its ability to take wire up to 14AWG. The manufacturer claims the wire pull-out test passes IEC 60999-1.

I also deliberately oriented the terminal block on the PCB so that the wires lay across the face of module, rather than off the edge, to encourage the wires to be cable tied to the module to provide mechanical relief. The module is so small and lightweight that I envisaged that it would get installed into many a flying plane by simply cable tieing it out of the way behind the panel to something random such as a nearby wire bundle, securing the wires in the process.
In your case with your WigWag Module mounted to a panel (nice to see, thank you!), additional mechanical strain relief could be provided for the wires less than two inches away from the terminal block.

I did consider making the module fit into a DB15 or DB25 connector housing, however crimp pin connectors will only carry 5 amps, so you'd need to externally join 4x 20AWG wires to the one 14AWG wire to carry the same amount of current into the module, and then make another two external joins to cater for the two 10 amp loads. Messy (in my opinion), time consuming, two or three times the size and weight, another $12 cost for a crimp pin plug, requires extra solder splices, and inconvenient when compared to pushing home a single existing wire into a spring terminal block.

For the white Combo light connector I'd very much welcome your perusal of the Mouser or Digikey etc catalogue (Amazon, no thanks.) and I genuinely look forward to your suggestions for a better connector that is compact in size, will take 18AWG wire and is able to be surface mount soldered onto an aluminium PCB. The one I selected requires a minimum of 50 newtons of force (5kg from what I can work out) according to the data sheet to pull the wire from the socket.
I encourage you to add mechanical strain relief to the wires close by because I think you'll rip the connector off the board before the wires will come out!

I don't know what the third product is in your photos, but you'll note that the terminal block has a metal tab that clamps the wire into the terminal, rather than the screws making direct contact with (and very likely breaking) the wire strands.
Crimp or boot-lace ferrules are not needed for this reason according to the terminal manufacturers as shown above, but feel free to use them. I hope you've bought that $200+ crimp tool as well!
You could also use some nail polish (or the preferred aviation equivalent!) on the heads of the screws to stop them turning themselves loose.


I have to say I'm confused by your statement "To be VERY clear, these are sample photos of the type of connectors I'm referring to, not photos of my project!"
If you have an actual fault with or would like to return your Combo lights and Wigwag module, please contact either Flyboy Accessories or myself directly. Ultimately I think you'll be missing out on some great products if you do return them, but we would be happy to help you out, even 18 months after your purchase date.

If I have a design flaw with my products I'm very interested to hear from anyone about it so I can make Flyleds products the best they can be.


 
I’m an EE with well over 40 years designing systems, boards and semiconductors. In my experience, connectors and sockets of any kind need careful attention to detail.

If you own your aircraft long enough, eventually every connector will fail. Best to minimize them if you can.

This board, which I designed 40 years ago used to have sockets for the square hybrid devices. Our mechanical engineers engaged a major US connector manufacturer to design them. Unfortunately, the connectors failed so often that we had to eliminate them (the connectors, not the engineers). This board was purchased off ebay as a souvenir as a fully functional device.

A prize to whomever can identify this board by function.

Vern

59FCF139-029C-4B67-AE66-666D6F1E699B.jpg
 
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Hi Paul,

Thank you for your explanation of your rationale to use the push-in connectors on your product. I genuinely appreciate you taking the considerable time to do that.

I understand the need to use something that will carry the amps, accommodate the wires, and be relatively user-friendly for the end user. My comment was in response to a wire that simply pulled out of a connector under what I consider to have been minimal tension -- certainly far lass than what I apply to every one of my ring-terminal connections after I crimp them. This was caught before it had a chance to cause a problem, and it was on a product that was not flight critical. It was merely annoying. Upon further investigation, when the wire was re-installed into the connector, it seemed to be tight and secure -- but then again, it did the first time I installed it, too... so time will tell. But I'm currently satisfied enough to say it's good to go.

The Euro connector that failed, however, was on an ignition controller module that is VERY flight critical, and I was once again astonished that those are standard on that unit. That was on a different airplane, and the little 22 AWG wire simply broke underneath the screw after 100 hours of flying.

For a lighting unit, I honestly don't know, off the top of my head, what kind of connector would be better for a unit that has to carry 5+ amps per pin. If I was designing something like that myself, I'd probably further reduce the chances of an installation error by factory-soldering 18 AWG power wires to the board and providing some kind of built-in strain relief for them on the board or in a housing, and terminating them outside the housing with heavy-duty, locking automotive-style connectors of some kind. But that's just me. And my product would probably be too expensive and no one would buy it.

Sorry I ranted against the Molex Lite-Trap connectors. My first impression was "YGBSM." But I will give them the benefit of the doubt and see how things go in actual operation.

The green terminal blocks? Not a fan. Never will be, sorry.

(And for those of you saying that I should have ferrules on my bare wires, please show me in the various installation manuals where it specifies anything but bare wires.)
 
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I’m an EE with well over 40 years designing systems, boards and semiconductors. In my experience, connectors and sockets of any kind need careful attention to detail.

If you own your aircraft long enough, eventually every connector will fail. Best to minimize them if you can.

This board, which I designed 40 years ago used to have sockets for the square hybrid devices. Our mechanical engineers engaged a major US connector manufacturer to design them. Unfortunately, the connectors failed so often that we had to eliminate them (the connectors, not the engineers). This board was purchased off ebay as a souvenir as a fully functional device.

A prize to whomever can identify this board by function.

Vern

View attachment 9519

It appears to be the same circuit replicated over and over, so probably no an early pc, and it appears to be a line card of some kind. I agree with the other poster it’s telephony related. I’m going to guess an ISDN card.
 
The board

I’m an EE with well over 40 years designing systems, boards and semiconductors. In my experience, connectors and sockets of any kind need careful attention to detail.

If you own your aircraft long enough, eventually every connector will fail. Best to minimize them if you can.

This board, which I designed 40 years ago used to have sockets for the square hybrid devices. Our mechanical engineers engaged a major US connector manufacturer to design them. Unfortunately, the connectors failed so often that we had to eliminate them (the connectors, not the engineers). This board was purchased off ebay as a souvenir as a fully functional device.

A prize to whomever can identify this board by function.

Vern

View attachment 9519

The board has got 8 modules so that implies it is the heart of an ignition control system for a 1980's V8 Cadillac. Did I win the prize?
 
Interested in comments

I just saw your 'rant' and am pretty curious I must admit about a few issues, but the first one in particular:

1. If you did feel that the "connectors were inappropriate", why would you continue to install them?

To me, if I thought there was an issue, I would contact the supplier, chat to them, and if I still felt an issue, then either corrected the issue to my satisfaction or return them. That you did not do this, makes me wonder if a) this was not an issue at the time, or b) if it was, then what care was taken with the installation. It just seems that if you thought them so "inappropriate", why install them in the first place. Seems too much of a risk

But extending from that, general comments:
2. I have personally never heard of a failure of the wiring of any of the lighting gear you refer to in any other aircraft using these lights. In fact, all I hear from the threads are happy and contented customers. So again, interesting that this occurred with your installation. This seems at odds with others experiences.

3. I have used these products for nearly 7 years and never had an issue. Every annual inspection demonstrates that the connections are as tight and solid as a drum. But I must admit, I am very careful about what I install and how I install it. In the lighting case, I talked to the lighting manufacturer and he was very helpful. We talked through the connectors and the strain relief how that should be mounted etc.. and I was very happy with the solution. Again, never an issue, and I have tugged on them each annual.

BTW: If I had any concerns with any product, I bugged the suppliers from lighting to injector balancing, to EFIS, etc... I was very careful about what went into my plane. And if there was any doubt, I checked. I didn't take a chance and wait until failure.

After all, it is my life and the lives of anyone who travels with me. So if I am unhappy with anything, anything at all, it had to be rectified somehow before installation. I would consider anything less than that to be careless on my behalf.

You do say that you tightened these up and they now appear good. Maybe, just maybe, it was installer error and not a connector issue?? Could that be a possibility? Is there sufficient strain relief? Are they secured appropriately?

Personally, I would firstly look to myself if something failed. Especially if it seemed an uncommon issue from broad investigation. Then I would contact the supplier for information. From my experience in business and supporting other business with issues, human installation, operation error is the most common cause of failure. And as we know from aircraft accidents, the statistics in general firm that out as well.

Only once that was done and all possibilities for failure uncovered would I jump on a thread and put the question to everyone else to see what I could learn.

But this is just me and each to their own. :)


Time for a bit of a rant. Over the past two weeks, I have experienced TWO separate failures of what I consider to be inappropriate electrical connectors. One of them resulted in a loss of power to the affected unit. One was caught before it could cause any issues. On top of this, I have received several reports from acquaintances over the past few years of similar issues.

All of them are related to what I call "non aerospace-grade" wire connectors in a couple of common, apparently-accepted formats, and they are in many of our electronic units. (And yes, all of these installations were installed in accordance with the manufacturer's instructions and good building practices.)

For several reasons, I will not discuss any aviation manufacturer names on this thread, and I think we should leave that out of the discussion. I just want to point out what I think are connectors that should NOT be in electronics that are subject to vibration levels like that of a light airplane.

The photos below show the types of connectors I'm referring to. (These are not mine.) Both types require you to merely strip the wire and insert it into a recess. After that, the method of securing it is either 1). push the wire until it "locks" in place, or b). tighten a set-screw or plate onto the bare wire, flattening it down. The white one is called a "press-fit connector" or a "press connector," and the green one is called either a "pluggable terminal block," Euroblock, or Phoenix connector.

In my opinion, these are wonderful methods to secure your stereo speaker wires or your electronic hobby power supply cables, but they are alarmingly unsecure, subject to failure, and totally unsuitable for use in any aerospace vehicle except maybe a hobby drone.

Bare wires tightened under a screw? Or worse, pushing a bare wire into a hole and hoping it stays there? Why, oh why, are we so accepting of this kind of nonsense in our airplanes? I spent over $700 on some really nice wire crimping tools of various kinds for my airplane project. I don't want some kind of half-baked hobby connectors on my critical flight gear. Give me a ring terminal ANY day. I am now to the point where I will never buy an aviation product, no matter how awesome it is, if it requires me to use a Euro connector.

I've never had a Molex, CPC, D-sub, PIDG Ring/Spade, Deutsch, Seal-All, or other normal connector simply disconnect or fall apart under normal conditions. So manufacturers, please stop using unsuitable, cheesy connectors in your aviation products!

And don't get me started on those tiny 26 AWG wires coming out of that certain brand of trim servo!

Is it just me? Sigh...


i-kGWSf38-L.jpg


i-WpmNq7T-L.jpg


i-qHQP282-L.jpg
 
I’m an EE with well over 40 years designing systems, boards and semiconductors. In my experience, connectors and sockets of any kind need careful attention to detail.

If you own your aircraft long enough, eventually every connector will fail. Best to minimize them if you can.

This board, which I designed 40 years ago used to have sockets for the square hybrid devices. Our mechanical engineers engaged a major US connector manufacturer to design them. Unfortunately, the connectors failed so often that we had to eliminate them (the connectors, not the engineers). This board was purchased off ebay as a souvenir as a fully functional device.

A prize to whomever can identify this board by function.

Vern

View attachment 9519

16 port NT or Mitel analog line card.
 
I agree on not using molex connectors in aircraft. Most of the intermittent electrical problems I've seen can usually be traced back to molex connectors. Most of them are only good for 5 amps, and we have seen some really burned out due to placing them in the air conditioning circuits, which usually need around 20 amps.

I agree with Walt's lineup of connectors, but to be sure, ALLof them require the proper support aft of the pins, whether it is the integrated part of the backshell, or some other supporting mechanism. They also need to be securely fastened to the unit to which they are connected, If not, you can count on premature failures, which usually start as intermittents.

There have been some accidents of homebuilts in which the NTSB has been involved, and they have expressed concern about the wiring practices they have seen. Watch for an upcoming column in Sport Aviation soon that addresses some of these issues.

Vic


Vic
 
Rant pile-on!

Agree completely.

As an "experienced" senior avionics design engineer, I see all to often a certain naivete’ or ignorance of operational failure mode considerations in the hobbyist aircraft electronics offerings. (and environmental/EMI/power transients, but that is another thread)

The effect of any failure must be considered. For instance, if a wire or connector comes loose, will the unit fail? How will it fail? Will the loose wire short to something and propagate to another system? Will the pilots see an effect? Will the effect create a control or safety issue?

The point is, how error-proof is the termination of a wire in one of those Euro-style terminal blocks? How do you inspect the termination? What happens if a wire comes loose? What level of vibration has the design been qualified to?

The hair on the back of my neck stands up whenever I see those terminal blocks used on avionics (or worse, electronic ignitions). I won’t use them. I especially dislike that many are not connectorized (pluggable terminal blocks are available), so you have to remove every wire to replace a unit. Very susceptible to installation errors. BTW, this also applies to old screw terminal blocks, but at least a termination can be loose and not fall off if ring terminals are used.

Some of my connector selection criteria:
1. Wire termination = crimp
2. Wire insertion depth can be inspected = witness hole or similar visual means
3. Crimp tool = full cycle crimping, no “squish it till it looks good”
4. Polarized or keyed connector shell = no mis-mating
5. Positive latching or secured mating = latch or screws
6. Contacts are recessed or covered = no shorting to structure if the connector falls off

A D-sub with machined contacts meets most of these criteria (5 is not great) and are cheap. Backshells are a pain though, and good ones are pricey (Garmin and Positronic EMI). D-subs are my “go-to” for most (lower current) things. My “forest of tabs” grounding block includes a D-sub for dense grounding of wires. (BTW, pet peeve: D-subs are NOT all "DB". the "B" denotes the shell size! There is no such thing as a "DB9", <rant off>)

The newer automotive environmental connector systems are also quite good (Metri-Pack 150, etc), but are fairly large.

The old “Molex” (0.156” Amp Mate-n-Lok, etc) are not great and crude, but Molex makes some newer systems that are good (Mini-Fit Jr is small and light). I use Mini-Fit Jr for trim servos and other light wires. Just saying "Molex sucks" is not fair to the huge variety of connector types Molex makes.

I also use a few D38999 series III which are fantastic, but I have a nice box of free ones to pick from. Most of us don’t have that luxury. Plus, they are big.

Not all connections can achieve these criteria. Battery/contactor cable crimp lugs are a good example, and even Van’s had a run of under-crimped cables. So even the pro’s can get bit by not having a robust termination design.

I have used pluggable Euro-style terminal blocks in the past with good results, but it was on a ground system where the failure effect was “annoyed”. I have never had a salesperson try to sell me those into an avionics application or even suggest that they were appropriate for the application.

Caveat Emptor
 
1. If you did feel that the "connectors were inappropriate", why would you continue to install them?

Because they are popular, and have a good reputation in the RV community. The same reason people pick most of their products. I had no previous experience with the Molex Lite-Trap connectors. They looked a bit dodgy to me, but who was I to judge? Most RVers seem happy with the design.

You do say that you tightened these up and they now appear good. Maybe, just maybe, it was installer error and not a connector issue?? Could that be a possibility? Is there sufficient strain relief? Are they secured appropriately?

I said I merely inserted the wire into the connector again, and it seems to be tight again (just like the first time I did it). The wires themselves have always have been strain-relieved and secured. That's why I was so annoyed when one came out.

In addition to homebuilts and vintage aircraft, I fly lots of production aircraft, and there are good reasons why no manufacturer of production airplanes would allow a push-in bare-wire connector like this in their aircraft. It doesn't have the same margins of safety as other methods. No, I'm not saying that our homebuilts should have production-aircraft levels of systems engineering or products, but how far down the food chain of safety do we want to go with our electronics?
 
I have found the Deutsch DTM series connectors, which can use the machined pins used in circular mil connectors, to be a good option where there are a couple of wires to connect. They are available for up to 6 conductors.
 
Just me

I have found the Deutsch DTM series connectors, which can use the machined pins used in circular mil connectors, to be a good option where there are a couple of wires to connect. They are available for up to 6 conductors.

These are nice connectors. I am using them throughout. Only my flap motor has a molex since it matches what came with the flap motor. After this thread, i am considering changing that one out.
 
Here is another vote for Deutsch connectors. I use DTMs for singal and lower amp connections and DT's for larger gauge wires. It's easy to remember. If there is an M in the model it is a 'miniature" Deutsch connector. No "M" it is a larger standard-size connector.

The Deutsch are environmentally sealed and have positive locking backshells. They lock tight and are of high quality. They can be used with solid-barrel contacts (suggested for our purposes) or crimp type contacts (better for tractors and lawn mowers). The pins are easy to insert and remove from the positive-locking spring loaded retainers. In fact all you need is a small flat-tip screwdriver to release the retainers so the contacts can be extracted. The silicon rubber seals also provide for strain relief. They make legacy Molex connectors look like a Happy Meal toy surprise that can be impossible to de-pin and re-pin while providing loose connections without strain relief.
 
Rant pile-on!

Agree completely.

As an "experienced" senior avionics design engineer, I see all to often a certain naivete’ or ignorance of operational failure mode considerations in the hobbyist aircraft electronics offerings. (and environmental/EMI/power transients, but that is another thread)

The effect of any failure must be considered. For instance, if a wire or connector comes loose, will the unit fail? How will it fail? Will the loose wire short to something and propagate to another system? Will the pilots see an effect? Will the effect create a control or safety issue?

The point is, how error-proof is the termination of a wire in one of those Euro-style terminal blocks? How do you inspect the termination? What happens if a wire comes loose? What level of vibration has the design been qualified to?

The hair on the back of my neck stands up whenever I see those terminal blocks used on avionics (or worse, electronic ignitions). I won’t use them. I especially dislike that many are not connectorized (pluggable terminal blocks are available), so you have to remove every wire to replace a unit. Very susceptible to installation errors. BTW, this also applies to old screw terminal blocks, but at least a termination can be loose and not fall off if ring terminals are used.

Some of my connector selection criteria:
1. Wire termination = crimp
2. Wire insertion depth can be inspected = witness hole or similar visual means
3. Crimp tool = full cycle crimping, no “squish it till it looks good”
4. Polarized or keyed connector shell = no mis-mating
5. Positive latching or secured mating = latch or screws
6. Contacts are recessed or covered = no shorting to structure if the connector falls off

A D-sub with machined contacts meets most of these criteria (5 is not great) and are cheap. Backshells are a pain though, and good ones are pricey (Garmin and Positronic EMI). D-subs are my “go-to” for most (lower current) things. My “forest of tabs” grounding block includes a D-sub for dense grounding of wires. (BTW, pet peeve: D-subs are NOT all "DB". the "B" denotes the shell size! There is no such thing as a "DB9", <rant off>)

The newer automotive environmental connector systems are also quite good (Metri-Pack 150, etc), but are fairly large.

The old “Molex” (0.156” Amp Mate-n-Lok, etc) are not great and crude, but Molex makes some newer systems that are good (Mini-Fit Jr is small and light). I use Mini-Fit Jr for trim servos and other light wires. Just saying "Molex sucks" is not fair to the huge variety of connector types Molex makes.

I also use a few D38999 series III which are fantastic, but I have a nice box of free ones to pick from. Most of us don’t have that luxury. Plus, they are big.

Not all connections can achieve these criteria. Battery/contactor cable crimp lugs are a good example, and even Van’s had a run of under-crimped cables. So even the pro’s can get bit by not having a robust termination design.

I have used pluggable Euro-style terminal blocks in the past with good results, but it was on a ground system where the failure effect was “annoyed”. I have never had a salesperson try to sell me those into an avionics application or even suggest that they were appropriate for the application.

Caveat Emptor
Mike, great info. I have a couple of questions if you will indulge me.

Do you have a recommended d-sub shell? I found one that was a dream - easy to install the wire holder, long thumb screws easily captured by the shell, two threaded screws to hold the shell together, metal - very high quality. Unfortunately I don't know where I got it.

What would you recommend we use to connect our panel to the aircraft? What I did was just wire everything directly with no massive connector(s). This is fine when everything is working and no changes are needed. I just added something behind the panel which was not too difficult, but I realized if I needed to cut a hole in my panel or do something more impactful that being able to remove the whole panel would be a good idea. The D38999s look nice, but seem to be very hard to work with - like adding a pin or removing one - perhaps there is something better from another industry? I have about 200 wires going to my panel! :eek:

I'm a little uncomfortable with the battery bolts - seems like having a fat wire connected to a little 6mm screw locked with a star washer is kind of weak. Any idea why we would not push the manufactures to use something better, like double bolts?

scotchlok-31000-series-lugs.jpg

Thanks!
 
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