Sparks flying in the cockpit

[Adi]

From the Mooney that spent several months this year AOG with various CO problems (https://mooneyspace.com/topic/34014-carbon-monoxide-reading-on-ground/) comes the second part of the saga..

Today on a flight I saw, out of the corner of my eye, what seemed to be electrical sparks. I wasn't even sure if it was real or if I was imagining it. Luckily, I record all my flights in case something interesting happens (maybe I'm jinxing it) so I have a video which shows me that it was real: https://photos.app.goo.gl/n1Weaq2VjF8memFB9

It happened soon after I put the gear down and, interestingly, just as I turned the mixture control.

I tried looking under the panel on both sides but I didn't see anything obviously broken (no scorched/uninsulated wire). I also thought perhaps the prop control cable is brushing against something but when actuating it on the ground it seems to be well enclosed in a metal tube that precludes it from contacting anything pilot side of the firewall.

I'll be having my mechanic take a look, but I suspect this will be a very hard problem to diagnose / reproduce. At the same time, it's quite concerning that it could develop into something worse like an electrical fire. I thought I'd post here in case someone has any experience with something like this.

This is a 1983 M20J.

Adi

 

Edited December 31, 2020 by Adi

[xcrmckenna]

I would check up at your panel light switch.


Sent from my iPhone using Tapatalk

[gacoon]

Tough to see, on one pic you are adjusting the prop control and there is something that looks like what you were seeing.  I see that the sun is coming in from the right (?) side of the aircraft.  The sparks (?) seem to move in relation to your wrist as you adjust the prop control.  I wonder if this is some kind of visible issue caused by the sun coming thru the plexi-glass window, older windows can cause weird stuff.  Since you can record this I would try it again with the sun not coming in directly into the cockpit.

Could be static build up on aircraft - but from the flight conditions in your video I dont think this would be the case??

[Lionudakis]

That will get your attention ! Find it before it happens again

[EricJ]

Yikes!   Definitely want to get that sorted out.

Pretty much all of the things you have in that region need to be checked, first for loose connectors, chafed wires, clearances, etc.   The voltage regulator is right there, the 12V cigar jack, and the panel light controller.   It looks like the sparks may be coming from further back than that, so just get some good eyes on everything back there.

I did notice one thing in the pic:   whatever that white/blue ground wire is that is attached to the yoke collar has an improper terminal on it.   Spade terminals are pretty much verboten in aviation, it should be a ring terminal instead.   I doubt that's the problem unless it is loose, and it's a bit of a nit, but if you're in there doing things it would be easy to fix.

 

[PT20J]

The “sparks” appear to follow the motion of your right hand which is in bright sunlight. Do you wear a ring on that hand? Might be a reflection.

[1001001]

1 hour ago, EricJ said:

I did notice one thing in the pic:   whatever that white/blue ground wire is that is attached to the yoke collar has an improper terminal on it.   Spade terminals are pretty much verboten in aviation, it should be a ring terminal instead.   I doubt that's the problem unless it is loose, and it's a bit of a nit, but if you're in there doing things it would be easy to fix.

 

I don't want to start a thread drift, but this is not the case.

 

http://www.aeroelectric.com/articles/faston3.pdf

 

"I was talking aboutFastOn (push on spades) in an Oshkosh forum about fouryears ago. A gentleman purporting to be an IA jumped upand chastised me soundly for recommending such a thingin airplanes . . . he allowed as how, ". . . you'd never getsuch a technique certified in a production airplane." Asgently as I could, I reminded him and the audience thatCessna had been using the FastOns for over 30 years. Thereason that he was UNAWARE of this condition is becausein 30 years, it's never posed a problem worthy of an Airwor-thiness Directive . . . he didn't immediately buy into the idea. . . but peek behind the panel of a 1965 C-172 and tell mewhat kind of terminals you find on the rocker switches . . ."

Edited December 31, 2020 by 1001001

[EricJ]

1 hour ago, 1001001 said:

I don't want to start a thread drift, but this is not the case.

 

http://www.aeroelectric.com/articles/faston3.pdf

 

"I was talking aboutFastOn (push on spades) in an Oshkosh forum about fouryears ago. A gentleman purporting to be an IA jumped upand chastised me soundly for recommending such a thingin airplanes . . . he allowed as how, ". . . you'd never getsuch a technique certified in a production airplane." Asgently as I could, I reminded him and the audience thatCessna had been using the FastOns for over 30 years. Thereason that he was UNAWARE of this condition is becausein 30 years, it's never posed a problem worthy of an Airwor-thiness Directive . . . he didn't immediately buy into the idea. . . but peek behind the panel of a 1965 C-172 and tell mewhat kind of terminals you find on the rocker switches . . ."

It's not a fast-on.   What appears to be there is a spade (or fork) terminal, like this:

https://www.digikey.com/en/products/detail/te-connectivity-amp/8-34541-1/2259022

instead of a ring terminal, like this:

https://www.newark.com/amp-te-connectivity/34148/terminal-ring-8-stud-crimp-red/dp/66H7042

A fork terminal can be pulled away or fall away from the stud if the stud fastener comes loose.   Fast-on connectors at least require connect/disconnect force (when not damaged) that makes them fairly common.

While it is true that very little about electrical details are actually regulatory, AC 43.13 does say that ring terminals are "preferred", I can also tell you that you will likely fail the written and practical examinations on this for an A&P if you don't recognize the use of a ring terminal with the proper wire and stud hole size.   At least our DMEs were always hammering on us about this.   

It is a nit, but an unpicked nit grows into a louse, and this is an easy fix.   I can't tell what circuit that wire is for, but it would be easy to put a ring terminal on there and ditch the fork.

 

[Guest]

3 hours ago, EricJ said:

Yikes!   Definitely want to get that sorted out.

Pretty much all of the things you have in that region need to be checked, first for loose connectors, chafed wires, clearances, etc.   The voltage regulator is right there, the 12V cigar jack, and the panel light controller.   It looks like the sparks may be coming from further back than that, so just get some good eyes on everything back there.

I did notice one thing in the pic:   whatever that white/blue ground wire is that is attached to the yoke collar has an improper terminal on it.   Spade terminals are pretty much verboten in aviation, it should be a ring terminal instead.   I doubt that's the problem unless it is loose, and it's a bit of a nit, but if you're in there doing things it would be easy to fix.

 

Both Mooney and Cessna use 1/4” spade terminals in a number of circuits with varying degrees of success.  Screw on terminals would have been a much better choice.

Clarence

[EricJ]

7 minutes ago, M20Doc said:

Both Mooney and Cessna use 1/4” spade terminals in a number of circuits with varying degrees of success.  Screw on terminals would have been a much better choice.

Clarence

Nomenclature overload...what's there is a fork terminal used in a screw-on termination.    Fork terminals are also called spade terminals, which is a nomenclature overload with the push-together fast-on terminal like our binary contributor mentioned.

 

Edited December 31, 2020 by EricJ

[GeeBee]

The thing about spade terminals is a proper one has a lock, in that the female portion positively grips and the male portion and locks in place with a click. Unfortunately that feature can be worn out by too many assembles and disassembles at which point both ends need to be replaced. What EricJ is talking about (fork terminal) has absolutely no captive feature other than the torque of the screw and hopefully a internal tooth lock washer (in which only 25% of the teeth engage). Fork terminals are also prohibited on boats let alone airplanes. 

I will also add that blue/white ground wire is not only improperly terminated, it is improperly routed, secured and likely to chafe.

 

 

[EricJ]

2 hours ago, PT20J said:

The “sparks” appear to follow the motion of your right hand which is in bright sunlight. Do you wear a ring on that hand? Might be a reflection.

Looking at it again, I suspect this is actually what's happening.

[RLCarter]

15 minutes ago, EricJ said:

Looking at it again, I suspect this is actually what's happening.

I agree, there is one (1) spark that shows up on the panel 

[Adi]

Hi folks,

Thanks for your input all!

I took the plane to LAC Avionics at SJC today and they found the problem almost immediately.

There were two loose bolts that were touching a bus. You can see one of them in the first picture:

The two loose bolts actually fused together.

And you can see the black burnt areas, that's probably where the metal comes from that flew out in the form of sparks. 

Obviously they weren't always arcing, but they were close to a ground connector and probably depending on the acceleration in the airplane they would occasionally touch.

As to where they came from, my strong suspicion is that they were dropped while installing the EDC for the CGR30P/C install. Here's a picture of the EDC, note that there are identical bolts there.

The CGR was installed by LASAR. I'm going to make a separate post about the whole experience with this install, but tl;dr: it took 6 weeks after they quoted me 1.5 weeks, and now this.

I am having LAC do an inspection of the CGR install to make sure there are no other problems hiding. But this is very concerning.

Adi

[GeeBee]

Is Jerry Baxter still at LAC?

 

[EricJ]

Wow, good find!    Getting the right set of eyes on a problem always seems to be a good idea.    

 

[carusoam]

Speaking of vocabulary...

Looks like a pair of lock nuts got welded together...

For anyone that hasn’t seen the sparks fly... watch the copilot yoke shaft about 2/3 of the way through the video...

The spark and its reflection are only visible for about a second... and only if you are looking right at it... there is also a bit of a crackle in the sound at the same time...  00:22 - 00:23

Might be of interest to @oregon87 and @LASAR to see...

note the blue arrow... in the screen shot... the spark came all the way out...

Great camera work!

Best regards,

-a-

 

[Yetti]

The nyloc nut is sitting in between terminals of a Cutler and Hammer Solenoid.    Had it fallen differently you could have had a huge issue such as exploding battery/ big ass electrical fire.  You can be certain that the nuts did not unscrew themselves.

[Adi]

Not sure about Jerry, it's my first time at LAC

> Great camera work!

Thanks! I spent a bunch of time getting the setup just right, and now it's mostly set and forget on each flight. It's already paying off

 

Yetti, would you mind annotating the picture explaining where the terminals are exactly, just for my curiosity? You could paste the image into https://jspaint.app/ for an easy way to do so.

Loyd at LAC also explained the gravity of the situation but I did not exactly understand what role this component plays and exactly where the terminals are and how they are energized.

[Yetti]

 

That is the nut in between a negative and positive.  My guess would be the new box is mounted with the same nuts.  Might have dropped several and not found them.  

It's bad practice to drop things and not make sure they come out the other side.

Don't like the way the ring terminals are bent wonky on the connection to the left in the picture.  

 

 

Also on the new box the wires going into the db9 connector should be tied or ty wrapped.  

 

[Yetti]

The routing on the RG400 is wonky too.  The braided translucent cable.

[1001001]

17 hours ago, EricJ said:

It's not a fast-on.   What appears to be there is a spade (or fork) terminal, like this:

https://www.digikey.com/en/products/detail/te-connectivity-amp/8-34541-1/2259022

instead of a ring terminal, like this:

https://www.newark.com/amp-te-connectivity/34148/terminal-ring-8-stud-crimp-red/dp/66H7042

A fork terminal can be pulled away or fall away from the stud if the stud fastener comes loose.   Fast-on connectors at least require connect/disconnect force (when not damaged) that makes them fairly common.

While it is true that very little about electrical details are actually regulatory, AC 43.13 does say that ring terminals are "preferred", I can also tell you that you will likely fail the written and practical examinations on this for an A&P if you don't recognize the use of a ring terminal with the proper wire and stud hole size.   At least our DMEs were always hammering on us about this.   

It is a nit, but an unpicked nit grows into a louse, and this is an easy fix.   I can't tell what circuit that wire is for, but it would be easy to put a ring terminal on there and ditch the fork.

 

Good point.  For some reason I could not see the photo you were commenting on at the time, and was only reacting to your mention of spade terminals being improper. 

I would definitely agree that if a screw terminal is used, it should be a full ring and not the fork style. 

I guess I'd still disagree with the historical logic that prefers screw and ring terminal connections over the friction style, given that (at least according to Bob Nuckolls) they require at least a 200 G acceleration in the axial direction to separate them.  Certainly if a ring terminal is used, the screw and ring hole diameters should be matched to minimize the possibility of the joint working loose.

I apologize for the drift.

[1001001]

11 hours ago, Yetti said:

 

That is the nut in between a negative and positive.  My guess would be the new box is mounted with the same nuts.  Might have dropped several and not found them.  

It's bad practice to drop things and not make sure they come out the other side.

Looking at those nuts the cad plating is intact.  I'd say that indicates they were dropped in there and never installed.  They look brand new and have never seen a wrench.

[Cruiser]

the shell of the connector is missing ...

there should be a cover over the black part of the connector where the wires are coming out. The back of the shell clamps over the wires to prevent them from pulling out of the black part and to protect the connection. Those wires should be secured and tie wrapped for support. 

[EricJ]

2 minutes ago, Cruiser said:

the shell of the connector is missing ...

there should be a cover over the black part of the connector where the wires are coming out. The back of the shell clamps over the wires to prevent them from pulling out of the black part and to protect the connection. Those wires should be secured and tie wrapped for support. 

I noticed that as well, that there's no strain relief on the wires.  

Between the missing backshell, dropped and unrecovered nuts, and fork terminal attached to the yoke collar, I'd opine that whoever did the relevant installs was less than highly recommendable.