Found the elevator electric trim problem!!

[Yooper Rocketman]

I had my IA look at the pitch trim servo and pitch servo today.  I ran the trim switch through the range multiple times and it worked every time.  I also turned on the autopilot and adjusted the flight director to command a pitch action and the trim wheel moved every time after a short delay.  He was convinced we needed to send the pitch trim servo in for OH, but I was pretty stubborn that thought it had to be in the electric trim switch.  Hey...the trim servo doesn't know whether the adjustment command is coming from the autopilot or the electric trim switch.  

I noticed my trim switch is a dual switch with the thumb applying pressure to both parts of the switch for function.  He said the red switch on the left activated the clutch, the black on the right ran the actual servo motor.  I showed him how if I just activated the red switch, the manual trim wheel would lock like it did during the failure mode until I let go of the switch.  This convinced me even more it was in the black trim button.  At my request he removed the trim switch assy from the yoke, as I convinced him even if I was wrong, the switch repair would be much less than sending the servo out for OH.  He said the switch looked good and he could hear a positive "clicking" of the contacts upon activating the switch.  I crawled into the plane and wanted to pull the switch out further from the yoke, so cut the wire ties on the wires in the cavity of the wire chase in the yoke.  

This is what I found.  Yep, a 5 cent butt connector to wire failure!  Two high level aviation techs were convinced I should send the trim motor in.  I'm sure glad I stuck to my diagnosis based on actual symptoms rather than bow to the "most common failure" found on the trim system.

Tom

[RLCarter]

nice find..easy fix. Might consider posting on the same thread where you had the issue, kinda completes it if you know what I mean

[LANCECASPER]

1 hour ago, Yooper Rocketman said:

I had my IA look at the pitch trim servo and pitch servo today.  I ran the trim switch through the range multiple times and it worked every time.  I also turned on the autopilot and adjusted the flight director to command a pitch action and the trim wheel moved every time after a short delay.  He was convinced we needed to send the pitch trim servo in for OH, but I was pretty stubborn that thought it had to be in the electric trim switch.  Hey...the trim servo doesn't know whether the adjustment command is coming from the autopilot or the electric trim switch.  

I noticed my trim switch is a dual switch with the thumb applying pressure to both parts of the switch for function.  He said the red switch on the left activated the clutch, the black on the right ran the actual servo motor.  I showed him how if I just activated the red switch, the manual trim wheel would lock like it did during the failure mode until I let go of the switch.  This convinced me even more it was in the black trim button.  At my request he removed the trim switch assy from the yoke, as I convinced him even if I was wrong, the switch repair would be much less than sending the servo out for OH.  He said the switch looked good and he could hear a positive "clicking" of the contacts upon activating the switch.  I crawled into the plane and wanted to pull the switch out further from the yoke, so cut the wire ties on the wires in the cavity of the wire chase in the yoke.  

This is what I found.  Yep, a 5 cent butt connector to wire failure!  Two high level aviation techs were convinced I should send the trim motor in.  I'm sure glad I stuck to my diagnosis based on actual symptoms rather than bow to the "most common failure" found on the trim system.

Tom

Which is the main reason I haven't pulled my yokes off to have them covered in leather or powder coated - I don't want the connections that now work perfectly desoldered or spliced. Someday I'll either get up the courage to try to cover them in place or take it to someone I trust to pull the yokes.

[carusoam]

Way to go Tom!  

Problem solving, MS style!

Thanks for sharing all the details and photos.

Best regards,

-a-

[MB65E]

Nice work Tom! I'm suprised they used butt splices in the yokes! 

Good luck with the cylinders too. 

Rocket Ship!

-Matt

[Yetti]

technically the butt splice did not fail.  The technician failed to strip the proper amount of wire.    I would solder it and heat shrink it.    And everyone on Mooneyspace would be up in arms talking about creating stress risers in the wires....  Then I would respond that the wire is is soldered to the switch a couple of inches away from there. 

[Marauder]

Unfortunately I have seen this type of troubleshooting in the past. In my industry it's called "taking the shotgun approach". We have techs who will replace everything and leave all the components in place rather than understanding the nature of the failure and proceed with troubleshooting in a logical approach and replacing the broken component. My belief is they feel it's better for the customer to get them up and running than spend the time to do it right.

In our aviation world, it just means more down time and cost. Glad to hear there are some old school trouble shooters still out there.


Sent from my iPhone using Tapatalk Pro

[TonyK]

The days of schlepping your Anvil case with your tools and Oscope are long dead.  It's now more expedient to to component replacement and swap rather than in place field repair. It also brings more to the bottom line even if it means leaving something inop and down for a longer period of time.

[peevee]

25 minutes ago, Marauder said:

Unfortunately I have seen this type of troubleshooting in the past. In my industry it's called "taking the shotgun approach". We have techs who will replace everything and leave all the components in place rather than understanding the nature of the failure and proceed with troubleshooting in a logical approach and replacing the broken component. My belief is they feel it's better for the customer to get them up and running than spend the time to do it right.

In our aviation world, it just means more down time and cost. Glad to hear there are some old school trouble shooters still out there.


Sent from my iPhone using Tapatalk Pro

It's really frustrating to read the stories around here of people's a&p actually taking components apart and fixing them. I need one of those a&ps and I can't find one. Every shop I've tried throws parts at the problem until it goes away.

[peevee]

4 minutes ago, TonyK said:

The days of schlepping your Anvil case with your tools and Oscope are long dead.  It's now more expedient to to component replacement and swap rather than in place field repair. It also brings more to the bottom line even if it means leaving something inop and down for a longer period of time.

You would think they would want the billable hours. I'm not sure our guy marks up parts much. Hours should be much more profitable. Maybe not. Maybe it's better to bill an hour on 5 small projects than 3 or 4 hours fixing something like that. It's not like our guy is getting rich off us, shops always full but I don't think it's very profitable.

[Yooper Rocketman]

When I shared the symptoms with the 30 year avionics tech (no longer working for my FBO, took a higher paying job in Florida) he was pretty good at zeroing in on the two key factors that should have been analyzed; how it worked with the A/P and how it failed with the yoke switch.  What bothered me all along (I delayed fixing this for 6-9 months because I didn't believe sending the servo out would fix it) was the analysis stopped there, yet the information seemed pretty clear.  It HAD to be something separate of the servo since it never blinked when using the A/P.  He said he was going to call King but, after several weeks when I queried him, he said he couldn't get in touch with them and we should just send the servo out.

As far as saving time by sending out components, it would have taken more time to remove and replace the servo than I had finding the problem.  It look less than an hour.  Maybe it's a mindset, but in my truck dealership, you do not pay for component replacement that DOESN'T fix your problem.  AND, with my mechanics "Incentive Program"  (monthly bonuses based on flat rate times and quality of workmanship) a mistake like this one will have the mechanic paying for the misdiagnosed component replacement out of his bonus instead of the customer.  That creates a much more diligent troubleshooting process when they are held accountable for getting it right THE FIRST TIME.  My top techs routinely pull $400 to $800 monthly bonus checks and the quality going out the door is outstanding.

I guess I was a little cynical with the first post, but it really PO's me when I can't "technically" work on my plane (no A&P <yet>) and if not for my background and attitude towards maintenance, I would be spending a lot more to fly my plane.  Makes me feel bad for those with less or little mechanical background, as they are totally at the mercy of their mechanic/FBO .  Far too many in the vocational fields today (all fields, not just aviation) are using the shotgun approach as Marauder pointed out.

The one good thing is, in the end, this forum helps all of us by sharing information and saving us money.

Tom
 

[211º]

There is nothing better than thinking a problem through logically and then systematically creating a plan to isolate the issue step by step until Occams Razor takes over.  Brilliant.

[Robert C.]

LOL, you beat me to it. Just saw the post and was going to respond.

There have been several similar incidents like this reported here on Mooneyspace (including one by me).

Chafed wires through the yoke was the problem. So you were right to check the wires

With that failure mode what'll happen is that when the yoke is moved the chafing wires cause the fault. So when trouble shooting on the ground you don't move the yoke like you're flying when playing with the trim and you can't replicate. My AP remembered this problem from a Piper he worked on many years ago and he was right!

[carusoam]

Preference for simplicity in problem solving...

https://en.m.wikipedia.org/wiki/Occam's_razor

MS, sharing things that work...

Best regards,

-a-

 

[cliffy]

Did a 1000 hr landing gear AD on a Comanche a couple of years ago and decided to take the wire bundle apart in the wheel well going to the gear warning. Found 5 butt splices in 12" of wire, two of which were lose. I'm not a fan of butt splices in tight spaces.

43.13 has a diagram of "electrician splices". They work great when done correctly.

Twist correctly, solder correctly and cover with heat shrink tubing.

Trouble shooting is a lost art today. Most mechanics are just parts changers.  

[LANCECASPER]

23 minutes ago, cliffy said:

Twist correctly, solder correctly and cover with heat shrink tubing.

In automotive applications I really like these. Once you heat the connection with a heat gun or lighter it melts the solder and shrinks the tubing and makes a great connection.

https://www.amazon.com/gp/product/B06XD1F5ZG/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

[Yetti]

When I say solder I mean mechanical connection then solder

[thinwing]

I think the shops are all too busy doing ads b installs along with avionics upgrades...they use their "good "guys for the wiring bundle design and installs...repairs..especially older stuff gets the shotgun approach done by the bottom rung new hire

[bradp]

Take a look at this method for connecting wires in tight places such as the yoke.  The butt method is definitely not preferred.  This method may or may not have been used on one of the experimental aircraft close to my hangar.  If you want them very strong just put a dab of solder on the Dsub connector terminal and when it's time to remove the yoke simply de solder.  

 

 

[Yooper Rocketman]

Every electrical wire connection we (Steve and I) made on the Lancair were soldered.  We had several vendor supplied items too.  Thus far the only failed connections (there have been several) were non-soldered terminals.

Tom

[Mcstealth]

On June 14, 2017 at 7:37 AM, Marauder said:

Unfortunately I have seen this type of troubleshooting in the past. In my industry it's called "taking the shotgun approach". We have techs who will replace everything and leave all the components in place rather than understanding the nature of the failure and proceed with troubleshooting in a logical approach and replacing the broken component. My belief is they feel it's better for the customer to get them up and running than spend the time to do it right.

In our aviation world, it just means more down time and cost. Glad to hear there are some old school trouble shooters still out there.


Sent from my iPhone using Tapatalk Pro

Well, I was guilty of this just last week. I had a freezer that would not defrost. Probably the thermostat inside the box I say to myself. Amazon the part, get it in the mail, slap it on.  No love. Oh, it must be the defrost timer is bad. Same drill, same result. It has to be the connections then, it can't be the inline heating element, they never go bad. Trouble shot all the connections, messed around for a few weeks with this damn box. It can't be the element,mthay last forever........... Okay, let's ohm out the element just so I can get back looking for the real problem........ Hmmmm. No continuity. I'm holding my leads wrong, or its on the wrong setting.......Still no continuity........Dumb,sh;t. You just became a parts replacer.....

[DonMuncy]

Sometimes this approach is logical and effective. If you lack the equipment or knowledge, and your last resort is to call the expert, often, googling, picking the most likely bad (or least expensive) part, can save you having to pay the expert charge. You simply must realize what you are doing and be willing to take the hickey of sometimes buying unneeded parts. And this approach relies a lot on the fact that your time is free.

This is a poor approach for a professional, but some of them do it anyway. Unless he carefully explains to you that his time charges are such that the replacement part gamble is worthwhile.

[RLCarter]

On June 16, 2017 at 6:33 PM, bradp said:

Take a look at this method for connecting wires in tight places such as the yoke.

 

 

The the only thing I would add is to stagger the connectors so that you don't end up with a bulge

 

 

 

[Piloto]

On ‎6‎/‎16‎/‎2017 at 7:33 PM, bradp said:

Take a look at this method for connecting wires in tight places such as the yoke.  The butt method is definitely not preferred.  This method may or may not have been used on one of the experimental aircraft close to my hangar.  If you want them very strong just put a dab of solder on the Dsub connector terminal and when it's time to remove the yoke simply de solder.  

 

 

Instead using the pins I just strip the wires and solder the ends. No need to get the pins and crimping tool. Soldered connections last for life.

José

[jetdriven]

There's a reason every wire on a Boeing is crimped. They must get an approval to solder a wire, which is rare.