servo failure after corrosion treatment

[DXB 2,053]

So I had an STEC-30 installed about a year ago - it worked perfectly, and I loved it.  I then had my plane treated with ACF-50 a few months ago.  Last weekend my altitude hold stopped working- the Alt hold light comes on when I try to engage it, but it does nothing - i.e.  no trim alarms etc.   So I took it to the avionics shop today.  They said that they found a ton of gunk inside the elevator servo that looked like the anti-corrosion material settling out into it. I feel like I'm being punished for trying to take care of my plane.  My avionics shop spent hours removing and cleaning up the servo and got it working again.   On the way home this evening it initially worked fine and then quit working.  Again!  It seems like they would want to protect such components in the tail when applying the corrosion spray.  I'm not going to accuse the well known shop that did the corrosion treatment of anything - nothing good would come of it.

This post is really just a primal scream to help me cope with the vicissitudes of aircraft ownership. Of course I'm call the avionics shop again in the am.  

However I am also curious if anyone has had similar experiences and/or ideas on how to resolve the issue.

[cnoe 1,147]

Yes indeed. The servo clutch will soak that stuff up like crazy. And just covering the servo with a plastic bag isn't enough. You have to wrap it thoroughly and tightly closing every little opening. And I wouldn't open it back up for a good while. Don't ask me how I know this.

The good news is that the "fog" gets into places you wouldn't believe and really does protect you from corrosion.

[jetdriven 4,418]

The shop applying the corrosion fog should know better 

Edited November 17, 2016 by jetdriven

[DXB 2,053]

1 hour ago, jetdriven said:

The shop applying the corrosion fog should know better 

Great. Now I'm really pissed - 1st world problems I realize. 

Venting here. Calm in the real world.

[carusoam 12,021]

Ever see the smoking rivets caused by the anti corrosion fog spray....?

It is proven to get into some really tight spaces.

My C had an empty shelf back there.  There was nothing for the spray to get into that wasn't welcomed...

Not so much a first world issue,  closer to the 1%er.  How many of us fly Moonies? 

Best regards,

-a-

[Andy95W 4,269]

Strange- I CorrosionX my plane last spring and now my STEC won't even test properly.  I thought I had wrapped the servos but now I'm starting to wonder.

So, what's the solution? Send out the servos for cleaning?

[Hyett6420 2,749]

Am just about to have this done so i am watching this thread REALLY closely.  Can M20doc or any other mechanic  shed any light on this?  

[PTK 1,685]

This has peaked my interest also. My pitch servo started acting up after corrosion x tx. It decides when it wants to hold pitch or altitude. On the first flight of the day it will not respond until 5 or 10 minutes into the flight. Then it works! The good folks at Autopilot Central helped me diagnose it by doing some ground tests and said to me that they need to go through it and change a solenoid. It's the one servo that's a pain to remove too! I wonder if it's related to the corrosion tx. 

[DXB 2,053]

I talked to the shop that did the corrosion spray.  They don't cover the servos to protect them.  Apparently the ACF-50 is very safe for electronics - they advertise it with a TV dunked in a vat of it and still functioning.  So the guy who sprayed it assumed it's safe for everything.  Turns out it's also a really great lubricant that makes the servo clutch not hold.  I think the light bulb came on for them - hopefully they will pay more attention in the future.

 

[Hyett6420 2,749]

1 hour ago, DXB said:

I talked to the shop that did the corrosion spray.  They don't cover the servos to protect them.  Apparently the ACF-50 is very safe for electronics - they advertise it with a TV dunked in a vat of it and still functioning.  So the guy who sprayed it assumed it's safe for everything.  Turns out it's also a really great lubricant that makes the servo clutch not hold.  I think the light bulb came on for them - hopefully they will pay more attention in the future.

 

Oh shite.  That's worrying.  Not that they did it but that an aircraft shop was unaware that it is an "oil" and thus would bugger servos.   You would assume that any shop that did anti corrosion on aircraft would be knowledgeable on its effects on aircraft parts.  

[cnoe 1,147]

Oh shite.  That's worrying.  Not that they did it but that an aircraft shop was unaware that it is an "oil" and thus would bugger servos.   You would assume that any shop that did anti corrosion on aircraft would be knowledgeable on its effects on aircraft parts.  

Once the servo clutch is contaminated it must be disassembled, cleaned, and reassembled with the proper torque value. They don't do this for free either. Note that you can't simply spray it down with a solvent/cleaner and expect it to work again.

And let me re-emphasize that you must SEAL the servo to prevent this problem and not simply cover it up. If the applying facility doesn't understand this you'll very possibly have trouble post-application.


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[Hyett6420 2,749]

21 minutes ago, cnoe said:

 

Once the servo clutch is contaminated it must be disassembled, cleaned, and reassembled with the proper torque value. They don't do this for free either. Note that you can't simply spray it down with a solvent/cleaner and expect it to work again.

And let me re-emphasize that you must SEAL the servo to prevent this problem and not simply cover it up. If the applying facility doesn't understand this you'll very possibly have trouble post-application.


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grrr, that sounds really annoying if they bugger that up.

[Danb 2,156]

i went through this years ago in my J, after many attempts I ended up replacing with new.

[DXB 2,053]

3 hours ago, cnoe said:

 

Once the servo clutch is contaminated it must be disassembled, cleaned, and reassembled with the proper torque value. They don't do this for free either. Note that you can't simply spray it down with a solvent/cleaner and expect it to work again.

And let me re-emphasize that you must SEAL the servo to prevent this problem and not simply cover it up. If the applying facility doesn't understand this you'll very possibly have trouble post-application.


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Yep- spraying it down with solvent did nothing. This is a total PITA.

[DXB 2,053]

I flew it again without any further service.  The pitch servo ground checked fine and then held just fine in the air.  Weird.  Is it typical for the problem to be intermittent?  I'm not going to rush to get it fixed until I watch it for a while.  

[NotarPilot 529]

Corrosion treatment has been on my list of things to do to my plane. Reading this thread is seriously making me reconsider. 

[jetdriven 4,418]

Check out Boeshield T9 or Dinitrol AV8. Both apply like corrosion-X but then the lighter component evaporates out and it stops running and weeping out of the seams. My plane looked terrible after corrosion-x treatment with oily residue coming from every seam for years.  

Edited November 25, 2016 by jetdriven

[Hyett6420 2,749]

1 hour ago, NotarPilot said:

Corrosion treatment has been on my list of things to do to my plane. Reading this thread is seriously making me reconsider. 

i would urge ALL owners to corrosion treat, having just spent a lot of fixing the issue.  Just make sure you learn form this thread as well.

[Bennett 783]

Check out Boeshield T9 or Dinitrol AV8. Both apply like corrosion-X but then the lighter component evaporates out and it stops running and weeping out of the seams. My plane looked terrible after corrosion-x treatment with oily residue coming from every seam for years.  

I have had ACF-50 fogged in on every airplane I have ever owned over the last four decades. The aircraft serviced by LASAR (261, and now the 201) are done on an every third year schedule. They are very though in their application. Not cheap, but I think this preventative maintenance is important.


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[cnoe 1,147]

Check out Boeshield T9 or Dinitrol AV8. Both apply like corrosion-X but then the lighter component evaporates out and it stops running and weeping out of the seams. My plane looked terrible after corrosion-x treatment with oily residue coming from every seam for years.  

Has Aviation Consumer or another reliable source reviewed these? Like you I dislike the post-application weeping but I won't forgo treatment because of it. Sadly I have a half-gallon of C-X left I'd planned on using at next annual.


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[cnoe 1,147]

I Corrosion X my plane pretty much every year during the annual. I've gotten the application down to well under a pint now.  Plexus cleans up any streaking without too much trouble. I know where the streaks normally form now, so I just incorporate those areas into my post flight leading edge wipedown routine. 

Under a pint? I need a better fogger setup.[emoji846]


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[MB65E 788]

I'd have to read the can again but I believe it says it's safe for electrical connections. Much like a contact cleaner or other fluids that are conductive. I would honestly think it was purely coincidental that it may have caused a servo issue. 

I have used corrosion X as a cleaner too. Wiping down a filthy wheel well, or cleaning a brake caliper(while disassembled). It leaves a film behind that can be wiped down or left on for even better protection. 

The seams on the wing will collect the fluid and weep slightly. That kinda makes me feel good as it's still working. 

-Matt

[cnoe 1,147]

I'd have to read the can again but I believe it says it's safe for electrical connections. Much like a contact cleaner or other fluids that are conductive. I would honestly think it was purely coincidental that it may have caused a servo issue. 
I have used corrosion X as a cleaner too. Wiping down a filthy wheel well, or cleaning a brake caliper(while disassembled). It leaves a film behind that can be wiped down or left on for even better protection. 
The seams on the wing will collect the fluid and weep slightly. That kinda makes me feel good as it's still working. 
-Matt

Agreed, there should be no electrical issues. The problems occur when it penetrates the servos' clutch mechanisms thereby "lubricating" the friction plate(s) and upsetting the delicate setting that allows you to manually overcome the control forces if needed.


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[MB65E 788]

53 minutes ago, cnoe said:

 

Agreed, there should be no electrical issues. The problems occur when it penetrates the servos' clutch mechanisms thereby "lubricating" the friction plate(s) and upsetting the delicate setting that allows you to manually overcome the control forces if needed.


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I see, that makes sense.

-Matt

[NotarPilot 529]

21 hours ago, Hyett6420 said:

i would urge ALL owners to corrosion treat, having just spent a lot of fixing the issue.  Just make sure you learn form this thread as well.

That's good to know Andrew and I may reconsider based on your recommendation and experience. I'm also hoping to repaint within 2 years, if I can pull it off. I think I heard somewhere that you shouldn't treat the plane within 2 or 3 years of a future paint job. Is there any truth to this?