Flight Control Pushrod Corrosion

[zuutroy]

Hi,

I have a J in for my first annual and the engineer was pretty horrified at the state of the flight control rods. He says they shouldn't have been signed off in previous years if anything like this. Any thoughts? I'm new to ownership so don't really have any experience to go off.

 

Thanks.

[1964-M20E]

Hard to tell from the photos but IMHO it probably is not an issue but I'm just a pilot.  I'd try to scuff with scotch brite pads and generously apply corrosion X.

[RLCarter]

The 2nd photo looks like it has stalagmites growing off it, some of the other stuff looks like dried lube and dirt build up. Most of the hardware needs replaced

[Igor_U]

If I were a betting man, I'd say that service manual specifies minimum tube wall thickness.

You could clean the corrosion with Scotch brite pads and refinish the tubes with epoxy primer or such. Hard to say from your pictures but definitely some corrosion on tubes and elsewhere.

 

[Vance Harral]

First photo definitely looks like rust on steel components.  The others are harder to tell.

I've taken various control rods out of our airplane over the years that looked awful in-situ, but that turned out to be nowhere near as bad as I feared.  Sometimes, discoloration is just "gunk" - build-ups of dirt, grime, lubrication, etc.

Where there is actual corrosion, it's sometimes just "light surface corrosion" that can be cleaned and repainted with minimal trouble once the rod is completely out of the aircraft.  Scotch-brite or similar abrasives as others above have suggested.

Even if there's pitting, it's not necessarily a deal-breaker.  The parts in question can be bead blasted and repainted per techniques in AC43-13 Chapter 6, if they're not "bad".  But defining "bad" seems complicated to me, and maybe just boils down to the mechanic's judgement.  The oft-cited ten percent wall thickness is a reasonable standard, but note that AC 43-13 and the infamous Mooney SB 208 use this with respect to structural steel tubing, which is not the same as control pushrods.  Our own very experienced A&P has been known to look at discolored spots here and there and say things like, "Well, yeah, that might rust all the way through in another 50 years or so.  You don't need to do anything about it this year."  This used to make me more nervous until I pulled and cleaned and carefully inspected a few such rods.  In our case there was nothing of concern, but I don't mean to be cavalier about it - I still think you don't really know until you look closely.

In summary, I'm not sure "horrified" is an appropriate reaction by your mechanic.  I don't think you were in any particular danger flying this airplane the last year.  But it would probably be good to pull the rods out of the airplane and have a close look at them.  Odds are they won't require anything other than cleaning, paint, and new AN hardware.  Not particularly expensive in the grand scheme of things.  Just the thoughts of a pilot and owner who likes to assist with maintenance, though - I'm not an A&P.

[Igor_U]

2 hours ago, Vance Harral said:

  The oft-cited ten percent wall thickness is a reasonable standard, but note that AC 43-13 and the infamous Mooney SB 208 use this with respect to structural steel tubing, which is not the same as control pushrods. 

Vance,

I agree that 10% thickness reduction standard applies to structural tubing; also quick look at SM did not reveal anything about the push-pull rods.

However, years ago at the annual, my IA found out worn (Elevator?) control push-pull tube he wasn’t comfortable with. To my understanding, on ’67 only, that tube slides over phenolic block in the belly (so it clears the tubular structure) and got slightly spot-faced as it was not greased generously…

IIRC, my IA contacted factory regarding that wear and I think they answered “no wear was allowed”. I don’t know where was this coming from. Contacting MSC (D. Max), the responses was, if it’s not bad, they clean it, refinish it and rotate the tube 180 degrees.

So, answer would be: it depends. Mainly of you mechanic and how comfortable he/she is signing the repair.

I ended up getting a new custom replacement tube, modified from Ovation by LASAR since original was not available. It wasn’t exactly cheap but I was doing my own maintenance with IA’s supervision and inspection so labor was free.

 

Regards,

[Marauder]

5 hours ago, zuutroy said:

Hi,

I have a J in for my first annual and the engineer was pretty horrified at the state of the flight control rods. He says they shouldn't have been signed off in previous years if anything like this. Any thoughts? I'm new to ownership so don't really have any experience to go off.

 

Thanks.

When I first saw these photos, though I was looking at an early Mooney. Surprised to see it is a J. I would certainly pull these and have them cleaned up. I had mine removed and the long sections painted. Also had the rear assembly cleaned up and painted. What is more troubling for me is that it appears that a portion of the tail isn't zinc chromate painted. My 75 F is completed painted and I thought all J models were painted with some type of anti-corrosion paint. Was the plane involved in an accident where skin sections were replaced? 

[Vance Harral]

1 hour ago, Igor_U said:

So, answer would be: it depends. Mainly of you mechanic and how comfortable he/she is signing the repair.

I agree with your "it depends" assessment.

As another example similar to yours, one of the tubes for the elevator trim system in our airplane runs through a nylon grommet, and is subject to wear as described in Service Bulletin M20-185.  On the first annual after we bought the airplane, our A&P/IA inspected this tube and found it worn beyond the limits described in the SB.  The SB (not an AD) prescribes replacement of the tube, but the mechanic had the tube built up with a weld instead, per techniques described in AC 43.13.  He judged this satisfactory because the tube isn't subject to bending or tension or compression loads, only torsion.  It was significantly faster and less expensive than replacement.

Another Mooney owner I spoke with about this insisted it was an "illegal" repair, but there's simply no basis for that position.  Service bulletins aren't mandatory, so replacement of the tube isn't mandatory.  The mechanic used approved data from AC 43.13 to make and sign off a repair he believed adequately addressed the problem, which by definition makes the repair legally airworthy.  It's fine to debate whether it's a good idea vs. replacing the tube, but it's not "illegal".

(For what it's worth, that repair was made 14 years ago and has held up just fine - including a detailed inspection just this year when we overhauled our trim system).

[zuutroy]

1 hour ago, Marauder said:

When I first saw these photos, though I was looking at an early Mooney. Surprised to see it is a J. I would certainly pull these and have them cleaned up. I had mine removed and the long sections painted. Also had the rear assembly cleaned up and painted. What is more troubling for me is that it appears that a portion of the tail isn't zinc chromate painted. My 75 F is completed painted and I thought all J models were painted with some type of anti-corrosion paint. Was the plane involved in an accident where skin sections were replaced? 

It had a gear-up about 8 years ago but I'm not 100% sure what body work was required at the time. 

Thanks for all the input. I'll ask the engineer if he might consider a cleanup job where possible. I assume replacing all of the rods would be fairly pricey. 

[Yetti]

The flaky crusty stuff seems concerning.  The discoloration stuff will clean up pretty well.   just a PP

Edited March 23, 2018 by Yetti

[Guest]

11 hours ago, zuutroy said:

Hi,

I have a J in for my first annual and the engineer was pretty horrified at the state of the flight control rods. He says they shouldn't have been signed off in previous years if anything like this. Any thoughts? I'm new to ownership so don't really have any experience to go off.

 

Thanks.

Sadly this is all too common on Mooney’s.  Removal, cleaning and inspection is the only way to know for sure.  We have an Acclaim in the shop which had similar issues.  Some caused by environmental issues, some by old age and never having the primer painted with a top coat.  

On any that I remove I also spray LPS 3 down the inside of the tube after painting the outside.

Clarence

[bradp]

Also check your belly drain - looks like water has been sitting in the bottom of the skin.  May have created a greenhouse in the empennage.  I was getting water in the bottom after flying though rain one day and tracked it down to water that was getting sucked up next to the rotating beacon.   Check the seal / gasket around that and antennas.  If this bird sits out of doors, get an empennage cover from Bruce’s.  It will at least keep a majority of the water out.  

[jaylw314]

On 3/22/2018 at 12:39 PM, Vance Harral said:

The mechanic used approved data from AC 43.13 to make and sign off a repair he believed adequately addressed the problem, which by definition makes the repair legally airworthy. 

Semantics alert!   IIRC, AC43.13 provides "acceptable" data for minor repairs.  the official MM or an engineer's sign off would provide "approved" data for major repairs.

The question becomes whether the repair of the tube is a major or minor repair, the answer to THAT is, again, probably "it depends".

Also, I thought the last time I looked in the tailcone of my plane, I recall large parts of it were not zinc chromate painted?  I could be wrong, I'll check next time I'm in the hangar.  It's an '86 J

Edited March 24, 2018 by jaylw314

[Guest]

On 2018-03-22 at 3:39 PM, Vance Harral said:

I agree with your "it depends" assessment.

As another example similar to yours, one of the tubes for the elevator trim system in our airplane runs through a nylon grommet, and is subject to wear as described in Service Bulletin M20-185.  On the first annual after we bought the airplane, our A&P/IA inspected this tube and found it worn beyond the limits described in the SB.  The SB (not an AD) prescribes replacement of the tube, but the mechanic had the tube built up with a weld instead, per techniques described in AC 43.13.  He judged this satisfactory because the tube isn't subject to bending or tension or compression loads, only torsion.  It was significantly faster and less expensive than replacement.

Another Mooney owner I spoke with about this insisted it was an "illegal" repair, but there's simply no basis for that position.  Service bulletins aren't mandatory, so replacement of the tube isn't mandatory.  The mechanic used approved data from AC 43.13 to make and sign off a repair he believed adequately addressed the problem, which by definition makes the repair legally airworthy.  It's fine to debate whether it's a good idea vs. replacing the tube, but it's not "illegal".

(For what it's worth, that repair was made 14 years ago and has held up just fine - including a detailed inspection just this year when we overhauled our trim system).

I’m not sure how a weld repair could be made leagally on a trim tube, unless of course he was able to determine alloy and heat treatment and that the weld repair would meet those requirements.

SB M20-208 provides all information on airframe structural tubes subject to the SB, SB M20-185 does not provide this information and I doubt that Mooney would provide it.

Clarence

[autoalain]

Folks, I had a gear up in year 2000,  went to lower my  johnson bar and it broke at very bottom due to rust, my AME never removed boot to check 

at annual, he said it was not on his mooney annual check list,  so if u have some rust underneath maybe  have a real good look if u have a  manual 

gear system.    Mike.  c-flrv    in canada with lots of snow.

[Vance Harral]

17 hours ago, M20Doc said:

I’m not sure how a weld repair could be made leagally on a trim tube, unless of course he was able to determine alloy and heat treatment and that the weld repair would meet those requirements.

That's a fair question and I don't have an answer for it.  I don't hold an A&P certificate.  I'm not skilled in the art of trim tube repair or the legal responsibilities of an A&P, and I didn't ask questions about the alloy and heat treatment when the repair was proposed.

... but it remains true that a licensed A&P with a long-time practice and a good reputation made the repair, logged it, and signed it off (most likely based on experience with similar repairs).  That makes it legal for me to operate the airplane.

Even if this particular repair can be traced to some black-and-white regulation, others can't.  I've spoken with enough mechanics to understand at certain points they're simply obligated to make reasonable interpretations of regulations that cannot cover every possible situation - just as pilots must do with the regulations governing operating of aircraft.  I'm sure there are "conservative" and "liberal" mechanics in this respect.  I respect the spectrum and try to be careful, but I don't lie awake at night worrying about it either.

[Guest]

5 hours ago, Vance Harral said:

That's a fair question and I don't have an answer for it.  I don't hold an A&P certificate.  I'm not skilled in the art of trim tube repair or the legal responsibilities of an A&P, and I didn't ask questions about the alloy and heat treatment when the repair was proposed.

... but it remains true that a licensed A&P with a long-time practice and a good reputation made the repair, logged it, and signed it off (most likely based on experience with similar repairs).  That makes it legal for me to operate the airplane.

Even if this particular repair can be traced to some black-and-white regulation, others can't.  I've spoken with enough mechanics to understand at certain points they're simply obligated to make reasonable interpretations of regulations that cannot cover every possible situation - just as pilots must do with the regulations governing operating of aircraft.  I'm sure there are "conservative" and "liberal" mechanics in this respect.  I respect the spectrum and try to be careful, but I don't lie awake at night worrying about it either.

Legal and signed off are not the same as correct and safe.  

There are shops that weld landing gear parts, engine crankcases etc, parts with high strength requirements which in many cases are heat treated.   They have processes and quality assurance systems approved by the FAA.

Clarence

[zuutroy]

Going to replace the two long pushrods that run through the tailcone. Any idea on what total labor time I should budget paying for? 

[Guest]

6 hours ago, zuutroy said:

Going to replace the two long pushrods that run through the tailcone. Any idea on what total labor time I should budget paying for? 

An hour each should be generous.  The elevator may take more than the rudder if you have an autopilot with altitude hold attached to it.

Just be sure that the installer installs the spacer washers used at the aft end, we just did a K model that had the same rods worked on and the spacer washers were left out.

Clarence

[zuutroy]

Thanks. It has the KFC150. I thought the tail had to come off to replace them. Does that not take a while?

[Guest]

Just now, zuutroy said:

Thanks. It has the KFC150. I thought the tail had to come off to replace them. Does that not take a while?

If you’re referring to the rods in the aft part of the fuselage, the battery door comes off and the last two inspection panels ahead of the tail close out strips.  A bunch of 1/4 turn fasteners on the battery cover, 10 screws per inspection panel, 2 bolts on the rudder push rod, two on the elevator push rod.

Clarence

[Guest]

I don’t know if this helps:

[carusoam]

Clarence,

You are really a Good Man!

It is great having your unique level of support here.

Best regards,

-a-

[Jerry Pressley]

if they don't clean up I have a few dozen extras.  jerry pressley

[zuutroy]

2 hours ago, acpartswhse said:

if they don't clean up I have a few dozen extras.  jerry pressley

Thanks. I'm not sure what the rules are in EASA-land regarding 8130 etc but I'll check.