Pitch control emergency

[PT20J]

7 hours ago, N201MKTurbo said:

You don't have the correct hardware. The IPC shows a castellated nut with a cotter pin.

Good catch! I was so focused on the bracket that I didn’t even notice the hardware. All the control system rod end should have castellated nuts and cotter pins. I’ll fix it next week during the annual inspection.
Thanks,

Skip

[carusoam]

Rich earned the Eagle Eye prize for the day on this one!

Go MS!

Best regards,

-a-

[0TreeLemur]

8 hours ago, N201MKTurbo said:

You don't have the correct hardware. The IPC shows a castellated nut with a cotter pin.

I looked at mine today.  My '67 has a very different looking part.   It has two slots that accommodate the end of the trim actuation tube, no Heim bearing.  An AN bolt passes through the entire mount and the end of the trim tube, which provides four penetrations through the mount!  No single failure path with this design.  It does have a castellated nut and cotter pin.  I took a photo but the iPhone focused on the wrong thing.

@Sam Judd what year is your Mooney?

[PT20J]

2 hours ago, Freemasm said:

While it would be appropriate with a clevis end, there’s no need to change to a castle nut with a heim installed. 

Interesting point. I agree that any locking nut, properly torqued, should clamp the ball sufficiently to prevent rotation and loosening. However...

Mooney uses castellated nuts with cotter pins on rod ends on all the engine and flight controls. The note 2 for the subject fastener combination item 44 in the IPC reads: All flight control rotating components must have double locking feature; castellated nuts, drilled shank bolts and cotter pins to secure each set of attaching hardware.

AC 43.13-1B paragraph 7-122 b. states:  Cotter pins are to be used on aircraft and engine controls, landing gear, and tailwheel assemblies. or any other point where a turning or actuating movement takes place.

Skip

[PT20J]

4 hours ago, Freemasm said:

For reference from my old AF parts manual (C, E, F, G)

 

This is interesting. Thanks for sharing that. According to this illustration, my hardware is correct but installed wrong -- bolt head should be on the outside.

I looked at several EAA videos describing rod end use and they all used fiber locking nuts rather than cotter pins for control applications. Also, I understand that it has been standard practice at Van's Aircraft to use fiber locknuts on control rod ends for the entire RV series. I looked in a Piper PA28 IPC and Piper uses cotter pins on engine controls and some flight controls, but some have self-locking nuts. Mooney doesn't seem to use cotter pins in the landing gear retract system as suggested in AC 43.13.

As I said earlier, if the fastener is properly torqued, I can't see that it makes any difference. And, since my trim bungees are in fine working order, and there are no logbook entries about work being done on the tail or trim system, it may well have come this way from the factory. Utilizing my "if it ain't broke, don't mess with it" philosophy, I'm going to check the torque on the bolt and leave it otherwise unmolested.

Skip

[EricJ]

The usual phrasing for when self-locking fasteners are allowed is that they must be "not subject to rotation".   As long as the spherical bearing in the rod end is free to move, e.g., isn't seized, the bolt won't be rotated in the joint.   I guess this is just Yet Another reason to keep the rod ends lubed.

 

[PT20J]

1 hour ago, EricJ said:

I guess this is just Yet Another reason to keep the rod ends lubed.

And, speaking of lube... Mooney specifies Triflow. I always thought that this was because it contained teflon and would not attract dirt which wears out the bearings. But then I noticed that Triflow dries to an oily film. I looked up the MSDS and it is 25-50% Heavy Naphthenic Petroleum Oil (whatever that is -- but it sounds, er, oily). So I sprayed some on a piece of aluminum, let it dry a few days and dipped it in some dirt which clung to it rather well. So, I called RBC, which makes Heim bearings and asked what the recommended lubricant was for aircraft applications. Sales took a couple of days to get an answer back from engineering and the answer was MIL-PRF-81322G grease (Aeroshell 22). 

Edit:

Someone will probably point out that some Heim bearings have zerk fittings. But I specifically asked RBC for a recommendation for the part number used for the connection to the aileron on a M20J which does not have a fitting.

Skip

[larrynimmo]

17 hours ago, PT20J said:Utilizing my "if it ain't broke, don't mess with it" philosophy, I'm going to check the torque on the bolt and leave it otherwise unmolested.

Skip

Skip!   Who are you kidding

[larrynimmo]

Sorry...missing this quote...

 

Utilizing my "if it ain't broke, don't mess with it" philosophy, I'm going to check the torque on the bolt and leave it otherwise unmolested.

[N201MKTurbo]

But haven’t we had a great discussion about nuts and bolts!

I know the Control hinge bolts on Mooneys have lock nuts instead cotter pins. I think they decided it was a PITA to put the cotter pins in.

Brice’s 310 has cotter pins on all the control hinges. 

[jaylw314]

On 10/18/2020 at 11:21 AM, PT20J said:

I looked at several EAA videos describing rod end use and they all used fiber locking nuts rather than cotter pins for control applications. Also, I understand that it has been standard practice at Van's Aircraft to use fiber locknuts on control rod ends for the entire RV series. I looked in a Piper PA28 IPC and Piper uses cotter pins on engine controls and some flight controls, but some have self-locking nuts. Mooney doesn't seem to use cotter pins in the landing gear retract system as suggested in AC 43.13.

Van's specifies nylon-insert nuts (and provides them with their kits) in most places.  In theory these can be reused and retightened more often without losing their locknut properties.  The downside, of course, is that if they lose their locking property, there's no way to confirm they're still in spec just by looking at them, as opposed to a cotter pin and castellated nut.  IIRC, the nuts to the elevator pushrod (the only control rod I have installed) in the RV-10 is a castellated nut and cotter pin.

[Sam Judd]

To tie this off, I've got the plane back. It took a ferry permit and conversations with three separate FSDOs, but at least everything is working again. The tail indeed had to be removed. It was about 6 hours of labor to drive to/from my mechanic's home base, do a temporary repair with cherry rivets and deal with the ferry permit/FAA. It was then another 6 hours or so to replace the temporary repair with the permanent one. 

@Freemasm I'll PM you to get an address to send the part.

[carusoam]

Great follow-up Sam!

All back together and flying now?

Best regards,

-a-

[0TreeLemur]

24 minutes ago, Freemasm said:

The NDE is back and the part is at the lab. There's no timeline but unless he/they are crushed with work it shouldn't take long. They love this stuff and are very well equipped and talented. Let's hope the fracture surfaces aren't burnished enough to hide any evidence.

  

Looking forward to the results.

[Ragsf15e]

Sheesh, that’s a scary one.  My ‘68 F is in annual right now and I’ll take a look at it for sure.

Did we ever figure out which year/models have the same/susceptible attachment as the one that failed?

[0TreeLemur]

5 hours ago, Ragsf15e said:

Sheesh, that’s a scary one.  My ‘68 F is in annual right now and I’ll take a look at it for sure.

Did we ever figure out which year/models have the same/susceptible attachment as the one that failed?

Our '67C has a beefier clevis-type connection with two points of failure. 

[Ragsf15e]

On 1/6/2021 at 5:50 PM, 0TreeLemur said:

Our '67C has a beefier clevis-type connection with two points of failure. 

My ‘68F has something that looks very much like the OPs part...

And for @PT20J, same type nut as yours.

Edited January 8, 2021 by Ragsf15e

[Yetti]

So in theory there should be no side to side loads placed on that part.   We know that some planes had issue with huck bolts on the hinge as the hinge should not allow side loading of the tail.   Did these planes have huck bolt issues?   But clearly with two extremely similar breaks the tab is under engineered.   There is room to increase the fillet or just beef up the whole part.  Two tabs on either side of the bearing would be super awesome.

[skykrawler]

Look at the assembly carefully and compare to the parts diagram explossion.  Perhaps it was re-assembled incorrectly placing side loads on the bracket.

Does seem like a control system failure.

Ill be checking mine tomorrow.

[PT20J]

2 hours ago, Yetti said:

So in theory there should be no side to side loads placed on that part.   We know that some planes had issue with huck bolts on the hinge as the hinge should not allow side loading of the tail.   Did these planes have huck bolt issues?   But clearly with two extremely similar breaks the tab is under engineered.   There is room to increase the fillet or just beef up the whole part.  Two tabs on either side of the bearing would be super awesome.

I made that mistake too, but @Freemasm corrected me earlier in the thread. The fact that the rod end is offset applies a torque to the bracket.

Skip

[Yetti]

3 hours ago, PT20J said:

I made that mistake too, but @Freemasm corrected me earlier in the thread. The fact that the rod end is offset applies a torque to the bracket.

Skip

Mmm even offset the hemi bearing should keep the forces in proper alignment.  I think.  I could also see where say someone ran an electric trim up against the stop that would be a more stress inducing point with the hemi joint in a bind.

 

Edited January 9, 2021 by Yetti

[Yetti]

This does seem worthy of a Service Bulletin.

[Bartman]

Here’s a thought. The jack screw is about the one thing that requires maintenance or rebuild. Is it possible the jack screw was serviced and installed “out of time” or out of adjustment enough that the tail hinge itself runs out of travel while at the same time the jack screw still has a couple more threads of rotation and more travel of the rod ?

[N231BN]

The rod attachment in question is not part of the jackscrew. It is the spring feedback to the elevator push rod.

[Ragsf15e]

Dude, thanks, that’s awesome.  One of us needs to buy your guys a 6 pack.