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Sam’s link, just slightly more live...
 

Looks like lots of metal flake was ejected with the failure...

which could have been instantaneously deposited... if it had failed slowly over time, there may have been a few days during an annual that those flakes would have stood out to good mechanical inspector...

https://photos.google.com/share/AF1QipN95icT-rkpXrkJCdSpbqeXXLT3PWJb3siWQ52RX4httQ_vNZEB67zMBHgFquWTkw?key=cnJGbmFKRFJCZkpqbGhRRkI3MlhuY21reWRTTDlB

-a-

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I took my '78 J out last Friday night to do a short night cross country and get my night currency back. After my first uneventful flight/landing, I ended up declaring an emergency doing pattern work.

A few points: First, great job handling a true emergency. Loud noises followed by controllability problems are scary -- especially at night. It's common to second guess your actions afterward whe

Hard to tell from the photos but speculation follows. - Looks like a typical fatigue failure. The straight portion of the crack propagated over time until it ultimately, abruptly, failed (more ir

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Hard to tell from the photos but speculation follows.

- Looks like a typical fatigue failure. The straight portion of the crack propagated over time until it ultimately, abruptly, failed (more irregular looking tear).

- The initial crack probably existed for a while based upon what appears to be fretting wear and some discoloration from the resulting exposure. 

- The surface irregularity the OP noted earlier was probably a (secondary) contributor.

It is up to you Mooney types to correct me here. As mentioned earlier, my memory/understanding of the related kinematics thinks that the loading on this part should be limited to the spring forces in the related linkage. The rigging should be taken to parade rest (easy to do since with the related upcoming surgery). I'd also check to see if there's slop in the linkage; worn/loose fasteners, wear in the rod end bearing, relative movement of the attach arm (don't know the correct part terminology) inside of the spring cans. Lack of existing pre-load here would be a bit of a surprise/concern. If this requirement isn't listing in any of the manuals, Mooney will probably have to weigh in. The fact that the later models appear to have changed the subject part material to steel makes you think.

Got to love Non-Destructive Engineers. Only they are allowed to call something a "crack". Everyone else must refer to them as an "indication" until so examined and proclaimed by the NDE.  A million years when I radioed the assigned NDE to come disposition a crack on a piece of steel structure, he tersely corrected my verbiage. I radioed back that I could see light and stick my finger through the indication but would await his expertise. Yep. was making friends back then, too.  

   

 

 

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BTW a quick update. From your latest posted pix, the NDE SWAG'd fatigue from bending (as opposed to a classic shear or tension load) caveating that he can't say for sure without personally analyzing the part (of course).  He is a pilot as well.

This is interesting. He was only given the link to your most recent photos. He didn't know the method of attachment. He also didn't know about the suspect witness marks near the bolt head from your original post. Couple the suspected change in related part material from Al to what appears to be (probably) 4130 for later long bodies. Reference prior post with related picture. Also, note the new design is a U bracket that would eliminate the aforementioned bending. Anyone else smell something?

Side note; every aircraft type person over here who's seen the photos also unsolicitedly remarks "been there for a while", "missed previously", etc. 

This could easily, conceivably, become a SB or (recurring) AD. (Sarcasm font on) That issuance will probably predate approval of the TruTrak APs for Mooney world. (Sarcasm font off, or not)    

Edited by Freemasm
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Hard to see how there would be a bending moment given the rod ends on each end of the tube and the linear action of the tube. The attached drawing from the M20J IPC only shows a rod end at the aft end, but the parts list does call out 2 for the assembly. My annual inspection is scheduled in a couple of weeks - I’ll be looking this part over very closely.

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508527242_Screenshot2020-10-08at12_44_17PM.thumb.png.423d273f5343464d36a446772a05d2c3.png661351447_Screenshot2020-10-08at12_51_29PM.thumb.png.1d115d88f41a70214cdeb35c8fcf742a.png

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A properly torqued bolt through a bearing would yield more of a shear load but a bending load still exists as there is a offset between the bearing and bracket. This would be aggravated if not properly torqued. The suspect witness marks near the bolt head could be related to a past, improper installation.

You've possibly added another variable. Maybe just a document error but still interesting:

Your drawing does not show a rod end at the point of interest. It appears to depict a clevis (no bearing). The alignment dashed lines are consistent with this. The bolt, castellated nut, and cotter pin in the parts list are also consistent with such an application/installation. The parts books I've seen all had plenty of errors. Some pix of the related location during your annual could at least be interesting. 

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6 hours ago, Freemasm said:

A properly torqued bolt through a bearing would yield more of a shear load but a bending load still exists as there is a offset between the bearing and bracket. This would be aggravated if not properly torqued.

This is correct, of course. I overlooked the offset. Thanks for pointing that out.

I was at the hangar today and decided to take a look at my 1994 'J. A couple of observations:

1. The bracket appears to be an aluminum T extrusion. The thickness of the "stem" to which the tube attaches is only about 0.08".

2. Mine shows a very slight bending of the "stem" to the outboard (presumably due to the offset pull force of the tube that attaches to the trim assist bungees). This is evident in the picture if you look closely.

I don't think this is a very robust design.

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IMG_3791.thumb.jpg.4262890a0c9c1706c8ae796c8869ef77.jpg

 

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2 minutes ago, PT20J said:

This is correct, of course. I overlooked the offset. Thanks for pointing that out.

I was at the hangar today and decided to take a look at my 1994 'J. A couple of observations:

1. The bracket appears to be an aluminum T extrusion. The thickness of the "stem" to which the tube attaches is only about 0.08".

2. Mine shows a very slight bending of the "stem" to the outboard (presumably due to the offset pull force of the tube that attaches to the trim assist bungees). This is evident in the picture if you look closely.

I don't think this is a very robust design.

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IMG_3791.thumb.jpg.4262890a0c9c1706c8ae796c8869ef77.jpg

 

It's lasted 30 years with sufficiently minor deformation that you have to look very closely to see it, but it's not a robust design? How long should it last? Mine's 20 years older, but it'll be sometime next week before I can look at it. 

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25 minutes ago, PT20J said:

This is correct, of course. I overlooked the offset. Thanks for pointing that out.

I was at the hangar today and decided to take a look at my 1994 'J. A couple of observations:

1. The bracket appears to be an aluminum T extrusion. The thickness of the "stem" to which the tube attaches is only about 0.08".

2. Mine shows a very slight bending of the "stem" to the outboard (presumably due to the offset pull force of the tube that attaches to the trim assist bungees). This is evident in the picture if you look closely.

I don't think this is a very robust design.

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IMG_3791.thumb.jpg.4262890a0c9c1706c8ae796c8869ef77.jpg

 

Ouch, that hurts just looking at it.   Based on the IPC excerpt you posted earlier it seems like maybe sometime along the way this was a double-shear attachment that got converted to a spherical rod end.   I don't think that conversion got implemented optimally.

The bracket could have been double-shear (a U to both sides of the rod end) but would have been more expensive to make.  I think this is a good item to add to the annual inspection list if it is implemented like this.  Now I gotta go look at mine sometime...

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On 10/8/2020 at 9:59 PM, PT20J said:

I don't think this is a very robust design.

 

Agreed.  Much more susceptible to the observed failure mode that started this thread than the design using the stamped part.  Requires careful inspection for fracture indications.  Luckily this failure does not result in an unrecoverable situation in a J. 

I wonder how this failure would affect the pitch control in a short body?   Anybody with a short body ever lived through this?

There are aircraft in museums that are newer than my C.  Next annual I'll spend extra time inspecting that little piece of extruded aluminum.

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On 10/8/2020 at 7:59 PM, PT20J said:

This is correct, of course. I overlooked the offset. Thanks for pointing that out.

I was at the hangar today and decided to take a look at my 1994 'J. A couple of observations:

1. The bracket appears to be an aluminum T extrusion. The thickness of the "stem" to which the tube attaches is only about 0.08".

2. Mine shows a very slight bending of the "stem" to the outboard (presumably due to the offset pull force of the tube that attaches to the trim assist bungees). This is evident in the picture if you look closely.

I don't think this is a very robust design.

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IMG_3791.thumb.jpg.4262890a0c9c1706c8ae796c8869ef77.jpg

 

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

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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,

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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?

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I previously mentioned an IPC inconsistency. I Strongly believe/other evidence points to this as being the case. The IPc also displays a clevis versus a rod end (also previously mentioned). A castellated nut would not be required with a bearing installed. Any rotation should occur between the bearing and eye.  The bearing pinned in the associated linkage is factory original. Have seen many similar vintages as “standard”. Vegas odds are on a IPC versus assembly drawing mismatch. While it would be appropriate with a clevis end, there’s no need to change to a castle nut with a heim installed. 

Edited by Freemasm
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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.

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4 hours ago, Freemasm said:

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

 

470289AD-327B-4C65-A941-CCDA7B2FCEC6.jpeg

ACD3777D-B1DA-4D38-B4AC-98B18EF6271F.jpeg

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.

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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.

 

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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.

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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. 

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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.

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