New Safety Alert from FD.?

[Bill3558]

Elevator pushrod nut. 

2023_02_FLIGHT DESIGN PRESS RELEASE_02-pdf.pdf

[Roger Lee]

This is about FD production and not an elevator push rod nut.

Flight Design, the European manufacturer of the F2 and CT series of aircraft reports that despite a challenging start of the year, they will ship the first new production F2-LSA models to the U.S. at the end of August 2023.

[Tom Baker]

I think Bill attached the wrong link. There is a new SB on the elevator pushrod nut.

PZ27400700_00.pdf

[Anticept]

I reported two separate instances of that nut years ago and it should have been secured with a cotter pin and not a self locking nut.

That bolt and rod end bearing are supposed to be free turning but they aren't always, and for such a critical nut that might be subject to rotation, it really should be a cotter pinned nut.

Everyone should be aware that the feedback form at the end is not optional; its part of the directive, they need that information.

[Bill3558]

Thank you Tom for posting the correct link. My mistake.  

[FredG]

Corey, I inspected the bolt and rod end on my plane today and I also looked at the SA.  As far as I can tell, the bolt through the rod end should be tight.  The only motion in that assembly should be of the spherical bushing in the rod end.  If the bolt were anything other than tight, its movement would gradually enlarge the hole it passes through and create wasted motion (slop) in the elevator control.

[Animosity2k]

21 hours ago, Anticept said:

I reported two separate instances of that nut years ago and it should have been secured with a cotter pin and not a self locking nut.

That bolt and rod end are supposed to be free turning but they aren't always, and for such a critical nut that might be subject to rotation, it really should be a cotter pinned nut.

Everyone should be aware that the feedback form at the end is not optional; its part of the directive, they need that information.

Corey, do you have a link to a replacement AN nut that has a cotter pin? I'd like to change mine out ASAP. Was just asking on the FB group what the best fix was and here you are as always helping out. 

[Anticept]

15 hours ago, FredG said:

Corey, I inspected the bolt and rod end on my plane today and I also looked at the SA.  As far as I can tell, the bolt through the rod end should be tight.  The only motion in that assembly should be of the spherical bushing in the rod end.  If the bolt were anything other than tight, its movement would gradually enlarge the hole it passes through and create wasted motion (slop) in the elevator control.

That's the thing about rod ends: they are SUPPOSED to freely move, but it can go unnoticed for a while when they don't. All the while that turning motion is trying to turn the nut. That's why it's very, very common to see cotter pinned bolts on rod ends, it adds a substantial level of security.

Nylon inserts can also deteriorate, such as with exposure to lubricants.

Relying on the feel of "slop" in the controls is not a good way to catch if there's an issue, it should be better prevented period in the first place.

 

  

28 minutes ago, Animosity2k said:

Corey, do you have a link to a replacement AN nut that has a cotter pin? I'd like to change mine out ASAP. Was just asking on the FB group what the best fix was and here you are as always helping out. 

 

You need to go experimental if you're going to be doing this. Not only are you substituting a part, but you'll be going against a safety directive while you are at it.

Silly as it is, that's how it is. Or get an MRA allowing you to.

That bolt going through this assembly is a metric anyways, so an AN bolt won't be appropriate. I don't know what DIN standard there is for cotter pinned hardware over in europe.

[Animosity2k]

1 hour ago, Anticept said:

That's the thing about rod ends: they are SUPPOSED to freely move, but it can go unnoticed for a while when they don't. All the while that turning motion is trying to turn the nut. That's why it's very, very common to see cotter pinned bolts on rod ends, it adds a substantial level of security.

Nylon inserts can also deteriorate, such as with exposure to lubricants.

Relying on the feel of "slop" in the controls is not a good way to catch if there's an issue, it should be better prevented period in the first place.

 

  

 

You need to go experimental if you're going to be doing this. Not only are you substituting a part, but you'll be going against a safety directive while you are at it.

Silly as it is, that's how it is. Or get an MRA allowing you to.

That bolt going through this assembly is a metric anyways, so an AN bolt won't be appropriate. I don't know what DIN standard there is for cotter pinned hardware over in europe.

Confused a bit, FD sends a Bulletin to check and replace a nut, but to replace the said nut I need a MRA or to go experimental? Wouldn't this SB come w/ a MRA for the recommended replacement part? 

[Madhatter]

Heim joint fittings must always be bolted tight,  it's the ball and socket that moves. Bolt and nut with cotter pin is for assemblies with relative movement with no bearing,  like 2 or 3 flat plates. 

[Anticept]

You also find them in a lot of control surface points even when they do have heim joints. Heim joints are great but they can lock up.

I found two aircraft where the nut had backed off on the heim joint and bellcrank that this SA calls out.

I found both heim joints on a stabilator control tab frozen too, and they were rotating the screws. It had not loosened the nuts yet and probably wouldn't very easily since those surfaces have the heim joint captured between two bolting points so that it's surrounded on both sides, while the joint for pitch in the center console only has one side attached to a bellcrank.

[Anticept]

2 hours ago, Animosity2k said:

Confused a bit, FD sends a Bulletin to check and replace a nut, but to replace the said nut I need a MRA or to go experimental? Wouldn't this SB come w/ a MRA for the recommended replacement part? 

 

The SA says to make sure the nylock nut is bolted tight. Not replace it with an AN and cotter pin. I'm saying they should be cotter pinned joints especially something as critical as pitch control.

[Animosity2k]

19 minutes ago, Anticept said:

 

The SA says to make sure the nylock nut is bolted tight. Not replace it with an AN and cotter pin. I'm saying they should be cotter pinned joints especially something as critical as pitch control.

I see, I'll just check tightness! 

[FredG]

Corey, if the Heim joint (spherical rod end bearing) locks up then it should be replaced.

For clarity, the sentence of your earlier comment that I took exception to was "That bolt and rod end are supposed to be free turning".  My only point is that "that bolt" should not be free turning... it should be tight (so that the only movement is between the spherical insert and the rod end in which it moves).  Leaving that bolt "free turning" will ruin the hole in the alloy bellcrank.  

[Anticept]

I'm sorry I see what you are saying. I was super confused as to what we are getting at. What I was saying is that the assembly of the bolt and rod end are moving together freely. However, when the bearing locks up inside the housing, it puts friction on the washers/nut/other surfaces, and can get the nut to back off.

[Madhatter]

Mooney has an insane amount of heim joints, that's why there is an AD to lube them all at annual. ALL aircraft have these with no issues, you just have to lube them.

[Anticept]

And I've had no problem with mooney.

Here is what I mean by a "captured" heim joint (pictured: mooney):

 

This is the pitch control one on flight design for their pitch control link.

 

I have had it TWICE with flight design where this nut they are calling out backed off. One of those nuts had NO GRIP. the nylock insert wasn't doing anything at all.

I had two of those heim joints on a tail lock up and had to be replaced.

I'm sorry but I vehemently disagree with the design choice of a nylock nut. I wouldn't be concerned if it were a captured heim joint, where the integrity of the joint didn't rely so heavily on the tightness of the nut and bolt.

[Madhatter]

Every aircraft in the entire world uses these nuts just about since the Wright brothers. The CT uses cheap hardware you find at Ace Hardware. I inventory thousands of them but they are AN or MS.

[Anticept]

On 11/2/2023 at 6:05 PM, Madhatter said:

Every aircraft in the entire world uses these nuts just about since the Wright brothers. The CT uses cheap hardware you find at Ace Hardware. I inventory thousands of them but they are AN or MS.

On critical control surfaces connections?

I don't have a wide exposure to lots of models, but I have NEVER seen a nylock on CONTROL SURFACE connections. I have seen them in many other places but flight design is the only one I have seen using them on control surface connections.

 

Edit: hell I dont even need a castle nut and cotter, it could just be a hole drilled in the bolt and hitch clipped. Something to keep the nut from completely backing off. That's all.

[Jim Meade]

Heim.  H E I M.

[Anticept]

21 hours ago, Jim Meade said:

Heim.  H E I M.

Thanks for the correction. Fixed

I almost never hear anyone call them heim joints, i keep forgetting its heim, not helm (after the first time i misread them), and never had anyone face to face say anything but "rod end bearing".