Control surface slack

[slowflyin]

Anyone now the tolerances for control surface slack/slop? All I can find in the service manual is rudder up and down.

[MB65E]

That's a good IA refresher question. I believe it involves an equation between the length of the flight control vs the slop measurement. The result must not be more than 3%. I'll look it up...

It's in some citation MM I know.

-Matt

[Guest]

There are no limit that I've seen for control surface free play, hence you could argue no play allowable, or it doesn't matter. There is however a limit for play at the tips of the stabilator and vertical play at the base of the tail cone/rudder.

Clarence

[cliffy]

Excessive slack in Mooney control surfaces can be traced most of the time to rod ends being worn but you probably already know that. Ideally, with our push-pull rods there would be minimal slack but in reality there will always be some play due to wear in all moving joints in the particular system. I don't know of a "limit"  but when I feel slack I trace it down by watching all joints when the control is moved in the slack position and replace what I see as being loose. That usually solves my issues. It's always been rod ends in my case. 

[rbridges]

Excessive slack in Mooney control surfaces can be traced most of the time to rod ends being worn but you probably already know that. Ideally, with our push-pull rods there would be minimal slack but in reality there will always be some play due to wear in all moving joints in the particular system. I don't know of a "limit"  but when I feel slack I trace it down by watching all joints when the control is moved in the slack position and replace what I see as being loose. That usually solves my issues. It's always been rod ends in my case. 

 

are those difficult/expensive to replace?

[Marauder]

are those difficult/expensive to replace?

During the last annual, I had my mechanic pull the rear horns and replace any worn Heim (I think that is there official name) joints while they were stripping, checking for cracks and repainting. I see $47 each. Figure an hour if they need to use the story boards.

[yvesg]

That's a good IA refresher question. I believe it involves an equation between the length of the flight control vs the slop measurement. The result must not be more than 3%. I'll look it up...

It's in some citation MM I know.

-Matt

Matt, can you confirm that 3% formula?

Yves

[MB65E]

Yves, I've looked for a day for the info. I thought someone else may have remembered the Formula and that's why I mentioned it. I remember the question but not the formula. I've looked thru the MMs I have. All but Mooney list the allowable play. Some examples are: The play in an Aileron trim tabs for Citation is +-2mm. All flight controls on an Extra 300 are +-1mm, with +-2mm listed for the elevator trim tab. I think "feeling" the play is easier to do than actually measuring it. A lot of times, putting a finger on the rodend and the horn is a good way to feel movement. I just wish we had somthing more for the OP. Stumped again, maybe I should call my PMI and ask. Lol.

-Matt

[yvesg]

Too bad! Woul be nice to find out.

Yves

[Sabremech]

I looked for some info on this today and could only come up with AC 43.13 referencing rod bearing wear as replace when excessive. I decided to give my FAA inspector a call and pose the question to him. He called me back after doing some research and could also only come up with the AC reference. Since Mooney hasn't addressed it, we're left to determine "excessive" on our own.

He did recommend looking into the bearing manufacturer and see if they give information on wear limits and/or a definition of excessive wear. I'm in the process of looking at bearing data for the various vendors who supply bearings to Mooney to see if an average of wear data can be determined. This won't directly relate to a solid number for flight control play, but could help determine some baseline for determining rod bearing replacement.

David

[BigTex]

Is the fix just a matter of un-screwing the old rod ends and replacing them?

[Sabremech]

Like Cliff and Matt posted, much of the play in the flight controls can be attributed to rod end bearings and hardware.

David

[cliffy]

If the worn rod end is the one that unscrews from the push rod Yes, it's unscrewed and readjusted. If it is on the end that is roll pinned in it's a different story.

As for allowable play, they don't come new with any play so I figure if I see play in one its time to replace it. JMO