M20J rudder rigging

[Grant_Waite]

Recently I had to remove my AeroTrim servo and rudder trim tab on my 77J. The head unit had gone bad, then the servo went bad. I was trying to fly a plane that wasn’t trimmed correctly and the trim tab made it especially dangerous on landings and takeoffs. It would get squirly a bit and didn’t fly straight in cruise worth a flip. After taking the tab off, it flys a lot straighter in cruise but I still need about 5 pounds of right rudder to keep the ball centered. My Stec55x will fight it in cruise with the yokes moving left and right unless I get the ball centered. The plane doesn’t roll at all so I think the aileron rigging is fine. My question is how have some of y’all done the rigging on the rudder? I’ve read the service manual on the steps. Looks like it’s C clamps on the pedals and turning 2 rod ends, one under the pedals themselves and another back under the elevator inspection panel. Then there’s another one on the right side of the rudder. What tips or advice does anyone have for doing this? A travel board isn’t needed to rig the rudder right? 

[EricJ]

If that was installed with an STC (which I would expect it was), your IA should file a 337 to show it was removed.   The installation instructions might be useful to make sure everything gets undone and restored to pre-installation configuration.

A travel board is useful for rigging the rudder, but not required.   You can do it with a protractor if boards aren't available.    You should probably have ailerons and flaps checked, too, since they all affect each other as far as flying straight is concerned.   As you mentioned, the SMM has the proper procedure for rigging everything.

 

[Grant_Waite]

54 minutes ago, EricJ said:

If that was installed with an STC (which I would expect it was), your IA should file a 337 to show it was removed.   The installation instructions might be useful to make sure everything gets undone and restored to pre-installation configuration.

A travel board is useful for rigging the rudder, but not required.   You can do it with a protractor if boards aren't available.    You should probably have ailerons and flaps checked, too, since they all affect each other as far as flying straight is concerned.   As you mentioned, the SMM has the proper procedure for rigging everything.

 

I honestly have no idea about the rudder trim thing. It says FAA PMA but my god I have no idea how they ever got it certified. The servos guts are the same as an rc helicopter. The motor is the one used on kids toys. This is pictures of a new servo the previous owner had bought. I inherited it with the plane. I haven’t had the damn thing working in over 9 months probably 

[EricJ]

2 minutes ago, Grant_Waite said:

I honestly have no idea about the rudder trim thing. It says FAA PMA but my god I have no idea how they ever got it certified. The servos guts are the same as an rc helicopter. The motor is the one used on kids toys. This is pictures of a new servo the previous owner had bought. I inherited it with the plane. I haven’t had the damn thing working in over 9 months probably 

Look in your maintenance records to see if there's anything related to that, especially STCs.   You can get the file of the history of submited 337s, registrations, and other documents for your airplane online from the FAA to see if there was anything ever filed for that.   If not, you can remove it with a logbook entry.    If there was a 337 for an STC, then it needs a 337 to delete it.   So it really depends on the submitted paperwork.   Looks like something worth removing, in any case. 

[Grant_Waite]

I did find a 337 for it. I do plan to put the new servo and hopefully the same head unit but working. You couldn’t leave the servo in place and disconnect the tab because the wind would have had its way with the connecting rod. Like I said it flew worse with it installed and it’s better without it. I think the trim was making up for the rudder being out of rig the whole time I’ve owned it.  

[Fly Boomer]

15 hours ago, Grant_Waite said:

I honestly have no idea about the rudder trim thing.

Should be in AFM/POH Section 9.

[N201MKTurbo]

The rudder is pretty simple. clamp the peddles and adjust the rudder so it is centered, then trim the trailing edge to center the ball. It is always best to check the nosewheel steering if you are messing with the rudder. Also double check that it makes it to the limits too.

Trying to center the ball with linkage adjustments will jack it all up.

[N201MKTurbo]

Also, there is a balancing procedure for the rudder. if you remove any mass from the rudder, it should be rebalanced. You don't want rudder flutter.