Trim Tab Actuator
 

Has anyone rebuilt or replaced the Trim Tab Actuator? I have found that the free play in my trim tab system is more than desirable. I replaced the bushing at the tab and that helped but I still would like to tighten the play. After doing some initial research on parts and rebuild it appears this is a very expensive device to rebuild or replace. Replace looks like it is out of the question as I have not found any replacement available. There were some old references to the full replacement part # 1432004-1 which is superseded by -6. There was some references to this part at like $2500-3000.00 range. Ridiculous, now I have been checking for replacement parts and have not been able to come up with the screw assembly - actuator #1432004-4. I can only imagine the price on this critter when the other end of this system, the sprocket is $312.00 and the internal thread screw is $200.00.

The other parts are basic bushings and seals and do not appear to be a problem but my concern is will only replacing the bushings and seals fix the play or do I really need the threaded parts? As I look at it the play is in the threaded parts and the rod end bearing. Also there are two connector tabs that connect the rod end of the actuator to the bell crank that look as though they were made from a beer can. These also have some play but I can't believe these cheap little items are in the system.

Am I just overreacting? Making a mountain out of a molehill? What were the tolerances when it left the factory? I have close to 1/2 inch of play up to down on the tab.

Hi Herb

I too found what I consider excessive play in my trim tab actuator, not as much movement as you have but enough for me to think that this may cause some elevator movement during flight (just an opinion). I looked for new (never found out the cost) and when not available found a secondhand unit that was almost new.

When I took the threaded rod out of the unit I just recieved and fitted it to my actuator all excessive play was gone, I then fitted my rod into the S/H actuator and there was the play. So it may only be the threaded rod.

I then fitted the second hand actuator and it's rod into my plane, no movement and new PN3A bearings to finish the task.

Second hand actuators and rods are not easy to locate, mine was by pure chance.

On ebay there are a number C337 parts for sale from airtransport, he is parting out a P337 and may have an actuator and threaded rod, providing they continued to use the same parts through to the G model. Sorry can't check that at the moment as I am currently O/S, again!

Hope this helps

Dave

Typically, the only thing that you change on these are #3, 4, 12 (from your diagram)at a cost of around 10 dollars. The rest of the parts are usually fine. You also need to get new retaining pins that are not shown in your diagram.

Cessna manual says to overhaul these at 1000 hrs or 3 years. and like Tony posted , those are the only item that usually need replacement. You should also check the links in the elevator, P/N 1432023-1 thats where we get the most movement

Kim

Thanks for the reply's
The actuator will be rebuilt with the new bearings. I know that there is some play in the #14 rod end bearing and that part is about $80. I have not had much luck on the #12 packing. Is that just an o-ring? I guess I will find out when we open it up.

O ring crosses to a ms28775-010
Kim