The Cessna 120-140 Association Forum

Vic White » Mon Jul 16, 2007 11:59 am

Tom Reddeck posted last month asking questions about repair of the trim tab actuator and didn't really get his question answered. Mine either, since he and I seem to have the same problem - apparent wear in the actuator itself that allows the push rod to move side to side. My thanks to those of you who responded, but most of the comments were about eliminating end play in the pushrod rather than correcting play in the actuator itself. I'll probably need to re-bush my pushrod too, but has anyone ever disassembled the actuator and successfully overhauled it? I'd appreciate any tips from you experience on how to do this. How about you Tye, ever sacrificed a trim tab actuator for science?
If it comes to it, I'll just have to replace it, but Tom reported some pretty outrageous prices for new ones. I've called several salvage companies in my part of the country, but without success. Anyone have good sources for salvaged replacements? Is it the same part used in 150s?
Thanks for your help!

Blue Skies,

Vic White, N76887
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by Tye Hammerle » Mon Jul 16, 2007 1:34 pm

Vic White wrote:
How about you Tye, ever sacrificed a trim tab actuator for science?

Hi Vic, Not yet. I think I have at least one in the parts pile. Since I'll need operational ones for my project fleet I'll see if I can dig it out and examine it. It might need some work. At least I can see how hard it'd be to take apart.
Tye mbr#6449

N2180V-48-14409, N1887V-47-14067, N73096-46-10316, N72971-46-10172, N77045-46-11499, N2928N-46-13189, N58712-40 PT-17-[75-341]

John C » Mon Jul 16, 2007 2:05 pm

Years ago there was an article in the news letter about disassembling one. Problem is when I got around to it, mine didn't match the one in the article. I managed to get enough slop out of other areas to fly again, but some day I'll have to come back to it. IIRC, the bushings are held in place by roll pins. Should be pretty easy to source or make, once they're out...

Tye Hammerle » Mon Jul 16, 2007 10:39 pm

I've got one about half way apart. There are four solid pins that seem to hold the two key pieces on. There are two pins on each end. They look like four nearly equi-distant spaced drive screw heads or rivets but are actually pins driven through the sidewalls of the outer and inner barrels. I need to get a new pin punch for this job. My cheapie couldn't take it anymore.

The end that holds the bolt for the pushrod out to the tab has a solid steel pin that safeties the threaded end fitting. The other end with the gear has a lock nut which holds the gear head barrel. There is a male and female slotted arrangement to engage the gear drive to the threaded rod which will push or pull the trim tab.

It seems so far that maybe the only things that need to come apart on this are the four pins which hold the two ends. Once those are removed it seems like the threaded pieces will come apart.

If I'm lucky I'll get a new punch tomorrow and will be able to finish getting it apart. So far I haven't butchered it up so I'm pretty happy.

I'm not sure what you could do to take up any slop in the threads though. It seems like there are two parts that might be worn, the threaded rod or the threaded housing. Taking up the slop means restoring the tolerances. But then maybe it's not what I think it is inside.

Stay tuned.
Tye mbr#6449

N2180V-48-14409, N1887V-47-14067, N73096-46-10316, N72971-46-10172, N77045-46-11499, N2928N-46-13189, N58712-40 PT-17-[75-341]

Vic White » Mon Jul 16, 2007 11:01 pm

Great Tye! I'm very interested to know if it can be re-assembled after its been apart. Could very well be a part that Cessna figured would never wear out during the expected life of the airplane. Any chance you could take a few pictures to post while your dismantling your specimen? I really appreciate all your help!

Vic White
N76887

Tye Hammerle » Mon Jul 16, 2007 11:50 pm

Some pictures. I think it can be re-assembled easy enough. You'll just need either some solid steel or roll pins the right size.

Tye mbr#6449

Tye Hammerle » Mon Jul 16, 2007 11:54 pm

Couple more

Tom Reddeck » Tue Jul 17, 2007 7:13 am

Thanks Vic and Tye for the follow-up on the actuator. Tye, your pictures are worth a thousand words as the old saying goes.
The problem with my actuator seems to be that the end that pushes the tab has lots of up and down movement where it comes out of the actuator. There is no side to side play, just up and down. There is no indication of worn gear drive, which would show up as in and out play. I suspect the end bushing on the actuator has oblong wear, allowing for the up and down movement.
Tye, wonder if you can detect any of that on your actuator, and if so what would it take to repair?
Thanks Tom

Tye Hammerle » Tue Jul 17, 2007 11:14 pm

Does the side to side play in the actuator allow the trim tab to move?

I did some parts manual reading today and found that the actuator I'm taking apart doesn't appear to be the same type as the ones in the 120-140 and 150 up to '77 parts manuals. I looked at the actuator 80V has and it's not the same as the one I've got apart. Wonder if this one is the new style.

I checked Preferred Air Parts to see if they had any available and found they have several.

I found that there are several part numbers which should be applicable. There are notes in the 150 manual to use part y when part x is depleted.

Here are some part numbers:

120-140 0310293-10

150 pre '63 0310293-2 or -12 or -14 or replaced eventually by 1260074-1.

Preferred Air Parts has New Stock, overhauled, and salvage actuators in the various part numbers. I didn't send in a request for quote but I might do that tomorrow.

Some more pictures of where I'm at now. I have it just about down to parade rest. The last bit seems to be a press fit.

Tye mbr#6449

N2180V-48-14409, N1887V-47-14067, N73096-46-10316, N72971-46-10172, N77045-46-11499, N2928N-46-13189, N58712-40 PT-17-[75-341]

Tye Hammerle » Tue Jul 17, 2007 11:16 pm
Another one.