Trim Tab Actuator

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Tom Reddeck » Wed Jul 18, 2007 6:52 am
Tye, I didn't think the actuator in your picture looked exactly like the one in my early model 140. The p/n of mine is apparently 0310293-10. Am told that it has been superseded by another p/n, perhaps the one you mentioned.
Regarding the problem with my actuator: With the elevator removed, and looking at the end of the actuator where it connects to the rod going to the tab.... There is up and down play on the connecting end of the actuator, where it comes out of the actuator. No side to side, just up and down, which translates to back and forth movement on the connecting link to the tab, allowing the tab to have excessive up and down movement.
Would be interested in what you find out from Preferred Air Parts.
Thanks for your help. Tom

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Vic White » Wed Jul 18, 2007 7:31 am

Tye,

Thanks, again for going through this and sharing with the forum. Every time I get the chance to look over someone else's 120/140 I wiggle the trim tab, and more often than not, there's some degree of movement. I've found only a couple that feel solid. I believe this is a problem we all have to some extent, but we don't really talk about it. I have a '46 and there's nothing in my logs about changing the actuator, so I'm guessing it's the original part #.
Tom was right in pointing out the nature of the movement at the end of the actuator. I did characterize it as side to side play in my first post but, he's right, it's actually up and down. I was laying under the stab the other day watching the actuator and pushrod as I moved the tab. The up and down motion is greatest when the elevator is at its full deflection, either up or down. This is probably the source of the wear on actuator in the first place. When the elevator is neutral, as in level flight, there is less up and down movement of the actuator shaft when the tab is deflected. I think this is because the pushrod aligns closely to the long axis of the actuator. Movement in this alignment is mostly end play in the actuator and wear in the pushrod ends. Tom might not have seen this with his elevator removed.
As I review your disassembly pictures, I'm less and less inclined to try and overhaul the actuator. It would require parts from other actuators which I don't have. If I'm buying actuators for parts, then I might as well buy a good one to replace my worn out one! Thanks for the tip off to Preferred Air Parts. I'll give them a call and see if they can help me out!

Blue Skies,

Vic White
N76887

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John C » Wed Jul 18, 2007 10:42 am
The up and down play is the same issue I have. As far as I can tell, from memory, my actuator is like the one Tye has pictured. Unless I miss my guess, the problem is in the part he has yet to disassemble, shown here. (Broken link...)

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Tye Hammerle » Wed Jul 18, 2007 2:51 pm

The actuator is round and held in the stab by a couple clamp like brackets. If you have no side to side play, rotate the actuator 90 degrees and see if the up down play is gone. Might be a quick fix that'll last until the actuator wears that side. Rotating it might throw off the adjustment a quarter turn.

Tonight I'm going to try heating up the actuator body to see if the inner part will come out easier.

edit: Thought about this some more and I think the chain guard on the gear end of the actuator wouldn't let you rotate it 90 degrees. Depending on how the chain guard is mounted to the actuator. On mine it's got two screws so it can't be rotated on the actuator body. If yours is clamped instead, you could rotate it. 180 degree rotation might help.

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]

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Tye Hammerle » Wed Jul 18, 2007 4:10 pm

Check out figure 19a in the 70-77 Cessna 150 parts catalog. That looks more like what we have and it shows a breakdown of the parts.

I sent in an RFQ to Preferred Air Parts on a couple different part numbers, new, and overhauled.

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]

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Tye Hammerle » Wed Jul 18, 2007 11:43 pm

Hold on to your hats....

0310293-16 NS $595 core charge $100
0310293-4 OH $495 core charge $100 (overhauled 1-98, wonder why they still have it.)
1260074-1 NS $974.25 core charge $100

I'm gonna gold plate this one while I have it apart. For those kind of prices you can have new bushings made for your worn out one. If it's bushings that are worn out.

I'm going to have to see if I have an original style in the pile somewhere.

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]

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Tye Hammerle » Thu Jul 19, 2007 10:36 am

Diagram from the Parts Manuals might help.

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Bob Tofsrud » Thu Jul 19, 2007 10:48 am

Tye
If that breakdown is typical of the actuator on our planes your right about turning it 90 degrees to help eliminate some of the movement. This shows the chain guard as a clamp on type.

Bob
2388N

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John C » Thu Jul 19, 2007 10:56 am

I think the one Tye disassembled is the original and the one in the illustration is a later style.

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Tye Hammerle » Thu Jul 19, 2007 7:29 pm

This picture is from fig 12 in the 120-140 IPC. It looks to me like the same style as the 150 manuals. The one I have seems quite different. This one has two snap-rings on the body whereas mine doesn't and the chain guard is a clamp type verses screwing to the end like mine.