OK, Question about elevator trim wheel force

[cliffy]

Has anyone ever changed out the tail jackscrew for a new one and found the trim wheel force went way down in flight?

 

I know its been discussed before  (I've seen some threads), I know all about proper lube of the system and adjustment of the chain drive on the wheel.

 

My trim wheel force still seems "stiff" to me. I'm thinking that after 50 years the jackscrew has enough pits in it from years (previous to my ownership) of poor lube that there is a drag on the nut especially at high loadings on the screw in flight. On the ground it is a lot easier to turn but not what I think it should be. Have had the jackscrew out, disassembled, cleaned and relubed to no avail. 

[JaredDavis]

Mine was tough on nose down. Turned out to be the dust duct binding. Also found the main bolt and nut was installed backwards.

[N201MKTurbo]

My new plane had a new jack screw and my old plane had the original jack screw. The one on the new plane was much stiffer, even after lubricating it.

 

Don't forget to check the trim wheel friction screw.

[jetdriven]

Can you explain the trim wheel friction screw? My 77 J is very stiff and hard to move.

[MB65E]

I recently changed the close tolerance bolts that attach the tail assembly to the upper left and right fittings. I would be sure to eliminate the bolt tightness first. Mine had some light corrosion on them and could not get them out easily! With several tricks, I was able to get them out and changed with out damage. The trim wheel now appears to be much easier to operate!

Plus flying around with known hardware in the tail feels nice too!!

-Matt

[carusoam]

Byron,

From the C's parts manual...

Figure 30 Trim Control System...

Above the floorboards, between the chain, under the trim wheel's gear. There are a few parts that indicate the friction screw's existence. It may be a screw adjustment on a brake....

-14. Screw, nut, spring and brake

I had this adjusted on my C once...

Best regards,

-a-

[larryb]

In my J the trim wheel became very stiff. The electric trim motor could hardly move it, and it was hard for me to move by hand. Turns out there was a dry pillow bearing supporting the trim tube, right near where the electric trim motor is in the tailcone. A shot of tri-flow was all it took. Difference was night and day.

[John Pleisse]

That trim wheel should be two fingers, Fellas......shouldn't require much out all. If you have a trim motor, check the chain tension.

[cliffy]

I can disconnect from the jackscrew and the trim system force is much better. Connected, while on the ground, the trim force is OK but airborne it gets stiff so, that is to my thinking of the jackscrew when loaded with  air loads. Ideas?

[chrisk]

  On 9/4/2014 at 9:00 PM, cliffy said:

I can disconnect from the jackscrew and the trim system force is much better. Connected, while on the ground, the trim force is OK but airborne it gets stiff so, that is to my thinking of the jackscrew when loaded with  air loads. Ideas?

 

You can try unloading it in the air too.  A little control opposite of how you want to trim, at the same time you trim.

 

Also, I suspect the jack screw doesn't have pits from 50 years of use, but grease that has gotten sticky with age, dirt, and lack of a good cleaning.  --Also keep in mind that I don't even know where the jack screw is, but I would guess in the tail. I am no expert in this area.  I have however read that others have had similar issues.

[cliffy]

The jackscrew has been properly cleaned and lubed after dis-assembly. I can unload it in air and release lots of resistance to turning, hence my postulation about the "rough" screwthreads. Still scratching my head. 

[Andy95W]

  On 9/6/2014 at 3:18 AM, cliffy said:

The jackscrew has been properly cleaned and lubed after dis-assembly. I can unload it in air and release lots of resistance to turning

You've described my trim exactly.

I always figured it was a tiny bit of resistance along the each component of the whole trim circuit: chain, gearbox, multiple universal joints, phenolic blocks going through bulkheads, aft gearbox. Each item, not that bad. Added together, considerable.

I think it could be worse, though. There is another thread:

trim noses up during bumpy flight

Started by CGinSD, May 22 2014 10:21 PM

http://mooneyspace.com/topic/12140-trim-noses-up-during-bumpy-flight/?hl=%2Btrim+%2Bnoses

[carusoam]

Has anyone put their hands on the brake and adjusted it?

Best regards,

-a-