Trim Tab jammed in full UP

[Joe]

1941 T'craft Deluxe needs help! Prior to take-off the yoke was in full forward position and I cranked the handle to full DOWN and then a couple of turns UP (as I always do). I could feel the cables slipping and hear a grinding sound.When I took off, I needed to crank full down and I still needed to push forward on the yoke to keep from climbing out too steeply. When I got back on the ground, I cranked the handle and now am stuck in full UP trim tab (trim tab is down). Any help to get unstuck will be greatly appreciated!!

Joe Cardella

[Chet Peek]

Re: Trim Tab jammed in full UP

I had the same thing with my F-19. Due to lack of lubrication on the jack screw in the trim, it had frozen up. Had to cut a hole in the fabric to lube it and free it up. There was no way to lube it until I cut the hole.

That's what happened to me, hope it helps.

Chet Peek

[Karl Rigdon]

Re: Trim Tab jammed in full UP

Joe.

Make your self a pair of hooks and remove the trim cable from the rear pully. There is spring pressure on the cable so you may need another pair of hands. Let the cable down on the axel bolt. Now you can work it loose. Once it is loose you can center the trim tab. Then center the crank in the cabin. Then work the cable back on the pully. Only make trim adjustments with the elevator in the neutral position to prevent the cable from slipping.

Karl

[jgerard]

Re: Trim Tab jammed in full UP

I have fixed that same problem on a few Tcrafts. What I did was access the and remove the trim cable from the fwd pulley. You can pull fwd on the cable and slip it out of the groove and off the pulley. This will remove all the tension from the trim cable system. Now you need to remove the 2 elevator horn access panels at the tail of the plane. Now you can turn the aft pulley by hand until you get the trim tab back to neutral. You will have to also run the fwd pulley to the neutral position if you have the trim position indicator still installed. The trim indicator mechanism will bottom out on you and stop turning,then turn it the other way until you hear it clicking. That sound is it skipping off the threads at the top of the crank. Now crank it back the other way about 2 turns and figure on that being the end of travel. Now count the number of turns back down till it stops and cut that number in half. Look back behind the baggage area where the trim cable runs between the rear spar carry through and the 2nd cross tube back from there. The pilots side cable should have a spring on it to keep tension. At either end of the spring are clamps holding the cable to the spring. Make sure this whole setup is centered before re installing the cable on the pulley. Turn the crank back up the other way now to the 1/2 way point and re install the trim cable back around the fwd pulley with the tab in the neutral position.

There is a small hole to lube the bushing where the jack screw shaft goes into the left elevator for lubricating it. Its real close to the pulley. You may have to scrape some old paint and gunk out of the way to find it. There should be an inspection cover on the bottom of the left elevator that you can pop off and squirt some lube into the jack screw its self.

If your headliner prevents you from accessing the fwd trim pulley you can loosen the cable where it attaches to the spring to relieve the tension. If your spring is on the other side(short run between cable guides) you need to move it over to the pilots side so you can get the right amount of trim tab deflection.

Oh yeah- Very important to keep any and all forms of lube off the cable otherwise it will slip. Go to a music store and buy some rosin for violin bow strings and rub it on the cable where it will be going around the pulleys to help add some extra friction.

[Jose]

Re: Trim Tab jammed in full UP

Thank you! Thank You! Thank you for the info. Trim tab is working and airplane flies just like it is supposed to.
Joe Cardella

[Hank Jarrett]

Re: Trim Tab jammed in full UP

Just remember, Don't EVER, EVER, EVER, move the trim unless the controls are in neutral!

[VictorBravo]

Re: Trim Tab jammed in full UP

Just remember, Don't EVER, EVER, EVER, move the trim unless the controls are in neutral!

Huh ?!? Don't use the trim unless the controls are neutral??? How are you supposed to have a useful working trim system when you're in the air? I actually had one five second period in all my years of flying where the controls were perfectly neutral...

[Hank Jarrett]

Re: Trim Tab jammed in full UP

OK, got to clarify. The controls don't have to be in EXACT neutral, but most folks either hold them full up (yoke in the gut), full down (hands off the controls) or ~neutral. If you look at the trim system when the controls are full deflected the cables are at a pretty nasty angle. It's REALLY easy to bind them and mess up the trim system (or at least cause the cable to slip). Hold the controls "close" to neutral.
SHEESH!!!!
Hank
(Afteter having to fix the system a couple of times I started to never move the trim unless the controls were (close to) neutral. Never had to touch the trim system since except to lube the jack screw and hinge.)

[Hank Jarrett]

Re: Trim Tab jammed in full UP

Before you say it I'm talking about ON THE GROUND!!! No, I DON'T fly with full deflection or none at all , but I would like a plane that COULD, even if I can't.
Hank