Cherokee trim barrel replacement

Timbeck2

Timbeck2

Final Approach
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Nov 4, 2015
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Timbeck2
I've got the maintenance manual, I've got a PMA'd part, I've got the instructions, I've got a A&P that will inspect my work. Anyone ever done it before and have some last minute tips or sign of the cross offering before I head out to the hangar?
 
Be sure to clamp the cables in place with a couple pieces of wood so they remain tight inside the airframe.
 
Yep - I've made some with some black RTV on them so they're more grippy. I'm also going to bead blast and paint the supporting structure while I've got it apart. I'm also going to take a LOT of pre-dissassembly pictures.
 
Watch for the special washers and/or nuts on the little steel tubes. They are beveled on the end and fit properly only one way. Set the free play of the barrel so that it is perfect now, so you don't have to re-visit it for many years. And of course, lube the parts well and with the correct grease.

Since you are in the area and dirty already, consider checking the stab pivot bolts for condition and any freeplay in the stab.
 
What little steel tubes? :confused2:

The only "special" washers I've found is on the brace that connects to the airframe and supports the top of the barrel. I'm at the unwinding the cable from the old barrel stage now.
 
My mechanic is "watching and assisting" on this one since he's never done one. My guess is that they don't wear out all that often or he'd seen it before - that and the fact that most the planes he works on are Cessnas. The threaded rod was loose enough inside the barrel to wiggle so that's why its being changed.
 
Timbeck2 said:
What little steel tubes? :confused2:

The only "special" washers I've found is on the brace that connects to the airframe and supports the top of the barrel. I'm at the unwinding the cable from the old barrel stage now.
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Sorry, my assumption. Cherokees have a few different versions of the structure back there. The older ones use small steel tubes to hold the trim system in place.
 
Timbeck2 said:
My mechanic is "watching and assisting" on this one since he's never done one. My guess is that they don't wear out all that often or he'd seen it before - that and the fact that most the planes he works on are Cessnas. The threaded rod was loose enough inside the barrel to wiggle so that's why its being changed.
Click to expand...

Correct. I've only seen one that needed replacing but several that needed the bushings replaced. The steel threaded rod that doesn't get proper cleaning and lube will, over time, wear the aluminum barrel to the point your elevator and trim will allow un-commanded movement (aka slop).
 
I got it replaced and it is smooth as a baby's thumb. The instruction were a little misleading by "take off one loop at a time, first from the top and then from the bottom." Nope, not how it happened. Took one loop off the top and POOF instant rat's nest of cable. I had marked everything on the cable and it's relation to the barrel and I managed to get it all back together as it was before. If I had to do it again I'll be more comfortable but there was a time there that I thought that I'd really screwed up beyond return.
 
Glad to hear. Piper trim systems are interesting.
 
One item in the instructions was to "replace the pins on the ends of the cable(s) which suggested to me that there were two separate cables. Mine wasn't. There was one continuous cable which wrapped around the barrel in opposite directions from the top and bottom of the barrel. Thankfully while the rat's nest was fully formed, I marked the center of the cable and the center of the barrel and transferred the barrel mark to the new one. I'm 100% positive that cable is exactly one the new one like it was on the old one. Glad its over and knowing what I know now, I stressed about it a little too much.
 
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