Trim Cable slippage

[Pacer 24C]

My trim cable slips at higher speeds in flight - example -I can run the trim full down on the ground but inflight I cannot get enough down trim at full throotle to keep from climbing- I there any adjustment other than the spring loaded pulley up front by the handle?? Maybe I need a new spring - or just need to make sure the cable is not oily?? Any ideas - Thanks

 

[Twofieros]

The trim cable is pretty simple setup. I suspect you have a combination of a few things stacking up against you. The grease on the jack screw is probably very old and rock hard, the pulleys could be loaded up with dirt and causing resistance, and the cable may be dirty as well. The cable should be oiled to prevent wear. There isn't a way to tighten the system. Your spring over the pilot may be damaged and not providing enough force but that would be difficult to do and unlikely the cause. I would start at the jack screw then hit the pulleys.

Tim

 

[Homer Landreth]

Hello Pacer24C: Probably one of the most forsaken lubrication points on the PAxx inspection checklist is the small hole that is within the tubing sleve that the Stabalizer pivots around. At the rear of the plane where the two stabalizer pieces join, there is a tube that passes through a slightly larger sleve that is part of the airframe. Some planes have actually been modified to have a grease zerk instead of that hole. If over the years there has been insufficient lubrication there, or if there has been corrosion built up within that sleve, then the tubing will be restricted in it's rotation. It will be OK on the ground, but airload will be enough to exceed the ability to move it through the whole range of travel or be just plain too tight to move it any more. Go back to that sleve and just take some LPS or WD40 and start nursing it into the hole and crank the stab up and down and keep at it until you feel that you have freed it up. If you can't free it up, then you will be relegated to removing the stabalizer and removing the through tube (that in and of itself can sometines be a real bear) and cleaning it up as well as the through sleve. Then go back together with it and keep it lubricated real good in the future. Another suggestion is non maintenance but pilot technique. Remember that good trim procedure is to hold the elevator in the position to keep the plane nose where you want it and trim off the pressure that it is taking to keep it there. In other words, don't be trying to fly the nose using the stab trim. You fly the nose and trim off the pressure. That technique relieves the airload from the ease of trim equation.

 

[Steve Pierce]

I would check both of the above posted areas. The jackscrew gets clogged up with old grease which gets worse in the winter and I have found lots of frozen rear liner tubes as well. I use a dental pick to clean the jackscrew threads along with a solvent. Just be careful not to get any kind of lubricant on the trim cable.

 

[Pacer 24C]

Thanks so much for the info - my jack screw is clean and nice grease, the sheeves are clean, lubed and free - I forgot about the rotation point at the back !! I will check it out - trim works great on the ground and for the most part in flight - just does not want to trim down at high speed - so I will check it out - thanks - Jeff

 

[andya]

I have taken some heavy twine and fished it around the jack screw a coupleo of threads and had some one else turn the crank while I fed a new section of string thru the jack screw as it turned and got a lot of the old grease cleaned out. Never thought of soaking the twine in solvent but that would be good. Downside, takes two people because the twine has to be held tight against the threads and fed new twine into the couple of loops to let new twine absorb the grease. I usually start with the trim full up or down and then get what could not be reached by cranking to the other limit.

 

[taildraggerpilot]

I've been using a lube called White Lightning, from the bicycle shop, on the jack screw. It's a wax based lube that is in a solvent solution. You apply the lube and as the solvent evaporates, the wax remains and adheres to the part. What is nice about this stuff is dirt does't accumulate and everything stays lubed. I usually apply a couple times each year.

 

[Pacer 24C]

I've been using a lube called White Lightning, from the bicycle shop, on the jack screw. It's a wax based lube that is in a solvent solution. You apply the lube and as the solvent evaporates, the wax remains and adheres to the part. What is nice about this stuff is dirt does't accumulate and everything stays lubed. I usually apply a couple times each year.

I think my problem was the rear pivot point - it was dry - almost look a alittle rusty - got it lubed and is getting better - was able to trim it drown for a full throotle run of 140+ mph - sure like your Plane with the tips - thanks Jeff