Sticky yoke

orange

orange

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Mar 23, 2014
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Orange
In the winter, the yoke on the planes that I rent seems to get sticky and doesn't move smoothly in the full range of motion. My last flight, the thing got stuck as I was starting to pull back for flare and I yanked it sending me airborne. Talk about a balloon! I told the school and they pretty much shrugged their shoulders. Wonder what they say if someone plants into the ground because of it.

What is a good product to use? Somebody once told me (or maybe I read) that wd-40 should not be used. Any suggestions? TIA
 
orange said:
What is a good product to use? Somebody once told me (or maybe I read) that wd-40 should not be used. Any suggestions? TIA
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What sort of Cherokee are you flying? LOL

This is indeed a common problem, particularly on PA-28s. The trick is that you need to clean off the crud that accumulates on the yoke shaft and in the rubber bushing that the shaft goes through. If you just squirt it with something like WD-40 you are solving the problem temporarily but it will be back soon.

Ask your A&P how to clean it and what lube to use.

-Skip
 
I use the same silicone I use on mybicycle chain. A bit ofthe liquid, run the yoke back & forth, then wipe off,the excess. Works great on the seat rails, too. Cleans and lubricates and doesn't create a build up like wd40.
 
A sticky yoke to the point of control problems... sounds like a very scary situation that should be investigated by the operator immediately. Did you report this to them? Could be much more serious.
 
First verify that you don't have something binding up the yoke like wiring or wear in the system or simply gunk in the block from someone else who tried to "lubricate" it. Then clean off the yoke with a good degreaser and then buy a bottle of 100% silicon treadmill lubricant. (about $10-14) Two or three drops should do it. Spread it around and wipe it off with a rag and you'll notice a difference immediately.
 
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Depends on the plane, but for a 172, you could have a bad pulley or a cable fraying.

A binding yoke is a grounding condition in my book!

This falls cleanly into the "how will this read in the accident report" category. When you ball it up, and the report reads "pilot flew plane with known mechanical deficiency", it isn't going to make you look good. That is, if you're still around to suffer the consequence of an investigation.

If a control issue gets a shrug of the shoulders, I would immediately take my money elsewhere.
 
Agreed, in most aircraft the yoke is not supposed to be bearing on anything. There's a hole in the panel, but it's supported by the structure in the rear. If it binds on the hole, something is bent.
 
Could also be a problem with the hinge on the stab. Maybe as simple as a buildup of lube that has congealed in the cold. I have seen a few places that lube hinges and such with a shot of LPS at the 100 HR. Leaves a sticky residue after a while. The book on cessna calls for dry lube on piano hinges and either light oil or moly grease on flap jackscrew, depending on year and model. Don't recall what the book calls for on elevator and rudder hinges though.
 
I think the real problem here is putting your beer on the glareshield. On those barrel rolls, it'll spill all over everything include the yoke. Some people clean that up afterwards, but others just take a nap in the plane and head home.
 
flyingron said:
Agreed, in most aircraft the yoke is not supposed to be bearing on anything. There's a hole in the panel, but it's supported by the structure in the rear. If it binds on the hole, something is bent.
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This actually isn't an uncommon problem on the PA28. The yoke doesn't move truly linearly, especially at the ends of its motion. The hole in panel has some play to account for that, but often, with the buildup of tolerances, it's not enough. That means the yoke shaft will rub on the bushing in the panel at times. This is generally fine, but when the shaft gets messy, dirty, sticky, or otherwise gunked up, it can bind on the bushing. I've experienced it, though not nearly so badly that I've had to jerk on yoke! Generally just feels like a lack of smoothness in the motion.

That said, it could definitely be something more serious, too. If the bind is anywhere further down the chain than the panel, it's a major problem. It's probably something cleaning and lubing will fix, but a check of the system is warranted.
 
Perhaps the maintenance shop isn't taking good care of the plane(s). Had the same issue at one place combined with tons of other maintenance issues such as balding tires that aren't getting replaced, etc. (we may even be speaking of the same school for all I know) and I changed rental schools and have had great luck ever since.
 
Pledge sprayed on the shaft and wiped off works in a pinch! :)
 
In the maintenance of the products we manufacture at work, which include a lot of metal with rugger o-rings and moving parts, we strongly advise to NOT use WD40 for sticky situations. The reason is that the WD40 is absorbed, swells the o-rings, and makes the movement even more difficult after the initial slipperiness of the lubricant decreases. Then you're in a constant motion of re-lubricating because the same thing will continue to happen.
 
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