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Rudder cable squeak

dpemmons

Active Member
I've owned 647RM for about 7 months but have only recently been able to fly it. The plane has about 150 hours on it. It's been sitting for a while so last weekend I took it out for a taxi test to make sure everything was feeling and sounding healthy.

During preflight I noticed a squeak in the rudder cables which I don't believe was there when I bought the plane (but it may have been). I spent today trying to track it down. I've found it's in the tail where the rudder cable plastic covering rubs against the SB750-10 snap bushing, on both sides but more pronounced on the right. Here's a video demonstrating the squeak: https://photos.app.goo.gl/hv5nH65pCiTW8FsE2

And here are photos of the bushing: https://photos.app.goo.gl/gXDHDCZMFg6S5G2r1

You'll notice the white shavings from the cable cover. It looks much worse than it is due the the magnification, but there's definitely some wear occurring. I'm unfamiliar with what SB750-10 looks like before it's installed so I don't know if what I'm seeing here is odd or expected?
 
My 12 makes the same noise. Also, last year at OSH, I was sitting in the new 12iS demonstrator and it made same noise with rudder cables. I believe noise imitates where cables pass through plastic bushing in rear baggage bulkhead.
 
The rudder cables on an RV lay slack when not under tension, so contact with the bushings is normal.

You might try wiping the cable down with something like LPS-2 or other heavy lubricant, and then put a some lube around the insides of the bushings too. And then just repeat that annually or as needed.
 
I also rotate the plastic bushings whenever I am in their neighborhood -- like during the annual Condition Inspection, etc.
 
I recommend replacing them every couple years as it?s very easy to do.

How does one replace them? That area seems pretty inaccessible?

I ended up spraying the plastic cable sleeve with silicone lubricant. Worked great. Now to figure out why my breaks and/or rotors squeal intermittently...
 
My first annual I found one poly sleeve detached on one cable. I reattached it with safety wire and never had any other issues with the cables after 6 years and 720 hours.
 
Sounds like the spray solution worked, so good. For the bushings at the very aft end of the empennage, you'd have to either cut in a new access port or remove the HS counterweight to allow access with your arm in through the back. Most likely, a well aimed shot of lube through the aft holes (with the tailcone fairing off) will do the job.

If you ever need to replace any other bushings, just reach in through the nearest access and push the old one out. It's easier to push out from the inserted side than to pull out from the stop side. If you have difficulty with this, you can take a screwdriver and collapse the bushing from the perimeter inward, and then pull out. You'll need to cut it to remove from the cable. Then use wire cutters, shears or whatever your sharp preference is, and cut your new bushing lengthwise, gently pry it slightly open to slide over the cable, and then push it into the bulkhead opening until it snaps, ensuring you have the slit at 90º to the wear point (generally clocked at 3 or 9). Done.
 
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Right - most snap bushings appear fairly easy to replace so long as they're accessible and whatever goes through them can be pulled through. These particular nuisance makers in the very aft end of the empennage, on the other hand.... I suspect I'll just have to keep them lubed during annual inspections.
 
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