Jack Screw movement

[Steve Pierce]

The parts manual gives a pretty clear picture of the installation as well as drawing 12989. There is a modified woodruff key prt. no. 41631 between the pulley and the jackscrew. Be sure and catch it. I use a flush set of side cutters to grab it and extract from the jackscrew. Look at the jackscrew installation drawing and if you have the Vagabond Drawing CD you can identify the washers which I have called out here:

5 part# 42961-02 Stabilizer Adjustment Screw
9 part# 12982-00 Stabilizer Adjustment Pulley
7 part# 80122-41 Washer measuring 1” O.D. x .375/.385” I.D. x .095” thick
10 part# 81342-05 Washer measuring 1 1/8” O.D. x .375/.385” I.D. x .062” thick
11 part# 85012-12 Washer measures the same as an AN960-616L amd depicted as such on the actual drawing
16 part# 80122-24 Washer measuring 3/4” O.D. x .328” I.D. x .062” thick
14 part#81342-08 Washer measuring 5/8” O.D. x .313/.323” I.D. x .032” thick
Not listed are the two AN5-7A bolts and AN365-528 nuts that hold the stabilizer yoke to the liner tube link assembly index #9 part# 14180-02. There is also an AN280-304 (#2Woodruff key) that is trimmed to .320/.334” long that retains the 12982-00 pulley to the 42961-02 adjustment screw.

I call all of these out and have the dimension noted in my parts manual because I find them installed incorrectly all the time. Before we had the drawings the only way to check was to order all new parts from Univair. Another instance where I find both drawing CDs from the Short Wing Piper Club invaluable.

[Steve Pierce]

It seems that I am a master at making a small project a big one!

You and me both.

[pa20]

Steve,
The information in Post #11, plus having the SWPC drawings will make this job much easier. Unfortunately, I will not be the last guy doing this job.
Thanks for your time.

[vk6ad]

Hi all

My problem is similar but different. I bought a new Univair yoke and went about reassembling everything with new Piper (Univair) washers. When I came to do up the jack screw nut there wasn't enough thread to satisfy AC43-13-1B. I took it all out and reassembled the shaft, pulley and washers with a dummy bearing 0.75 inch long per the Piper drawing. Everything looked great, with just the right amount of thread showing past the nut. Then I measured the bearing tube in the aircraft and found it is 0.915 inches long, a good 5/32 inch longer than Piper specified. Now I'm faced with machining some of the acme thread off the jack screw to extend the small diameter section where the pulley mounts, or somehow machine the tube in the airframe back to factory spec. Has anyone else had this problem? How did you fix it?

[Steve Pierce]

Sounds like someone did some repairs in the tail of your airplane. I have never seen the bushing that long on any rag and Tube Piper. I would try and shorten the bushing vs. modify the jack screw. Modifying the jack screw will limit the trim range and could adversely affect the flight characteristics at certain loadings.

[vk6ad]

Hi Steve
Thanks very much for your thoughts. The bushing quite possibly was replaced during one of the plane's rebuilds over the years.

[Glen Geller]

Sounds like someone did some repairs in the tail of your airplane. I have never seen the bushing that long on any rag and Tube Piper. I would try and shorten the bushing vs. modify the jack screw. Modifying the jack screw will limit the trim range and could adversely affect the flight characteristics at certain loadings.

Oy veh what a drag. Modifying the jackscrew would make it non-compliant. Sounds like the tube in the airframe is wrong and should be made right by somehow grinding it back to the proper length (while keeping the top end perpendicular,) or replacing it with a new correct component.
This is a very unfortunate situation, it's a shame the apparent repair was not done correctly. Is there a log entry in the airframe book about this?
I have replaced the jackscrew and yoke in my PA22 and that tube as I recall is at the backside of a cluster and difficult to reach in the first place. Good luck and keep your cool.

GG in Oregon

[Steve Pierce]

I think maybe a piloted spot facing tool could be used to machine the bushing squarely to size.

[vk6ad]

Steve, sorry I didn't reply sooner. Getting my plane back in the air is a little way down my job list at the moment.
Thanks for your advice about using a spot face tool. That looks like the perfect solution so I'll be pursuing it as soon as I can.
What a wonderful resource this group is.
Phil in Australia

[Steve Pierce]

Let us know how it goes.