Control Stick Slop

[Bcone1381]

https://bearhawkforums.com/forum/tools-technics-and-best-practices/86831-control-stick-deadband

This is a link to a topic on Control Stick slop previously reported on other aircraft. I am in the midst of fixing slop in my stick and at the end of this post I will share why I think it's important.

When my control stick its move L to R slop is seen at the red arrow hinge point on both sticks. This is the fulcrum of the slop and the bottom of the stick wiggles inside the torque tube like a teeter totter. I described my slop to Bob and it was deemed excessive, and a fix was concieved. Ream out the hinge tubing and insert an oversize bolt to remove slop.

The sticks are attached inside the toque tube via the interconnect tube. The 1/2" interconnect tube moves for/aft inside the larger torque tube. The yellow arrow points at the connection between the stick and the interconnect tubes. The two tubes have ample space but not excess space. Tight clearances of the design makes slop an issue.

My reamning of the rear stick went well, but the front did not. I admitted defeat early, and aborted the task before things got out of hand. Part of the issue was I reamed the control stick assembly in place instead of removing it from the airframe.

It only took me :40 minutes to remove the entire assembly after my fiasco. Right now the assembly is removed and at my Fabricator in Mason Michigan. They will be boring out the hinge tubing and pressing in a 4130 steel bearing that will give a slop free fit with a 1/4 - 28 bolt iaw the plans.

Why this fix is important. The clearance inside the torque tube is not generous. I had contact between parts inside the torque tube. I dismissed this problem for 5 years and never felt good about it. I trust my problem was a one off issue and the rest of the fleet is kosher. But contact inside there is the a precurser to a jammed elevator. And I just cant get that off my mind. A jammed elevator. So my advice is check your stick for slop, send it to a fabricator if you need to. You can get it out without removing belly fabric, and don't use castle nuts with cotter pins inside there. I see them gettiing hooked up on something. Add checking the stick for slop on your annual inspection checklist too.

[Pbruce]

“and don’t use castle nuts with cotter pins in there”. Hmm. Isn’t that the exact case (nut subject to rotation) for which use of a castle nut and cotter pin is mandated? Are you depending on the inner diameter of the tube to prevent the nut from coming off or do you have a different solution? Thanks. My bolt, castle and cotter seem ok in there (no contact) and not much slop. Maybe I’m missing something? The bearing sounds like a great idea. I’ll do it if it gets sloppy in future. Still fiddling with the fork at the idler though, so I have more than a passing interest in the whole assembly.

[TimTall]

There's lots of talk about the control stick slop. I have it. Maybe a 1/4" deadband in pitch and roll. I was thinking about how much of a non-issue it is while flying yesterday. I've never noticed it without looking for it in flight. If there is something wrong, and getting jammed, of course deal with it, but the design is fine.

[DBeaulieu]

Similar on my previous build of a Zenith 750...never noticed the slop with flight loads on the controls, regardless of being on wheels, skis or floats

[noema]

I fixed this L/R slop by TIG welding a donut onto the hinge tube, under-drilling and reaming it. The bottom of the sticks I secured with low profile castle nuts that also have nylocs in it (ACS has them). The bolt I cut and hand-drilled to allow for maximum L/R clearance.

While I generally like the simplicity and effectivness of the Patrol design, the torque tube and stick assembly is a bit finicky to get right. From a weight perspective it probably hard to beat though.

Screenshot 2024-07-26 at 11.57.15 AM.png

Screenshot 2024-07-26 at 12.27.36 PM.png

[Bcone1381]

“and don’t use castle nuts with cotter pins in there”. Hmm. Isn’t that the exact case (nut subject to rotation) for which use of a castle nut and cotter pin is mandated? Are you depending on the inner diameter of the tube to prevent the nut from coming off or do you have a different solution? Thanks. My bolt, castle and cotter seem ok in there (no contact) and not much slop. Maybe I’m missing something? The bearing sounds like a great idea. I’ll do it if it gets sloppy in future. Still fiddling with the fork at the idler though, so I have more than a passing interest in the whole assembly.

Here is some data. You make the call. I think a good argument to make is the designer trumps AC43.13. But I will be making my build so these nuts are easy to inspect on the preflight.

The text below (in bold and italics) and the attached drawing is cut and pasted from bearhawksafety.com. Its Title is Call out for bolts and nuts at bottom of the control stick. It was issued for the Patrol and LSA December 2013.

Hardware nomenclature.
-AN3-5a bolts are undrilled standard AN3 bolts. (letter "a" at the end is undrilled. absent letter "a" is drilled)
-AN364 nut is a standard low profile elastic stop nut. They are not castleated. The Castle nut is AN310, The thinner shear casatle nut is AN320.


Control stick hardware on Bearhawk LSA Drawing #26 and Patrol Drawing #29.

The bolts and nuts at the bottom of the control sticks are being called out to insure no interference with the torque tube throughout the travel range (see drawing below).

Install the nuts on the side of the control stick that has the most clearance with the inside diameter of the torque tube.

Screenshot 2024-07-26 at 9.53.39 AM.png