Trim tab play

C

crumast

New member
Has anyone encountered play in the elevator trim tab, originating where the torque tube engages the threaded rod,forward of the elevator? This rod has a solid square cross section, which slides within a square tube. That's where the play is. There's enough side-to-side play (not fore-and-aft)to allow movement at the trim tab. If you have, what was the fix? Tom Robinson
 
I thought that there was an AD or service bulletin for this on cruisemasters?
Maybe someone could chime in?
-Adam
 
The following information was published in May 1998 by the FAA and references the trim tab issue and related service bulletins. If you need copies of the SB let me know and I will email a scanned copy to you; the AD can be downloaded from the FAA website. The problem you describe might be different from the issue addressed by the SB (the taper pin issue). If so we would all really like to have more info based on what you are observing - maybe some pictures? Here is the text of the FAA advisory circular:
“Bellanca; Models 14-19, 14-19-2, 14-19-3; Cruisemaster; Elevator Trim Tab Flutter; ATA 5513
This article was submitted by the FAA Aircraft Certification Office (ACO), ACE-115C, located in Chicago, Illinois. Five reports have been investigated concerning in-flight tail flutter and/or vibration problems. Bellanca and the ACO are concerned that Airworthiness Directive (AD) 53-16-1 and Bellanca Service Bulletin (SB) 1 may not be adequate to prevent elevator trim tab failures. The trim tabs may be damaged by overtightening the taper pin fastener. Overtightening the taper pin may be the cause of some flutter/vibration problems. It was recommended that all operators of like aircraft immediately inspect the elevator trim tab system in accordance with AD 53-16-1 and Bellanca SB 1. Special attention should be given to the taper pin fastener. If any damage is found, it is suggested the trim tab be replaced prior to the next flight. Earlier Bellanca models may not be affected; however, they should be inspected for the conditions previously stated. Bellanca Models 14-19-3A and the 17 series have a different trim tab system and should be inspected in accordance with AD 68-23-8 and Bellanca SB’s 45 and 46. Bellanca and the FAA are working together to coordinate a new Service Letter and possibly an AD to address this issue.”
 
Where I'm referring to isn't in the linkage, which is on the exterior of the fuselage. On my 14-19, the exterior pieces are tight, including the taper pin connection. The area in question is within the fuselage, just forward of the elevator, next to the rear fairing on the left side. I'm sure the -2's and -3's have the same setup. It's a square section rod, which slides in a square tube. If I move the trim tabs trailing edge, I can see this square rod move laterally. Again, there is no movement fore-and-aft of the rod or linkage. I suppose a shim of some kind would take up the play. Tom Robinson
 
I am not sure just how similar to the Cruisair your connection is, but the rod runs clear from the trim tab control overhead in the cockpit to the worm gear set up that changes the motion from circular to fore and aft. That rod has bushings all up and down its length to keep it from whipping when being rotated. I believe the bushings are a resin phenolic block, and these are attached to structural members. If one of your bushings near the rear has come loose or disintegrated it could allow the lateral movement you are describing. If your rear fairing is off, look to see if there is any indication of a bushing that has come loose. I dont remember if they are screwed to the fuselage tubing or maybe laced. Some Bellancas that I have seen have the long rod running inside of a tube for much of its length, so the tube would not be attached by a bushing, but by something solid. A mirror and a flashlight will probably show you more. I hope this helps._____ Grant.
 
Tom, I know exactly what you are talking about. Had that problem described to me by another guy several years ago. Slop in the squared off tube; caused by wear of either (or both) the male or female part. The proper fix, replacement of either part, would be costly and time consuming. His solution, which I'm not suggesting you do, I'm simply describing it the best I can, was to insert a shim into the tube. If I recall he first used a feeler gauge to determine the thickness of the shim stock needed to take up the slack. He cut the stock to fit well into the female part, and left it long enough so the other end (pointing to the tail) could be bent sharply over the back of the square tube (now pointing at the nose) and tied down onto the tube securely with several wraps of tightly applied safety wire. The end was then bent again (now pointing at the tail) and another wrap of tight safety wire was applied. I hope that's clear. On his aircraft there's access just above the right horizontal stab and he inspects the area often and lubricates the male and female parts liberally. It solved the problem (trim is tight) and has been trouble free for years. He's a little embarrassed because it sounds so Mickey Mouse, but the worse that could happen should it jam for some reason is you land without trim...
Phil
 
Thanks Phil. That is pretty close to what I have in mind. It seems like the most simple, least costly, and effective way to go. Tom
 
Gotta love this forum - always learning something new! I had to run over to the hangar where I have the fuselage of a neglected -3 Cruisemaster to study the aft trim tab actuator mechanism. Sure enough there was a strip of shim stock wired into the square tube (see pic). Might have come this way from the factory - not sure. Makes sense because the shim stock is typically tempered to a high hardness - thus no wear should occur in contact with the moving rod. However where the softer steel contacts soft steel, wear continues. Good lubrication should minimize this problem. BTW, on all of my Cruisemasters the torque rod runs inside a tube from front to back. Thanks to Grant, Phil & Tom for the informative discussion.
 
My trim is getting loose in the same area, I was contemplating several ways to make it a better fit but I like the shim Idea better than any of mine.
 
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