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I originally posted this at the end of the thread titled "Trim Jackscrew Binding started by PeytonM a few days ago but I thought it might be more appropriate to create a new topic. I do think my Jackscrew needs some maintenance attention and that topic was full of fantastic information but I'm not sure it is the cause of my electric trim problems so I'm trying to reach anyone who has had to deal with similar electric trim problems. Manually, in flight, my trim wheel may feel a bit stiff but I've never considered it a problem and always assumed I had an electric trim problem. Sorry if I'm overlapping the mechanical trim system with the electric trim system but I'm thinking both must be considered. I have an intermittent electric trim problem with my 1980 Mooney M20K (231) which is equipped with a Bendix/King KFC-200 autopilot/flight director. Before asking some questions, I'll give you some background info. Through the course of troubleshooting this problem, I ran across a MooneySpace thread which really explained a lot about Trim Jack Screw Binding. I've always thought I had an electrical problem but after reading through this thread, there's a chance it could be a trim jack screw binding problem. I believe that my Jack Screw system needs some attention (including removal, inspection, cleaning, lubrication, and re-installation) but I still suspect an electrical problem. I usually use the electric trim and the intermittent problem has become more frequent. Often when using the split trim switch on the yoke, it trips the breaker, sounds an alarm and the electric trim is inoperable. Sometimes I reset the breaker but that generally does not work and I use the manual trim wheel. This problem usually does not occur on the ground and often may not occur on the next flight. I thought I’d start by making sure it is being maintained correctly, such as lubrication, so I looked through my aircraft service manual which does not provide a lot of information. After talking to the shop that has done my avionics work, I found out that the electric trim system service & maintenance is covered more thoroughly in some later Mooney manuals for the M20R and Bendix/King manuals including Honeywell Service Bulletin 292. They were kind enough to copy the related pages. From the pages they gave me, I discovered that there was an STC for the addition of a carrier bearing located on the trim shaft directly below the trim servo. From inspection, I can see that bearing has been installed on my Mooney. The pages also say there is a maintenance decal that is supposed to be installed at the same time to provide Annual inspection and lubrication instructions but my plane does not have that decal. I do not believe that this bearing has been inspected and possibly not serviced or lubricated in the 18 years that I have owned the aircraft. For about the first 10 years I owned the plane, I had a highly qualified Mooney specific IA doing my annuals and I worked with him and I do not recall ever doing anything with this bearing. He has passed away, and I do not think my current IA is aware of this bearing inspection or maintenance either. A few days ago, my friend (A&P) and I spent the day troubleshooting and planned to inspect the bearing (below the trim servo). I started by asking him to operate the trim wheel to see how it felt to him and he immediately thought that it operated too stiff. He noticed that there are smooth areas and stiff areas. As I worked the trim wheel, as he instructed, while he observed and felt the trim shaft from the avionics bay opening to the Jack Screw, he concluded that everything worked freely until it got to the Jack Screw system. At that point we stopped for the day and I did some on-line investigation and found the jackscrew binding thread. He and I have gone through all the comments and photos of that and believe that my Jack Screw system is not operating as freely as it should and needs some attention and could possibly be causing the problem with the electric trim. There is a number of weeks before we plan to remove the jack screw system so we decided to throw out some questions to get any help or ideas any of you have. 1. Do you think Trim Jack Screw Binding is a possible cause of my electric trim problem? 2. I saw some comments in that topic that their trim got so stiff that it "jammed" the electric trim. Has anyone's trim failure been like mine (where it trips the circuit breaker) or does it just not operate. 3. Do any of you with a KFC-200 system have any specific thoughts on trim problems that I should investigate? Have you been inspecting and lubricating the Carrier Bearing below the Trim Servo as I mentioned? It appears to be a difficult job due to access and the screws being behind the servo chain sprocket. Any thoughts? 4. Through all these comments, we didn't see anyone talk about replacing the jack screw boot. My boot looks just like all the photos in that topic. It seems well worn and disintegrating on the ends such that tiny threads and pieces come loose and are in the jack screw threads and grease which could be causing binding. We plan to replace mine and wondered if you all have replaced yours when doing this work? Where is a good place to purchase the boot? Any thoughts and ideas would be appreciated! Thanks for your help!

Our KFC200 has electric trim. If it turns out to be more cost effective to replace the KFC200 with the TruTrak than it is to repair our pitch servo, I have a couple questions. 1. Can we legally keep the electric trim from the KFC200 even though it would no longer be our autopilot? 2. Assuming we want to keep the KI256 (AI) and KI525A (HSI) until they fail, what parts can we legally remove? I'm guessing the control panel and the annunciator would have to go, but does the computer have to stay for the HSI to work? That is, does the HSI get its course and glideslope info through the computer or does it get the information directly from the (in our case) GTN650? Obviously, the pitch and roll servos would be replaced by the TruTrak servos. Thanks in advance for any collective knowledge. Bob

I have a 78 Mooney 20J with a Century III autopilot and electric trim. There is currently a problem with the pitch and the pitch and altitude hold, neither seem to work right in the air. But, separate from the problem, neither the Century III pitch or the altitude hold seem to work unless the electric trim switch is turned on. Is this correct, or should the Century III pitch functions work independent of the electric trim. Does the electric trim and the pitch servos work in conjunction when the autopilot is on? The electric trim switch in my case is on the pilot yoke, forward to trim nose down, back to trim nose up, and push down to disengage the autopilot. Thanks.

I’m the new owner of a 1991 Mooney M20M Bravo after a long search for a fast efficient plane. This is a great aircraft and the one that I purchased is low time with a relatively low time reman engine and prop with NDH. Two issues have shown up though since the purchase that puzzle me. The first is that the electric elevator trim switch on the yoke works well until I engage the autopilot. After the autopilot is disengaged, I have to manually trim the aircraft. I have noticed that this takes place every time I use the autopilot after the aircraft has been shut down. It seems almost like a clutch has not or will not disengage until power off. A question is “Would it be okay to pull the breaker on the autopilot (KFC150) after having been engaged and then disengaged in flight, then restoring power to the autopilot to see if the electric trim switch on the yoke begins to work again?” Second, the WX1000 stormscope worked perfectly on the first day that I flew the aircraft after signing the papers. Starting up the second day, the unit did not power up and has not since. Does anyone have any experience with the stormscope and this type of failure. Seems like a power issue but I wouldn’t know where to start. Both being avionics issues, can you recommend someone in the Alabama-Georgia area to look into these issues. They certainly don’t keep the plane grounded on a great VFR day but otherwise I’d like to solve both before having to deal with weather.

First flight yesterday...after takeoff and gear/flap retraction, the electric trim failed to move...uh oh...my plane isn't happy with me for not flying her for two weeks. Reset the trim breaker...and nothing. Ok, it's now hand trimming all the way to destination...no biggie but like all long bodies, they do require judicious use of trim especially for landing. After a bit of "prayer" on the ground....the electric trim worked just fine on the return trip. Go figure. I think it's just dirt in the trim switch on the yoke. What's the best way to clean it out? Should I unscrew it from the yoke and just spray contact cleaner on it?

So, at a loss here. Apparantly there is a fuse in the S-Tec box that keeps blowing when electric trim is in use by the autopilot. This makes the electric trim inop. Everything else works correctly i.e., trim servo, autopilot etc. Except, that once the fuse blows, only manual elevator tim is available. Avionics shop finds no shorts anywhere and no electrical faults on the trim servo. S-Tec's answer was to "loosen" elevator control cables, which does not make any sense in any Mooney! Any thoughts here? Thanks!!