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I had a stuck trim issue today and I can’t figure out what cased it. I have an M20V with G1000NXi. Everything was working fine with the autopilot. On the LPV approach I tried to capture both VNV and GP. It did not want to capture. When I switched the autopilot off on the G1000, the electronic trim and manual trim were stuck in the full forward position, so I had to pull back on the yoke. I tried to power cycle the autopilot on the toggle switch. Trim still stuck. I did not cycle the flight director and did not pull the autopilot circuit breaker. Used about 20lbs of force in the flare and needless to say the landing was rough. After the landing, the trim was back to working fine. Clearly the servo got stuck. What could have caused it in the first place? And what caused it to become unstuck? What is the fix?

I am troubleshooting rudder trim on 1990 Bravo. Worked fine on T/O and during flight, but when I tried to neutralize the trim for landing there was no response to panel switch, stuck in almost full left position for descent. My first thought was actuator failure, but the motor is fine. I was able to neutralize the trim in the hangar by applying power directly to the motor and it runs both ways. L limit switch is OK, R is inaccessible from the tail so I will have to find the time to drop the belly pan and get to it. Panel switch checked OK, but only the bottom half gets 24V on the common terminal. Unfortunately, I do not have the electrical schematics for the plane to chase this gremlin. Does anyone here have a pdf copy of the wiring diagrams to share? Any help would be greatly appreciated. Regards, Ivan

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!

My M20K has started to develop a trim problem and I'm having a hard time troubleshooting it. When in flight, I will intermittently experience an uncommanded trim up. My first thought was that this was runaway electric trim, but I don't think this is it because turning off the electric trim switch, and pulling the auto-pilot circuit breaker does not halt the issue. Also, the actual symptom is pretty sporadic. It won't just smoothly roll the wheel backwards, but rather it will kind of slip backwards in fits and starts. Sometimes I can go for a long while and the trim behaves itself, other times I find myself fighting it the whole flight. The autopilot doesn't seem to have any problem holding altitude when engaged, and if I either manually trim or use electric trim then the system behaves as expected. So I find this a real nuisance more than a safety of flight issue, although I do find myself having to leave my hand on the trim wheel a lot more than I should. I had them look at this during the last annual and Dugosh was not able to find anything wrong. They also didn't experience the problem on their test flight. Any ideas on how to figure this out?

Hello, Today I was fortunate to be able to fly my "new" 1975 M20F on my first cross country (in this plane). It was uneventful. Once I got to cruise the altitude of 7500 and trimmed the plane out I set the altitude hold on the S-Tec 30. That was real nice! First time I've ever had a autopilot. At some point, I looked back at the tail and saw that the elevator was in a slightly down position, as noted by the outboard part that is fore of the hinge point (that was up). Later when I cancelled the ALT Hold, there was no significant pitch up or down. Shouldn't the full pivoting tail section have the elevator perfectly lined up with the horizontal stabilizer? Seems in the configuration it was in, it would have a lot of drag. Thanks, Philip

I am searching for an electric trim switch for my 1984 M20J. The base of my trim control switch that mounts to the yolk has cracked. I believe this is an OEM switch assembly, but I cannot locate the correct part number to replace it. If anyone knows where I might look for the part number or where I can order a replacement, please contact me with any info. Thanks, Dan King dsking001@yahoo.com

1967 M20F, MANUAL TRIM. this is in regards to the trim wheel, what sort of backlash is normal? In other words, if you wiggle the wheel forwards / backwards what sort of slop do you see before movement of the trim actually occurs. i am seeing about 5-10 degrees. i am curious what others are seeing.

I had this functioning elevator (empennage) electric trim system removed from my M20C: Aero Trim Electric Trim System 800ET It was installed by a previous owner in 2000 with a yoke mounted switch. It was made by these folks, but is no longer available: http://www.aerotriminc.com/index.html My info and documentation on it is scant, but there does appear to have been a 337 filed for it. It's a pretty basic unit. At my prebuy the MSC mechanic commented that he rarely sees these still working, but mine worked ok until removal. I took it out because it was hooked to the avionics master and made the trim wheel hard to turn by hand with it on and impossible to turn with it off. I figured it was just a matter of time before the thing failed and froze my trim wheel, which is easy enough to manage without it. Anyway, I offer it for the price of shipping in case there's anyone out there who might need parts to fix theirs - I doubt it's worth installing if you don't already have one.

I've had the 92 model M20 J MSE for just about a year now and have flown it for ~120 hours. After various loading configurations I still come back to the same place on the trim indicator for the best take off's transitions. I have time in M20 C's and a few different J models (years) and have noticed the J models with three blade props feel exceptionally nose heavy as compared to the 2 blade C model. I realize there's more to it than 2 vrs. 3 blade prop configurations. I was trained to allow the plane to fly off the ground with minimal back-pressure, no more than about 5 pounds. There should never be a point in rotation in which you have to jerk or pull back hard on the yoke to initiate a positive rate of climb. My trim indication depicts ~2/3's back to get the ideal (smooth) transition to climb. The M20 C with the 2 blade prop has always been right on the neutral position for take off. So, my question is....... Are 3 blade M20 J's naturally nose heavy creating a condition requiring trim settings outside of the indicated neutral take off position? Thanks again for sharing knowledge! Rick

Hello All, (I've posted in the general section as similar trim issues probably apply to all models) Intro... I've had a beautiful '67 F for 4 years based here in the UK. I regularly use the machine for airways trips around Europe in the FL80-160 range, quite frequently between the UK and Germany. The Mooney flies sweetly and it very stable. When trimmed, its doesn't drift. On the Ground the tailplane assembly has minimal play. Most flights are pretty much hands off, being flown with the KFC200 AP. Issue... I've noticed when in the descent from the flight levels, which I'd usually do with power (say 20 inches MP), I obviously trim for the descent to relieve my arm in pitch down input but I run out of pitch down trim. As I trim down with the electric trimmer (left thumb) I can feel the the manual pitch trim wheel turning and it will eventually stop at its limit -and indeed, when i leave the electric trim and try the wheel manually, it doesn't go any further (i.e. the electric trimmer has taken the trim to its full down position) and beyond that, I don't force it obviously. So in other words with full trim forward in a 'with power' descent, hands off, the max rate of descent is about 400FPM. If i need a faster rate of descent, I need to hold the yolk forward with a little more pitch down. Its not a big issue, but in a descent from say FL140 at a high-ish rate of descent, my arm aches eventually! Obviously, I could cut more power and this would aid the rate of descent (slower aircraft = less lift and all that) but I presume i should have trim range which allows me to fly in a powered descent at >500FPM fully trimmed (i.e. without having to hold further pitch down 'manually') I'm guessing that, over the years, some kind of trim adjustment has become needed so the trimmer is 'centred' and I get as much 'down' as well as 'up'? At the moment I seem to lack pitch down trim travel. Has anyone any experience of this or its fix or other comments / knowledge which would help my understanding? Thanks for taking the time! Justin Carter

Purchased my M20K/Encore conversion last October. Been loving it ever since. But I've noticed the electric trim has been intermittent a few times, getting worse over time. Really screwed me up on short final the other day, so I had it looked at and it appears the servo has issues. The bad news from my mechanic: Anyone know of any other options for getting this servo replaced or overhauled? I'd love to not spend an additional $6k so soon on this airplane! Cheers, Nicholas

Hey guys. Just wanted to pass along what I found while searching for my "running out of trim" problem. It would seem there was old, semi-hard grease causing an artificial stop and would not allow the trim to go fully down, or up for that matter. Cleaned very well and re-greased. Trim now will roll stop to stop smoothly. I haven't had a chance to fly her to see if it fixed the problem, but the trim wheel rolls down an additional four "palm strikes" now so I have to assume all is well. I am thinking whoever did the annual on her before I bought her may have been a little lax. Here are the pictures of what I pulled out of the tail.

Panel: I have a 1981 M20J. I am based at 2L0 (Pineville, La.) KFC 200 Autopilot altitude hold was intermittent and then quit working completely. I had an avionics shop in Houma La. check out the problem and was told the trim servo motor was bad. Avionics shop could not locate a replacement "motor" but said I could have the motor rebuilt for about $2,500. However, nobody has a rebuilt servo motor either. He suggested a new servo for $4,800 or sending it a guy in California that won't quote a price for rebuilding the motor or servo. I called Autopilots central in Tulsa who said he would look at rebuilding it for about $1,000. I have owned the plane for a few months and before that I rented. Accordingly, I have no history on what shops to use or which one are reputable. Here are the questions: (1) does anyone have one of these motors or servos for sale? (2) Recommendations on a place to rebuild the servo or motor or both; (3) what kind of price should I really expect? Thanks, Lawrence.