MooneyAcolyte

After boroscopy today, I discovered an image of Josef Stalin on my exhaust valve. Hoe is this possible? Sent from my iPhone using Tapatalk

Ripped door seal? Cabin too noisy or hissing noises? Check out my video on how to make a new door seal for less than $100:

It's fixed! Thanks to all of you helping to diagnose this fault. As it turns out, we were spot on. Indeed, the microswitch inside the pitch servo (KS179) had failed. I went to Avionik Straubing (https://www.avionik.de), who did an EXCELLENT job. They took apart the KS179 (see attached) photo, fixed the micro switch, overhauled the motor (so I get another couple of years out of it), and lubricated the mechanical part. Due to the clear diagnosis, they were able to focus on the work that was actually needed. As a consequence, the repair was still rather affordable (€1100). I flew PH-FAR back from Straubing to Rotterdam and tested the AP extensively. PERFECT! Thanks again to everyone involved. This case is another demonstration of the value of mooneyspace. Signing off on this topic - Mooney Acolyte

Latest update: I have now an appointment with the avionics shop in Straubing (near Munich) in August for repair of the pitch servo. I'll keep you posted.

After studying the correct wiring diagram sent by @Jake@BevanAviation, I am now convinced the problem is with the PITCH servo (KS-177), not with the trim servo. As you can see, the PITCH servo has the "AUTO TRIM UP SENSOR" and "AUTO TRIM DN SENSOR" lines connected. Given the symptoms, the most likely root cause is a false trim sensing. The only other option is that the flight computer (KC 295) misinterprets correct sensor input. The procedure proposed by @Jake@BevanAviation is indeed designed to distinguish the two cases. For me, the next step is to perform this procedure. I'll share my results here.

15k$ I heard, installed. Don't quote me.

Wow! That's steep. Now with @Jake@BevanAviation's help I am 90% sure it's the trim servo KS179 (P/N 65-0052-04), I will talk to the avionics shop here in Midden-Zeeland (EHMZ). They are good, but VERY busy and not too customer-oriented. I'll share my journey here.

Latest update: started the test and found that the KC295 is connected to a KS179, not a KS272. If someone could point me to the right installation manual, that would be wonderful. Blue skies!

Thanks, found the right one now and have made a little test plan based on the schematics in the IM. Will report to when I will have had time to hook up the multimeter KS272 pin action J,H contact GND N +14V D check +14V for trim down P check +14V for trim up A check +14V if electric trim is ON C contact KC295 P2951/N R contact KC295 P2952/N, should have no command if KS272/F is open K contact KC295 P2952/F should have no command if JS272/L is open F contact KC295 P2952/T L contact KC295 P2952/d_ E contact KC295 P2952/y_

Hi @Jake@BevanAviation, couple of clarification questions: * the IM you are referring to is this the one at the link below, correct? * I find the connector of the flight computer to the pitch trim servo on page 130. In it, the main command and return lines appear to be "TRIM SERVO CMD +" and "TRIM SERVO CMD REFERENCE" (screen shot below). * I assume the check is to measure the DC voltage on "TRIM SERVO CMD +" on the flight computer side, correct? * I do not see a line that indicates the servo micro-switch. How can I test the command for a closed micro switch? Wouldn't that mean the computer must be connected to the servo? I'm sorry if the questions are overly stupid. Thanks for any help you can offer. Blue skies, Markus

Thanks, I‘ll try that and report here Sent from my iPhone using Tapatalk

OK, I'll try and share how it went. It's rather a part of the diagnosis than a standard operating procedure. While I have your attention @Jake@BevanAviation, my preliminary conclusion given the observation * electric trim works w/o AP * AP works w/o electric trim * AP passes PFT * FD works w electric trim * Pitch trim runs away pitch-down with AP enabled in any mode is that the issue is still the KC 295, not the trim servo. Would you agree? Thanks in advance for any guidance you can provide.

Latest update: still scratching my head. Based on the suspicion of water in the static line and/or the pressure transducer board, I took the KC 295 out, pulled the transducer board and inspected: no water. To be on the safe side, I put the board in the oven at 50degC for an hour and blew warm, dry air through the static lines. I put everything back together - no change. I tested again and found that the trim-down runaway occurs also without the altitude hold mode. The electric trim works without the autopilot. Next sep: test-fly autopilot with electric trim off. Any ideas to solve this mystery are welcome. Blue skies! Sent from my iPhone using Tapatalk

Thanks, I'll try that.

Please excuse my ignorance. The transducer board is inside the FC 295, correct?