NicoN

I joined a Ownership for a 1980 M20K in 2018; right after all 6 cylinders had been replaced. Analyzing the old logs from our EDM830 clearly showed, that the aircraft was flown often hot if not too hot with CHT over 400°F for a longer period of time. We came along to fly LOP to save the engine's life forever. Since then we are donig this; flying LOP with 58-65% power and CHTs never over 390; in cruis we have TITs of ~1535 and FF 8.8-9.2 gals. GAMI spread is also fine Now, again 2 cyl are with low compression. Even though the exxhaust valves are looking fine. The cylsa are loosing pressure via the valves and also into the crankcase. In-place-lapping improved one cyl and had no impact on the second. Now, the shop says, our problmes are caused by flying LOP!! and he sees those problems more and more often as people flying LOP and especially in TC Mooneys and Cirrus. Okay, what to do? If Mike Busch is right propagating LOP with lower CHTs then we made everything accordingly. But if not?

That looks exactly like ours when it broke

INteresting. In fact we still have some steam gauges installed. And I don't think that they changed something with the installation of the GI275

Correct. This was an issue when the plane came back from the installer of the GI275s: They removed a DG hooked to the C21 (NOT HSI!!!!!) And obviously they did NOT change the previous jumpering . It took me a while to convince the installer that the GI 275 is "talking" always HSI and not DG. After changing that (but where exactly) the hdg mode worked just fine. That is why I am searching for the problem in the C21 and not in the wiring itself So, the question is where the wires from our GI275 really go - directly into the 1D772? Or is something in between (a magic box?). After a couple of flights my co-owners started telling me that the HDG mode is failing. As I wrote: - the ground test is always fine - even in flight the hdg mode seems to work at least for a while - I tested the hdg mode even while on ground with external power for 30 minutes (!) moving the hdg bug left and right - fine! What I cannot test on ground is if engine vibration has some negative impact. That's why I am trying to understand the vibration test. Can the diagnostic logs tell me more? So far I could not check them. Some seem password protected.

Oaky, thank you. I forgot to say that NAV-Mode always works fine - forever. It is only heading mode which sucks. The C21 computer has a stack of 3 PCB. On the upmost Board, 8 caps (looking like grenades have been replaced. The rest not, as someone invested a lot of work in placing the original parts with their values facing down. AFAIK the C21 system is only the computer in the panel. - the motor is always working - I do not see any error messages - NAV/APPR work - wings level function is always perfect So, I think it is really a problem of the heading part. AFAIK, we only have the C21 flight computer 1D772 which is driven with the signals from the GI275 No transformers, no Radio-coupler I have the service manual and I am still not sure whichCD-xxx is where. The 1D772 has only ONE 37pin D-SUB connector - nothing else Is it labeled as CD-186 in the manual? Where is CD-175 or CD-194? According to the different manuals ist should be Pin 17 on CD-175 where the signal for Hdg comes in. But it could also be Pin 14 /CD-186

Our GI275 drives a Century 21 A/P. the wiring semms to be correctfor me. Basically it does what is expected. on ground, i can move the heading bug left or right from the lubber line and the control wheel starts turning. Same if I am taxiing; the control wheel moves if i change direction I did this a thousnd times: - In the ghangar - taxiing on the airport After take-off, it normally works also, but after 10 or 15 minutes, the A/P does not follow the Hdg bug any more. It simply continues flying the last heading. Whatever I do on the hdg bug - nothing happens; It keeps the wings level perfect but tha's it. Yesterday I was doing test turn using the hedg bug. and I think i had a moment where A/P stopped turning, returned to a wings level atttude After landing and waiting a couple of miuntes it worked again We already had an echange of several capacitors on the board ( It hink not all). It is the same situation, not better not worse Now the question: Can a failed vibration test be the reason that the heaidng mode quits (i.e. the GI 275 stops siganlling to the A/P)? I know, that sounds crazy

I recently treid to run the vibration test for our GI275 (double). I have never seen an exact procdure of how to do it. The screen said something to run the engine at max power for an extended period of time. - with max power, i easily exceed the 100% mark - with reduced power close to 100% it runs fro a coule of seconds. But I did not see a clear passed or failed sign. Weird. Has someone more information, especially what happens if the vibration ets is considered as failed? See my other posting about our problem with a century 21

Sorry for my english ... We have a weird autopilot problem (it is a Century 21 and we have 2 Gi 275 installed) in the hangar i can do the ground test, moving the heading bug to the left or right and the yoke is moving also. Do it with a small heading change, the yoke moves slowly, with large heading change (60° elft or right) the Ykoe moves faster - seems perfect. As soon as we are in the air, the heading mode has no effect anymore, the plane does not follow the commands. in nav mode the aircraft turns correctly. I can hear the motor running continously with the hdg bug set to somewhere (not in the middle). I opened the cover and can see that the aileron is running to the max position and then the motor seems to continue. What is weird: I can move the aileron easily with almost no power by hand and I can see the sliüpping process. My question: How much power is normal? I know, it is possible to override the motor but taht easy?

if it is not installed in your direct viewing field: - ask the shop to install the warning lights - in my opinion: go for all available sensor options

Has someone access to a service manual for the century 21 A/P?

I can give some hints, finally it worked. The shop tried hard but was too fast turning. We had the same problem: Our full circle ended not with 360° but with 390° easily - so exceeding by far! The solution: If you turn and stop, the indication on your GI275 seems to count down further. If you stop whenever GI275 commands "HOLD POSITION", it s internal oistion might be finallay 2-3° more. Do this 10 times and you have a large error. Solution: stop the turn not when the GI275 says, but around 3-4° earlier. Then wait for the indication to settle. Conntinue turning really slow!!!!!! 0.1-0.2°/s maximum! Stop, when the GI275 asks. With this method, we ended dead at 360° and the GI275 simply said "complete"- No nice chime or something The disappointing thing: the shop staff did not know this trick and also did not have a secret phone number of a Garmin evangelist!!!

We got GI275s installed the other day. Now, it seems that audio alerts can be heard ONLY on the cabin speaker - but not on headsets. According to the manual. it should be connected to Pin T - Altitude warning as an unmuted input. But does that include they appear on cabin instead of headsets?

We have a burned bulb in our A/P controller. This guy sits directly on top of the Co-pilots yoke, below is a small panel with the dimmers for panel and instruments light and the cigarette lighter socket. I am struggling of moving out the Controller. :-( AFAIK it has 2 little "claws" on the underside which should be operated with a screwdriver from the front The right one seems to be turned and unlocked, the left one I am not sure. removing the the screws for the panel with dimmers/cigarette lighter, I can bend that panel only a bit and reach the right "claw" with my finger tip. the left one is not reachable for me as the 2 dimmers are blocking. 1) is there a secret of how to pull the panel? removing the 2 screws seems not to be enough. I still cannot move this piece. And -please do not tell me it is bolted in place and I have to remove the cotroller first! 2) the controller seems to be a bit loos, but i cannot slide it out 3) and yes, for complet e removal I need to remove the yoke. But for now I cannot slide it even half of an inch.

On Ground it is really easy to operate. in the air you need much more power. Easy for me, but for my partner with a rotator cuff tear pretty hard. I had to adjust the cowl flap a couple of years ago when the cable was replaced. It tended to open on its own.

@wombat: I can confirm that you have TWO fuel senders. One on the outer edge of the fuel tank. This one is connected to A/C GND via the screws which touch the senders body. The next one is in the cabin wall and this one SHALL not have contact with the senders body and A/C GND. This is achieved by using "shoulder washers" which also isolate the screw shaft from connecting. Both senders are wired in series, so their resistancde is 60 ohms (I believe) together. If the inboard sender is connected to GND, then the outboard sender is useless. We had the situation that a hangar idiot lost one of the shoulder washers. Therefore, foru screws were isolated, one was not. That results in an indcation of maximum 18 gals instead of 36 (we have 72 gals). Not a real problem, becuase it takes a long time, then the needle goes below 18. But according to FAA rules your gauges only have to indicate the empty situation precisely - not the full.