I was doing that, but AP would then switch off.
That shouldnāt happen. Try climbing with vertical speed (ensure you are indicating higher than best rate of climb) then engage FLC at your aircraft best climb speed. I say indicate higher than best rate of climb so that your speed bleeds off more quickly rather than waiting around ages to engage FLC. Let me know how that works.
yeah itās full of bugs
Iāll try this evening and let you know, thanks!
Yes sir! The AP on all of the small GA planes I fly just wonāt keep a heading or function during NAV mode. They will hold altitude. I just want it to work and sadly it does not. And from reading this thread Iām surely not alone regarding thisā¦ Very frustrating.
My brother and I flew our Cesna 172 with glass cockpit. First flight was good. On the second one AP went crazy for both of us (weāve done exactly same flight both in single player). Once you press a AP button the airplane goes into steep climb. The trim goes all the way to nose up. We had to disengage AP to save airplane from stalling. And it happens every time we engage AP no matter what the altitude. We did set our AP for FLC 75kt. AP would hold Heading or NAV mode no problem itās just the trim goes crazy.
This is exactly my problem since 1.8.3. Iāve mostly been flying the Baron.
The APās lateral axis works fine whether using HDG, and and NAV/APR following GPS or radio sources. Itās the vertical axis thatās wonky now. And the vertical axis worked reasonably well before the patch.
What Iām seeing, whether I use VS or FLC, is a complete inability to hold the set speed (vertical or IAS, depending). The plane goes into increasingly large fugoids which ultimately either stall or overspeed the plane.
I also find the plane unable to hold a set altitude in ALT mode. In turbulence, it remains wherever the wind blew it, making no attempt to return to the set altitude. If you donāt intervene, it will gain or lose thousands of feet over time. In the absence of turbulence (Clear Skies preset, all layers zeroed), the plane will still trim itself into a slow climb just less than 100fpm (so VSI box is blank), but the altimeter slowly ticks upwards.
The strange thing is that our first flight had no issues. It behaved as pre patch. Only the second flight got all messed up.
Edit for more info: After we experienced problems in our 2nd flight my brother load up the first flight. Same flight plan, same altitude, same plane and AP was crazy anyways. So why did it worked without issues on the first flight and went crazy in all other flights after that?
I have no clue. Itās like how sometimes the game totally ignores your joystick but a return to the main menu usually solves that problem.
Thereās definitely something random going on. For instance, it seems like most folks have problems with vertical modes and horizontal is fine, but there are some folks say the exact opposite.
When I use FLC it can go haywire. Climbing or descending at extremes. Iām pretty sure itās a trim issue as when I look its always the trim thatās either at max negative or max positive.
I just use VS mode for climb and descent now. Works fine 
I have an issue where Iām in NAV mode in cruise after 20-30 minutes, hands off the control, and slowly the AP loses control and the airplane banks over to one side. I have video. From that point on, AP wonāt work correctly - itās as though the plane is balanced on a knife edge, it wants to bank over to either side unless I constantly correct it. an NAV/HDG donāt work at all. Throughout all of this, the vertical speed and altitude hold work fine.
I have experienced this in multiple airplanes and suspected my CH yoke, but now I am wondering if it is a bug. I have to exit the game to start over to get temporary relief. Would be curious to hear if anyone else seems these symptoms so I can eliminate my yoke. Another symptom. the magenta FD bar appears on the screen, tilted by about 30 degrees, even when the FD is turned off.
I have basically the same problems. Altitude is fine but NAV and HDG donāt work properly. When the aircraft starts to bank, it will go into a spin if not corrected. I also have CH yoke and pedals. Someone suggested I try adjusting the sensitivities, but alas, thatās no longer possible as of the last patch.
It happens all the time. It is not you.
@OrangeBacon8637 Interesting. So maybe itās an issue with CH yokes? I donāt have the pedals. @BetterSubset089 Thanks - good to know.
Just tried again with a different airplane - same results within 5 minutes of takeoff. Pretty much unplayable.
EDIT: found a post about editing XInput_Gamepad.xml file for sensitivity. trying that now.
Add on airplanes are starting to become available. Carendo makes a nice Mooney. Iām tempted to buy it and see if the autopilot on it will behave. Of course it may rely on the MSFS 2020 system to work and may do the same thing. Iām reluctant to try add ons. Installing them looks complicated. Iām afraid Iāll mess everything up.
Do you have your trim control mapped to an axis or to buttons?
This is exactly how my AP behaved when I mapped trim to an extra unused throttle wheel axis on my Fighterstick.
Mapped it to two buttons instead and all my vertical axis AP problems went away.
I think the trim-mapped-to-axis trim value gets constantly read by the sim and the AP fights it and it causes the APs PID loop to think it needs stronger and stronger inputs and somehow freaks out.
CH Yoke users. See this post if you have problems with NAV and HDG not holding. this thread has the file to edit to change the sensitivity settings. I used -50 for sensitivity and 3 for deadzone. Change the X-axis value for ailerons.
https://forums.flightsimulator.com/t/patch-2-controls-sensitivity-settings-not-showing/273486/29
The file location for Steam users is further down the thread. (\Steam\steamapps\common\MicrosoftFlightSimulator\Input)
Based on a short period of testing, it seems to be working.
EDIT: 
that lasted one flight. Had a one-plus hour flight this morning with no problems. now, after work, same old issue is back. argghh!
Actually, I have it on buttons on my stick and on an axis on my throttle. This has worked perfectly well since the alpha. In fact, putting it on an axis made manual trimming SO much easier than the wonky, accelerating way it works with buttons, and has never caused any problems before. But I also have buttons, on a separate controller, because some planes donāt accept axis inputs for trim.
Beware that the real altitude depends on the local pressure since the indicator is based on a barometer, so if there are turbulence, itās likely that pressure has dropped. But I think it would change by a few tens or at most hundred feets, not thousands. Also I suppose the AP should normally still reach the desired measured altitude, regardless of the local variations of pressure.
It goes into āsuicide modeā for me pretty consistently. In fact I find it rare to engage AP and have it settle in quietly and quickly. It seems that it doesnāt matter what my airspeed is, or if Iāve trimmed perfectly in level flight right away.
I find that AP engaged in the 208 B to be slightly more reliable when Iāve filed a flight plan with waypoints to GPS into (N-key, follow route).
I find that the AP in the 208 B Grand Caravan is much more insane than in the Cessna 172 Skylark, even though they both use identical G1000ās. Perhaps its the Rudder Trim on the Caravan, which does not exist on the 172?