Autopilot descending when it should be climbing

Hi All,

I just had to exit my flight just a few minutes ago because of what seems like an issue with the autopilot, but honestly I’m not really sure. I was doing a pattern at KMIA in a Cessna Citation X. I had the autopilot set to climb to 1500 and it did so but overshot a little. In trying to correct it, it pitched the nose down a little, understandable, then overshot again so pitched up, pretty normal stuff. Then, after it overshot yet again it pitched the nose down A LOT. Looking at the replay, it decided to make me descend at -1700fpm, and I could not figure out why. I tried desperately to recover but when I turned off the autopilot it pitched up massively (calibration issue on my end I assume). When I re-enabled the autopilot, it pitched down again. I’m really confused as to what happened and any help would be much appreciated.

NOTE: I would share the replay but every time I click share the app crashes

Hi! One thing to ask: did you use any positive Trim during your flight? And make sure to calibrate before turning off the Autopilot.

The reason being the aircraft has pitched down again is because you have not set the current altitude indicator. Say the aircraft has pitched up to 18,000 feet, but your altitude is set to 10,000. When the A/P key is pressed, the aircraft will automatically pitch down to descend to the indicated altitude, from the current 18,000 to 10,000 feet. Please note that there is a chance that I may not understand you properly with the information given.

I suggest you checking the replay again.

In other problems, you might check the current Weather information in Miami Region. This region usually consists with severe storms nearby, including really high wind gusts. This also could be a possible reason to why the Autopilot pitches up and down.

Yes, used 4% positive trim. The AP was fully on, ALT, SPD, VS and HDG were all selected when this happened.

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Did you turn on the V/S, then adjust it?

You did say that the app crashes every time you try to share the replay. How about you try screen recording the cockpit view of the replay? Will this be a possible solution?

Will do when I get home, thanks

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