I was doing the Flight 1000 which is EGLL - EGHD. I was using the Beechcraft 1900D for the first time and I successfully took off from EGLL and was going for 9000. After going to 2500 I just turned the Autopilot (w/ ALT) on which would take me to 9000 ft. But, something unexpected began to happen. The plane just got it's nose up, and it was completely vertical in the air! It stalled and started turning here and there but I immediately turned the autopilot off and gained control of the plane. I was trying to figure out what went wrong and I thought it was something weird and I just turned the autopilot on once more, and the same thing happend. I thought it is a problem with the Beechcraft 1900D or maybe it's just me doing something wrong because I was flying it for the first time. I just changed the plane to Dornier 228-100. I have flown this plane a lot of times before and I know everything about it, so I just relaxed and turned Autopilot on again to reach 9000, this time heading (HDG) also on. And this time it was terrible! The plane first got vertical in the air and started to bank towards left, now there was a 90 degree left bank and the plane was vertical and stalling, I turned the autopilot off again and this time I couldn't control it. The plane just turned and twisted left-right-left-right, went up and went down and stalled for a while then it went face-first to the ground and crashed.
I am very confused and I just don't know what went wrong. The autopilot? The Plane? Or something else? :s