The other day, I was on a medium range flight from Beijing to Tokyo in a 737-400, but I experienced something VERY strange. First of all, Normally, I rotate at 147 kts with flaps at 5, and I have never have any problems. I rotated at 10 degrees, and climbed for 1500 ft at 20 degrees, until I was high enough, then I lowered the nose/flaps, and activated the autopilot to climb at 1800 fpm, at 250 kts at 10 degrees. That was supposed to be my normal procedure, but instead, the plane decided to raise its nose to 25 degrees, which was too high for the autothrottle, which failed, sending me into a stall. Thanks to quick reactions, I deactivated the autopilot/autothrottle, in hopes of figuring something out, yet knowing that most of my flight would be manual, until this problem was reparied. Instead, I fell into yet another dillema, I had my aircraft trimmed to climb properly, which it was doing at first, but then, it veered upwards, so I took control again, and by the time I got everything back to normal, it was too late. Unfortunatly for the 737, I had a big bunch of Mountains straight ahead. It was very nervewracking as you might predict, and I dont want this to happen again. If you have any solutions to this problem, feel free to post them. BTW, This happens very rarely, but when it does, I get diasastrous results.
Thank you and Take care all.
I think I am correct in saying that the 737 AP and most others will give ROC over speed? Therefore if you are too heavy for example hot day etc then if you want 2000fpm the ac may only be able to give 700fpm. This should not happen in the 737 generally but it depends on the conditions. I do think this was more of a bug than anything else as the TO was as it should be. Just thinking it could have been that in order to go for speed rather than ROC it has pitched up sure you pressed IAS after selecting 250kts? I know you should not have to just thinking of a reason. This would of course contradict the AT ROC over speed issue that I suggested earlier!
I have that problem too with some aircraft, specially the 767-200. I figured out the problem 2 days ago. The Yaw Damper in the AutoPilot didn't work and that made my aircraft to climb 25 degress or more and stall. I decided to change the aircraft. Now, the Yaw Damper worked perfectly and my plane didn't climb to 25 degrees or more.
This may sound strange but it worked for me. Try to select the Yaw Damper (Y/D) in the AutoPilot.
Tell me if it worked for you.
When this happens again, I will be sure to tell you.
I always hand fly the departure from liftoff to around 10,000'. Then I engage the AP.