Autopilot ascending strangely

Hello, as I type I am setting to FL120 in a British Airways 747, but an issue is that the aircraft keeps rapidly switching between nose up at full throttle, and nose level at half throttle. is there a way to fix this and how is it caused?

VS: 4000
ALT: 12000
HDG: 20
SPD: 233

Samsung S2 Tablet

I use a Logitech Attack 3 joystick

I have experienced similar issues where the autopilot is unable to situate itself at the given flight level.

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Turn autopilot off get level and turn it back on. That sometimes works for me

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Yeah, that is what happens in the similar problems.

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As @Captain_Skywalker, you were too low, probably stalling.

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Okay, now I was descending to 5,000, and the aircraft kept descending at an alarming rate, much faster than the -500 I set it to. My speed was 220, and when I turned off AP and slowly pitched up, it began a stall. Why is this happening?

Did you have flaps 10 at that moment?

I had no flaps. The thing is, I increased speed to 270, well over the limit, and it still didn’t gain lift when I leveled it

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Well, BA only has the -400, so that. :p

I would turn off auto pilot use my falls to get to slow down and level off make sure the trim is at zero and once you switch the autopilot back on change the rate of climb

At 220kts you should have had flaps. And the aircraft will pitch until it reaches an enough clean speed, over 280kts: https://quizlet.com/9166725/boeing-747-400-limitations-flash-cards/
Of course, it depends on your weight.

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Flaps shouldnt cause this
Speed could be the issue, is the weight balanced, trim properly adjusted.

Lack of flaps.

Now I get what you mean. When transitioning from flaps 10 to 5, the aircraft nose will pitch up a lot. The same for landing, when transitioning from flaps 5 to 10.
We really need an FMS to tell us at least the correct flap speeds (and V1 and 2) with the current weight.

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