Boeing 747-400 flaps question

I was trying the 747-400, to test the flap retraction.
I takeoff with flaps 20° and begin retracting as per what I have gathered from several websites (PPRUNE etc…): at a Vref 30 (for 292030kg) of 156kts, I retract flaps 20 at Vref 30+20 (176kts), no problems. I reach flap retraction speed for 10° (Vref 30+40, 196kts), and the aircraft sinks, from +2000VS to -1000VS.
What did I do wrong? This doesn’t happen with the B737-700.

Your weight must be too high. I don’t know, you seem really fancy to me, to use a website like that.


Probably nothing by the sounds of I, there is a nose bump if you are using autopilot. If you ascend manually you can control the ballooning and sinking of the aircraft attitude under flap retraction.

Welcome to the forum by the way.

Even when I ascend manually, it’ll sink from +2000 to -1000, and then go back up violently.

Thank you.

You need to control that just like real world. There is probably a larger speed needed for the jump in flap on a 747, increase By 10kts and see what happens.

I don’t fly the 747 often the model is abit wooden. 737 it’s flaps 5 still at 190kts retracting to 0 above that

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It may be that the 747 is a bit old, the 737-700 being newer (?).

I tried the 737/57/67, and those are way lighter than the 747. Maybe I need more trim to counteract the nose down due to the weight.

Yeah I mean, trim obviously only used during manual flying. I don’t know when they plan to add auto trim to avoid this, it’s coming on the 787, wether it will be on all models, no idea.

Autotrim on the 787? Really?

As far as I can tell, either that or it’s a bug which causes the nose bump. I have no idea about coding,

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