B787-9 autopilot issue

So right now I’m making a transatlantic from London to Miami, when I reached my cruising altitude of 40,000ft at a speed of Mach 0.85 on autopilot, the plane started going up and down even when I had the vertical speed set to 0. In flying over Ireland right now and it’s still doing these oscillations of the nose going up and down between 0 degrees and 7 degrees nose up, the plane also goes from 900fpm going up then 900fpm going down too. Other then that the plane is flying just fine, nothing wrong except for this weird bug in the autopilot, could you fix this in the future please?

Device: IPad 9th Generation 2021
Operating system: iOS

Hi @DuduGamerLuis3 , welcome to the community

It looks like you might be a bit too heavy for the altitude you are currently flying at. You’re at 84% load at FL400

You’re also flying with a reasonably strong crosswind. This can have some impact if the winds are gusting and moving the aircraft around, the autopilot may try and correct for it.

I suggest you have a look at this handy guide to step climbing:


Hi, the issue is you are too heavy at that altitude. You’d need to step climb. Start off at like 35000 instead.

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Unrelated to the issue since you already got the solution:
I strongly recommend you DO NOT enable VNAV that far out, since the AP might start descending and you might not notice it and end up having overspeed violations :)


Alright thanks man! Yeah it’s most definitely the weight, now my load is at 61% and it’s flying smoothly (Just entered USA).
Appreciate the feedback!

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