Strange behavior for B747-400 on AP

Hello IF folks,

I was flying 747-400 today from Mexico City to KORD. Takeoff went well and 10 min after, with AP ON with HEADING/GPS, ALT, VS and SPEED, suddenly the plane turn dramatically and AP was disengagged. i didnt unerstand what happens. You can see it in my replay file here at time (advance to 16 min and 05 sec)

Also, at multiple occasions during the flight, when the plane needs to turn heading to follow FPL, the bank angle was so aggressive and high.

Any idea what I am missing here ?

Thank you in advance.

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I am unable to watch the replay, but what altitude were you at, VS, speed, fuel load. Basically all the specs, cause to me it sounds like you were too high while too heavy

around FL150 with VS 1600 ft/min

Load around 50%

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Hmmm, that does not sound like too aggressive of a climb. Strange, what speed were you at and what were the winds like? Cause I have experienced this type of issue before but that was because I was too high, while too heavy or struggling for speed.


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Speed IAS 325 kts

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I notice that is your Target speed, but was that the actual speed that was achieved when the issue began?

Dont know if it could be related but airport altitude is 8000 ft

I dont recall. must be near target. is there a way to get this info ?

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If while in the replay you turn on the HUD it should show you.

And no wind at all. Weird

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Was that your speed while level? This looks like you are already on your way down to the ground.

same. This is 1 sec before drama

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Okay, I am stumped then, does not match issues I have had before.

Could it be because AGL in this case was 6000 ft and 325 kts is too fast ?

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That’s not going to be the cause of it, no. But that is still way too fast.

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I tried now to reproduce it on Solo but all good

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Can dev team look into it to see if there is a bug ?

Unless you can reproduce it, it’ll be hard to look closer at since there’s only so much a replay captures.

We’re keeping an eye out for this thing though since we’ve had a few similar reports of strange behaviour after AP disconnect.

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Thank you. But in my case AP disconnect by itself without any explicit reason