772 autopilot issue

Hi,
I am currently in a 772 cruising over the Atlantic at fl360 and unexpectedly, the autopilot keeps pushing the throttle up to around 95% power for no real reason. I am comfortably holding my speed at mach 0.85 so not really sure what’s happening.

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What are the winds?

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How heavy are you?

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Fluctuating around 30 kts as a head/crosswind

47% 214,191 kg.

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Hmmm, your weight, altitude and the winds sound fine. Just to make sure, your flaps and gear are up, right?

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Yes, that is confirmed

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This sounds to me like your winds being updated. For example, your headwind component might have decreased which caused the autopilot to throttle up to gain the extra airspeed lost due to the decreased headwind component.

How often does this happen?

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Fairly constantly, after your point, I’ve checked winds and it does it in coordination

Alright - yup this means that the autopilot is simply trying to gain the airspeed lost due to the winds changing. You might also notice that sometimes your headwind component may increase which will cause the autopilot to decrease the thrust instead. This is not really an issue as this is how it’s meant to function by design.

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Ok thank you

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Is your VS stable?
(Asking because my throttle has that behavior but due to unstable VS)

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I would suggest maybe flying to a lower altitude maybe FL330 for safely.

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Sometimes this happens I believe due to lag or network issues where suddenly the throttle moves up not in a gradual manner…

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its not a bug. but one thing you’ll notice is the AP is anything but smooth, annoyingly so…

i could manually bring the aircraft to my cruise of mach .83, preset SPD to mach .83, and it will still abruptly reduce thrust and slowly increase it again. I literally end up much slower then I set, and it fights to regain the speed

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This won’t make a difference in this case unfortunately.
Plus he was at FL360 so if anything he should lower at FL340 or FL320 if he uses the IFR semi-circular séparation rule 🤓😉

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I agree with you.

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