777 auto pilot not working

When ever I’m flying on auto pilot on the 777-300 the aircraft goes up and down 700 ft and doesn’t stay stable at the altitude i put. Why is this happening?

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Possibly winds?

It happens everytime i fly that specific plane

What’s your airplane load? Might be too heavy for your cruise altitude. Might need to step climb.

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My Load is only 48%

What was your v/s before the A/P leveled off?

2000 was my v/s

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2500was the v/s then switched to 2000

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Alright so that might be a tiny bit of your issue. So I’ve had this happen a few times to me where it will just bob up and down. So I suggest about 1000 feet before your cruise alt, you lower your V/S to about +500. I do this now and I don’t have any issues. So hopefully this helps.

This right here is the solution. For the A321 and the 777 no matter your weight before you level off you want to decrease your vs to at most 1000fpm. This ensures that the aircraft doesnt oscilate. So 1000ft out from your cruise altitude lower your vs to 1000fpm. 500ft out lower it further to 500fpm. From there is should be fine. You may have minor oscilation of +/- 100fpm but that wont cause any problems.

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I have experienced this issue on A321 a few times and its a knowen issue. Just setting ONLY the altitude OR the VS to 0 helped me to keep the airplane stable. It also helps a lot not to fly with more than 320 kts ;) just set a smooth Cruising Speed.

Hopefully this helps you, too.

Note: if you dont set an altitude and keep VS to 0 you altitude could change a little.

What was your airspeed and altitude?

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