B777 instability in cruise

Hello all
I’m cruising with a b777 at FL390, but the aircraft is not stable at this altitude and it keeps pitching up and down up to 250 fpm… Any idea how to resolve this issue?

Whats your weight?

I would recommend using this next time you fly as your aircraft gets lighter you can climb to higher altitudes.

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It was 206690kg when i took of… still have 1303nm out of 1515 total distance

Yeah to heavy for that altitude. Try what I said above.

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Have climbed to FL410 but still pitching

You have to go lower not higher

Hello! As I’ve mentioned in another topic:

One trick that usually resolves this is to disable ALT and control your altitude using VS only.

Thanks mate… I’ve flown 777 a lot but it’s the first i’m facing his issue… Is it normal to continue the flight in that way🤔?!

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In what way? With ALT turned off or bobbing? I would try the trick I mentioned first… otherwise, i would probably end the flight in case it escalates and throws you off completely.

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I meant bobbing up and down… If i turned of ALT mode; would the aircraft make a drastic attitude change? How can i continue the flight without ALT turned on? I still have 1200 nm until the destination

Not if your VS is set to 0.

I disconnected the ALT mode and the aircraft did a drastic pitch up reaching a stall point although my V/S was set to 0… So i quit the flight😔🤦‍♂️

Odd. I need to check that… sorry to hear! :(

Thanks mate for your help🙏…
I was firstly cruising at FL390 according to the FPLN generated by SimBrief, i did a gradual decrease in V/S before reaching the cruise altitude (as recommended), the aircraft still bobbing up and down up to 250 fpm, i increased my altitude to FL410 but with no change… I disconnected the ALT mode and it did a drastic pitch up and ruined my flight 🤦‍♂️… It is not the first time i fly B777 but it’s the first time i see such thing…

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