How to stop this?

So in almost every aircraft i fly especionally these bigger ones (like the A350 shown here) when its on LNAV the wing go left, right, left, right… without any reason. First i thought it was winds but it isnt because when i take hand control i can fly normally without doing it and you can see here there isnt any crosswind only tailwind. Does anyone have a solution?


Assuming you’re trying to cruise at FL400 (the pic isn’t too clear), your aircraft is most likely too heavy to cruise at an altitude this high. Best option is to simply reduce your altitude and come back when lighter.

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Building off the reply above this one, make sure you’re cruising at a speed that’s more appropriate for the aircraft flown. I see a lot of people flying 737’s and A320’s at Mach .86…sometimes when flown too fast the aircraft will begin to oscillate left and right or vice versa. The A350 is most comfortable around Mach .83 and Mach .85.

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I typically see this when I’m about to stall. What is your speed?

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Based on aircraft behavior based on weight and distribution, you will be less effective at attempts to cruise at higher FLs when at higher loads. Furthermore, you can use sites such as simBrief which can help you predict and pre-plan step-climbs to coordinate fuel-burn and what is economically realistic. :)

Of course, there are many other possible scenarios. Based on my years with the community, and knowing a lot of users who just take the A330 Neos and A350s as the high fliers of the sky: this typically happens. Step-Climbs are initiated to improve effectiveness and economically sustainable numbers when it comes to commercial aviation and freight. I would highly recommend looking into step-climbs further down below.

skip to 3:45 of video below:

More comprehensive:

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Ok, understood

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Its M0.80, ill reduce altitude i think its that based off people saying that

Thank you :)

M0.80 is too slow for the A350. The A350 cruises around M0.84-0.85.

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Too high and engines aren’t as efficient where there is thin air that high. Try descending to a lower altitude (FL300-380) and you should be okay.

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You could also be flying too slow.

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The A350 can cruise at FL430 but fuel must be burned to reach this flight level. Cruising that high has little benefits on shorter sectors, you’ll burn more fuel climbing there than saving. Mostly on very long haul routes would cruising that high yield fuel savings, or if the aircraft is light weight to begin with. Hope that helps!

As indicated by @Tsumia ,@Duke and @sfahyaviation still too heavy for the thinness of the air at that altitude is most likely. And as @sfahyaviation, @Butter575 and @BennyBoy_Alpha said, speed is related to that: the heavier you are as you go higher, the more speed you need to keep the wing flying.

At some point you can’t go fast enough, and always your AoA (angle of attack) has to make up the difference in lift. But it can only go so far.

High AoA is a symptom of being at too high a “density altitude” - being too high and heavy for the attainable speed.

You haven’t shown a cockpit view to accurately show the AoA number, but your external view still gives away a strong clue. Assuming you are level at FL400, your pitch up angle gives the AoA.

It looks like you have a quite a significant pitch angle, so a significant AoA (again assume level flight).

So, for whether it’s still too early to step climb higher for your speed and weight, AoA often gives you a good hint.

For reference, at the right cruise altitude for your weight, AoA should be around 2’.

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