Autopilot on the A321

Hello!

I’m currently flying an A321 at M0.85 at 40000 ft. It’s at 237 knots airspeed, which isn’t that slow, yet the plane is oscillating right and left repeatedly, as if it were flying too slow. I’m afraid that the plane will stall at any moment and crash into the ocean. I’m not sure what’s happening, I’ve flown an A321 at this altitude and speed and it worked fine. How should I correct this?

Thanks!

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Mach .85 is too fast. Back it down to Mach .78 or .79.

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It might be due to turbulence, also that’s quite a high altitude, i for one have never flown and A321 at that height, just keep an eye on it.

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If M0.85 is too slow, the A321 will stall if I go any slower.

Then you need to decrease your Flight Level too ;)

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There’s 100 knot headwinds, but I’ve seen the A321 handle this before. Multiple times.

Yeah, i’d decrease altitude and see what happens, 380 should be alright.

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As Levet has said you would need to reduce your airspeed and your altitude to continue flying straight without the fear of nose diving, just curious did you do a step-climb?

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No, I went straight up.

At FL380. Still oscillating.

In this instance i would normally do a step climb for a smaller aircraft just to know how well it’d handle at each altitude, as FL400 is quite high :)

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You still might have too much weight for FL380. Drop down to 340 and see the difference.

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Weight is one of the factors, you shouldn’t have gone straight to FL400, you should’ve started at a lower altitude. How heavy are you?

Descending to FL340. Still oscillating on the way down, but not as bad.

Also, have you tried switching off HDG, levelling out yourself then reenabling it?

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At FL340, a bit better, but still oscillating.

If it’s oscillating, recalibrate, then disarm the Vertical speed until you can get the aircraft under control. Winds, aircraft total weight and cruise speed are the main factors here. You should be able to stabilize the aircraft at FL340 and a Mach Speed of .79.

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Tried recalibrating and resetting the autopilot, still oscillating.

I would assume it’s the winds and the weight of the aircraft.

correct me if i’m wrong though :)

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What we can’t see is your cargo weight, amount of pax and the fuel onboard so we are generally speaking based off the description you gave on how the aircraft is responding to the conditions. As mentioned previously in a comment. Be careful with going straight to such a high cruise unless you are really light on fuel and cargo.

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