Issue with all 747 variants in the autopilot cruise

I’ve had an issue with the 747-400 when flying on autopilot in calm weather. The autopilot seems to be causing the aircraft to rock back and fourth (left to right) without any manual input.

I’ve tried changing speed, made no difference, the weight and balance is even.
Any help is appreciated.

Unfortunately I can’t seem to be able to add the video of this issue on here.

Thanks.

Not too sure if this is the right category for this issue, but it didn’t seem to fit in with the support category as it appeared to only be for technical issues.

This behaviour usually happens when the aircraft is too high for your weight.

Whats your aircraft load percentage and your current cruise altitude?

I agree with @BennyBoy_Alpha 's questions. In addition it could be usefull to know what device type you run it on and/or your frame rate at the time of the issue (if known).

Also, have you tried briefly turning off AP, and reengaging it after steadying by hand?

I’m using a Google Pixel 7a, the phone is only 2 months old. I’m not sure what the frame rate was at the time, but I have had the same issue several years ago on a 747-8 on a Motorola phone.

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I was cruising at 36,000ft at 51% load. The fuel (72,706 KG) was split equally between the L and R tanks, I had 281 pax (21,669 KG) and 13,051 KG of cargo split equally between the front and back.

And no I forgot to try turning A/P off and back on again.

In the 747 (particularly in IF because its an old model) - this is too high.

Oh wow okay, thanks for letting me know. Is 30-34,000 a more suitable altitude? I’ll do a couple of test flights soon and i’ll come back if a lower altitude hasn’t fixed this issue.

Yes - 30-34K is more suitable.

In the 747 - try and stay quite low (because it also helps with fuel burn - which is a tad broken on the 747)

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Do you have a HUD screen shot you can upload taken at the cruise conditions when the rocking occurred? Preferably when your VS is roughly zero.

Thanks for all of your help everyone. The altitude fixed the problem. This morning I climbed to FL360 and I was able to get the same issue.

I then descended to FL320 and there were no problems at all.

Thanks for all of your help and tips to get this fixed.

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