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Guest fenixAH

Oscillation during cruise

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Hey, when I reach cruising altitude and cruise using VNAV, the autopilot keeps pointing the nose up and then down. I noticed that the throttle is also always being adjusted forward and back by the autothrottle continuously. How can I fix this problem??Thanks in advance.

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I have the same issue and have found the only way to stop it is to turn the AT off. There seems to be some coupling between the 'nodding' and the autothrottle possibly inducing a self perpetuating oscillation.I have found that by disconnecting the AT and setting power maually I can stop the oscillations within a few cycles (four to five) and then it's fine. I don't see it as much as I used to before V1.1, but it is certainly present when using 'accelerated' flights above 4x. By turning AT off it is very very much rarer.On a flight from EGLL to KSFO yesterday with real weather on, I saw it every 5 mins until the AT was off and then it only occurred once in about 15 to 20 mins and was connected to changes in head wind speed and direction, and changes in the amount of cloud (caused by Jepessen weather updates perhaps?). Perhaps these changes are increasing the processor load and it takes longer to pick up and correct the nodding whilst it adjusts the weather and visuals.I also select VFR flying as it stops ATC whingeing about altitude excursions whilst the sim sorts itself out.I'm using a Sony VAIO PCV-RZ504 (3.4GHz P4-HT), 2GB RAM, 256MB nVidia 6600 and Hotas Cougar controls. Monitor is Sony 23" 16x9 display running at 1920*1200. VC mode on.Rick.

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Alright, but do you get it if you don't use accelerated time because I get mine when it's one 1x also.

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Yes but much more rarely than I used to, and again disconnecting the AT resolves it - well at least it has so far.Rick

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Make sure that you have correctly loaded the 777 using the load manager, and that you have the correct Centre of Gravity figure entered into the FMC.

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That makes a major difference as an incorrect CoG makes things worse - as it did with V1.Overall V1.1 is much much better (in my personal experience).Rick

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