Altitude.

[jwoody18 4]

I am having trouble with the altitude on the 747X. I am currently in flight from EGLL to KLAX with VNAV selected, cruising at FL350. I went to do something, but when I returned, the aircraft was violently pitching up and down. (Gaining and loosing altitude) I attempted to manually fix it, but when I re-engaged VNAV it started to do the same thing. Anyone know what I'm doing wrong?

 

 

Regards,

Woody

[clipper759 4]

Are you using a weather program or real-world weather?

[jwoody18 4]

Are you using a weather program or real-world weather?

 

I am using real word weather.

[clipper759 4]

Are you using FSUIPC for weather smoothing? Using real-world WX without FSUIPC's smoothing functions can cause lots of issues with High Fidelity add-ons like PMDG.

[Paul_Smith 92]

That is a common symptom when using acceleration. You can normally get away with 4x for a while, but time spent at 8x or higher usually ends up causing the up and down motion you describe. Since the cause is the aircraft and the autopilot being unable to keep up with changing events, the only cure is to move away from the extremes. Drop your acceleration to 2x or less while you make the other adjustments, reduce your airspeed a little so you have a larger margin of error before you hit overspeed, lower your altitude a little, again so you have a larger margin for error, and consider switching to static weather for the period you want to accelerate.

 

Weather issues usually cause lateral problems rather then vertical ones.

[jwoody18 4]

Are you using FSUIPC for weather smoothing? Using real-world WX without FSUIPC's smoothing functions can cause lots of issues with High Fidelity add-ons like PMDG.

 

I am in fact using FSUIPC.

 

That is a common symptom when using acceleration. You can normally get away with 4x for a while, but time spent at 8x or higher usually ends up causing the up and down motion you describe. Since the cause is the aircraft and the autopilot being unable to keep up with changing events, the only cure is to move away from the extremes. Drop your acceleration to 2x or less while you make the other adjustments, reduce your airspeed a little so you have a larger margin of error before you hit overspeed, lower your altitude a little, again so you have a larger margin for error, and consider switching to static weather for the period you want to accelerate.

 

Weather issues usually cause lateral problems rather then vertical ones.

 

I'm not using time acceleration.

[clipper759 4]

Have you tried increasing both Pressure & Temperature smoothing? I would say double them if you are able.

[jwoody18 4]

Have you tried increasing both Pressure & Temperature smoothing? I would say double them if you are able.

 

No. I'll try it. Thanks.