Altitude Oscillation (Porpoising?) B777-300

[r_stopnicki 92]

Hello to all:

 

I have recently (I believe that after the most recent update) started to experience a dizzying experience with the B777-300 (Interestingly enough, it does not happen in any of the various PMDG or other add-ons I own).

 

At cruise altitude (i.e. FL370) it continuously oscillates with variations of 500-1000 feet and corresponding changes in air speed as the AP tries to compensate for the descents and ascents.

 

It happens with ASE on or off, it happens on-line (VATSIM/IVAO) or off and with either VNAV or ALT HLD selected.

 

It is obviously quite disrupting and, looking at a porpoising screen for a long flight is no fun.

 

I have tried to search the forums, although the search-words I have selected were not very successful.

 

Does anybody else experience this problem? 

 

Thank you!

Roberto

[scandinavian13 5,192]

 

 

Does anybody else experience this problem? 

 

Loading the aircraft via the CDU or via an external load manager?

 

Do you have a trim axis assigned to your hardware?

[r_stopnicki 92]

Hi Kyle.

 

I load the aircraft via the CDU (although I truly only change the fuel).

Yes, I have a trim assigned to my SAITEK Pro Yoke.

 

Thx for the lightning speed response!!!

 

Regards,

Roberto

[scandinavian13 5,192]

 

 

Yes, I have a trim assigned to my SAITEK Pro Yoke.

 

Disable this assignment and see if it has any effect.

[r_stopnicki 92]

No change

:mad:

Roberto

[downscc 1,327]

FL370 is easily above where you want to be in a loaded B77W.  How does FL370 compare with the optimum and maximum altitudes provided by the FMC Cruise page?

[r_stopnicki 92]

Hello Dan:

 

The FL maximum provided by the FMC was FL390. I only had 35% fuel., so I was not that heavy.

 

Thinking as you did, I descended to FL310 en-route and still had the issue.

It was still oscillating (although not with 1000 foot deviations and annoying alerts) on the approach STAR procedure; finally quieted down on short final.

 

I will take the -200 for a "spin" and I will report back.

 

Thank you for your comments.

Roberto 

[downscc 1,327]

Roberto, this is not a bug in the aircraft.. it has something to do with your configuration. You said it happens with no weather so that rules out the most common source of a pitch/speed oscillation problem. Oscillations of 1000ft are very wrong, not something minor, which is why Kyle asked about payload/fuel load method. I'm agreeing with him, something may have corrupted the aircraft.cfg file. Do you have any addons, such as TOPCAT, that directly access aircraft weight and balance?

[r_stopnicki 92]

Hello again Dan:

 

I am repeating this morning's flight, step by step, but in the -200 rather than the -300. I have been at FL370 for the last 25 minutes and it is "rock solid". The -300 started to oscillate as it entered the FL300's in the climb.

 

(I should have remembered that I had a beautiful flight two days ago in a freighter .... a  -200  ... duhh)

 

Something obviously got broken in the -300 and I will follow "advice # 2" of one of my kids .... re-install!!

 

(Advice # 1 is ... "close all the windows, then open them again .... that sometimes works" ... ) :-)

 

Thank you for your interest and your advice.

I will report back as soon as I can accomplish all of this.

 

Regards,

Roberto

[r_stopnicki 92]

The uninstall/reinstall trick worked.

Whatever was broken is now fixed.

I am happy.

 

Thank you Kyle and thank you Dan.

Roberto

[Raphael_Chacon 42]

Using P3DV4.3 and Oscillation ghost came here on the PMDG 777-300ER ....    Unistalled and reinstalled the 300 expansion only and it worked for mee too.....   👺Exorcism was successful 🤣