high Latitude problem

[ivi96 0]

Hi everyone,

I had some issues with the autopilot during my previous flight, from Glasgow to Seattle with PMDG 747. I was cruising at  FL380 with LNAV,VNAV and CMD set and after 3 hours flying normally the AP went crazy: 

The aircraft started to turn to the left with constant bank angle of 5* ( F/D was inviting me to turn to the right following the FMC) and the altitude was fluctuating between FL380 and FL370, I tried to disconnect the autopilot but It didn't let me take control of the aicraft, so I renstalled PMDG 747 and made a test flight along another route ( Milan LIMC - Male VRMM) and the aircraft didn't have any problem for the whole flight. I tried again Glasgow - Seattle: same issue as before. I noticed It happens always while I'm closed to the 70N parallel. 

Any ideas? I really want to fix it....

[Biggles2010 343]

You might do better to post this in the Avsim PMDG User to User forum. More likely to get an 'expert' response.

Edited April 4, 2020 by Biggles2010

[ivi96 0]

alright thank you, I'll try there