The above screen shots is demonstrating that the LNAV goes nuts. I was about 20 mins into the flight and it starts to circle.
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It doesn’t look like it’s circling to me. It clearly shows that first it’s trying to get to LOPEZ, then LACIE, then TWIIN. So the destination point is changing. What happened right before LOPEZ that caused it to go off track? Were in you in a turn? Did you modify the flight plan? Maybe it tried to get to a waypoint and couldn’t get to it, so it’s still trying to follow the flight plan. The default autopilot is pretty dumb so don’t expect it to “just work”.
Given that bank angle, it sure looks to me like it’s trying it’s hardest to get on the nav track. If your flight plan has some severe turns, it’s possible that the plane just physically can’t do it. In that case, you need to intervene with a DIRECT TO.
Also, IIRC the default nav data has some questionable procedures. Does this only happen for certain routes?
I could not send the video. Trust me it circled for 10 mins before I killed the flight. Around LACIE. I made it from NEWARK to this point with no issues. The flight path was relatively straight. No crazy turns. The autopilot put the plane into that bank angle. I did intervene and the autopilot wants to go back to LOPEZ. It has happened since the update last week. It’s absolutely crazy. I have tried simple direct and it would just go off course. Pretty straight forward.
It sounds like the autopilot did not register that it had already hit LOPEZ.
Is this an arrival or a departure or in the middle of the flight?
If it’s an arrival and LOPEZ is the IAF, then this could be the Flyback bug which has been reported as still existing.
If this is a departure, did you delete any Discontinuities prior to LOPEZ in the flight plan? Sometimes people delete discontinuities without understanding that this is not always a good idea.
If this is in the middle of the flight, then you should watch to see if the aircraft actually registers that LOPEZ has been reached. The PFD should count down the distance to LOPEZ and switch to LACIE and you should see similar indications on the Legs/FlightPlan page. Or the Progress page.
I just attempted a flight from KSAN to KPSP, it got about 1/2 way and started circling, and losing altitude… just kept circling and losing altitude until it hit the ground, it did a nice bounce, before it came to stop, engines at throttle still!!!
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Do you see in your photos where TWIIN and LACIE are indicated in the MFD? (upper right) Why at those moments did the plane think it was going to those waypoints? Did you do a Direct To?
To address the issue from Vonzeigler. This is what has been happening to me. I have FS create the flight path and let it run. I am not making any changes during flight. It’s random when it decides to begin circling.
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I’m having the same problem. Autopilot not following LNAV nor DIRECT TO nor VNAV.
Hello,
what you’ve set to fmc as aircraft can follow some logical path? What positions AP deck switches have?
I have planned the routing on the FMC. Dep ZSSS via LAMEN A593 SADLI Y590 ELGEP B576 OLMEN to Dest RKSI.
AP active “switches” LNAV / VNAV / AT
Engine goes to IDLE after take-off.
On enganging AP it simply starts a shallow left turn… sometimes the VNAV engages.
Tried DIRECT TO LAMEN and nothing.
Tried HDG and didn’t follow SELECTED HDG either.
FYI installed SALTY stable 5.01 // CS777 with Salty compatibility
I see here some mistake,
if i understend correctly VNAV isn’t implemented on def stock. If you want use HDG mode you need click it’s button to set it active.
Other side??
Corrected 
aaaaaah some kind of addon? Then sry…
Not really a bug report since a mod was involved so moved to #third-party-addon-discussion:aircraft and closed as Topic Author selected solution.