Is this just my navdata being too old, or do have more serious issues?It's an LFPG addon.

Check to see if the addon modified FS's magnetic variation data - that can cause this sort of thing.

I've also had a bad AFCAD file play havoc with the magnetic variation. But when this happens, it's usually my heading that's off by around 30 degrees.

Now have a look at these!!!! This is the same issue.These 2 screen shots are the FS9 744, and the FSX 744. Both in EXACTLY the same location, using EXACTLY the same flight plans. Yet, when in FSX, the FMC always shows this behaviour unless actually CROSSING the waypoint. It appears i

PS Sorry, I don't know how to do what you suggest:-hmmm

it's getting worse every flight - won't even hold a flight plan now. The aircraft gradually veers away from path, then goes into 'silly' mode, going from left to right!it's only the 744 doing it. I've tried screen shots, but whenever I load FSX, every screenshot i take is just BLACK! I'm running latest drivers and have tried earlier vervions.Anyone - PLEASE?

Phil - have you installed any add-on sceneries?If so, try this. Go to the scenery library and turn off the addon scenery. You can always go back and turn them on.Restart FS and see if there is any change.Just for grins, make sure your international settings in the OS (MS XP or Vista) are using decimals for tenths separator (US custom) not commas (European custom).Keep trying, it is probably something really easy to fix but hard to find.

Thanks, will try that next. I just uninstalled EVERY single PMDG application on my PC, removed ALL remnents, and ran a registry scan to remove all other PMDG entries. Sorted every other aspect of my PC, defragged, then reinstalled all the PMDG stuff. All to no avail, which i'm sure most here could have told me anyway.I can't fly with LNAV at all now! Works fine when flying on AP using other MCP settings - bizarre!

I have seen that with one airport so far so I landed it completely manually. Would not line up with the runway at all.Also have seen one that did line up with the runway but not where it should have been.I put it down to bad data either in the AFCAD or the NavData. Have not had any issues with any other airports.John Veldthuishttp://www.virtualpilots.org/signatures/vpa475.png

Nope - not that either. Don't know what difference it could make but have deactivated all 3rd party scenery anyway.It's really strange - did you notice how the route on the ND won't run 'heading up'? Also, the aircraft is always deviating to the right of any routes.I've over cooked it now with this and need to go to bed. I'm quite ill at the mo, and 16 straight hrs at the PC isn't good even for healthy folk.Hopefully, all you 'very nice chaps' on the east side of the pond will have me sorted by the time i wake up:-lol Must sleeeeeeeeeeeeeeeeeeeep now!

Can I PLEASE have some input from PMDG??? I cannot fly using the FMC in LNAV!!!

It must have something to do with a corrupted add-on scenery or the magdec.bgl. I had the same Problem some time ago with FS9. Jan-Paul

I no longer have any addon scenery activated.PMDG, can I please have some help?????Even if you don't know what to suggest, can you please say that.

After getting next to no help here from PMDG, i tried emailing tech support.I got what appears to be a standard response suggesting i remove my entire FSX installation and start again!!!!! I think we all know how that goes.... When everything else is working just fine?If anyone has any ideas on this, however remote and unlikely, please let me know.Thanks

Here is another very basic example of what's happening;This simply an inserted route from KSAN to KSFO via OCN. Nothing complicated.Look how the aircraft goes way over to the right before trying (most times unsuccesfully) to cross the waypoint.http://forums.avsim.net/user_files/181937.jpg