Compass and ND headings are incorrect

[AvA757Pilot 6]

Occasionally, when I start up the -700 I find that my magnetic compass and ND headings are both showing incorrect values. They will both indicate the same heading but it is off by about 130 degrees (i.e. I am facing 340 but the indicators show 210). This affects the LNAV function and makes navigation just a tad difficult.It does not happen at every airport and I have thus far only seen it operating at somer airports in the USA Northwest.

[downscc 1,327]

Please sign your full name in this forum.The mag var is greater in the NW than elsewhere in the contigious US, but not that much. Try turning off add-on sceneries and look for a difference.

[AvA757Pilot 6]

Please sign your full name in this forum.The mag var is greater in the NW than elsewhere in the contigious US, but not that much. Try turning off add-on sceneries and look for a difference.

This does not appear to be a mag variation problem. I also just tried a flight in the USA southeast and the effect was the same. What I suspect is that it may be related to the fact that last night I d/l a SID/STAR cycle. This may be screwing me up now and of course, I neglected to save the old file as a backup so now I am not quite sure how to unravel that mess.Roger Curtiss

[downscc 1,327]

It's not possible for the navdata files to corrupt the headings, these are just text files read only by the pmdg FMS.Hope this helps: http://ops.precisionmanuals.com/wiki/How_t...Tracking_Errors

[AvA757Pilot 6]

Thanks Dan. And also, just to clarify, I was experiencing this problem before I did the SID/STAR d/l...just not on the east coast. I will try disabling some scenery and see if that makes a difference.Roger Curtiss

[AvA757Pilot 6]

I did the old tried and true shutdown FS and restart it. Sure enough, when I did that and repositioned the airplane at KSEA the compass/ND headings were working just fine. So it is an intermitent thing and I suppose I can live with that...until 737NGX arrives!Roger Curtiss