Success!!! I think I have figured out and corrected a major contributor to this phenom. The culprit seems to be duplicate AFD files. Something clicked when people kept saying it must be something to do with third party scenery or a bad AFD file. That's when I realised that in some third party scenery, payware included, the AFCAD or AF2 file for the new airport is in "Scenery" folder of the new scenery itself. If you do as I do and look for and install further, updated AFCAd files then the possibility exists that you have two AFD files working fo the same airport that may have slight differences in frequency and alignment info. So I downloaded a program I remembered from a while back, Scanafd, available here on Avsim http://library.avsim.net/download.php?DLID=45600Scan all your scenery folders and locate those that register as having more than one AFD. Then look carefully at the location of each. Those in the Addon Scenery/scenery folder have priority over all others but if you have two for the same airport but with different names, they will conflict. Choose one to keep and dump the other. Be careful not to dump any AFD that comes up as a duplicate but that deals with taxiway signs or specific visual and ILS approaches.This took me about two hours to do since I have tons of scenery and ended up with over 200 duplicates that I had to go through but in the end my landing at ABQ (one of the problem airports) was More centered than ever int he last few months. http://forums.avsim.net/user_files/189609.jpgNow I'm not saying this is the absolute solution, but so far it has worked for the one flight I did. I will be testing other airports and let you guys know how it goes.Feel free to post your responseAnson

Had the same problem and additionally aircraft always to the right of the magenta course line when following FMC preprogrammed route using LNAV.Resolved both of these problems by doing critical realignment of IRS following PMDG procedure in the FMC Manual.Also managed to calibrate the FMC heading by postioning the A/C on R27L EGLL and then uploading the runway heading [273deg} to the FMC POS INIT page of the FMC.I did not find a procedure for calibrating heading within the manual or indeed I have been searching forums with no success but managed to stumble through it during the irs realignment process.Would be grateful if anyone could provide information on this.New to this forum so be kindMaurice