HiI have been using RC 4.3 for a long time with no problems at all, but suddenly ATC tells me that I´m drifting off the assigned airway and need to fly a certain heading until I´m back on course. The problem is that I´m flying my filed flightplan exactly, according to the nav display in PMDG NGX, and the correct heading according to the RC display. This happens on every flight and ATC is pretty angry with me...Any suggestions?

Sounds like you may have changed the heading deviation value. The smaller the number the more fussy the controller will be. Check the value in Settings.

On the PMDG navigation it is sensitive to the magdec.bgl which contains the magnetic deviation database that many products use. It is in FSscenerybasescenery. Some add-ons change that. There is a discussion on this in the AVSIM PMDG support forum. See if you get off track in a non-PMDG aircraft. This also might might create a HDG difference between what RC sees and what RC wants.PMDG Airacs supply their own navigation databases. To check for any errors, use a flight planner that exports to FS and the PMDG FMC. Then in the FMC import that plan. The FMC and RC will then both use the checkpoint coordinates in the .pln file.If this occurs anywhere near airports make sure your makerwys is up to date from:http://forum.simflight.com/topic/66136-useful-additional-programs/and rebuild the RC database. You also might as well update FSUIPC as well from:http://forum.simflight.com/topic/66139-updated-modules/If you are on a very long leg RC can get an error due to Great Circle navigation. Increase your tolerance a little bit in the RC General options tab as Ray stated.

if you can duplicate the problem, make a log, instructions pinned to the top of the forum. send me the log, and tell me where it happened to you. i'll tell you what happenedjd

Thanks for your suggestions. I will check it out on my next flight and return if the problem occurs again.