Hi, Bought the 737 yesterday, and what a excellent aircraft it is! I did a search for 'drift' but nothing came up so here it is....I was on a flight today, CRZ 35,000, and the aircraft was drifting 10nm left of track. Is this reasonable for the autopilot? Aircraft trk was 314, wind was 224/16.Thanks.Jamie Blethyn, UK

What I think the problem is that the course your plane is on is the direct course to your waypoint, 200+ nm down the line. Solution: closer together waypoints ;-) Not sure if this is normal behavior of the AP....

Hey, that's what FSbuild gave me as the route! What's the distance between North Atlantic waypoints - up to 300nm! In a video i saw, i didn't see the aircraft 10nm off track - even with a 50kt crosswind!CheersJamie Blethyn, UK

Jamie --Didn't realize that was on an Atlantic route. I don't think you can get much closer than what you have. You will noticed the phenominon(sp I know) between any two waypoints, but not as exaggerated as in your example.

My guess is the plane is flying the great circle route and the map is displaying the great circle incorrectly. Some panels do this better than others.Any chance you could take a look at this PMDG for the update? Set up a really long direct route, say KJFK to KLAX and see how it does.Lee Hetherington (KBED)

Being a long flight, maybe the inbalanced fuel issue's so strong it's pushing the plane off-route? I don't know, can't test since I don't have it... Just assuming from the posts I've seen here.Cheers,[a href=http://sgair.net" target="_blank]http://sgair.net/mike/banners/daniel_small.jpg [/a]Click the Banner to visit the FFX Website.

Jamie,I have also had this drifting effect, on much closer waypoints, it has todo with wind, coming back from Coolangatta to Sydney (YBCG-YSSY), with my 140KTS wind that was off to my left, pushed the plane right, and away from the line. The plane SHOULD correct this, and "crab" into wind to fly along this line. I missed the "TOD" too..Before you "MY GOD THE WINDS your problem" - In Real-Life.. these are normal winds for these Flight Levels..Regards,Sean

Gents,Lee, in another thread was spot on with reasoning behind the long legs problem. It is due to the calculation of magnetic variation for the course.The AFDS (automatic flight director system) when in LNAV mode calculates and commands roll based on a target **track** NOT heading. Wind is therefore immaterial. Ofcourse the track target commanded by the FMC has to be "correct". It is now fixed and thanks for bringing it up.Cheers,Vangelis======================================= E. M. Vaos Precision Manuals Development Group www.precisionmanuals.com=======================================