I'm experiencing a pretty significant lateral cross track error with a valid route programmed into the FMC and LNAV/Autopilot engaged. As you can see in the attached screenshot, my lateral track to the current waypoint (LAS VOR) is about 10 miles off course center. This happens pretty regularly with my flights and I cannot figure out why.Conditions of aircraft during X-track errors:FMC Programmed with a valid flight plan, (dept, dest, waypoints, rwys)Autopilot engaged, LNAV engaged, VNAV engaged.VOR 1 and 2 autotune switches activated on MCP.Flight Director ONAutothrottles EngagedWeather:Flightsim 2004 realweather option, winds aloft download, no dynamic change.Alcohol content of Pilot in Command:Variable, higher on weekendsI'm wondering if this problem might be orginating with the AIRAC cycle for October 2003 perhaps? I haven't downloaded the very latest yet as I wanted to solicit professional opinions on what's going on first.Thank you and Happy Halloween.http://forums.avsim.net/user_files/46343.jpg

Hi JamesI don't really know what the problem is but if your bird is really flying on the correct track with an offset it could be the LAT/LNG problem that has already been mentioned several times in the forum. Compare the LAT/LNG in your FMC (on the REF page) with the one of the FS (hit Ctrl+Z). Is there any difference?If yes than try to change the FS2004 stettings to the U.S. system. the problem is the different writing style of the LAT/LNG ending.I'm just guessing but several people have reported problems where the ND had an offset shift of multiple miles. And when you say you experience this problem not for the first time it could really have something to do with this...Hope I could help you. Let me know if it worked...CheersMartin

Thank you Martin, I'll give your suggestion a shot and report back.

Martin,I tried another flight today and as far as I know my FS2004 and Windows XP are indeed set to the USA Region (I live in the States).But I also did indeed find a slight mismatch between FS2004's LAT/LON and the one listed on the 737 FMS POSIT REF page, a few seconds difference in both Lat and Lon. What is happening is that the FMC is taking me out on a parallel, albeit offset lateral track instead of tracking the course centerline. This seems to be cumulative (the lateral offset error) until nearing the waypoint (closing in on about 30 miles) and then FMC then seems to alter the parallel offset lateral track and flies directly to the waypoint until passage. The FMC is therefore not missing any waypoints in terms of station passage but is just taking me way off centerline between those waypoints as I mentioned at the top of this thread. At waypoint passage itself the FMC is always spot on.I have no idea what's causing this. Weird huh?Thank you for input!

Hi againYep, that's indeed strange. But you say there is a difference in the FMC POS INIT REF? I had a look at the old posts in the forum but none of the other reports say something about cumulative error. And also the way the error is cumulating and how the FMC tries to correct the error is new to me.I think I can't help you with that but it's really strange. Someone from PMDG might have to answer this question.Sorry that I can't help you more...RegardsMartin

It's a known problem, James. Robert Randazzo has already responded on the forum regarding this issue. I don't know if this has been looked at, yet, in SU2Cheers.Ian.

Thanks Ian. I suspected that something wasn't quite right with this situation - I'm glad PMDG is aware of it then.

Hi,The problem appears when you have long distances between waypoints. A/C is flying on a great circle course but the path is drawn as a straight line between the waypoints. That's why you get "offset" from the drawn path in between points.Regards,

Okay. But isn't this a bug with the PMDG avionics that this occurs and can it be patched to reflect how the real aircraft ND display works? Thank you.

>Okay. But isn't this a bug with the PMDG avionics that this>occurs and can it be patched to reflect how the real aircraft>ND display works? >>Thank you.It is patched in SU2 to correctly reflect the actual path flown. One of the many improvements :)

Cool! Me think I am going to be liking the SU2 patchy big much.Thank you.

Oops. To be frank, nope... This perticular issue is not yet fixed in SU2.Will be in 800 900...There's an easy workaround if you don't want the xtrack error : create along-track wpts on very long legs, about 40 - 50 nm apart.anthonyAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Ummm, there's an even easier fix, 767PIC V2, which will be competing very soon with PMDG. :) So who's gonna come out on top in the sales department when all the dust has settled? Methinks the product with the least amount of inherent flaws/bugs, things that require 'workarounds' because they weren't designed and properly beta tested in the first place. :) Food for thought guys. I really believe the SU2 will ultimately determine the long range success of the PMDG 737, to the extent it addresses the buggy avionics. I hope the future SU2 can accomplish all that it should.

:-)I'm not too sure how to react to this motivation post... so.. hmmm... I won't...anthonyedited for typoAnthony MertonPrecision Manuals Developmenthttp://www.precisionmanuals.com

Hi James,>I hope the future SU2 can accomplish all that it should. Well this is really the point. Do you mean "what *you* think SU2 should fix" or do you mean "what PMDG thinks it should fix"? I would say the former.I'm sure you all have been looking around the forum and read between the lines that there are some major imporvements and bug fixes in SU2. But will they fall into *your* category of fixes?I'm sure some things will be well welcomed by you, but not by others. And vice versa. Please be humble and patient. >...because they weren't designed and properly beta tested in the >first place.Well. You just got a reply that it wasn't implemented and thus not beta tested. Be sure though it has been brought up between the beta team and the developers. We have been concentrating on other more important things though.After all you seldom fly between waypoints that are several hundred miles apart. And if you do you'd better plan your flight a little more thorough.Just my two cents,