problems with track !!!!

[FLEX1978 373]

Hi Marek,A screenshot would help a lot.Rob

[Viennaman 0]

how am i doing a screenshot - the plan eis now almost 45 degrees to the courseMarek

[bsmonroe 0]

I have never been able to get the VNAV to work at all.Between waypoints, the aircraft holds to the path in the display - then starts to drift. It gets off course enough that the MS ATC starts complaining.It begins to drift back on to the course about the time the waypoint is reached - but it "spins" over the waypoint in much the same way that a VOR needle does when the waypoint is reached.If you want screen shots I'll try to get some.Brian

[Mats_J 2]

Brian,Screenshots would help alot.FYI VNAV will not have anything to do with drifting off the path (unless in a vertical sense).For lateral FMC guidance you use LNAV, for vertical FMC guidance VNAV should be used.Please confirm you have LNAV engaged and active, A?P is engaged and active, the flight plan has been checked and confirmed without any discontinuations and that all preflight entries for the FMC has been populated when this occurs.Hope it helps,

[bsmonroe 0]

Mats,I do apologize - I actually was referring to LNAV.This is a flight from KSEA to KSFO. Default Weather is used - (with the option "update every 15 minutes for real weather" checked) - FSUIPC is the latest version (as of March 5th).All preflight in the FMC has been done and no blank fields are input. Compass is set to NORM (not TRUE). I screwed up when aligning the IRS so that only the Right IRS was aligned (still can't remember to right click the knobs!) - but that shouldn't make a difference. This happens no matter which IRS is used.After takeoff - LNAV/VNAV is engaged - display shows "CAPTURE" but track is already off. (Range is set at 40).http://forums.avsim.net/user_files/186277.jpgIt gets worse as we proceed between the waypoints.http://forums.avsim.net/user_files/186278.jpgApproaching WANTA we begin to move closer to the "track"http://forums.avsim.net/user_files/186279.jpgWe intercept WANTA - but not on track - and immediately begin our turn. However, FSX and FSC report that we did NOT fly over or intercept the waypoint.http://forums.avsim.net/user_files/186281.jpgThis is a shot after leaving WANTA with the range bumped up to 20NM - you can see the extent of the deviationhttp://forums.avsim.net/user_files/186282.jpgAnd (with the range turned back to 40), you can see that as we approach LTJ, we once again draw closer to the track.http://forums.avsim.net/user_files/186283.jpgOn more than a few occasions, the plane flew so far off the track that even the FMC realized that the waypoint was missed - so the aircraft turned AROUND, flew a 180 over the waypoint, and then continued back on course! Fuel planning is out the window.(By the way, even the VNAV does some strange things: the aircraft will climb steadily at 1800 FMP - then suddenly will zoom into 5100 feet and then suddenly level back to 1800 FMP. This appears to occur because of the thrust setting - but it is a little jarring.Hope this helps - I would love to be able to fly the aircraft!Brian

[bsmonroe 0]

*blushing* Almost forgot: This is FSX running on Windows Vista Ultimate 32 with SP2.This is an AMD 64 Dual Core processor, 4GB memory, 200GB Hard Drive.

[Mats_J 2]

Brian,Looking at your screen shots I notice some things. You have BO AUTOLANd which I guess is due to the IRSs not being properly aligned.Your problems with VNAV could be that you don't have A?T in any mode. See the FMA top of the PFD. The left field (A/T mode) is blank. Use TO/GA when taking off or push N1/VNAV once airborne to get into VNAV PATH mode.Your LNAV problems looks to be the same as we have encountered before. It seems the AFDS can get corrupt in some rare occasions. You might want to try a reinstall to see if this will remedy the problem.Hope it helps,

[bsmonroe 0]

Mats,I will test it.Brian

[bsmonroe 0]

I am convinced I have a corrupted AFDS.No matter what I do, pushing the N1 button will not light up the far left column. It is always blank. The lights for VNAV and LNAV come on on the autopilot panel - but it seems that there is no connection whatever to the AFDS. In fact the autothrottle doesn't work at all - even with VNAV enabled (and lit), if I back off the throttles the aircraft stalls.And even with all three columns lit up - the tracking is still way off.As soon as I get my new download link I will reinstall and see if that makes a difference.http://forums.avsim.net/user_files/186284.jpg

[Dougal 165]

Yo Brian!!!I REALLY feel for you man. I'll tell you why.........I had exactly the same issue about 6 weeks back. If you do a search for my username, you'll no doubt find at least two separate threads, with screenshots, relating to this. I got very little help on this. But, to be fair, it does seem like a very rare glitch indeed.First off.... the bad news: There was never a 'sensible' fix, or, for that matter, even an explanation of the issue from PMDG. The only suggestion given to me was a COMPLETE reistall of FSX!!! Now the really bad news..... That didn't work. Although I understand it did for someone else. Seems it only happens to that extent with some Vista installations.I was eventually told to sit tight as a patch was due out in "a few days". Well, I think that was about 4-5 weeks back now!After completely reistalling Vista AND FSX (and FS9) twice, I finally gave up on Vista, and reisinstalled my Windows XP-Pro!! Never a problem since, that hasn't been of my own making.In all honesty Brian, unless something has changed since then, from my experience, I wouldn't go trying to 'tweak this' or 'tweak that' in the hope of fixing it. For me, that just made things even worse I'm affraid.Sorry to dampen things even further for you, but it IS the same problem. Go find my posts and see.PS..... See Ryan - told you it wasn't a one off!

[tf51d 284]

>Yo Brian!!!>>I REALLY feel for you man. I'll tell you why.........>>I had exactly the same issue about 6 weeks back. If you do a>search for my username, you'll no doubt find at least two>separate threads, with screenshots, relating to this. I got>very little help on this. But, to be fair, it does seem like a>very rare glitch indeed.>>First off.... the bad news: There was never a 'sensible' fix,>or, for that matter, even an explanation of the issue from>PMDG. The only suggestion given to me was a COMPLETE reistall>of FSX!!! Now the really bad news..... That didn't work. >Although I understand it did for someone else. Seems it only>happens to that extent with some Vista installations.>>I was eventually told to sit tight as a patch was due out in>"a few days". Well, I think that was about 4-5 weeks back>now!>>After completely reistalling Vista AND FSX (and FS9) twice, I>finally gave up on Vista, and reisinstalled my Windows>XP-Pro!! Never a problem since, that hasn't been of my own>making.>>In all honesty Brian, unless something has changed since then,>from my experience, I wouldn't go trying to 'tweak this' or>'tweak that' in the hope of fixing it. For me, that just made>things even worse I'm affraid.>>Sorry to dampen things even further for you, but it IS the>same problem. Go find my posts and see.>>PS..... See Ryan - told you it wasn't a one off!It's not only Vista, I running Win XP FSX SP1, and the same thing happens, it is really bad on trans-atlantic flights. I even posted a Video of it a while back, and was told, there was work on the LNAV in an upcoming patch/service pack and it should be better. My 744x has been in the maintenance hanger since, awaiting this patch. Here's the video!http://youtube.com/watch?v=ZDkX9aOHXqk

[Dougal 165]

Wow! That's the first time i've seen it that bad on XP. I know the issue is there with XP, but on mine it's to a much lesser degree - certainly close enough for transatlantic flights.Ryan....... PLEASE???? What's the score on the update? Weeks back you told me "a few days"!

[tf51d 284]

It gets that bad when waypoints are far apart, that's why it's especially bad with trans-Atlantic flights. If way points are within a few miles it's not that bad. Noticable but not that bad., Similar to the screenshots above!! It also won't look as bad if you have the ND range greater than minimum.

[Dougal 165]

I see that yet again, just like the last time this issue came up, there's a resounding silence from PMDG.I think this page is should be renamed..... *PMDG - Users Helping Users* ;-) 'cos without some of you guys here, I'd be grounded a lot more often.

[bsmonroe 0]

Complete reinstall (including a complete UNinstall first using the uninstaller - not deleting files) has accomplished nothing. The same strange problems persist: bizarre behavior when using the VNAV and LNAV (holding at 1800FPM with sudden forays into 5100FPM and not being able to hold course).This problem is only occuring with PMDG aircraft - all other add-on aircraft are working fine.Oh well - maybe someday....(Of course, it is made clear that PMDG recommends XP and SP1 during the install - and I am running Vista and SP2 so I have no beef with PMDG.)