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Strange LNAV Problem

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flilot View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flilot Quote  Post ReplyReply Direct Link To This Post Topic: Strange LNAV Problem
    Posted: November-20-2007 at 12:32pm
The past few days, I've had a trange LNAV issue with the ATR.  It appears that whilst LNAV mode is selected on the AP, the aircraft cannot follow the flightplan between waypoints in a straight line.

The aircraft swings to the left, even though the flightplan, and the flight director, are both telling the aircraft to align in the opposite direction. This is illustrated below:



The aircraft then realises its heading in the wrong direction, and heads back to the right...

The aircraft then seems to think that it has over compensated in the turn, and swings back to the left, ad infinitum.  A better illustration is the map of the flightplan, as flown by the aircraft:



The aircraft has been fine up until now.  No new addons or configuration changes have been made to FSX.  The flight above was between Helsinki Vantaa EFHK and Jyvaskyla EFJY.

Any ideas are welcome!
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Jarmo Stenvall View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jarmo Stenvall Quote  Post ReplyReply Direct Link To This Post Posted: November-21-2007 at 9:34am
I also have same issue with autopilot, and I have no idea what is causing that. Cry Only few flights has gone well so far, when autopilot has been able to navigate straight line betveen two NAV points...


By the way, I have FSX version of ATR 72-500


Jarmo
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Hans Hartmann View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hans Hartmann Quote  Post ReplyReply Direct Link To This Post Posted: November-24-2007 at 3:25pm

I think updating the magvar.bgl file (magnetic variations) could cause problems like that. Did you do something like this?

Best regards,
Hans
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flilot View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flilot Quote  Post ReplyReply Direct Link To This Post Posted: November-24-2007 at 3:48pm
No I haven't.

Also, the flights after the problem seem to be going fine.  Just EFHK to EFJy seems to  have the problem at present.
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Aaron EIWF View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Aaron EIWF Quote  Post ReplyReply Direct Link To This Post Posted: November-28-2007 at 4:28pm
I believe that this LNAV problem is caused by pushing the reset on the standby ADI. Once i stopped doing this the LNAV went back to normal.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flilot Quote  Post ReplyReply Direct Link To This Post Posted: November-28-2007 at 5:36pm
I've never done that, either.
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ptisinge View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ptisinge Quote  Post ReplyReply Direct Link To This Post Posted: December-09-2007 at 7:19pm
I've never pushed the reset, but I'm getting a terrible LNAV during every flights I've tried since Acceleration pack. Before that I used the ATR and had no problem at all, now it's just impossible to fly the ATR in LNAV (not to mention that I can't fly the VC during rain because of the blue texture). I hope there will be a fix for that because my ATR is just not functionnal at all anymore
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Hans Hartmann View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hans Hartmann Quote  Post ReplyReply Direct Link To This Post Posted: December-10-2007 at 3:44am

flilot,

can you post the exact flight plan please? I'm very busy these days (as you can see from the time I need to answer) but I will try that flight again with VC++'s debugger running. Perhaps I'll be able to find the reason (if I can repro the problem at all)

Best regards,
Hans
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ptisinge View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ptisinge Quote  Post ReplyReply Direct Link To This Post Posted: December-10-2007 at 6:04am
Is it something happening only to people with Acceleration expansion or is anybody having the problem only using SP1?
If it's an Acceleration problem only, I might try to use a double install, XP SP1 and Vista Acceleration so that I can still play the ATR when I want...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flilot Quote  Post ReplyReply Direct Link To This Post Posted: December-10-2007 at 3:10pm
Hi Hans,

You can download the flightplans from this link (I saved them into Flight Simulator X PLN files):
Download Flightplans

Thankyou for your time looking into this.

Regards,
Carl
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ptisinge View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ptisinge Quote  Post ReplyReply Direct Link To This Post Posted: December-10-2007 at 4:33pm
Is that FSX SP1 or Acceleration Flilot?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flilot Quote  Post ReplyReply Direct Link To This Post Posted: December-10-2007 at 5:35pm
FSX SP1
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ptisinge Quote  Post ReplyReply Direct Link To This Post Posted: December-10-2007 at 8:02pm
OK, thanks Flilot. That's bad news for my plans. I guess I'll make more tests to see whether that happens all the time or not. In my case it happened during two attempts to fly YSSY to YBBN. When LNAV was activated after TO, the plane immediatly went far toward the left while the FD was pointing far on the right. I solved the problem by flying with HDG, which caused no problem (no oscillation at all), then back to LNAV, which worked for 10 minutes before going far on the left again.

My flight path looked like yours Flilot: I oscillated but always toward the left side just as it seems the case for you.

Could it be any FSUIPC issue? Which version are you using Flilot? I'll check which one I have when I ll be back home tonight.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote flilot Quote  Post ReplyReply Direct Link To This Post Posted: December-11-2007 at 8:50am
I have FSUIPC 4.20 for FSX
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Hans Hartmann View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Hans Hartmann Quote  Post ReplyReply Direct Link To This Post Posted: December-11-2007 at 2:45pm
FSUIPC is not used in the FSX version, so that can't be the problem. I'm goign to check the flight plans tomorrow evening.
Best regards,
Hans
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ptisinge View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ptisinge Quote  Post ReplyReply Direct Link To This Post Posted: December-11-2007 at 7:02pm
Thanks for looking into that Hans.
The only thing I am a little bit worried with is that it never did that with the YSSY to YBBN route before (I flew this one many times), so if there's something special to be found in the flight plan file, why would it show up only now?
I have FSUIPC 4.20, and my problems appeared after installing Acceleration, FSUIPC 4.20 and PMDG 747X. These are the only things that were installed between my last working flight and the LNAV problems. I'll try other routes I'm used to fly often to check if LNAV works fine or not there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ptisinge Quote  Post ReplyReply Direct Link To This Post Posted: January-07-2008 at 1:39am
I didn't have much time to make lots of tests, but I had 2 flights with no problem in France, while I had a total of 5 flights with the problem present while flying in Australia. On YSSY YBBN, standard FS flight plan imported, I get the plane doing this terrible shilf on the left at each  waypoint. I noticed that on another flight toward Townsville, the problem ceased after the first waypoints.
If you want to test my most problematic flight, try a default flight plan from MS FSX, YSSY-YBBN high altitude route, that's always resulting into LNAV problems for me.
Thanks for the help Smile
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Post Options Post Options   Thanks (0) Thanks(0)   Quote druidnz Quote  Post ReplyReply Direct Link To This Post Posted: February-10-2008 at 8:48pm

I have had this same problem, I am using the ATR to fly routes around New Zealand. One thing that really puzzles me is that it seems to happen more often when heading north, heading south seems to work just fine.

A default IRF route from NZDN to NZCH seems to always cause this problem.

It has never worked since the day i purchased the product, and while i am still really happy with it, just a little frustrating that i can only fly south using the LNAV.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote flilot Quote  Post ReplyReply Direct Link To This Post Posted: February-18-2008 at 11:36pm
Hans, did you ever get the chance to look into this?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Jørgen Quote  Post ReplyReply Direct Link To This Post Posted: February-21-2008 at 3:10am

Hello Flilot

Maybe I am wrong, but:

I can see that your heading is 330, so I assume that you have been flying on that heading not using LNAV. Then you select LNAV, and the aircraft doesn't fly according to the flightplan.

What happens if you in the FMC put the next waypoint on your flightplan into the top of the legs once more?

If your are flying using HDG or manually into a line between two waypoints and then select LNAV, my suggestion works.

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