B747-400 Heading problem (LNAV) on FS9

[Guest B744F]

Hello !I have a problem with my B747-400 PMDG, when I engage the LNAV, the plane continue to follow the purple line, then suddenly, it starts to turn to the left, after to turn to the right, etc... and don't follow the route anymore.Please help me ! :'(

[yos233 1]

Its a freaky little bug that everybody seems to think is the wind (I for one do not belive this at all), you put it on manual heading hold for a few minutes and then reset LNAV.

[MrPlaneDriver 41]

(...) you put it on manual heading hold for a few minutes and then reset LNAV.

It has already happened to me just once. I did exactly what Eric said and never happened again. I also don't believe this bug is due a wind matter.

[Guest B744F]

Well I tried a flight...I did what you said, but the plane miss the waypoint during the LNAV engaged and after he tried to go back to take it...And like that, it's impossible to do a normal flight on time...Well... I'm going to be crazy !... I noticed that the plane isn't correctly aligned when I start immediately on the runway, and on the gate too...I don't know why it is the only plane who have this problem ! So thank you for your help, but I need to fix this problem, because I'm irritated right now and I want to fly my Boeing 747 !!!If someone can help me, please it will be very nice !

[MrPlaneDriver 41]

I don't know about FS9, but the Active Sky Evolution causes exactly the same problem in FSX. Many people who use this software together with PMDG aircrafts complain about this bug. I've read in this forum by a PMDG developer that the way which ASE uses FSX's weather engine affects the control of airplanes with high-fidelity autopilots.Here is what the developer said and his suggestion to stop this:

The issue is the fidelity of our autopilot combined with the way ASE controls wind in FSX - it's been very well documented both here and at HiFi's forum. Basically, their weather engine is injecting tons of tiny microscopic windshifts using FSX's turbulence feature every second to keep things "on track" - this is invisible on the Shift-Z wind display because they happen so quickly that it doesn't log them in its polling period. Most lower fidelity autopilots don't see them, but ours does and it can confuse it. Making the AP not respond to them would cause other aspects of the flight model to become less realistic and we elected not to change anything. FS9 doesn't have the issue because its turbulence modelling is different. The turbulence in FSX is really unrealistic, it often creates 2-3G accelerations on the aircraft, which is on the extreme end of severe turbulence in real life and is very uncommon.What you can try is checking "Disable Turbulence and Thermal Effects on Aircraft" in the FSX weather options, and check Suppress Turbulence in FSUIPC's weather options. This seems to mitigate most of the issue in lieu of a change to the way HiFi smooths wind.

Although he says it doesn't happen in FS9, won't hurt if you try. Perhaps it works.Then post the results.

[Guest B744F]

I have reinstalled FS9, and installed only the PMDG 747-400.Now on fs9 I have FS9.1, PMDG747-400 V1.2, IVAO and FSUIPC 3.93 installed with IVAO and unregistred version.But the plane continues to go off the route...On FSX, I didn't use any software for the weather, I have only other aircrafts like wilco, captain sim,... only planes add ons.

[downscc 1,327]

Full names in this forum please.Does the problem continue if you clear all weather? If so, get a registered copy of FSUIPC and use it to smooth the weather variations (both FS9 and FSX have the same problem). It is a very common problem with the realistic automatic flight systems found in the pmdg simulations, the default and other add-ons not so much.

[Guest B744F]

Hello,My full name is Hartz C

[miguelpp 25]

Hello,My full name is Hartz C

[downscc 1,327]

Time for some screen shots taken without weather and with the LNAV errors so we can see what you see. There's not a known heading bug, but there is a reason for what you are experiencing and now time to figure that out.

[Tabs 2,790]

EDIT - Hartz, I just saw your screenshots you attached to your support ticket. Please read my reply carefully, you're not configuring the aircraft correctly at all.

[Guest B744F]

Tabs, it was to show you screenshots, so I did a "fast flight".So I did the registry from Flight one and it works now, thank you !

[Tabs 2,790]

Ok, so it was the magvar issue then... thanks.

[pride545 30]

Full names in this forum please.Does the problem continue if you clear all weather? If so, get a registered copy of FSUIPC and use it to smooth the weather variations (both FS9 and FSX have the same problem). It is a very common problem with the realistic automatic flight systems found in the pmdg simulations, the default and other add-ons not so much.

That is ther second time u have said something about full names and everyone on the post has signed their full names. What's up?

[Guest B744F]

And I forgot to say thanks to all people who tried to help me ! :DHave a nice flight !