747X nodding up and down in flight

[engwerda 0]

On any given flight with the 744X once at cruise my 747X will not maintain stable flight. With LNAV and VNAV armed and operating it descends at 100 fpm down and the 100 fpm up in the time it takes to say it. I have REX 2 but no weather is enabled and there are no other weather programmes operating. FS weather is set to predictable with no winds aloft. I do not have a registered copy of FSUIPC.Anyone else have this problem? I no longer use VNAV in the descent phase because of the rollercoaster on the way down with +2000 fpm and - 1500 fpm common. FLTCH handles it much better and then I can usually re-engage VNAV below 10,000 but often just use VS to achieve the same result. Is there a fix for these cruise oscillations though? The anomalies in the VNAV descent phase I can live with although the LDS767 for FSX never does this however the "nodding" up and down in the 747 cruise phase is most disappointing and off putting. Gerry

[MrKen 3]

On any given flight with the 744X once at cruise my 747X will not maintain stable flight. With LNAV and VNAV armed and operating it descends at 100 fpm down and the 100 fpm up in the time it takes to say it. I have REX 2 but no weather is enabled and there are no other weather programmes operating. FS weather is set to predictable with no winds aloft. I do not have a registered copy of FSUIPC.Anyone else have this problem? I no longer use VNAV in the descent phase because of the rollercoaster on the way down with +2000 fpm and - 1500 fpm common. FLTCH handles it much better and then I can usually re-engage VNAV below 10,000 but often just use VS to achieve the same result. Is there a fix for these cruise oscillations though? The anomalies in the VNAV descent phase I can live with although the LDS767 for FSX never does this however the "nodding" up and down in the 747 cruise phase is most disappointing and off putting. Gerry

Mine does that too, but only about +/- 75' from the target path. Descent is worse as you mentioned. It doesn't sound like the sudden windchange problems, those are usually a lot more pronounced and also affect lnav. Most people just use flch at te beginning of their descent to get it stabilized.

[engwerda 0]

So this is an undocumented "bug" is it? Thanks for the reply Kenneth but I cannot believe that you and I are the only ones to experience this! Any chance of a fix or a service pack do you think? Gerry

[MrKen 3]

So this is an undocumented "bug" is it? Thanks for the reply Kenneth but I cannot believe that you and I are the only ones to experience this! Any chance of a fix or a service pack do you think? Gerry

There will be no updates to the 744. There's a rumor that they may to a whole new version, but I haven't bothered to do a search & confirm it.Basically yeah, it's just one of those things you just have to deal with as far as I know. I've never read about any sort of fix for it.

[guy 24]

So this is an undocumented "bug" is it? Thanks for the reply Kenneth but I cannot believe that you and I are the only ones to experience this! Any chance of a fix or a service pack do you think? Gerry

You are not the only one.I and many others also experience the ROLLERCOASTER especially during descent!Make a search for "oscillation" in the forum and you will see. For example here where Mr Randazzo himself acknowledges the problem and tries to blame the weather :http://forum.avsim.n...__fromsearch__1 I also think that we have to live with it!Fortunately it's otherwise a superb plane ! Guy

[MrKen 3]

The temperature variation mentioned by rsr is interesting. I've never watched it closely enough to notice.

[fstulm 4]

Hello all I also see that unpleasant/unrealistic oscillation in cruise level without any weather at all. Very dissapointing in deed. LEVEL-D 767 does not do this, nor does 737. Another very nasty issue is the erratic aileron/yoke vibration as the airplane takes turns with AP engaged in heading select for example. Just look at the controls and yoke while requesting a larger heading change and/or heading hold after has started turning. John Gabriel

[sheepfu 3]

On any given flight with the 744X once at cruise my 747X will not maintain stable flight. With LNAV and VNAV armed and operating it descends at 100 fpm down and the 100 fpm up in the time it takes to say it. I have REX 2 but no weather is enabled and there are no other weather programmes operating. FS weather is set to predictable with no winds aloft. I do not have a registered copy of FSUIPC.Anyone else have this problem? I no longer use VNAV in the descent phase because of the rollercoaster on the way down with +2000 fpm and - 1500 fpm common. FLTCH handles it much better and then I can usually re-engage VNAV below 10,000 but often just use VS to achieve the same result. Is there a fix for these cruise oscillations though? The anomalies in the VNAV descent phase I can live with although the LDS767 for FSX never does this however the "nodding" up and down in the 747 cruise phase is most disappointing and off putting. Gerry

Are you running any outside weather programs? I had this issue until I changed the depiction mode in ASE.

[engwerda 0]

Branton, No, No weather programmes running at all with FS weather set to clear at zero rate of change so I think that weather as a cause is clearly not the culprit. I can live with the nodding up and down in cruise by changing the view so it is not so noticeable but any VNAV enabled descent is out of the question. I wonder if that happens with the new NGX? regards Gerry

[Alex B. 0]

I've run into the same problem too.  I've even turned off the yaw dampers, and at one point, it held the altitude programmed in the FMC.  One thing I have noticed...when the plane is heavy with fuel, it does its up and down motion.  As you burn it off, it doesn't do it as much.  None of my other PMDG aircraft do this.  Any ideas?

[guy 24]

Hey !  This thread is almost three years old ! :smile:

I saw those PITCH OSCILLATIONS on the 747X especially during VNAV DESCENT, where they were so strong(+-300 ft/min)  that I had to use VS instead. On cruise they were only light.

Apparently not everyone sees this, but i  saw it on two different computers and at least in my case (and many others also) it had NOTHING to do with WEATHER or WIND or TEMPERATURE as it was SYSTEMATIC and happened also with weather and wind completly OFF.

As I wrote already three years ago above, I am afraid we have to live with it (and wait for the 747 V2)

 

One thing I never tried, but that you could try is to add a flight-tuning section to the aircraft.cfg(see default aircraft)  and augment the PITCH-STABILITY (to for example 1.5 perhaps).  Maybe that will help. :smile:

 

Guy

[Cooper382 21]

I have that Problem, too (with the 747-LCF Addon). The PMDG Support says that the Weather-Tool could be the reason. I'm using REX Ess + Overdrive HD.

 

I was told, to check if the Problem still exist if I choose clear Weather, but I don't have the Time to check it, yet.

[Alex B. 0]

Not too sure but looked at 2 things:

FS Pax

Trim air

I uninstalled and reinstalled the planes.  Did a test w/out FS Pax.  No issues.

Loaded up in Beijing, got to cruise FL310...started bobbin.  Killed FS Pax...no probs.  Now with FS Pax, had PMDG load map/chart/whatever you wanna call it, Lufthansa seating.  For FS9 when I load it, it has the PMDG aircraft on the load sheet, but for my FSX, it didn't, just says set up is for PMDG 744, Lufthansa seating.  Anyway got right one and will test next flight.

 

Trim air...I noticed it wasn't on.  Turned it on, and thus far as I type this, plane is flying normal at FL350.

 

Will keep ya posted.

 

BTW...using REX Overdrive/Opus for weather.

[Werner747 107]

Hi everyone,

 

the answer lies, as far as I can tell, in how the aircraft is loaded.   I use TOPCAT and and found that in some instances when I have heavy loads and a heavy fuel load, it tends to do this.   It has nothing to do with the weather though.   It has everything to do with the load.   Make sure that you check that your loads are within the C of G limits.

 

This is what solved the problem for me :-).

 

Kind regards

[Alex B. 0]

Ok, update...

Flew last nite and stll was going up & down without FS Pax running.  

Found the correct payload model.  Got it going, at cruise and doing fine.

So far.....