Wind Smoothing and PMDG 744X

[John Veldthuis]

I have no trouble at all unless I use ASX with real weather and then only when descending. Once I get down to around 14,000 the plane seems to have a mind of its own and even the autopilot can not keep it straight.

Have attached a screen shot. To me winds were steady from one direction, I had suppress gusts on and 1degree/3secs.

After this screen shot I tried to get back on track but went one way then the next. As soon as I turned off the wind smoothing all was well again. As I said, Everything thru takeoff, climb and cruise and only on descent did this happen.

Had it happen two for two now.

[cshark172]

Did you have suppress turbulence for both clouds and winds on as well? I was having the same heading problems until I suppressed gusts/turbulence from to winds page, and supress turbulence from the clouds page. With all these suppressions on, the PMDG 747x held heading for me. I can report that the winds appeared to stay steady. I had smoothing set to 3 seconds per knott/degree. I am having some problems now with TAT changes of 5-10 degrees C during cruise---really causes the Airspeed to fluctuate significantly. I have the temperature smoothness set to 50, but there doesn't seem to be much difference.

One thing of interest is that the HDG problem was there in 4.217, seemed to be OK in 4.218 and is now back again. I missed the betas between 4.218 and 4.231, so not sure when it reappeard.

Kyle

[John Veldthuis]

Yes I had both turbulence and gusts suppressed in the winds tab but not in the clouds tab. Will try that and see what happens. Currently running 4.2.3.1 and did not try it before that.

[Pete Dowson]

Did you have suppress turbulence for both clouds and winds on as well? I was having the same heading problems until I suppressed gusts/turbulence from to winds page, and supress turbulence from the clouds page. With all these suppressions on, the PMDG 747x held heading for me.

In the next update (4.232), probably later today, I have separated the directional variability from the turbulence, with its own suppression option defaulted ON. I'm anxious to learn if it is the +/-2-8 degree fluctuations in wind direction which are upsetting the 747X, or just the frequent small changes in turbulent conditions all round. I'd like to discuss this with PMDG when we have some conclusions.

So, perhaps more tests with the 747X but with cloud and wind turbulence allowed, variance suppression left defaulted, will show us more.

I've also raised both the QNH and OAT smoothing to more prominence, fitting them onto the "Miscellaneous" page. Not enough about these for a page to themselves! ;-)

Later

Pete

[Pete Dowson]

In the next update (4.232), probably later today ...

Okay, 4.232 is available now. Please change to that. The "variance" is now suppressed by default, separately from the other wind effects. I need to find out what component of all this is upsetting the PMDG 747X autopilot's lateral control -- is it wind smoothing itself, with the effects being irrelevant, or is it wind variance, or turbulence, or is it completely indeterminate (as it would appear to be from the results so far reported here)?

Once I know what is causing it (and I am asking PMDG to help here too) I might be able to allow for it somehow, but the way things appear to be at present, with it being unpredictable, I would have to document a warning to all PMDG users to avoid the facility altogether. And of course I'd rather not do that.

Oh, you can play more easily now with pressure and temperature smoothing (on the Miscellaneous page). And the turbulence amplitude is adjustable by an INI parameter (but not in FSX whilst flying). I've turned it down by default to half what it was -- down to its value in 4.217.

Looking forward to some really insightful analytical feedback, if you can manage it! Not pictures, please, I prefer words unless there really is no way to describe something.

Thanks & Regards

Pete

[John Veldthuis]

Okay that seemed to do it for me. Did a flight from SBNT to FHAW and while there was a couple of jumps in airspeed while climbing the cruise was fine. Descent was also fine with a couple of small pushes of to either side but barely noticeable.

Had all three suppressions on in the winds and turb in the clouds.

[Pete Dowson]

Okay that seemed to do it for me. Did a flight from SBNT to FHAW and while there was a couple of jumps in airspeed while climbing the cruise was fine. Descent was also fine with a couple of small pushes of to either side but barely noticeable.

Had all three suppressions on in the winds and turb in the clouds.

Other reports seem to indicate that the only option causing a problem is CLOUD turbulence, so you could try allowing all the other stuff except that.

If this turns out to be correct (and I don't understand it at present), then maybe I should change the defaults, allowing Variance but suppressing cloud turbulence only.

I'd like to get to the bottom of it though. I'll be doing some experiments on this, probably Monday now.

Regards

Pete

[Pete Dowson]

I'd like to get to the bottom of it though. I'll be doing some experiments on this, probably Monday now.

I've done some experiments and made some changes to the way the turbulence is handled. Please see if version 4.233, now available in the FSX Downloads announcement, is better.

Regards

Pete

[Pete Dowson]

Please see if version 4.233, now available in the FSX Downloads announcement, is better.

FSUIPC 4.234 is now up and waiting for you. The main change is that it tries much harder to eliminate the silly spurious thin wind and temperature layers.

Regards

Pete

[Pete Dowson]

I tried to reproduce the wind direction swings without success. But in the process i spotted a couple of areas where I could improve things somewhat.

So, please move on to version 4.235 for further tests.

This is becoming a daily thing, isn't it? It's certainly a lot of work!

Regards

Pete