737 BBJ rough turns

[Mike.cbr]

Good evening PMDG

Since the latest update (realeased yesterday) at least the 737 BBJ , don’t know about other variants cause I haven’t try it, the turns on air between points are so rough now against the other update wich it was a lot smoother. I’m 100 sure something has been changed cause I usually check this kind of things and it wasn’t happening from a long time ago. I beg you please to check this for me cause there is something wrong now or something that you have changed and you beta team didn’t notice.
Thanks in advance and I’ll be waiting your answer.

kind regards

[JonSleeper]

I've had this problem in the 738 on a couple flights so far. At one point it way overshot the magenta line on approach after a turn. The course lines on the map between points sometimes don't connect. I should note I'm on the AAU2 beta.

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[Mike.cbr]

I would like to see an answer from PMDG team since I tried to open a ticket and it is no possible , this is the only way I guess….. thank you. cmakris

[Emi]

The course lines on the map between points sometimes don't connect.

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This is a case of you asking the plane to do things that it can't do.
It can't take the turn at the speed you command it to do.
Solution: Reduce your target speed by inserting a speed restriction at the waypoint which doesn't connect.

[cmakris]

I would like to see an answer from PMDG team since I tried to open a ticket and it is no possible , this is the only way I guess….. thank you. cmakris

There are changes on the roll channel but there none of the betas as far as I am aware complained that is to rough now

[Mike.cbr]

There are changes on the roll channel but there none of the betas as far as I am aware complained that is to rough now

we’ll definitely there is something off , it specially happens on cruise , just compared on two different pc cause my brother has the PMDG also but not with the latest update , same time , weight , route , BBJ and FL and the latest update it’s so rough on turns on cruise. No doubt something is off. Please check this since now it’s worse.

kind regards

[DDowns]

we’ll definitely there is something off , it specially happens on cruise , just compared on two different pc cause my brother has the PMDG also but not with the latest update , same time , weight , route , BBJ and FL and the latest update it’s so rough on turns on cruise. No doubt something is off. Please check this since now it’s worse.

kind regards

As Chris said, none of us betas saw anything like you are describing although I'm not exactly sure what "rough on turns" actually means. We have seen a very slight twitch in the roll out on the new course that is the AFDS making fine adjustments and a few of us thought it was troublesome but I found it to occur without a pattern. To me, a "rough" turn implies a jerky roll into or roll out of a turn and no other users have reported this. I've flown this build in beta and since release almost daily.... I don't see rough turns. There is no way to "check this" if we don't see it.

The most likely suspect is your controller or there are MSFS assists enabled.

[Dave5150]

I noticed this as well. At first I thought it was turbulence, but the turns are all very jerky, no longer smooth. It would be nice to downgrade to the previous version until they fix the bugs.

[DDowns]

I noticed this as well. At first I thought it was turbulence, but the turns are all very jerky, no longer smooth. It would be nice to downgrade to the previous version until they fix the bugs.

Still looking for a description of the "bug." There is a tendency to see a problem report that has never appeared before and suddenly others see it too.

Full name on all posts here please Dave5150 this is a rule we all agreed to when we joined the forum.

Perhaps it would be constructive if there were a video of the AFDS actions during a course change in LNAV mode. Let's see what you guys are trying to explain.

[teropart]

Very interesting. I agree with turn roughness in current release. Flew 3 flights yesterday (my commendations to dr Vaos for very good AP behavior in single engine ops, did OEI approaches and go-arounds, and it is very good), one thing I did see was sort of spikiness just as the turn commences. Once I think it twitched left and then started right turn per fpl. I also notice a kind of ”notch” just before the wpt where it almost resets or recalculates everything for the turn. This was ”rough” compared to earlier situation

[Mike.cbr]

Yeah same as what teropart and Dave5150 said , it usually happen during cruise , sometimes when the turn commences is so hard , like it does it very abrupt , and even when it still on the turn it recalculates and makes it more bank very hard, looks like turbulence but it’s not…. it also lose a bit of the FL Desiree also a have to say that on the turn I can see the problem that we had a long time ago that the aircraft is bouncing a bit up and down up and down , but less than the problem we had a while ago. Happen on every single turn….. DDowns cmakris

[DDowns]

Yeah same as what teropart and Dave5150 said , it usually happen during cruise , sometimes when the turn commences is so hard , like it does it very abrupt , and even when it still on the turn it recalculates and makes it more bank very hard, looks like turbulence but it’s not…. it also lose a bit of the FL Desiree also a have to say that on the turn I can see the problem that we had a long time ago that the aircraft is bouncing a bit up and down up and down , but less than the problem we had a while ago. Happen on every single turn….. DDowns cmakris

This is not what I see at all, never. By any change did you not turn off the MSFS Turbulence setting? Another rated pilot has commented that if a real AFDS encountered the unrealistic MSFS it would disconnect and perhaps do airframe damage.

[Mike.cbr]

This is not what I see at all, never. By any change did you not turn off the MSFS Turbulence setting? Another rated pilot has commented that if a real AFDS encountered the unrealistic MSFS it would disconnect and perhaps do airframe damage.

Well none of PMDG said we have to turn msfs turbulence off , they just post some little changes and no advise from them so why should we ? even if that is true, why should we turn off msfs turbulence and not PMDG adjust his airplane to the platform like everyone else ? Also I have to say as other people are saying that before this update turbulence was on and (msfs settings the same as I have it now) so there is a problem in your side (PMDG). If everything was ok and after the update is not for so many people something is wrong.
Thanks

[teropart]

I have turbulence on Low setting. Was not an issue before. Likely not now either, the roll channel has just changed a bit

[DDowns]

Well none of PMDG said we have to turn msfs turbulence off , they just post some little changes and no advise from them so why should we ? even if that is true, why should we turn off msfs turbulence and not PMDG adjust his airplane to the platform like everyone else ? Also I have to say as other people are saying that before this update turbulence was on and (msfs settings the same as I have it now) so there is a problem in your side (PMDG). If everything was ok and after the update is not for so many people something is wrong.
Thanks

MSFS added the turbulence setting at least two system updates ago. True, the Introduction document has not been edited to reflect this.

The problem is neither I nor any other beta test sees the same issue you are reporting. I do not doubt what you see, I am only trying to understand why you and a few others see it but it's not been reported up to now. This is why I asked earlier for a video recording..... this will give the support team something to work with other than the descriptions I've seen so far.

Right.... lets get rid of the custom AFDS coding and use the defaults like everyone else except Fenix that does it's processing completely outside MSFS..... please be realistic.

Let's define the problem and go from there. Show what you are seeing so others that don't see it can grasp what is being said.

[Helibrewer]

I would say roll is slightly more aggressive but it is not problematic, at least for me.

[Stearmandriver]

LNAV roll guidance was too aggressive to start with; if it's worse after this update that's all the reason I need not to take the update. Thanks for the reports.

The actual airplane rolls very smoothly into and out of constant bank turns in LNAV. Why wouldn't it? It's not as though it's waiting to react to needle sensing or something like capturing a localizer; the FMC knows exactly where the airplane is, exactly where the course segment is that it needs to be on, exactly the groundspeed and wind... It has all the variables necessary to calculate how to complete a turn smoothly.

The PMDG has always had a tendency to twitch aggressively back and forth in bank during the turn, sometimes rolling the wrong way before going the correct one. The flight guidance itself does this even more aggressively which is super weird, as the flight director and auto flight inputs are generated by the same computer and so should always match exactly (in other words, the autopilot will always keep the FD perfectly centered.)

I really do hope they get this sorted eventually (not to mention RF leg support.). It's one place where the PMDG code really does not stack up favorably to other devs like Fenix. 737s simply don't behave like this.

[Togapiloto]

I'm glad to see others have noticed the very jerky AP turns that to me seem to have gotten worse since this last update. Instead of the normal smooth rolling into and out of turns, the AP now forces a very hard roll into and out of turns.Rolling out it reduces bank until almost to level flight and then jerks out of the last few degrees of bank. This happens whether the turn is ninety degrees or just a few degrees along the LNAV path.

I sure hope this can get sorted out because it really is not realistic (unless your flying an F-16).

Lynn Lawless

[DDowns]

LNAV roll guidance was too aggressive to start with; if it's worse after this update that's all the reason I need not to take the update. Thanks for the reports.

The actual airplane rolls very smoothly into and out of constant bank turns in LNAV. Why wouldn't it? It's not as though it's waiting to react to needle sensing or something like capturing a localizer; the FMC knows exactly where the airplane is, exactly where the course segment is that it needs to be on, exactly the groundspeed and wind... It has all the variables necessary to calculate how to complete a turn smoothly.

The PMDG has always had a tendency to twitch aggressively back and forth in bank during the turn, sometimes rolling the wrong way before going the correct one. The flight guidance itself does this even more aggressively which is super weird, as the flight director and auto flight inputs are generated by the same computer and so should always match exactly (in other words, the autopilot will always keep the FD perfectly centered.)

I really do hope they get this sorted eventually (not to mention RF leg support.). It's one place where the PMDG code really does not stack up favorably to other devs like Fenix. 737s simply don't behave like this.

I will not disagree with you Andrew, LOL I'm not even type rated, but I want to explain how what you describe as the function of the FMC in executing a turn differs from my understanding. First of all, this thread contains as many different statements of a problem as there are contributors going from "rough turns" to twitchy, or spiky to your aggressive. My literal engineering mind interprets these all differently and that's why I asked for a video so both the beta team and Dr EMV could see what is the reported issue.

"flight director and auto flight are the same computer so should always match perfectly," implies that there should never be a deviation of the FD steering needles from aircraft commanded pitch and roll. That is interesting. The lateral path that the AFDS is following is created by the FMC computer and it is the AFDS that "chases it." The AFDS cannot anticipate, it only follows. This was the major change when we went to LNAV V2.0 what seems like an age ago. LNAV V1 was created in the days of FS2004 where we didn't have the computing power of today and that LNAV created a lateral path based on what was achievable with the early AFDS and that early AFDS didn't try to follow the lateral path exactly but approximately to the extent that the path was sort of like the RMS value of the individual segments. This is not how the real systems work. PMDG got closer to the real systems with LNAV V2.0 where now the FMC creates the lateral path one segment at a time and the AFDS by PMDG endeavors to always minimize cross track error (with allowances that reduce the twitch between segments and allow a smooth reduction of a cross track error in excess of 0.10 nm). I think EMV's challenge now is a balance between how the FMC path calculation accommodates changes in course where it must construct the turns path and the AFDS that blindly follows the change from straight segment to an arc path to another straight segment.

I though we were pretty close when we tested B0069, a few of us noted the twitch when rolling out on the new track and there was even some discussion over how significant it was. I didn't think it was significant and I guess PMDG didn't either because there were no changes on release. This is the backstory on why I've asked the contributors to this to document with video.... let's see it.

As for the aggressive roll into and out of a turn I cannot comment. I interpret what you are saying as PMDG initial roll rate is too high and the roll rate should increase from level to full bank value in a smoother manner, ramp up the roll rate so to speak such that maximum roll rate is halfway to the maximum bank perhaps. That very well could be because the FMC calculated track during the change in heading is too circular and what might be required is a more hyperbolic, or simply the radius of the turn be larger?

[Stearmandriver]

I can't comment on this latest update as I haven't tried it (and probably won't, based on what I'm hearing.). So my comments are directed at the previous version, which does incorporate LNAV 2.0.

I often see flight guidance that "bumps" or "spikes" back and forth during a turn, sometimes even leading with a turn in the wrong direction before bumping back in the correct direction. Effectively, this results in the PMDG staying mostly on the LNAV path, but not in a smooth manner. There are constant fairly aggressive adjustments in bank angle, and the appearance is that the aircraft is indeed "chasing" the lateral path - and having trouble doing it. This often also results in displaced flight guidance which the autopilot then seems to try to follow.

In the aircraft, the lateral path is generated by the FMC and handed to the master FCC. The FCC generates both the autopilot AND flight director commands, so the two sets of guidance are equal. Effectively, this means that there is never (excepting some instantaneous displacements from significant turbulence) a time when you see a flight director displacement while the autopilot is flying.

As far as following a lateral path, there is no sense of the aircraft chasing anything, as it knows well in advance in LNAV where it's going to turn. While I'm sure the path is recalculated continuously during the turn, functionally the aircraft smoothly rolls into a set bank angle and stays there until it smoothly rolls out. To borrow a term from the sim world, the effect is very much "on rails". You can see this in any video of a 737 flying an RNAV procedure.

I only mention it on a desire to make the PMDG better; I'm not trying to play "gotcha.". The PMDG 737 is still, in its present state, leaps and bounds above anything I'd ever have expected to see on a desktop sim. This is just one area where it could improve.

[Dave5150]

Guys, can we roll back to the previous version? This version really misses the mark. LNAV used to be so smooth, now it's like a toddler is at the controls.

[David Whittington]

For version 3.0.69 of 737-700, I agree that there is a lack of gradual bank into and out of a waypoint turn of 40 degrees of heading change or so. I am testing out of SEATAC (KSEA) at 2000ft on climbout at 240 knots and later at 10000 feet turning back to the right which is south or so. I noticed at the start of the turn to RENBE a bank of maybe 5-20deg, a quick return to almost level and then a resumption of the full bank.The same kind of a "bump" happened upon the end of the turn to waypoint I have MSFS turbulence at the low setting and have done this particular route (one that I fly going south back to San Diego - in real life as a passenger as well) - 16L over closer to Mt. Rainier and then toward Mt. Hood many times as it is beautiful in VR. I don't believe it did this in the previous version.I am not on any MSFS beta.



Dave Whittington
[email protected]+RTX3080ti

[Bart]

Noticed the same issue yesterday flying the 737-700 and 600. Rolling into and out of turns in the cruise is not smooth anymore.