40 minutes ago, Bobsk8 said:

I just did an AP approach  into KOMA  using a procedure turn outbound on the LOC radial, and I forgot to reset the bank limiter back to 25,  ( it was still at 10) and I quickly noticed that the turn was going to be way too wide. I moved the limiter to 30, and the turn tighten up with no problem. So  the bank limiter works when you are on autopilot and NAV mode. 

I just checked the FCOM and here's what it says regarding the Bank Angle Selector

Quote

• sets maximum bank angle for AFDS operation in HDG SEL or VOR
modes
• commanded bank angle can be selected at 10, 15, 20, 25, or 30 degrees.

To the extent that the back course of the LOC might be considered a VOR mode, your observation is consistent with that definition. I believe that much of the discussion in this thread refers to LNAV mode, i.e., lateral navigation guidance is provided by the FMS. The referenced role of the Bank Angle Selector does not provide for its limiting the angle of bank when in LNAV mode. The FMS itself calculates the required bank angle based on the relevant conditions of flight, e.g., speed and altitude. Whether it does so correctly seems to be in question.

Agree with Jrw.  Bob did say in "Nav mode", so I'm taking that to mean VOR/LOC vs LNAV?  The bank angle selector, both in reality and in the PMDG, does not affect bank angle in LNAV.  I've specifically tested this in the PMDG.  There is (correctly) no effect in LNAV.

Maybe I am confused, I had the LNAv button lit, and it was following the waypoints in the FMC. Isn't that the LNAV mode?

9 minutes ago, Bobsk8 said:

Maybe I am confused, I had the LNAv button lit, and it was following the waypoints in the FMC. Isn't that the LNAV mode?

That is LNAV mode, you're right. In that case, the bank angle selector does not have any effect on back angle used; the FMC is calculating that.  If you saw a change in bank angle concurrent to changing the bank angle selector, it was just coincidence that the PMDG LNAV decided to make one of its abrupt bank angle corrections at the same time.

5 minutes ago, Stearmandriver said:

That is LNAV mode, you're right. In that case, the bank angle selector does not have any effect on back angle used; the FMC is calculating that.  If you saw a change in bank angle concurrent to changing the bank angle selector, it was just coincidence that the PMDG LNAV decided to make one of its abrupt bank angle corrections at the same time.

That is some coincidence, because it happened instantly in the middle of the turn, as soon as I adjusted  the bank angle switch. The aircraft went from 10 degrees to 25 degress.  You try it. 

 

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Edited February 22, 20233 yr by Bobsk8

Just to keep it simple and eliminate any confusion.

 

As it was mentioned, bank angle selector has no effect while in LNAV. 

While in LNAV, FMC will limit bank angle to max 30 degrees by FCC, below 200 ft is limited to 8 degrees, between 200 ft up to 400 ft is limited to 15 degrees and above 400ft up to 30 degrees.

4 minutes ago, Bobsk8 said:

That is some coincidence, because it happened instantly in the middle of the turn, as soon as I adjusted  the bank angle switch. The aircraft went from 10 degrees to 25 degress.  You try it. 

 

. 

I have; I've tested PMDG's LNAV more than most.  😉  Unless this has changed in a recent update (and I know of no updates to LNAV recently), the bank angle selector (correctly) does not affect LNAV.  It would not be uncommon to see the bank angle change you describe in a standard PMDG LNAV fluctuation though.

But if you prefer, just keep the bank angle selector on 25.  There's no reason to change it anyway. The only reason it's ever changed in real life is passenger comfort and convenience for the FAs who might in the middle of their service during enroute vectors; considerations that are non-existent in the sim.  But in reality it would certainly be at 25 if in heading mode in the terminal phase no matter what.

 

14 minutes ago, Bobsk8 said:

 

Again, this has nothing to do with the original issue i posted. 

On 2/21/2023 at 4:19 AM, roi1862 said:

Anyone else noticing LNAV getting degraded

Getting back on track, I closely followed the LNAV behavior on a flight at at FL380 and M.78, zooming in to the maximum resolution of the ND. I was unable to confirm the behavior the OP described. At course turns as large as 25 degrees, the LNAV closely followed the magenta line with a smooth roll into a bank of 15-20 degrees and no overshoot or hunting after the new course was established.

Not sure if that helps. Perhaps someone could suggest a specific instance in which degraded behavior was observed and others could check whether this is generally the case.

Best wishes.

7 minutes ago, jrw4 said:

Getting back on track, I closely followed the LNAV behavior on a flight at at FL380 and M.78, zooming in to the maximum resolution of the ND. I was unable to confirm the behavior the OP described. At course turns as large as 25 degrees, the LNAV closely followed the magenta line with a smooth roll into a bank of 15-20 degrees and no overshoot or hunting after the new course was established.

Not sure if that helps. Perhaps someone could suggest a specific instance in which degraded behavior was observed and others could check whether this is generally the case.

Best wishes.

My experience is the same as yours, no issues at all. I just did a 35 degree coarse change at FL370 at .77, nice smooth curve from one heading to the next. 

Edited February 22, 20233 yr by Bobsk8

I just happened to stumble upon this thread while doing VEGT - VNKT. While doing Katmandu's  RNAV AR runway 20 approach last night i did notice that the aircraft tracked the approach within the (RNP 0.3) with the actual Nav performance being .06-.07 but it did so by taking little "bites" so to speak ( Bank/Roll out/ Bank). So yeah i have to agree its not quite as smooth as one graceful shallow descending arc to final.

But then again i didn't notice this behavior at all until reading this thread. So while its nice if PMDG can smooth it out eventually its something i can live with. 

Edited February 22, 20233 yr by Maxis

 Lets just do this 🙂  

So from the beginning, plane makes initial turn at 33 degrees bank angle, already wrong. It then shallow it, and then again sharpen it. Now do the same in the Fenix for example and you get smooth turn at 15 degrees bank from start to end.

Thanks. Why don't you file a ticket with PMDG and see how they respond? That looked like a 70-80 degree turn at M.78 with a 40 kt wind starting as a tail wind and ending as a cross wind. I feel that overall LNAV did a good job of tracking the course without wandering or overshooting the new course. I'm totally ok with that behavior, but I guess that the turn could have been initiated earlier at a lesser bank angle, etc.

I try to fly realistic routes out of Flight Aware or Edi-Gla and I can't recall having to deal with such a sharp turn at cruise, but I sure wouldn't say that it doesn't happen. If that's "degraded" it must have been very good way back when. Let PMDG know about it and suggest a fix.

6 minutes ago, jrw4 said:

Thanks. Why don't you file a ticket with PMDG and see how they respond? That looked like a 70-80 degree turn at M.78 with a 40 kt wind starting as a tail wind and ending as a cross wind. I feel that overall LNAV did a good job of tracking the course without wandering or overshooting the new course. I'm totally ok with that behavior, but I guess that the turn could have been initiated earlier at a lesser bank angle, etc.

I try to fly realistic routes out of Flight Aware or Edi-Gla and I can't recall having to deal with such a sharp turn at cruise, but I sure wouldn't say that it doesn't happen. If that's "degraded" it must have been very good way back when. Let PMDG know about it and suggest a fix.

Yes, it was better at some point (i do this route and this exact turn quite often). The issue is not the tracking as i already said, its the turn calculations. This turn IRL would be quite noticeable in the cabin at cruise. 

I do the same route with Fenix as well and its aces the turn each and every time very smooth and precise.  

Is it a deal breaker ? no. Is it a showstopper ? no. Its simply an issue 🙂

ill ticket it.