PMDG 737 LNAV too aggressive last patch ?

[roi1862 611]

1 hour ago, synape said:

I also don't like PMDG 737's LNAV turn behaviour. DME Arc procedures are always jerky and not at a continuous gentle turn rate. And it always turns at 30 degrees no matter the altitude is. By comparison, Fenix A320 is such a joy and very gentle during turns.

Yes Fenix LNAV is really good. On the other hand the VNAV is lacking. Well, i guess each one with the up’s and down’s 🙂 

[jrw4 626]

By any chance do you have a video of this LNAV behavior? I haven't tried a DME arc recently, but will now look to do so.

[ThomseN_inc 1,128]

I absolutely understand what the OP means. IMHO it is not only the bank angle that is too steep even for slow turns. But its also the roll rate in some scenarios where its not necessary.

Even in HDG mode the plane rolls immediatly when dialing a new heading. I am no expert but i think in the real plane there is a small delay between selecting the heading and the plane starting to turn.

This could use some tweaking indeed.

[Bobsk8 12,944]

50 minutes ago, ThomseN_inc said:

I absolutely understand what the OP means. IMHO it is not only the bank angle that is too steep even for slow turns. But its also the roll rate in some scenarios where its not necessary.

Even in HDG mode the plane rolls immediatly when dialing a new heading. I am no expert but i think in the real plane there is a small delay between selecting the heading and the plane starting to turn.

This could use some tweaking indeed.

There are a few airline pilots that fly the 737, and I don't hear them complaining about the flight behavior??/

[ThomseN_inc 1,128]

8 minutes ago, Bobsk8 said:

There are a few airline pilots that fly the 737, and I don't hear them complaining about the flight behavior??/

But that doesn't mean there is no issue does it?

[Bobsk8 12,944]

22 minutes ago, ThomseN_inc said:

But that doesn't mean there is no issue does it?

Well if I am trying to judge if there is something wrong with an aircraft's behavior, and I have a choice of asking some pilots that fly it for a living, or someone  that just flies it on a simulator on their PC, I am going with the pro pilots. 

Edited February 21, 2023 by Bobsk8

[ThomseN_inc 1,128]

1 minute ago, Bobsk8 said:

Well if O am trying to figure out if there is something wrong with an aircraft's behavior, and I have a choice of asking some pilots that fly it for a living, or someone  that just flies it on a simulator on their PC, I am going with the pro pilot. 

Then we might ask one of those RL pilots.

[V1ROTA7E 718]

I’m an airline pilot on the 737-8 and LNAV is fine….for a $70 plane, there’s not much to complain about. A few quirks, but it’s a sim, and no sim is absolutely perfect. 

Edited February 21, 2023 by V1ROTA7E

[Bobsk8 12,944]

3 minutes ago, V1ROTA7E said:

I’m an airline pilot on the 737-8 and LNAV it’s fine….for a $70 plane, there’s not much to complain about. A few quirks, but it’s a sim, and no sim is absolutely perfect. 

But you probably aren't as smart as some of the "aviation experts" on this forum"? 😉

Edited February 21, 2023 by Bobsk8

[ThomseN_inc 1,128]

27 minutes ago, Bobsk8 said:

But you probably aren't as smart as some of the "aviation experts" on this forum"? 😉

What a great person you are....

[jrw4 626]

8 hours ago, roi1862 said:

Anyone else noticing LNAV getting degraded

There was a major update to the lateral guidance system that was made in the update published on 23 July 2022. I don't recall any further updates involving that aspect of the model.

[roi1862 611]

1 hour ago, V1ROTA7E said:

I’m an airline pilot on the 737-8 and LNAV is fine….for a $70 plane, there’s not much to complain about. A few quirks, but it’s a sim, and no sim is absolutely perfect. 

If you tell us that the real thing takes turns in cruise with usually 2 consecutive turns which at least 1 of them at 30 degrees bank angle i would say ok, as i trust you know your thing… 

@Bobsk8 and for you, what would you say about endless of issues that passed initial beta and after few patches got fixed/changed ? The pilots approved the beta right ?  I mean look at Fenix that you know well. All the pilots said its working great and like the real thing. Since then it went through many changes and still waiting for complete rewrite of basically the whole thing.

Edited February 21, 2023 by roi1862

[jrw4 626]

So I did try an approach with a DME arc, the ILS RWY 7R at KDAB after a short flight over from KJAX. I flew the OMN transition with a 90 degree turn at OMN and another at HANAV, the IAF for the DME arc. From just north of OMN, the approach was flown at the flaps up maneuver speed for the B737, which was around 190 kts, with flaps 1 being deployed as I approached the localizer course.

Overall the LNAV seemed spot on. The right angle turns were taken at 30 degrees of bank, and the turns on the DME arc were taken at around 20-25 degrees, with a gentle roll in and out. I did not observe overshooting and the need for corrective turns at any point. The PMDG FMC does not yet permit curved segments, so the DME arc was represented by a set of short straight line segments defined by pseudo waypoints. PMDG has reported that an updated system that permits curved LNAV segments is in the works, however.

It would be interesting to see videos of the LNAV system's misbehavior.

 

[roi1862 611]

48 minutes ago, jrw4 said:

So I did try an approach with a DME arc, the ILS RWY 7R at KDAB after a short flight over from KJAX. I flew the OMN transition with a 90 degree turn at OMN and another at HANAV, the IAF for the DME arc. From just north of OMN, the approach was flown at the flaps up maneuver speed for the B737, which was around 190 kts, with flaps 1 being deployed as I approached the localizer course.

Overall the LNAV seemed spot on. The right angle turns were taken at 30 degrees of bank, and the turns on the DME arc were taken at around 20-25 degrees, with a gentle roll in and out. I did not observe overshooting and the need for corrective turns at any point. The PMDG FMC does not yet permit curved segments, so the DME arc was represented by a set of short straight line segments defined by pseudo waypoints. PMDG has reported that an updated system that permits curved LNAV segments is in the works, however.

It would be interesting to see videos of the LNAV system's misbehavior.

 

Again. the issue is not on the approaches and low altitude as the plane is allowed as much bank angle as needed anyway (up to 30 degrees in normal ops). The problem is at cruise and high altitude where the LNAV supposed to be in what's called 'soft mode' and ideally not overshoot 15 degrees bank angle. 

[ThomseN_inc 1,128]

4 minutes ago, roi1862 said:

Again. the issue is not on the approaches and low altitude as the plane is allowed as much bank angle as needed anyway (up to 30 degrees in normal ops). The problem is at cruise and high altitude where the LNAV supposed to be in what's called 'soft mode' and ideally not overshoot 15 degrees bank angle. 

You heard what Bobsk8 said. Its all how its supposed to be! 😉