Track distortion problem

[Val77]

Hello ! Thank you for this awesome add-on.

But I have some problem with LNAV calculation (wave-shaped road) especially when I made a "Direct To" on SID departure

FMC database : Default > NavdataPro 1509
SID : OKTET6E/6A (CONV and RNAV) at LFMN. Same problem at LFKJ and also on a few other location.

Speed/altitude limitation disappear, except FL380 while my CRZ LVL is FL320 : 

 

 

Edited May 7, 2016 by Val77

[WR269]

Had something similar last night flying the RNAV02 approach to MTHG...approaching waypoitn TG15 in a sweeping left turn, appears the next two waypoints were way too close on the left turn and it cut the turn towards TG13 instead of TG14....then it corrected back to the right as if going back to TG15, then turned hard left as if doing a left orbit....at this point I disconnected the autopilot as the surrounding terrain does not leave much room for trial.

[JRBarrett]

In the case of "bent" tracks at MTHG, it similar to the issue I responded to in another topic entitled "Cheesy route drawing at KPSP".

Like the RNAV approaches at Palm Springs, the RNAV02 approach at Toncontin is an RNP RNAV approach which uses curved leg segments.

Typically, the FMS in a r/w 737-300 would NOT be capable of flying RNP. At the time that the FMS in the Classic 737 was designed, curved RF legs did not exist.

Not all RNAV approaches are RNP, but those which are, cannot be flown by a "stock" 733.

That's not to say that other types of distorted track displays in the IXEG 737 might not be caused by programming bugs, but in this instance, it is a limitation of the real aircraft, which might very well display similar track distortion if an RNP approach was attempted.

[Val77]

Thank you for your answer JRB.  

So for my "problem" of speed/altitude limitation disappearing (as u can see in the picture 2) it does not happen again if profil VNAV is complet > I had not selected an arrival...

Quote

if an RNP approach was attempted.

And a track distortion can happen on a basic RNAV Departure too ?

++

[JRBarrett]

Thank you for your answer JRB.  

So for my "problem" of speed/altitude limitation disappearing (as u can see in the picture 2) it does not happen again if profil VNAV is complet > I had not selected an arrival...

if an RNP approach was attempted.

And a track distortion can happen on a basic RNAV Departure too ?

++ [emoji4]

The results with a true RNP approach are unpredictable, since the FMS is not capable of dealing with curved leg segments - but other strange graphics artifacts on normal RNAV approaches or departures may indeed be bugs which have to be addressed by the developers.

The issue with incorrect or disappearing speed/altitude constraints may be something else entirely. I believe it was mentioned that improvements in this area may be forthcoming in the next patch.

[Litjan]

Hi guys,

I think the issue you are seeing reported in this thread may actually be a bug. When turning directly to a new waypoint, the plane should just make a simple turn, not re-intercept the line between the current position and the new waypoint.

We will look at that during the tuning phase...

Jan

 

[tkyler]

The route drawing "rules" are a bit complicated.  With over a million possible route combinations, we are going to improve the LNAV 'rules' for various situations during a tuning phase.  The "bend" is not a bug, its as intended for the moment.  It is a "re-intercept" of the leg between the two waypoints, which IS valid for legs over a certain length...though that length is not defined anywhere, but more "common sense"

-tkyler

Edited May 7, 2016 by tkyler