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I've noticed that in the PMDG 737 that on RNP approaches it does not draw the arc on some of the RNPs. Here are some examples of what the PMDG does. It makes performing RNPs difficult and irregular. It completely skips the arc and goes direct to the waypoints included. I have no idea if the 777 or 747 does it, but the NGX does.

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Posted (edited)

Hi Clayton.  Most likely this is a problem with Navigraph.  I notice that if the arc length is less than some distance, maybe 4 nm, that they drop the pseudofixes that generate an arc.  I've also noticed a few that are missing regardless of arc length, but I don't see a pattern.  Regardless, unless the Navigraph data is providing these pseudofixes the segment is going to be a track to fix because ARINC data format is not supported in the navdata structure used by PMDG.

Edit:  I should qualify that the Navigraph data is heavily manipulated to turn ARINC data into the very old macro language syntax still used by PMDG and it would be fair to say it is a shared problem.

Edited by downscc

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The NGX can't fly RNP I thought due to navdata limits  

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Posted (edited)
16 hours ago, fakeflyer737 said:

The NGX can't fly RNP I thought due to navdata limits  

Sure it can, but only down to 0.50 in the software version simulated.  What is missing is the database required for radius to fix (RF) segments.  If the RNP approach doesn't have RF segments then to the casual user you will have no problem flying the approach using the 0.50 minimums.  If there are RF segments, they are present in the data as short TF segments approximating the arc, and the fidelity of the simulation goes out the window.

Edited by downscc

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