MMUN ILS DME TWO 12L

[xterminator24]

Navigraph 1605 Navdata

Route:  MKJS/07 PETSI1 PETSI DCT FROST UR640 AVSEB UM782 CUN MMUN/12L 

I was flying into MMUN this afternoon and came across something the 737-300 seemed to want to fly differently than in the chart. This route was a bit unique in that there was no STAR but an available approach from my final route fix (CUN).

Approach Chart:

I was approaching from SE into CUN (113.6). The approach should have flown me on Outbound Radial 326 to 9DME then a left turn to intercept the localizer.

If you look at the CDU, for the approach, it was very close, but wanted to leave CUN on a 316 heading:

I recognized the issue and flew the outbound radial using VOR/LOC mode. You can see that my course is very different than the one being drawn on the PFD:

There are 3 approaches listed for ILS12L in the NavData... This was the 2nd one. The file seems to indicate CUN as a "fly by" waypoint with a Hdg_Crs_value of 326. As shown above, the CDU plotted a course of 316 which I believe to be incorrect.

 

Thanks for all the hard work trying to figure out all of the intricate details of the NavData!

 

[Litjan]

Yeah, this would also explain the overshoot on the turn to final. Good catch - we will look at it!

Jan

 

[xterminator24]

Rather than start a new topic, I'm going to add to this one. It appears this departure issue could be caused from a similar issue. it overshoots the final turn despite flying a perfect DME arc.

MMUN   ENEBA1A  off 12R

 

You can see from the PFD, that it is going to overshoot the R356 radial, then turn back to it. I would expect it to turn onto the radial before passing it. Not a huge deal but it does seem similar to the original post in this thread.

[Litjan]

Hmm, I think the problem is that the last two waypoints before turning onto final are VERY close together. So the plane can not "lead" the turn as it usually wold - this would cause it to miss the last waypoint. Or maybe the waypoint is an overfly type?

Can you include a debug.txt for us to look at? Description how in the "Bug reporting guide" in the documentation.

Jan