[FIXED v1.2r3] In LNV mode the aircraft fails to register that a specific waypoint has been passed

[Caspian]

Flight: PAJN - EGAA

Route: CGL CANYO VQ HI 73N110W RB YIO JULET 72N060W 71N050W 70N040W 68N030W 64N020W ERAKA/N0467F350 BEL

Cruise level: FL350

During this flight, the aircraft flew normally until passing YIO whereupon it failed to recognise that we had reached that point. It continued to fly the same track beyond the point, rather than turning for the next point. The DTG simply started to increase. There were no discontinuities on the LEGS page. After passing the fix, the legs page still showed YIO as the next point.

This happened to me and two friends who were flying the same route. I was also able to reproduce (screenshots below).

While reproducing the scenario, after the aircraft had passed the fix I then put it into heading mode and started a left turn... as soon as I did this, the aircraft suddenly realised it had passed YIO and set JULET as the next fix.

 

Image 1: having reached the fix, the aircraft simply continues on the same track, still in LNV1 mode.

 

 

Image 2: Legs page that corresponds with Image 1 - the aircraft has now flown 6.1 miles beyond YIO.

 

Image 3: Taken just after the first two images.

 

Image 4: Immediately after the first three images, I put it into heading mode and initiated a left turn. As soon as the aircraft started to turn, the FMS realised that we had passed YIO and sequenced JULET as the next fix.

Edited January 21, 2022 by skiselkov

[skiselkov]

Found the source of the problem. Fix will be in update 2. Thank you for reporting.

[Caspian]

20 minutes ago, skiselkov said:

Found the source of the problem. Fix will be in update 2. Thank you for reporting.

Nice work!

[Caspian]

What was causing it, out of interest?

[Graeme_77]

Report 2433

Fixed in v1.2r3, January 24, 2022

The information on the issue says "Leg end course needs to be determined from the leg end point, not start point". There's no further info but it seems like there was a course confusion where on a long great circle track the final course inbound to the end waypoint is substantially different from the course outbound from the first waypoint. I'm guessing here but perhaps the aircraft was using the course outbound and this was causing some navigation confusion at the end of the leg. 

Edited January 24, 2022 by Graeme_77