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Wrong indications of End of Descent on Navigation Display?

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First of all, a little disclaimer: I know almost nothing about Airbus systems and even after partial reading of a Thales FMS manual found on the Internet I am still not sure if what I observed are real issues (bugs) with the simulation or if it is actually simulated correctly. Maybe there's even some form of PEBKAC involved; I would be grateful if someone with more knowledge of the Airbus FMS could help to figure out which of these observations are bugs, expected behaviour or pilot-induced errors. ;)


I captured the following possible issues in a video. Unfortunately, I just noticed that for issue #1 I entered the actual expected EOD as constraint to the correct waypoint by coincidence (therefore, please ignore the comment at 1:05; EOD actually is at ARPEG, I just miscalculated the required distance when I added the annotation). However, the issue in general is reproduceable on different flight levels and in different descent situations, I just partially screwed up my bug documentation. Sorry about that, I hope it is still helpful...




Versions are:


  • Aerosoft A319 Professional v1.1.0.0
  • Prepar3D v4.3.29.25520


Possible issue #1: EOD displayed behind actual EOD on managed route


To reproduce, simply dial in an altitude on cruise level and start descending in managed mode. Estimating the descent distance by calculating GS/60 * delta/VS instantly reveals that the EOD arrow is shown at a wrong position. My video shows that issue two times:


  1. Immediately after initiating the descent from cruise level (right at the beginning of my video), the EOD is displayed at a waypoint very far away. I am not quite sure if maybe that actually somehow makes sense in an Airbus FMS, so maybe that's not an actual bug. However, there didn't seem to be any constraints in the flight plan that would obviously hint at the EOD indicating some planned altitude instead of projecting the actual EOD.
    After having issued a Direct to a waypoint in unmanaged descent (V/S mode) behind the expected actual EOD (video: 2:30 - 3:00), the EOD appears to show at the correct location.
  2. Returning to managed mode (video: 3:30) pushes the EOD indication much farther away again. Looking at the FMS flight plan (video 4:00) shows that the estimated altitudes don't make any sense as estimations because those altitudes have already been left. The next constraint is FL140 at DOMUX. Maybe that is okay as well for Airbus systems, the question is: Should those altitudes show live estimations (as I think would be the case in a Boeing) or should they actually just be a one-time calculated vertical flight path? If the latter is correct, altitudes in the flight plan may make sense as they could have been calculated for a more shallow FPA towards the FL140 constraint at DOMUX at time of issueing the Direct. But then, why didn't the FMS try to catch the calculated path after returning from V/S mode to managed descend mode? If a more shallow FPA has been calculated, 1000ft/min is way too steep to regain & follow the vertical flight path.



Possible issue #2: EOD remains on planned route when changing to HDK/TRK mode


To reproduce, just change lateral mode from NAV to HDG or TRK while in a descend. Turning away from the original route shows that the EOD marker remains on the now inactive planned FMS route. From looking at the Thales manual it seems as if the EOD should instead be indicated on the ND's solid track line?


That issue occurs two times in my video:


  1. at 1:15 after engaging HDG mode manually
  2. at 6:55 after FMS engaged HDG mode due to entering a flight plan discontinuity


Possible issue #3: EOD skips flight plan discontinuity


I deleted a waypoint to produce a flight plan discontinuity. The EOD marker appears on segments after the discontinuity (starting at 5:15). EOD this time seems to be projected to the correct position when laying it on the track by range instead of track distance (which cannot be calculated due to the discontinuity). Adjusting the altitude updates the EOD projection but only down to the first waypoint of the route after the discontinuity (6:05 - 6:25). I am completely unsure how a real FMS would handle that situation, maybe the simulation is fully correct in this case.


Maybe yet another issue: Is it correct that segments after the discontinuity are shown with solid lines? They cannot be joined as long as there is a discontinuity in front of them in the flight plan.


As already mentioned above, entering the discontinuity segment of the flight plan changes lateral navigation to HDG mode but the EOD remains on the then inactive track.

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