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Pilot Waypoints

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I was trying to enter some pilot (PBDxx) waypoints last night and ran into some behavior that doesn't seem right.  This is all on (A319 CFM to be specific).


Flight plan was


My goal was to insert a waypoint between BOY and KBZN, along that line 40 nm from KBZN from which I would then turn to join the RNAV approach for KBZN/30.  The reason for this was I had entered such a point into my PF3 flight plan (those familiar with PF3 will know it aids with descent instructions when your last waypoint isn't too far out) and while I could have flown it manually, I instead decided to try and learn how to enter it into the FMGS.  Regardless whether this is a "normal" or realistic approach procedure or not, it was the situation I found myself in - and, well, aviate, navigate, communicate, etc. to get through it... So into the Airbus toolbox I went.


As the bearing between BOY to KZBN is 307, it stood to reason that entering a point at KBZN/127/40 would give me what I wanted but what I was getting on the ND was making no sense at all.  After a CTD (see the end of the post) I reentered through an autosave and decided to just try to figure it out.


It took me some time to figure out what was going on (and I'm still not quite sure I've figured it out), but for the first pilot waypoint, it seems that regardless of the "Place" entered, it simply computes a point based on the entered bearing and distance from the next waypoint on the flight path.  Subsequent pilot waypoints then compute based on the last previously entered pilot waypoint.


Note the entry vs. display of PBD01 and PBD02:  (Ignore the "ILS12"; prior to the CTD but evidently after the autosave I had changed the approach and wasn't focusing on that at this point.)





Being ridiculous now; this waypoint should be a good 1500 nm away:



And finally, SITRE if the FAF for KBZN/30:



Additionally, if I try entering a navaid as the "place", I would get the navaid selection list, as expected.  In this instance, I was selecting COD (Cody VOR).  Upon selecting from the list, however, the pilot waypoint screen would reappear empty, and all subsequent attempts to enter a navaid would return the selection list for COD - even after I tried entering BOY (Boysen Reservoir VOR).  Not until I tried re-entering KBZN did this seem to clear up and act normally.  I think the same issue as this post:



About the CTD:  While I only have limited experience with Boeing FMCs, for my initial attempt I resorted to Boeing logic and tried inserting WAYPT/BRG/DIST into the flight plan through the scratchpad - and got an instant CTD (didn't check the event logs as I assumed it didn't even leave one - can check later today if desired).  Clearly a stupid action on my part (it wouldn't have even worked on the NGX as there is no first slash) but perhaps a fix could be explored to trap such an error and return "bad format" instead?




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As far as I know, you can't enter a PBD waypoint from an Airport, instead the place has to be a NavAid or Waypoint.


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31 minutes ago, DaveCT2003 said:

As far as I know, you can't enter a PBD waypoint from an Airport, instead the place has to be a NavAid or Waypoint.



It was accepting them, and treating them just the same as the waypoint I did try (SITRE) but I had limited success with the navaids selection list killing my entry.  It seems in either event it's not working properly, but at least now I know that and have a way around it.


I'm curious now to try a PB/PB waypoint and see how that works.  I got rather single-minded last night just trying to figure out where the PBD was getting its P from.  (The waypoint I was trying to add would be indeterminate from a PB/PB standpoint being as they'd be colinear.)

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