Position update prompt on A320 PROG page

[Check Airman]

Hi guys,


I’ve noticed in the FCOM, the progress page example shows both GPS PRIMARY, and an UPDATE prompt at 3L.


I was under the impression that position updates are not possible with GPS primary. All the planes I’ve flown have GPS, and I’ve only ever seen the update prompt before IRU alignment.


I was thinking the FCOM diagram is just there as an example, but it’d usually say somewhere that the prompt is absent with GPS.


What gives? Is my understanding wrong?

[pineteam]

Is it an old A320?? On some old models we could still use position udpate even with GPS primary.

[MENELAUS]

As the old and bold are wont to say,”if it’s got dust on it, don’t touch it”. Sadly it’s behind a Mcdu screen and therefore that’s easier said than done.
It is obviously a hark back to pre GPS days, not dissimilar to the Boeing purge function used to remove inaccuracies after a long period of IRS only nav, or with dubious DD or VOR D updating etc. However it does appear even now on certain models of Airbus, and I can confirm, unfortunately, that it does still work. To be fair to AIB it does give you ample opportunity to confirm your actions. However, it will do exactly as it says on the tin, and update your posn, (albeit quite briefly as the GPS Positioning starts to reassert itself again), to the place selected.

[pineteam]

Yes. A friend of mine told me many moons ago he inadvertently inserted a VOR in the position update slot in the progress page during flight. From what I remembered he told me it created a temporary map shift but because the GPS is primary, the systems recomputes progressively an accurate position.

[MENELAUS]

Yes. A friend of mine told me many moons ago he inadvertently inserted a VOR in the position update slot in the progress page during flight. From what I remembered he told me it created a temporary map shift but because the GPS is primary, the systems recomputes progressively an accurate position.

That reflects my experience. It is temporary, but not temporary enough if you get my drift. Esp if oceanic !

[pineteam]

Hahaha! I can imagine! xD

[Check Airman]

Is it an old A320?? On some old models we could still use position udpate even with GPS primary.

Can’t be too old. It was a NEO.

Odd that I’ve never seen it here.

[pineteam]

That’s weird indeed.

From memory, last time I saw this was on A321-100 equipped with Honeywell FMS.

[A320 Glider]

From my memory, this is only available on certain mods.

The old A320s still flying will sure have this option still. The new ones definitely not.

[Fursty Ferret]

Depends whether Honeywell or Thales FMS. Pretty sure even fairly modern Honeywell FMGCs have the ability to ruin your day in this fashion, but I remember a notice a couple of years ago mentioning that the "feature" was removed from our Thales aircraft.

[Checkboard]

I remember seeing this when I transferred to the airbus eight years ago or so.. I triggered it once when playing and had a big map shift. Pulled heading and set up a VOR/DME position to reset the map, and then continued. No big deal - but yes, it's not a necessary feature with GPS.