GPS Primary?

[srilion]

Hi all!

On A330 MCDU 'PROG' page, what exactly does "GPS Primary" mean?

Cheers

[Luke SkyToddler]

It means that the GPS-derived aircraft position is being used as the primary source of aircraft navigational data by the FMGS, with the ADIRS position being used to monitor it.

[ilang]

Internal functions automatically monitor individual satellite failures and the integrity of GPS signals. If a failure is detected, up to [6] minutes is allowed to re-acquire GPS signals. If the GPS cannot be recovered, GPS PRIMARY LOST is displayed and a smooth transition occurs to navigation using DME/DME or VOR/DME radio position updates - if available. If radio updates are not available (e.g., out of range) NAV ACCURACY OWNGRADE and IRS ONLY NAVIGATION messages will be displayed in the scratchpad if certain other conditions are met.