Sorry but the ADIRU/IRS itself is
NOT updated by GPS or any other source during flight.
The FMC or FMGC is, but not the ADIRU/IRS
Hence the Airbus requirement to do an "IRS Performance check" at the end of each flight.
– IRS PERFORMANCE...........................................CHECK
•
Residual ground speed check:
— If the residual ground speed indication on any IRS MONITOR page is greater than 15 kt, make a Maintenance Log entry identifying the associated IRS. Perform this check within 2 min of aircraft stop.
Position error check:
•
— If any radial distance error on the POSITION MONITOR page is greater than the limits in the table below, make a Maintenance Log entry identifying the associated IRS and stating the BLOCK/NAV time and error in nautical miles.