The aircraft must remain completely stationary.
You cannot just turn it on and fly. The system needs to "learn" where it is while the aircraft is perfectly still. ltn-92 manual
Once alignment is complete (indicated by a "Ready to Nav" light), the system enters NAV mode. It now provides continuous updates on the aircraft's position, ground speed, and wind data. ATT (Attitude Only) The aircraft must remain completely stationary
Watch the "Status" countdown on the CDU. Once it reaches the required precision level (often indicated by a "0" or "NAV" light), move the selector to NAV. Troubleshooting Common Issues ltn-92 manual