Final answer:
The ON BATT light on the ADIRS panel indicates the system is operating on battery power, potentially due to a failure in the aircraft's main power supply or a maintenance check.
Step-by-step explanation:
The ON BATT light on the ADIRS (Air Data Inertial Reference System) panel indicates that the system is operating on battery power instead of normal aircraft electrical power. The ON BATT light on the ADIRS panel indicates the system is operating on battery power, potentially due to a failure in the aircraft's main power supply or a maintenance check.
This may occur if there is a failure in the aircraft's main power supply or if the ADIRS has been manually set to the ON BATT position to check the battery's health during maintenance. If the light illuminates during flight, it is considered abnormal and pilots need to refer to their emergency procedures as it might imply the potential loss of critical flight data provided by the ADIRS units.