Multiple ADAHRS units may be installed to provide redundancy for critical flight data. If the PFW ADAHRS source selection is set to Auto, and attitude or air data from the default ADAHRS source becomes unavailable, the PFW will automatically switch to using attitude and air data from another valid ADAHRS source. The selected ADAHRS source can also be manually changed by the pilot. In either case, a message appears on the PFW to indicate that an alternate source of attitude and air data is being used (e.g. ‘ON AHRS2’ and 'ON ADC2').

If a standby flight display (SFD) is present, and all installed ADAHRS sources are unavailable, the messages ‘ON AHRS SFD’ and ‘ON ADC SFD’ will appear. These messages indicate that the PFW has reverted to using attitude and air data from the standby flight display instead of a dedicated ADAHRS unit.

If redundant sensors are installed they will be continuously monitored and compared. If the difference between the outputs of two or more sensors exceeds a specified amount, a message appears on the PFW and the discrepancy is annunciated as a ‘MISCOMP’ (miscompare) in amber. The comparison monitoring will be provided for attitude, heading, airspeed, and altitude. If an AFCS is installed and configured, it will disconnect when a miscompare event occurs. If not enough sensor data is available to make a comparison, it will be annunciated as a ‘NO COMP’ (no compare) displayed in white.