In a dual ADAHRs please put both the R9 in PFD mode and ADAHRS select to auto.
- find the difference between the two.
- If you find a difference in air data - perform the ADU Cal
- if the Attitude has the difference - perform the IRU Cal
- if the Heading is off - perform the Mag Cal
- if you do the IRU Cal you will need to also do the Mag Cal
If the two R9s are in agreement, then you need to check the blind coordinator.