As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER DEPARTING PDK THE CREW RECEIVED MULTIPLE CAS MESSAGES, AP 1&2 FAIL, TF 1&2 FAIL, FD 1&2 FAIL, AOC UPLINK FAIL, AND AT FAIL. THE CREW DECIDED TO RETURN TO PDK. TECHNICIANS FOUND AHRS VERTICAL SPEED INERTIAL RATE OUT OF TOLERANCE AT -57.0 FT/MIN. THEY REMOVED A FAULTY AHRS AH-1000 P/N HG2205AB03 S/N 56139126 AND INSTALLED A NEW UNIT P/N HG2205AB03 S/N 56220998 IAW AMM PC-24-A-E34-21-0001-00A-720A-A. ALL OPERATIONAL CHECKS GOOD.