As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 6405 - IAD-HPE - DURING CLIMB-OUT RETURNED TO IAD DUE TO CAPTAINS ADI FLAGGED AND HORIZON TUMBLED IN FLIGHT. AIRCRAFT LANDED AT IAD WITH NO FURTHER INCIDENTS. MAINTENANCE REPLACED NR ADI, OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)