As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FRA - FLT 193 - AFTER TAKEOFF, CREW NOTED THAT THE FMC'S WERE NOT UPDATING AND WERE APPROXIMATELY TEN MILES OFF IN POSITION. FLIGHT RETURNED TO FRA AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE REALIGNED THE IRU'S SEVERAL TIMES. BITE CHECK OF THE FMC'S WAS SATISFACTORY. (M)