As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED LOST FMS, THEN LOST NAV 1 IN FLIGHT EN ROUTE FROM DCA TO TYS. CREW DIVERTED TO IAD AND LANDED WITHOUT INCIDENT. USING AIRCRAFT MAINTENANCE MANUALS, MAINTENANCE PERFORMED CHECKS OF NR 1 NAV SYSTEM. NO DEFECTS NOTED. MAINTENANCE DEFERRED FMS PER MEL. SDR WILL BE REVISED WHEN DEFERRAL IS CLEARED. MAINTENANCE SUBSEQUENTLY CLEARED DEFERRAL BY REMOVAL AND REPLACEMENT OF FMC (FLIGHT MANAGEMENT COMPUTER) NR 1 AND PERFORMANCE OF CHECKS USING AIRCRAFT MAINTENANCE MANUALS. AIRCRAFT RELEASED FOR SERVICE.