As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 2099 - AFTER DEPARTURE FROM DEN, THE CAPTAINS HSI WENT INOP. AIRCRAFT RETURNED TO DEN WHERE GP EXPRESS MAINTENANCE REPLACED THIS HSI WITH A SERVICEABLE UNIT. SYSTEM GROUND CHECKED SATISFACTORY AND AIRCRAFT WAS RETURNED TO SERVICE. (Z)