As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
20 MINUTES AFTER DEPARTURE, THE NG INDICATION DROPPED TO 20 PERCENT AT FULL POWER. ALL OTHER ENGINE PARAMETERS WERE NORMAL. THE PILOT DECLARED AN EMERGENCY AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE NG INDICATOR. OPS CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.