What was found
ENROUTE TO DROP OFF PATIENT, PILOT REPORTED TAIL ROTOR GEARBOX CHIP WARNING LIGHT IN FLIGHT; FIRST IT FLASHED, THEN REMAINED STEADY. PILOT COMPLETED UNSCHEDULED LANDING AT NEARBY AIRPORT. WHEN MECHANIC INSPECTED T/R GB CHIP DETECTOR; MULTIPLE METAL FLAKES/SPLINTERS WERE FOUND. COULD NOT DETERMINE IF PARTICLES WERE FLAKES OR SPLINTERS, FAULT ISOLATION MANUAL STATES "LEAD TO SERIOUS DAMAGE. 1 AT 3 MM, 1 AT 2 MM, 4 AT .5MM IN SIZE. ALSO FOUND APPROX 12-15 SMALL BUT VISIBLE METALLIC PARTICLES. GEARBOX REPLACEMENT NEEDED. AFTER GEARBOX WAS REPLACED WITH SERVICEABLE UNIT IAW MM, GOUND CHECKS COMPLETED AND CK FLIGHT COMPLETED. ACFT RETURNED TO SERVICE 8/18/10.