What was found
DEN FLIGHT 4182 RETURN TO FIELD, NR 1 ENGINE VIBRATION. MAINTENANCE REPLACED FAN BLADES SERIAL NUMBERS IHI7274N, IHI7276N, IHI7280N, IHI7281N, IHI7289N, IHI7291N, IHI7297N, IHI7298N, IHI7302N, IHI7303N. OPERAITONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.