What was found
ATB, PERFORMED AIR TURN BACK TO ANC DUE TO EXCESSIVE AIRFRAME VIBRATION WHEN NR 2 ENGINE THROTTLE ADVANCED. DID NOT SHUT DOWN NR 2 ENGINE. CORRECTIVE ACTION: FOUND NR 2 ENGINE FAN BLADE PLATFORM MISSING AND DAMAGE TO FAN BLADES AND OGV'S. PERFORMED FULL BORESCOPE OF ENGINE WITH NO SIGNS OF DAMAGE. BLENDED CONTAINMENT CASE, PER ERA 536292-14. REPLACED WHOLE BLADE FAN SET, IAW B737 AMM 72-21. INSPECTED FAN AND BOOSTER ASSEMBLY, PER B737 AMM 72-21. PERFORMED TESTS, PER B737 AMM 71-00.