What was found
NR 4 ENG LOUD BANG, HEAVY VIBRATION, DECAYING N1, N2 AND INCREASING EGT, ACCOMPANIED BY VIOLENT YAW TO THE RIGHT. HEAVY VIBRATION FELT WITH THROTTLE ADVANCEMENT. PREPARED AIRCRAFT FOR THREE ENGINE FERRY, INSPECTED AIRCRAFT AND FOUND IT SAFE FOR THE FLIGHT INTENDED. WRITE-UP STILL OPEN TILL ENGINE CHANGE.