What was found
MEM - FLT 3857 - THE PILOT REPORTED THE NR 1 ENGINE HAD INDICATION FLUCTUATIONS, LOUD BANGS, AND VISUAL INDICATION OF SPARKS COMING OUT OF THE TAIL PIPE. THE CREW SHUT DOWN NR 1 ENGINE AND RETURNED TO MEM, LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE NR 1 ENGINE AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE. (M)