What was found
WHILE PERFORMING PHASE 54 INSPECTION FOUND THE LEFT PYLON PRECOOLER/HEAT EXCHANGER RUPTURED. RUPTURE CAUSED DISCOLORATION OF THE AFT ENGINE BEAM WITHIN THE PYLON AND INTO AIRCRAFT FUSELAGE. THE STRUCTURE WITHIN THE PYLON, AIRCRAFT SKIN AND ASSOCIATED FRAMES AND STRINGER SHOW SIGNS OF HEAT DISCOLORATION. THE PHASE 54 CONSISTS OF A VISUAL INSPECTION OF THE PRECOOLER/HEAT EXCHANGER EVERY 600-HOURS / 12-MONTHS. AIRCRAFT WITHIN INSPECTION INTERVAL. PRECOOLER/HEAT EXCHANGER TT 4056-HOURS, LIFE LIMIT 4800-HOURS. NOTE: THE LEFT PRECOOLER/HEAT EXCHANGER FAILED CAUSING HEAT DAMAGE AND WAS REPLACED 05/NOV/2018. AFT ENGINE BEAM REPLACED DUE TO HEAT DAMAGE 19/MAY/2019.