What was found
PDIS 573 71-00 6503 17MAY21 STN OPEN U DURING DEPARTURE CLIMBING THROUGH 3000 FEET DURING POWER REDUCTION HAD 3 SEPARATE AUDIBLE BANGS WITH MODERATE RIGHT YAW- ENGINE INDICATIONS APPEARED NORMAL - UNEVENTFUL EMERGENCY RETURN LANDING ACCOMPLISHED - EMERGENCY DECLARED SHGN 21MAY21 16:39 STN REMOVED #1 ENGINE (S/N 702919) AS PER WORK CARD 71T0001-GE. REPLACEMENT ENGINE (S/N 702820) INSTALLED AS PER WORK CARD 71T901-GE. FACT 23MAY21 20:22 STN ENGINE INTALLATION TESTS ACCOMPLISHED IAW MM 71-00-00-5-1 REF WRI 71-00/6509. ALL TESTS SATIS. OK FOR SERVICE.