What was found
RETURN TO FIELD DUE TO NR 2 ENGINE COMPRESSOR STALL. TEARDOWN CONFIRMED THAT THIS WAS A GROUP-3 SURGE. GROUP -3 SURGES RESULT FROM EXCESSIVE BLADE TIP CLEARANCES IN THE AFT STAGES OF THE HP COMPRESSOR. THE HP COMPRESSOR IN THIS ENGINE WAS A SEGMENTED CASE CONGIGURATION, INCORPORATING A HAYNES REAR HOOK. PER THE REQUIREMENTS OF AD 2003-19-15, THIS ENGINE WAS REMOVED AND CONVERTED TO THE RING-CASE CONFIGURATION (RCC). THE RCC CONFIGURATION IMPROVES RETENTION OF HP COMPRESSOR BLADE TIP CLEARANCES, THEREBY ELIMINATING GROUP-3 SURGES.