B727-200 HAD ENG COMPRESSOR STALL IN ZID CLASS A.

Narrative

ENROUTE CVG; DEN; AT FL 190 AND 320 KNOTS CREW NOTICED LE FLAP ANNUNCIATOR (AMBER) LIGHT ILLUMINATED ON FORWARD PANEL. SPEED REDUCTION TO 240 KNOTS WAS INITIATED BY THE FO. CAPT AND FE INITIATED ABNORMAL CHKLIST. DURING THE CHKLIST A VERBAL INDICATION OF A COMPRESSOR STALL WAS NOTED BY CAPT; FO AND FE. CAPT RETARDED ALL THREE THROTTLES AND ALL INDICATIONS OF A COMPRESSOR STALL CEASED WITH ALL THREE ENGS INDICATING NORMALLY. CAPT; FO AND FE DISCUSSED THE OCCURRENCE. CAPT BELIEVED THAT ENG TWO HAD COMPRESSOR STALLED. FE BELIEVED HE SAW FLUCTUATIONS IN ENG THREE READINGS; BUT COULD NOT BE SURE. CAPT CONTACTED DISPATCH AND MAINT AND RELAYED ALL ABOVE INFO. MAINT ADVISED CAPT TO TURN ON ENG TWO ANTI-ICE; RELATING THAT COMPRESSOR STALLS WERE COMMON ON THAT ENG. CAPT ADVISED THAT BEFORE ANY ACTION WAS TAKEN THAT HE WOULD LIKE TO ADVANCE EACH THROTTLE INDIVIDUALLY TO CONFIRM WHICH ENG WAS COMPRESSOR STALLING. MAINT AGREED. UPON ADVANCEMENT OF THE NUMBER TWO THROTTLE THE ENG COMPRESSOR STALLED. THE FLC ADVISED MAINT AND OPENED THE ENG TWO ANTI-ICE. CAPT AND FE REFERRED TO ABNORMAL PROC (ENG TWO STALL AT ALT). COMPLETION OF THE ABNORMAL PROC RESTORED ENG TWO TO NORMAL OP. ENGS ONE AND THREE WERE ADVANCED WITH NORMAL INDICATIONS. AFTER DISCUSSION WITH ATL DISPATCH; MAINT; AND THE FLC; ALL WERE IN AGREEMENT THAT THE FLT COULD BE OPERATED NORMALLY TO DEN. CAPT AND FE ALSO COMPLETED ABNORMAL PROC FOR THE LE FLAP PROB. DURING THE PROC IT WAS OBSERVED THAT THE WING ANTI-ICE SWITCHES WERE OPEN. AMBIENT TEMPS FROM PUSHBACK TO FL 190 WERE ALWAYS BELOW + 10 DEGS C. CAPT AND FE CLOSED WING ANTI-ICE SWITCHES AND LE FLAP ANNUNCIATOR LIGHT EXTINGUISHED. FLT CONTINUED NORMALLY TO DEN. UPON ARRIVAL AT DEN MAINT ADVISED THAT AFTER PERFORMING A VISUAL INSPECTION ON ENG TWO THAT PART OF THE COMM TWO ANTENNA MAST WAS FOUND JUST AHEAD OF THE INTAKE. THE PART HAD APPARENTLY SEPARATED FROM THE ANTENNA; WENT THROUGHT THE S-DUCT; AND LODGED ITSELF AT THE ENG INTAKE. THE PART DID NOT BECOME INGESTED AND WAS INTACT WHOLE. CAPT ADVISED MAINT THAT THIS WAS THE PROBABLE CAUSE OF THE ENROUTE COMPRESSOR STALL. CAPT ALSO ADVISED THAT A COMPLETE BOROSCOPE INSPECTION WOULD HAVE TO BE COMPLETED ON ENGS TWO AND THREE BEFORE HE WOULD ACCEPT THE ACFT. MAINT AGREED IT SHOULD BE NOTED THAT COM 2 COMS WERE NORMAL DURING THE ENTIRE FLT. SINCE ONLY A PORTION OF THE ANTENNA HAD SEPARATED IT ALLOWED COM 2 TO FUNCTION NORMALLY; PROVIDING NO CLUE TO THE FLC. THE FLC; DISPATCH AND MAINT WERE CONVINCED THAT ENG TWO HAD COMPRESSOR STALLED DUE TO THE NATURE OF THE S-DUCT AND ITS ASSOCIATED STALL TENDENCIES. SINCE THE ABNORMAL PROC RECONCILED ALL INDICATIONS THE FLT WAS CONTINUED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: MAINT TOLD RPTR THAT THE UPPER VHF ANTENNA HAD BECOME DISBONDED. THIS ACCOUNTED FOR ITS PARTIAL SEPARATION. THE ANTENNA PART WAS LODGED IN THE ENG INTAKE CAUSING AIRFLOW DISRUPTION. THIS WAS THE REASON FOR THE COMPRESSOR STALL. OPENING THE TAI VALVE INCREASES ENGS STALL MARGIN. THE ENG WAS NOT DAMAGED.