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 first officer. Captain and flight engineer initiated abnormal checklist. During the checklist a verbal indication of a compressor stall was noted by captain, first officer and flight engineer. Captain retarded all three throttles and all indications of a compressor stall ceased with all three engines indicating normally. Captain, first officer and flight engineer discussed the occurrence. Captain believed that engine two had compressor stalled. Flight engineer believed he saw fluctuations in engine three readings, but could not be sure. Captain contacted dispatch and maintenance and relayed all above information. Maintenance advised captain to turn on engine two anti-ice, relating that compressor stalls were common on that engine. Captain advised that before any action was taken that he would like to advance each throttle individually to confirm which engine was compressor stalling. Maintenance agreed. Upon advancement of the number two throttle the engine compressor stalled. The flight crew advised maintenance and opened the engine two anti-ice. Captain and flight engineer referred to abnormal procedure (engine two stall at altitude). Completion of the abnormal procedure restored engine two to normal operation. Engines one and three were advanced with normal indications. After discussion with atl dispatch, maintenance, and the flight crew, all were in agreement that the flight could be operated normally to den. Captain and flight engineer also completed abnormal procedure for the le flap problem. During the procedure it was observed that the wing anti-ice switches were open. Ambient temperatures from pushback to fl 190 were always below + 10 degrees C. Captain and flight engineer closed wing anti-ice switches and le flap annunciator light extinguished. Flight continued normally to den. Upon arrival at den maintenance advised that after performing a visual inspection on engine 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 engine intake. The part did not become ingested and was intact whole. Captain advised maintenance that this was the probable cause of the enroute compressor stall. Captain also advised that a complete boroscope inspection would have to be completed on engines two and three before he would accept the aircraft. Maintenance agreed it should be noted that communication 2 communications were normal during the entire flight. Since only a portion of the antenna had separated it allowed communication 2 to function normally, providing no clue to the flight crew. The flight crew, dispatch and maintenance were convinced that engine two had compressor stalled due to the nature of the s-duct and its associated stall tendencies. Since the abnormal procedure reconciled all indications the flight was continued. Callback conversation with reporter revealed the following information: maintenance told reporter that the upper VHF antenna had become disbonded. This accounted for its partial separation. The antenna part was lodged in the engine intake causing airflow disruption. This was the reason for the compressor stall. Opening the tai valve increases engines stall margin. The engine was not damaged.

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Original NASA ASRS Text

Title: 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.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.