Narrative:

Level at FL310, this flight was normal until we felt what I will describe as a bump, followed by a vibration, another bump, and then everything was normal again. There were no unusual engine indications or warning lights. I disconnected the autoplt and throttles, and found no abnormal control inputs. I moved the throttles and noted normal engine response and gauge readings. My first officer and I believed the vibration was airframe in nature, ie, small door open, spoiler float, etc. I had the flight attendants scan the outside for panels, spoilers, flaps, etc. They saw nothing unusual. We talked to maintenance control, discussed all possibilities, and decided maybe the APU door was open -- nothing that should affect the flight from safely continuing. All flight characteristics and engine indications remained normal until during the arrival at 12000 ft, the #2 engine began to compressor stall -- with large engine gauge fluctuations and noise. We followed all checklists for severe damage, engine shutdown, and single engine landing. We declared an emergency, briefed the flight attendants and passenger, and landed without further incident. By the time all checklists and briefings were completed, we were on final.

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Original NASA ASRS Text

Title: A B737-400 EXPERIENCED COMPRESSOR STALLS DURING ARR AT 12000 FT FOLLOWING SEVERAL SMALL THUMPS AT CRUISE. ENG SHUTDOWN, EMER DECLARED FOLLOWED BY NORMAL APCH AND LNDG.

Narrative: LEVEL AT FL310, THIS FLT WAS NORMAL UNTIL WE FELT WHAT I WILL DESCRIBE AS A BUMP, FOLLOWED BY A VIBRATION, ANOTHER BUMP, AND THEN EVERYTHING WAS NORMAL AGAIN. THERE WERE NO UNUSUAL ENG INDICATIONS OR WARNING LIGHTS. I DISCONNECTED THE AUTOPLT AND THROTTLES, AND FOUND NO ABNORMAL CTL INPUTS. I MOVED THE THROTTLES AND NOTED NORMAL ENG RESPONSE AND GAUGE READINGS. MY FO AND I BELIEVED THE VIBRATION WAS AIRFRAME IN NATURE, IE, SMALL DOOR OPEN, SPOILER FLOAT, ETC. I HAD THE FLT ATTENDANTS SCAN THE OUTSIDE FOR PANELS, SPOILERS, FLAPS, ETC. THEY SAW NOTHING UNUSUAL. WE TALKED TO MAINT CTL, DISCUSSED ALL POSSIBILITIES, AND DECIDED MAYBE THE APU DOOR WAS OPEN -- NOTHING THAT SHOULD AFFECT THE FLT FROM SAFELY CONTINUING. ALL FLT CHARACTERISTICS AND ENG INDICATIONS REMAINED NORMAL UNTIL DURING THE ARR AT 12000 FT, THE #2 ENG BEGAN TO COMPRESSOR STALL -- WITH LARGE ENG GAUGE FLUCTUATIONS AND NOISE. WE FOLLOWED ALL CHKLISTS FOR SEVERE DAMAGE, ENG SHUTDOWN, AND SINGLE ENG LNDG. WE DECLARED AN EMER, BRIEFED THE FLT ATTENDANTS AND PAX, AND LANDED WITHOUT FURTHER INCIDENT. BY THE TIME ALL CHKLISTS AND BRIEFINGS WERE COMPLETED, WE WERE ON FINAL.

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.