Narrative:

On descent into las starting around 8000 ft, we initially experienced 2 loud thuds, which occurred in quick succession. This happened at least 4-5 times between 8000 ft MSL and 1500 ft AGL. Initial reaction was that it was a bird strike (large) though none had been seen or reported. The aircraft yawed slightly to the right each time yet the engine instruments appeared normal. Power at the first occurrence was at the low to mid range. These thuds were felt throughout the airframe from front to back and this elicited an immediate inquiry from the flight attendants via interphone. Flight controls and pressurization seemed normal. After the first occurrence we continued the approach in a routine fashion while looking for any abnormalities with none being detected. After each subsequent occurrence we became increasingly alarmed and engrossed in trying to determine a source or cause. I considered the possibility of heavy bags or freight falling in the forward bin or even something exploding (compressed gas canisters or explosive material) though again, no pressurization problems were noted. The first officer was concerned about a flight control problem because of the yaw after each jolt, so we agreed to hand fly and configure the aircraft early and high, and again no problems were detected. We were descending towards the airport this whole time and by approximately 2000 ft AGL, I determined that our best course of action was to proceed and land as soon as possible. All of this time, no engine anomalies were ever detected or verified. Between the decision to continue the approach and landing and the high level of concern over the multiple occurrences of this continuing bang, and the inability to determine its source, we overlooked performing the 'before landing checklist.' I was engrossed in flying the aircraft, (airspeed, attitude, confign, and pointing at the runway) and landing as soon as possible, and did not have a specific mental trigger to call for the before landing checklist. As we approached 1000 ft, we asked tower to look over our aircraft for anything abnormal and for the proper confign. The landing was uneventful. It seems in retrospect and upon consultation with maintenance in las we may have experienced multiple compressor stalls, but had no way to determine this airborne because we had not been able to detect any abnormality on the engine instruments. Also, with a combined 35+ yrs of flying turbine pwred aircraft, neither my first officer nor myself had ever experienced a compressor stall and this did not occur in a flight regime that I would have suspected it. It seems to me that all of our checklists need some specific 'trigger' to help assure their completion, ie, 10000 ft, 18000 ft, etc, but in the case of the before landing checklist, there isn't one. Supplemental information from acn 619587: it seems to me that all of our checklists need some specific 'trigger' to help assure their completion, it could be procedure for the pm to simply pull out the checklist in anticipation of the call from the PF to insure it is eventually called for. Also, our QRH may need descriptors for compressor stall added to the right hand pages, instead of at the end of a long sentence dealing with multiple possible problems. This particular situation is not addressed in the QRH. The QRH mentions stalls and a procedure to follow, but with no associated engine anomalies, in this situation, which engine would one shut down as the checklist describes.

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Original NASA ASRS Text

Title: THUMPS, THUDS AND YAWS DURING DSCNT DISTR A B737-300 FLT CREW, AND FORGET TO RUN THE BEFORE LNDG CHKLIST PRIOR TO LNDG AT LAS, NV.

Narrative: ON DSCNT INTO LAS STARTING AROUND 8000 FT, WE INITIALLY EXPERIENCED 2 LOUD THUDS, WHICH OCCURRED IN QUICK SUCCESSION. THIS HAPPENED AT LEAST 4-5 TIMES BTWN 8000 FT MSL AND 1500 FT AGL. INITIAL REACTION WAS THAT IT WAS A BIRD STRIKE (LARGE) THOUGH NONE HAD BEEN SEEN OR RPTED. THE ACFT YAWED SLIGHTLY TO THE R EACH TIME YET THE ENG INSTS APPEARED NORMAL. PWR AT THE FIRST OCCURRENCE WAS AT THE LOW TO MID RANGE. THESE THUDS WERE FELT THROUGHOUT THE AIRFRAME FROM FRONT TO BACK AND THIS ELICITED AN IMMEDIATE INQUIRY FROM THE FLT ATTENDANTS VIA INTERPHONE. FLT CTLS AND PRESSURIZATION SEEMED NORMAL. AFTER THE FIRST OCCURRENCE WE CONTINUED THE APCH IN A ROUTINE FASHION WHILE LOOKING FOR ANY ABNORMALITIES WITH NONE BEING DETECTED. AFTER EACH SUBSEQUENT OCCURRENCE WE BECAME INCREASINGLY ALARMED AND ENGROSSED IN TRYING TO DETERMINE A SOURCE OR CAUSE. I CONSIDERED THE POSSIBILITY OF HVY BAGS OR FREIGHT FALLING IN THE FORWARD BIN OR EVEN SOMETHING EXPLODING (COMPRESSED GAS CANISTERS OR EXPLOSIVE MATERIAL) THOUGH AGAIN, NO PRESSURIZATION PROBS WERE NOTED. THE FO WAS CONCERNED ABOUT A FLT CTL PROB BECAUSE OF THE YAW AFTER EACH JOLT, SO WE AGREED TO HAND FLY AND CONFIGURE THE ACFT EARLY AND HIGH, AND AGAIN NO PROBS WERE DETECTED. WE WERE DSNDING TOWARDS THE ARPT THIS WHOLE TIME AND BY APPROX 2000 FT AGL, I DETERMINED THAT OUR BEST COURSE OF ACTION WAS TO PROCEED AND LAND ASAP. ALL OF THIS TIME, NO ENG ANOMALIES WERE EVER DETECTED OR VERIFIED. BTWN THE DECISION TO CONTINUE THE APCH AND LNDG AND THE HIGH LEVEL OF CONCERN OVER THE MULTIPLE OCCURRENCES OF THIS CONTINUING BANG, AND THE INABILITY TO DETERMINE ITS SOURCE, WE OVERLOOKED PERFORMING THE 'BEFORE LNDG CHKLIST.' I WAS ENGROSSED IN FLYING THE ACFT, (AIRSPD, ATTITUDE, CONFIGN, AND POINTING AT THE RWY) AND LNDG ASAP, AND DID NOT HAVE A SPECIFIC MENTAL TRIGGER TO CALL FOR THE BEFORE LNDG CHKLIST. AS WE APCHED 1000 FT, WE ASKED TWR TO LOOK OVER OUR ACFT FOR ANYTHING ABNORMAL AND FOR THE PROPER CONFIGN. THE LNDG WAS UNEVENTFUL. IT SEEMS IN RETROSPECT AND UPON CONSULTATION WITH MAINT IN LAS WE MAY HAVE EXPERIENCED MULTIPLE COMPRESSOR STALLS, BUT HAD NO WAY TO DETERMINE THIS AIRBORNE BECAUSE WE HAD NOT BEEN ABLE TO DETECT ANY ABNORMALITY ON THE ENG INSTS. ALSO, WITH A COMBINED 35+ YRS OF FLYING TURBINE PWRED ACFT, NEITHER MY FO NOR MYSELF HAD EVER EXPERIENCED A COMPRESSOR STALL AND THIS DID NOT OCCUR IN A FLT REGIME THAT I WOULD HAVE SUSPECTED IT. IT SEEMS TO ME THAT ALL OF OUR CHKLISTS NEED SOME SPECIFIC 'TRIGGER' TO HELP ASSURE THEIR COMPLETION, IE, 10000 FT, 18000 FT, ETC, BUT IN THE CASE OF THE BEFORE LNDG CHKLIST, THERE ISN'T ONE. SUPPLEMENTAL INFO FROM ACN 619587: IT SEEMS TO ME THAT ALL OF OUR CHKLISTS NEED SOME SPECIFIC 'TRIGGER' TO HELP ASSURE THEIR COMPLETION, IT COULD BE PROC FOR THE PM TO SIMPLY PULL OUT THE CHKLIST IN ANTICIPATION OF THE CALL FROM THE PF TO INSURE IT IS EVENTUALLY CALLED FOR. ALSO, OUR QRH MAY NEED DESCRIPTORS FOR COMPRESSOR STALL ADDED TO THE R HAND PAGES, INSTEAD OF AT THE END OF A LONG SENTENCE DEALING WITH MULTIPLE POSSIBLE PROBS. THIS PARTICULAR SIT IS NOT ADDRESSED IN THE QRH. THE QRH MENTIONS STALLS AND A PROC TO FOLLOW, BUT WITH NO ASSOCIATED ENG ANOMALIES, IN THIS SIT, WHICH ENG WOULD ONE SHUT DOWN AS THE CHKLIST DESCRIBES.

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.