Narrative:

On arrival, we were cleared visual approach. Aircraft was slowed normally and flaps extended to 5 degrees. Gear was extended and flaps extended to 15 degrees. At approximately 1100-1200 ft, tower advised us that a T38 was on close in right base to our runway and would extend to follow us. Almost simultaneously, we received a TCASII TA. We both began looking for the T38. He was sighted at 1 O'clock position. No factor. By this time, we had passed through 1000 ft. Flaps were extended to 30 degrees and before landing accomplished. Normal callouts were made. At approximately 300-400 ft, we heard a thump which sounded exactly like a bird strike. We continued the approach. The air was quite choppy as is usual for afternoon summer days. On very short final, I noticed that the first officer was having to hold approximately 20 degrees of right aileron (average, while contending with the bumps). By this time, we were in the flare and made a normal touchdown. Taxiing in, I asked the first officer if he felt that he was having to counteract a left roll tendency and he agreed that he was. We decided to leave the flaps extended and have the spindles checked, also to check for a bird strike. I called the dispatcher for a patch to the desk in maintenance. I told him the whole scenario and requested to have contract maintenance come look at the aircraft. He agreed and we called them. While we were waiting, I went out and looked at the flaps. When I lifted up on the trailing edge, it was evident that there was a problem, because I could lift the trailing edge of the left outboard flap probably 6 inches, but couldn't budge the right one. Contract maintenance showed up and he agreed that it didn't look right to him either. He called the maintenance desk. They were in the process of sending him a facsimile concerning a spindle inspection when we were advised that a mechanic was in the gate area non-revving. I asked him to come look at the aircraft. He did and immediately advised us that the spindle was, in fact, broken. This was our last leg for the day, so we went to the hotel after I was sure that the aircraft was to be taken OTS. I have had many bird strikes in my career and had we found any evidence of another, we might not have had the spindle examined thinking that the thump was just another unlucky bird. The reason that I am filing this report is due to one, possibly two, procedural deviations. One was the fact that we were distraction by the TCASII alert and failed to be configured by 1000 ft. Two, we did not go around after the spindle failure. Had the 'thump' occurred during flap extension, I would have suspected a failure. However, it did not, and I did not think about a possible failure until we were almost on the ground. I think that continuing the landing was the best decision at that stage of the flight. I understand why the spindle failure procedure was written and I agree with it and would have complied with it had it happened during flap extension (as I would have suspected a failure). Supplemental information from an 620174: by the time I decided that pop/bang and the abnormal control inputs might mean a single spindle failure, the aircraft was nearly in the flare. The captain had heard the pop/bang, but the control inputs I had been using for the variable winds made it hard for him to detect the aircraft flying abnormally. I let myself get distraction by 2 aircraft and numerous birds. With the focus of controling the aircraft in gusty winds on short final and never having experienced a spindle failure, I was slow to realize the actual problem. The problem is what to communicate when on short final, and the person who should be focusing on controling the aircraft is trying to decide what the problem is.

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Original NASA ASRS Text

Title: A B737-200 ON FINAL APCH AT 800 FT HEARD A THUMP AND PF REQUIRED 20 DEGS OF R AILERON INPUT TO CORRECT FOR L ROLL, WHICH WAS LATER DETERMINED TO BE A SPINDLE FAILURE.

Narrative: ON ARR, WE WERE CLRED VISUAL APCH. ACFT WAS SLOWED NORMALLY AND FLAPS EXTENDED TO 5 DEGS. GEAR WAS EXTENDED AND FLAPS EXTENDED TO 15 DEGS. AT APPROX 1100-1200 FT, TWR ADVISED US THAT A T38 WAS ON CLOSE IN R BASE TO OUR RWY AND WOULD EXTEND TO FOLLOW US. ALMOST SIMULTANEOUSLY, WE RECEIVED A TCASII TA. WE BOTH BEGAN LOOKING FOR THE T38. HE WAS SIGHTED AT 1 O'CLOCK POS. NO FACTOR. BY THIS TIME, WE HAD PASSED THROUGH 1000 FT. FLAPS WERE EXTENDED TO 30 DEGS AND BEFORE LNDG ACCOMPLISHED. NORMAL CALLOUTS WERE MADE. AT APPROX 300-400 FT, WE HEARD A THUMP WHICH SOUNDED EXACTLY LIKE A BIRD STRIKE. WE CONTINUED THE APCH. THE AIR WAS QUITE CHOPPY AS IS USUAL FOR AFTERNOON SUMMER DAYS. ON VERY SHORT FINAL, I NOTICED THAT THE FO WAS HAVING TO HOLD APPROX 20 DEGS OF R AILERON (AVERAGE, WHILE CONTENDING WITH THE BUMPS). BY THIS TIME, WE WERE IN THE FLARE AND MADE A NORMAL TOUCHDOWN. TAXIING IN, I ASKED THE FO IF HE FELT THAT HE WAS HAVING TO COUNTERACT A L ROLL TENDENCY AND HE AGREED THAT HE WAS. WE DECIDED TO LEAVE THE FLAPS EXTENDED AND HAVE THE SPINDLES CHKED, ALSO TO CHK FOR A BIRD STRIKE. I CALLED THE DISPATCHER FOR A PATCH TO THE DESK IN MAINT. I TOLD HIM THE WHOLE SCENARIO AND REQUESTED TO HAVE CONTRACT MAINT COME LOOK AT THE ACFT. HE AGREED AND WE CALLED THEM. WHILE WE WERE WAITING, I WENT OUT AND LOOKED AT THE FLAPS. WHEN I LIFTED UP ON THE TRAILING EDGE, IT WAS EVIDENT THAT THERE WAS A PROB, BECAUSE I COULD LIFT THE TRAILING EDGE OF THE L OUTBOARD FLAP PROBABLY 6 INCHES, BUT COULDN'T BUDGE THE R ONE. CONTRACT MAINT SHOWED UP AND HE AGREED THAT IT DIDN'T LOOK RIGHT TO HIM EITHER. HE CALLED THE MAINT DESK. THEY WERE IN THE PROCESS OF SENDING HIM A FAX CONCERNING A SPINDLE INSPECTION WHEN WE WERE ADVISED THAT A MECH WAS IN THE GATE AREA NON-REVVING. I ASKED HIM TO COME LOOK AT THE ACFT. HE DID AND IMMEDIATELY ADVISED US THAT THE SPINDLE WAS, IN FACT, BROKEN. THIS WAS OUR LAST LEG FOR THE DAY, SO WE WENT TO THE HOTEL AFTER I WAS SURE THAT THE ACFT WAS TO BE TAKEN OTS. I HAVE HAD MANY BIRD STRIKES IN MY CAREER AND HAD WE FOUND ANY EVIDENCE OF ANOTHER, WE MIGHT NOT HAVE HAD THE SPINDLE EXAMINED THINKING THAT THE THUMP WAS JUST ANOTHER UNLUCKY BIRD. THE REASON THAT I AM FILING THIS RPT IS DUE TO ONE, POSSIBLY TWO, PROCEDURAL DEVS. ONE WAS THE FACT THAT WE WERE DISTR BY THE TCASII ALERT AND FAILED TO BE CONFIGURED BY 1000 FT. TWO, WE DID NOT GO AROUND AFTER THE SPINDLE FAILURE. HAD THE 'THUMP' OCCURRED DURING FLAP EXTENSION, I WOULD HAVE SUSPECTED A FAILURE. HOWEVER, IT DID NOT, AND I DID NOT THINK ABOUT A POSSIBLE FAILURE UNTIL WE WERE ALMOST ON THE GND. I THINK THAT CONTINUING THE LNDG WAS THE BEST DECISION AT THAT STAGE OF THE FLT. I UNDERSTAND WHY THE SPINDLE FAILURE PROC WAS WRITTEN AND I AGREE WITH IT AND WOULD HAVE COMPLIED WITH IT HAD IT HAPPENED DURING FLAP EXTENSION (AS I WOULD HAVE SUSPECTED A FAILURE). SUPPLEMENTAL INFO FROM AN 620174: BY THE TIME I DECIDED THAT POP/BANG AND THE ABNORMAL CTL INPUTS MIGHT MEAN A SINGLE SPINDLE FAILURE, THE ACFT WAS NEARLY IN THE FLARE. THE CAPT HAD HEARD THE POP/BANG, BUT THE CTL INPUTS I HAD BEEN USING FOR THE VARIABLE WINDS MADE IT HARD FOR HIM TO DETECT THE ACFT FLYING ABNORMALLY. I LET MYSELF GET DISTR BY 2 ACFT AND NUMEROUS BIRDS. WITH THE FOCUS OF CTLING THE ACFT IN GUSTY WINDS ON SHORT FINAL AND NEVER HAVING EXPERIENCED A SPINDLE FAILURE, I WAS SLOW TO REALIZE THE ACTUAL PROB. THE PROB IS WHAT TO COMMUNICATE WHEN ON SHORT FINAL, AND THE PERSON WHO SHOULD BE FOCUSING ON CTLING THE ACFT IS TRYING TO DECIDE WHAT THE PROB IS.

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.