Narrative:

A practice hgs CAT III approach was briefed for runway 2R at bna planned with 40 degree flaps. After skags; the landing gear was lowered and flaps selected to 15 degrees. At approximately 1500 ft AGL; the flaps were selected to 40 degrees and the landing checklist was performed. When the checklist called for 'flaps' we both noticed that the flap indicator showed an improper position for the flaps. The left side was at 10 degrees and the right side was at 15 degrees. At that point I opted to break off the approach and the pilot monitoring notified ATC that we needed a go around to sort out a flap issue. Go around thrust; flaps 15 degrees; and the landing gear up were called for and we climbed to 3000 ft MSL and received vectors from ATC. With the flap handle at 15 degrees the flaps remained split. Some asymmetry could be felt in the yoke. During the go around; the pilot monitoring opened the QRH to the 'flap; trailing edge: asymmetrical' and was reading through the steps and the notes. He moved the flap lever to the 10 degree position in compliance with step #1 of the QRH. Although; during the event; I don't remember being aware that he did. I called for flaps 5 degrees as we accelerated to approximately 190 KTS. The pilot monitoring then began to read the warnings; notes; and steps aloud. During his reading; the flaps moved on their own to the 5 degree position matching the flap handle. At this point I judged that we had a normal system. Further accelerating we selected the flaps up and the flaps moved up normally. We had a completely clean aircraft which confirmed that the normal operation of the flap system was restored. I made the decision that we no longer needed to reference the QRH. I called for flaps 5 degrees and the flaps came down and positioned normally to 5 degrees. I then called for the landing gear down and flaps 15 degrees and the flaps moved normally to 15 degrees. I briefed the passenger that we had opted to terminate our first approach due to a problem getting our flaps positioned properly and that the issue was now resolved and that we would be starting another approach shortly. At that point we asked for vectors to final and continued a practice hgs CAT III approach to runway 2R. Calling for flaps 25 degrees and then 40 degrees; the flaps extended normally. The landing checklist was performed and an uneventful landing was accomplished. The flaps were raised normally after taxiing clear of the runway. Maintenance was called to the aircraft and a logbook entry was made. Maintenance troubleshot the flap system but couldn't duplicate the problem. Maintenance signed off the logbook and we continued our trip. No further flap problems were experienced on subsequent approachs. In retrospect; I see that I erred in calling for flaps to 5 degrees after the go around. I see now that the flap handle should have remained in the 10 degree detent (detent to lesser indicating flap) and that I should have completed the entire QRH checklist and remained in an abnormal landing confign throughout the subsequent approach and landing. I have experienced 4 major system failures in the B737-300 during an 8 day period which is alarming and indicates to me that these aircraft are aging with problems. Maintenance checks and procedures should perhaps be more stringent and frequent to ensure that our aircraft operate as they were designed. In this case of flap system failure; a go around was warranted. During a go around; the most important goal is to get the aircraft away from the ground. Our procedures: go around thrust; flaps 15 degrees; and landing gear up; are ingrained in us from day one. This is the procedure we used. There are no memory items in the QRH checklist for 'flaps; trailing edge: asymmetrical' but yet the checklist in its first warning (not step) states: 'check performance data for runway length requirements using current runway conditions and the current flap setting (assumed worst case). Check current WX. If a safe landing cannot be made; divert. Accomplish this performance review as soon as practical. Once the flaps are extended; they should not be retracted. The drag penalty may make it impossible to reach an alternate airport. Do not use FMC fuel predictions with the flaps extended.' that is an exceptionally lengthy warning and the important part for pilots during a go around is: 'once the flaps are extended; they should not be retracted.' I take that to mean that the flap handle should not be moved up on a go around with subsequent on schedule flap retractions. If not touching the flap handle or moving the flaps is such a critical issue; then it should be a bold face memory item and be step #1 of the checklist. 1) flap lever -- do not move. This would prevent us from making a wrong move on a go around. Once the aircraft is back at pattern altitude; the situation could be properly analyzed and the appropriate notes and warnings could be read and the appropriate steps of the current checklist could be properly completed.

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Original NASA ASRS Text

Title: B737-300 FLT CREW INCORRECTLY RETRACTS FLAPS ON GAR FOLLOWING A FLAPS ASYMMETRY INDICATION ON FINAL APCH.

Narrative: A PRACTICE HGS CAT III APCH WAS BRIEFED FOR RWY 2R AT BNA PLANNED WITH 40 DEG FLAPS. AFTER SKAGS; THE LNDG GEAR WAS LOWERED AND FLAPS SELECTED TO 15 DEGS. AT APPROX 1500 FT AGL; THE FLAPS WERE SELECTED TO 40 DEGS AND THE LNDG CHKLIST WAS PERFORMED. WHEN THE CHKLIST CALLED FOR 'FLAPS' WE BOTH NOTICED THAT THE FLAP INDICATOR SHOWED AN IMPROPER POS FOR THE FLAPS. THE L SIDE WAS AT 10 DEGS AND THE R SIDE WAS AT 15 DEGS. AT THAT POINT I OPTED TO BREAK OFF THE APCH AND THE PLT MONITORING NOTIFIED ATC THAT WE NEEDED A GAR TO SORT OUT A FLAP ISSUE. GAR THRUST; FLAPS 15 DEGS; AND THE LNDG GEAR UP WERE CALLED FOR AND WE CLBED TO 3000 FT MSL AND RECEIVED VECTORS FROM ATC. WITH THE FLAP HANDLE AT 15 DEGS THE FLAPS REMAINED SPLIT. SOME ASYMMETRY COULD BE FELT IN THE YOKE. DURING THE GAR; THE PLT MONITORING OPENED THE QRH TO THE 'FLAP; TRAILING EDGE: ASYMMETRICAL' AND WAS READING THROUGH THE STEPS AND THE NOTES. HE MOVED THE FLAP LEVER TO THE 10 DEG POS IN COMPLIANCE WITH STEP #1 OF THE QRH. ALTHOUGH; DURING THE EVENT; I DON'T REMEMBER BEING AWARE THAT HE DID. I CALLED FOR FLAPS 5 DEGS AS WE ACCELERATED TO APPROX 190 KTS. THE PLT MONITORING THEN BEGAN TO READ THE WARNINGS; NOTES; AND STEPS ALOUD. DURING HIS READING; THE FLAPS MOVED ON THEIR OWN TO THE 5 DEG POS MATCHING THE FLAP HANDLE. AT THIS POINT I JUDGED THAT WE HAD A NORMAL SYS. FURTHER ACCELERATING WE SELECTED THE FLAPS UP AND THE FLAPS MOVED UP NORMALLY. WE HAD A COMPLETELY CLEAN ACFT WHICH CONFIRMED THAT THE NORMAL OP OF THE FLAP SYS WAS RESTORED. I MADE THE DECISION THAT WE NO LONGER NEEDED TO REF THE QRH. I CALLED FOR FLAPS 5 DEGS AND THE FLAPS CAME DOWN AND POSITIONED NORMALLY TO 5 DEGS. I THEN CALLED FOR THE LNDG GEAR DOWN AND FLAPS 15 DEGS AND THE FLAPS MOVED NORMALLY TO 15 DEGS. I BRIEFED THE PAX THAT WE HAD OPTED TO TERMINATE OUR FIRST APCH DUE TO A PROB GETTING OUR FLAPS POSITIONED PROPERLY AND THAT THE ISSUE WAS NOW RESOLVED AND THAT WE WOULD BE STARTING ANOTHER APCH SHORTLY. AT THAT POINT WE ASKED FOR VECTORS TO FINAL AND CONTINUED A PRACTICE HGS CAT III APCH TO RWY 2R. CALLING FOR FLAPS 25 DEGS AND THEN 40 DEGS; THE FLAPS EXTENDED NORMALLY. THE LNDG CHKLIST WAS PERFORMED AND AN UNEVENTFUL LNDG WAS ACCOMPLISHED. THE FLAPS WERE RAISED NORMALLY AFTER TAXIING CLR OF THE RWY. MAINT WAS CALLED TO THE ACFT AND A LOGBOOK ENTRY WAS MADE. MAINT TROUBLESHOT THE FLAP SYS BUT COULDN'T DUPLICATE THE PROB. MAINT SIGNED OFF THE LOGBOOK AND WE CONTINUED OUR TRIP. NO FURTHER FLAP PROBS WERE EXPERIENCED ON SUBSEQUENT APCHS. IN RETROSPECT; I SEE THAT I ERRED IN CALLING FOR FLAPS TO 5 DEGS AFTER THE GAR. I SEE NOW THAT THE FLAP HANDLE SHOULD HAVE REMAINED IN THE 10 DEG DETENT (DETENT TO LESSER INDICATING FLAP) AND THAT I SHOULD HAVE COMPLETED THE ENTIRE QRH CHKLIST AND REMAINED IN AN ABNORMAL LNDG CONFIGN THROUGHOUT THE SUBSEQUENT APCH AND LNDG. I HAVE EXPERIENCED 4 MAJOR SYS FAILURES IN THE B737-300 DURING AN 8 DAY PERIOD WHICH IS ALARMING AND INDICATES TO ME THAT THESE ACFT ARE AGING WITH PROBS. MAINT CHKS AND PROCS SHOULD PERHAPS BE MORE STRINGENT AND FREQUENT TO ENSURE THAT OUR ACFT OPERATE AS THEY WERE DESIGNED. IN THIS CASE OF FLAP SYS FAILURE; A GAR WAS WARRANTED. DURING A GAR; THE MOST IMPORTANT GOAL IS TO GET THE ACFT AWAY FROM THE GND. OUR PROCS: GAR THRUST; FLAPS 15 DEGS; AND LNDG GEAR UP; ARE INGRAINED IN US FROM DAY ONE. THIS IS THE PROC WE USED. THERE ARE NO MEMORY ITEMS IN THE QRH CHKLIST FOR 'FLAPS; TRAILING EDGE: ASYMMETRICAL' BUT YET THE CHKLIST IN ITS FIRST WARNING (NOT STEP) STATES: 'CHK PERFORMANCE DATA FOR RWY LENGTH REQUIREMENTS USING CURRENT RWY CONDITIONS AND THE CURRENT FLAP SETTING (ASSUMED WORST CASE). CHK CURRENT WX. IF A SAFE LNDG CANNOT BE MADE; DIVERT. ACCOMPLISH THIS PERFORMANCE REVIEW AS SOON AS PRACTICAL. ONCE THE FLAPS ARE EXTENDED; THEY SHOULD NOT BE RETRACTED. THE DRAG PENALTY MAY MAKE IT IMPOSSIBLE TO REACH AN ALTERNATE ARPT. DO NOT USE FMC FUEL PREDICTIONS WITH THE FLAPS EXTENDED.' THAT IS AN EXCEPTIONALLY LENGTHY WARNING AND THE IMPORTANT PART FOR PLTS DURING A GAR IS: 'ONCE THE FLAPS ARE EXTENDED; THEY SHOULD NOT BE RETRACTED.' I TAKE THAT TO MEAN THAT THE FLAP HANDLE SHOULD NOT BE MOVED UP ON A GAR WITH SUBSEQUENT ON SCHEDULE FLAP RETRACTIONS. IF NOT TOUCHING THE FLAP HANDLE OR MOVING THE FLAPS IS SUCH A CRITICAL ISSUE; THEN IT SHOULD BE A BOLD FACE MEMORY ITEM AND BE STEP #1 OF THE CHKLIST. 1) FLAP LEVER -- DO NOT MOVE. THIS WOULD PREVENT US FROM MAKING A WRONG MOVE ON A GAR. ONCE THE ACFT IS BACK AT PATTERN ALT; THE SITUATION COULD BE PROPERLY ANALYZED AND THE APPROPRIATE NOTES AND WARNINGS COULD BE READ AND THE APPROPRIATE STEPS OF THE CURRENT CHKLIST COULD BE PROPERLY COMPLETED.

Data retrieved from NASA's ASRS site as of January 2009 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.