Narrative:

On approach vectors I called for flaps 15 degrees from flaps 11 degrees. The captain lowered the flaps and noted that the leading edge slats did not go to 'land' position. We repeated this by moving them to 11 degrees then back to 15 degrees and the slats went from 'takeoff' to 'disagree' to 'takeoff' instead of to 'land.' (this action changes the slats from mid to full extend.) we broke out of the operating manual and ran the abnormal flap confign checklist. We also notified company maintenance and they agreed with our diagnosis of the problem. Our checklist choices were 'abnormal flap confign' and 'slat disagreement light.' we did not however, have a slat disagree light, which seemed odd to me but I couldn't figure out why if they were supposed to be in 'land' and were actually in 'takeoff' we would have 'takeoff' instead of 'disagree' illuminated. Running the abnormal flap checklist called for landing at last correct flap/slat position. We declared an emergency and landed at flaps 11 degrees, slats 'takeoff' with no problems. The company mechanics investigated the system and worked for about 45 mins when they found the problem. The flaps did go to the full extend position when we selected 15 degrees, as they should, however the annunciator does not change from 'takeoff' to 'land' until flaps 25 degrees or greater is selected. Therefore we created our own emergency, as a normal indication of flaps 15 degrees is 'takeoff' slats. Being new to airline flying, and new to the airplane I was sucked into my captain's diagnosis of a perceived problem. Also at our airline it is customary for the PNF to handle the emergency and PF to handle radios, so I didn't pay as much attention to the problem as I could have. In retrospect, had we checked the reference manual or recalled from training we would have caught our non-problem. Also, our maintenance coordinator confirmed our diagnosis of a problem, so we learned not to 'blindly' accept the experts opinion. Supplemental information from acn 395979: I told the first officer that I would fly the approach. I asked our company pilot occupying the cockpit jump seat for any input he may have and if he was comfortable with our preparations. He was not qualified on the type and had nothing he wanted to add. We flew an unhurried approach to an anti-climatic landing. I was called to the phone to speak with the same maintenance coordinator I had talked to in-flight. 'Captain, I believe what you had was a normal indication...' and he referenced me to the reference manual page describing the slat advisory lights. I agreed with him and accepted full responsibility for the incident. I also told him, however, that in-flight I had merely described symptoms to him and that he concurred that we probably had a malfunction. He was silent for a moment and then said that later he went to his reference manual. I feel that several human factors influences were at play with this event. This 'second opinion' of a problem convinced me to take the actions I was contemplating and helped to seal my failure to make use of one of my resources, my own aircraft reference manual. Why did my misconception finally exert itself? It is obvious that I was not focusing on the slat lights during initial approach confign, although I focus on them very closely during critical phase, checklist operation: flaps/slats 11 degrees, 11 degrees, takeoff and flaps/slats 40 degrees, 40 degrees, land. During approach confign, after selection of a particular flap setting I would look at the flap indicator for verification but was omitting the slat lights from my scan. That is now a former habit of mine.

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Original NASA ASRS Text

Title: AN MD88 FLC PERFORMS AN EMER LNDG AFTER HAVING HAD A SUPPOSED FLAP SLAT PROB.

Narrative: ON APCH VECTORS I CALLED FOR FLAPS 15 DEGS FROM FLAPS 11 DEGS. THE CAPT LOWERED THE FLAPS AND NOTED THAT THE LEADING EDGE SLATS DID NOT GO TO 'LAND' POS. WE REPEATED THIS BY MOVING THEM TO 11 DEGS THEN BACK TO 15 DEGS AND THE SLATS WENT FROM 'TKOF' TO 'DISAGREE' TO 'TKOF' INSTEAD OF TO 'LAND.' (THIS ACTION CHANGES THE SLATS FROM MID TO FULL EXTEND.) WE BROKE OUT OF THE OPERATING MANUAL AND RAN THE ABNORMAL FLAP CONFIGN CHKLIST. WE ALSO NOTIFIED COMPANY MAINT AND THEY AGREED WITH OUR DIAGNOSIS OF THE PROB. OUR CHKLIST CHOICES WERE 'ABNORMAL FLAP CONFIGN' AND 'SLAT DISAGREEMENT LIGHT.' WE DID NOT HOWEVER, HAVE A SLAT DISAGREE LIGHT, WHICH SEEMED ODD TO ME BUT I COULDN'T FIGURE OUT WHY IF THEY WERE SUPPOSED TO BE IN 'LAND' AND WERE ACTUALLY IN 'TKOF' WE WOULD HAVE 'TKOF' INSTEAD OF 'DISAGREE' ILLUMINATED. RUNNING THE ABNORMAL FLAP CHKLIST CALLED FOR LNDG AT LAST CORRECT FLAP/SLAT POS. WE DECLARED AN EMER AND LANDED AT FLAPS 11 DEGS, SLATS 'TKOF' WITH NO PROBS. THE COMPANY MECHS INVESTIGATED THE SYS AND WORKED FOR ABOUT 45 MINS WHEN THEY FOUND THE PROB. THE FLAPS DID GO TO THE FULL EXTEND POS WHEN WE SELECTED 15 DEGS, AS THEY SHOULD, HOWEVER THE ANNUNCIATOR DOES NOT CHANGE FROM 'TKOF' TO 'LAND' UNTIL FLAPS 25 DEGS OR GREATER IS SELECTED. THEREFORE WE CREATED OUR OWN EMER, AS A NORMAL INDICATION OF FLAPS 15 DEGS IS 'TKOF' SLATS. BEING NEW TO AIRLINE FLYING, AND NEW TO THE AIRPLANE I WAS SUCKED INTO MY CAPT'S DIAGNOSIS OF A PERCEIVED PROB. ALSO AT OUR AIRLINE IT IS CUSTOMARY FOR THE PNF TO HANDLE THE EMER AND PF TO HANDLE RADIOS, SO I DIDN'T PAY AS MUCH ATTN TO THE PROB AS I COULD HAVE. IN RETROSPECT, HAD WE CHKED THE REF MANUAL OR RECALLED FROM TRAINING WE WOULD HAVE CAUGHT OUR NON-PROB. ALSO, OUR MAINT COORDINATOR CONFIRMED OUR DIAGNOSIS OF A PROB, SO WE LEARNED NOT TO 'BLINDLY' ACCEPT THE EXPERTS OPINION. SUPPLEMENTAL INFO FROM ACN 395979: I TOLD THE FO THAT I WOULD FLY THE APCH. I ASKED OUR COMPANY PLT OCCUPYING THE COCKPIT JUMP SEAT FOR ANY INPUT HE MAY HAVE AND IF HE WAS COMFORTABLE WITH OUR PREPARATIONS. HE WAS NOT QUALIFIED ON THE TYPE AND HAD NOTHING HE WANTED TO ADD. WE FLEW AN UNHURRIED APCH TO AN ANTI-CLIMATIC LNDG. I WAS CALLED TO THE PHONE TO SPEAK WITH THE SAME MAINT COORDINATOR I HAD TALKED TO INFLT. 'CAPT, I BELIEVE WHAT YOU HAD WAS A NORMAL INDICATION...' AND HE REFED ME TO THE REF MANUAL PAGE DESCRIBING THE SLAT ADVISORY LIGHTS. I AGREED WITH HIM AND ACCEPTED FULL RESPONSIBILITY FOR THE INCIDENT. I ALSO TOLD HIM, HOWEVER, THAT INFLT I HAD MERELY DESCRIBED SYMPTOMS TO HIM AND THAT HE CONCURRED THAT WE PROBABLY HAD A MALFUNCTION. HE WAS SILENT FOR A MOMENT AND THEN SAID THAT LATER HE WENT TO HIS REF MANUAL. I FEEL THAT SEVERAL HUMAN FACTORS INFLUENCES WERE AT PLAY WITH THIS EVENT. THIS 'SECOND OPINION' OF A PROB CONVINCED ME TO TAKE THE ACTIONS I WAS CONTEMPLATING AND HELPED TO SEAL MY FAILURE TO MAKE USE OF ONE OF MY RESOURCES, MY OWN ACFT REF MANUAL. WHY DID MY MISCONCEPTION FINALLY EXERT ITSELF? IT IS OBVIOUS THAT I WAS NOT FOCUSING ON THE SLAT LIGHTS DURING INITIAL APCH CONFIGN, ALTHOUGH I FOCUS ON THEM VERY CLOSELY DURING CRITICAL PHASE, CHKLIST OP: FLAPS/SLATS 11 DEGS, 11 DEGS, TKOF AND FLAPS/SLATS 40 DEGS, 40 DEGS, LAND. DURING APCH CONFIGN, AFTER SELECTION OF A PARTICULAR FLAP SETTING I WOULD LOOK AT THE FLAP INDICATOR FOR VERIFICATION BUT WAS OMITTING THE SLAT LIGHTS FROM MY SCAN. THAT IS NOW A FORMER HABIT OF MINE.

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.