Narrative:

When the copilot and I arrived at the airport we found that we would be flying an medium large transport Y that had a history of trouble with the leading edge devices indication system. The system was fixed the night before and when we arrived in the cockpit it appeared to be normal. About 10 mins before departure, however, the amber transit light began blinking at random so we called maintenance and they decided to render the system (transit light) inoperative and defer maintenance action in order to protect the on time departure. 2 mechanics appeared in the cockpit to effect the deferral. There was a discussion between them about the correct circuit breaker to be pulled and then there was a discussion about whether there was a second circuit breaker to be pulled. They were obviously under some stress because it was now only a couple mins before departure and the company was putting great emphasis on having punctual departures. After completing their procedures the leading edge amber light was on steady but I concluded that was normal with the circuit breaker pulled and the system inoperative. We departed on time and as we taxied there was some confusion as to our sequence for takeoff. We found ourselves in a discussion with the tower as to our assigned sequence because it was the tower's intention to have us depart ahead of 2 aircraft that were, in fact, taxiing ahead of us. This situation interrupted our pre-takeoff checklist. When I advanced the throttles for takeoff the takeoff warning horn sounded and I taxied clear of the runway to resolve the problem. We were unable to see the problem and I strongly suspected the leading edge indicating system even though it was supposed to be inoperative. We called maintenance and they were also unable to resolve the problem so we returned to the gate. At the gate the mechanics found the flaps at position 1. That is normal for the medium large transport X which comprises 90 percent of the fleet. However, the Y model is not certified for takeoff at flaps position 1 and flaps 1 will produce a takeoff warning horn. Fortunately, the only harm here was a delay of the flight. There are several factors that led to this situation. In my opinion one of the most important is the time pressure on the mechanics that deferred the leading edge indicating system. Had I felt that they had the time to be methodological in their approach I don't think that I would have so strongly suspected the leading edge system. Another important factor is dealing with a large fleet of aircraft wherein about 10 percent of the aircraft have a nonstandard takeoff flap position. A minor factor is the interruption to the takeoff checklist and the fact that the company had just published a new graphic for the presentation of the flap settings and takeoff speeds that was unfamiliar. Even so, we did some things right. When we were unable to resolve the cause of the takeoff warning horn we sought help and persisted until the situation was resolved. It would have been very easy to assume that the cause was the leading edge transit light and takeoff anyway. I certainly accept the embarrassment of selecting the incorrect flap position and delaying the flight to the embarrassment of taking off with an incorrect flap position.

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Original NASA ASRS Text

Title: TKOF ABORTED ACCOUNT ACFT EQUIP PROBLEM.

Narrative: WHEN THE COPLT AND I ARRIVED AT THE ARPT WE FOUND THAT WE WOULD BE FLYING AN MLG Y THAT HAD A HISTORY OF TROUBLE WITH THE LEADING EDGE DEVICES INDICATION SYS. THE SYS WAS FIXED THE NIGHT BEFORE AND WHEN WE ARRIVED IN THE COCKPIT IT APPEARED TO BE NORMAL. ABOUT 10 MINS BEFORE DEP, HOWEVER, THE AMBER TRANSIT LIGHT BEGAN BLINKING AT RANDOM SO WE CALLED MAINT AND THEY DECIDED TO RENDER THE SYS (TRANSIT LIGHT) INOP AND DEFER MAINT ACTION IN ORDER TO PROTECT THE ON TIME DEP. 2 MECHS APPEARED IN THE COCKPIT TO EFFECT THE DEFERRAL. THERE WAS A DISCUSSION BTWN THEM ABOUT THE CORRECT CIRCUIT BREAKER TO BE PULLED AND THEN THERE WAS A DISCUSSION ABOUT WHETHER THERE WAS A SECOND CIRCUIT BREAKER TO BE PULLED. THEY WERE OBVIOUSLY UNDER SOME STRESS BECAUSE IT WAS NOW ONLY A COUPLE MINS BEFORE DEP AND THE COMPANY WAS PUTTING GREAT EMPHASIS ON HAVING PUNCTUAL DEPS. AFTER COMPLETING THEIR PROCS THE LEADING EDGE AMBER LIGHT WAS ON STEADY BUT I CONCLUDED THAT WAS NORMAL WITH THE CIRCUIT BREAKER PULLED AND THE SYS INOP. WE DEPARTED ON TIME AND AS WE TAXIED THERE WAS SOME CONFUSION AS TO OUR SEQUENCE FOR TKOF. WE FOUND OURSELVES IN A DISCUSSION WITH THE TWR AS TO OUR ASSIGNED SEQUENCE BECAUSE IT WAS THE TWR'S INTENTION TO HAVE US DEPART AHEAD OF 2 ACFT THAT WERE, IN FACT, TAXIING AHEAD OF US. THIS SITUATION INTERRUPTED OUR PRE-TKOF CHKLIST. WHEN I ADVANCED THE THROTTLES FOR TKOF THE TKOF WARNING HORN SOUNDED AND I TAXIED CLR OF THE RWY TO RESOLVE THE PROBLEM. WE WERE UNABLE TO SEE THE PROBLEM AND I STRONGLY SUSPECTED THE LEADING EDGE INDICATING SYS EVEN THOUGH IT WAS SUPPOSED TO BE INOP. WE CALLED MAINT AND THEY WERE ALSO UNABLE TO RESOLVE THE PROBLEM SO WE RETURNED TO THE GATE. AT THE GATE THE MECHS FOUND THE FLAPS AT POS 1. THAT IS NORMAL FOR THE MLG X WHICH COMPRISES 90 PERCENT OF THE FLEET. HOWEVER, THE Y MODEL IS NOT CERTIFIED FOR TKOF AT FLAPS POS 1 AND FLAPS 1 WILL PRODUCE A TKOF WARNING HORN. FORTUNATELY, THE ONLY HARM HERE WAS A DELAY OF THE FLT. THERE ARE SEVERAL FACTORS THAT LED TO THIS SITUATION. IN MY OPINION ONE OF THE MOST IMPORTANT IS THE TIME PRESSURE ON THE MECHS THAT DEFERRED THE LEADING EDGE INDICATING SYS. HAD I FELT THAT THEY HAD THE TIME TO BE METHODOLOGICAL IN THEIR APCH I DON'T THINK THAT I WOULD HAVE SO STRONGLY SUSPECTED THE LEADING EDGE SYS. ANOTHER IMPORTANT FACTOR IS DEALING WITH A LARGE FLEET OF ACFT WHEREIN ABOUT 10 PERCENT OF THE ACFT HAVE A NONSTANDARD TKOF FLAP POS. A MINOR FACTOR IS THE INTERRUPTION TO THE TKOF CHKLIST AND THE FACT THAT THE COMPANY HAD JUST PUBLISHED A NEW GRAPHIC FOR THE PRESENTATION OF THE FLAP SETTINGS AND TKOF SPDS THAT WAS UNFAMILIAR. EVEN SO, WE DID SOME THINGS RIGHT. WHEN WE WERE UNABLE TO RESOLVE THE CAUSE OF THE TKOF WARNING HORN WE SOUGHT HELP AND PERSISTED UNTIL THE SITUATION WAS RESOLVED. IT WOULD HAVE BEEN VERY EASY TO ASSUME THAT THE CAUSE WAS THE LEADING EDGE TRANSIT LIGHT AND TKOF ANYWAY. I CERTAINLY ACCEPT THE EMBARRASSMENT OF SELECTING THE INCORRECT FLAP POS AND DELAYING THE FLT TO THE EMBARRASSMENT OF TAKING OFF WITH AN INCORRECT FLAP POS.

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.