Narrative:

We were cleared for takeoff runway 13R and I taxied onto the runway. The copilot advanced the throttles and the takeoff warning horn sounded. I took control at less than 20 KTS. I quickly scanned the items I knew would give us such a warning. Everything appeared to be in the proper position. I deployed and reset the speed brake lever and advanced the throttle without getting a takeoff warning. The tower operator wanted to know the reason for the warning because his supervisor would want to know. I told him that the speed brake lever down detent had given the false warning. Once again we were cleared for takeoff. As I taxied to the runway, I pushed the #3 speed brake test button only to get another takeoff warning. We taxied clear of the runway once again, and called our maintenance base. I noticed that the lights on the overhead leading edge device annunciator panel were out and that the green leading edge flaps extended light on the forward instrument panel was out as well. (Note: I successfully tested the overhead panel on my preflight and the green light was definitely on when we read the second item on the before takeoff checklist shortly after leaving the gate.) we moved the flap lever to different position without changing these indications. Checking further, we found that the circuit breaker for the leading edge position indicator had popped. We reset the breaker and received the proper indications. We completed the flight normally. After arriving in denver, I discussed this situation with den maintenance. We discussed the speed brake reset feature, which apparently was not part of the problem and the nature of the popped circuit breaker. Since the circuit breaker in question is the yellow- capped one for this system, it is possible that the latching mechanism has been weakened by the daily cycling of this circuit breaker and perhaps the breaker was not solidly reset during preflight even though it allowed a successful preflight and before takeoff checklist to be completed. We agreed that we should watch and see if it popped again before writing it up. The next 2 legs were completely uneventful and the circuit breaker stayed in the entire time. A possible factor to be considered in this situation is that different aircraft configns exist for the takeoff warning system and test. Some aircraft must be tested by the #3 speed brake button and some by advancing the throttle. Which confign you have can be determined by the presence of a sticker marked 'takeoff' near the #3 button. This difference contributed to my failure to be able to rule out the speed brake reset as the cause of the takeoff warning. Even though I test the takeoff warning horn on preflight with the throttle or with the button as the aircraft confign dictates, this time after resetting the speed brake handle, I mistakenly relied on advancing the throttle to tell me that the system was working. My seat position is such that the 3 speed brake buttons are not readily visible to me unless I duck my head to look under the glareshield. Since the warning horn was silent with throttle movement, I felt that resetting the speed brake had resolved the problem when it had not. Only when I remembered to use the test button did I discover that we had not yet idented the real problem correctly.

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Original NASA ASRS Text

Title: AN MLG ABORTED 2 TKOFS BECAUSE OF A POPPED CIRCUIT BREAKER.

Narrative: WE WERE CLRED FOR TKOF RWY 13R AND I TAXIED ONTO THE RWY. THE COPLT ADVANCED THE THROTTLES AND THE TKOF WARNING HORN SOUNDED. I TOOK CTL AT LESS THAN 20 KTS. I QUICKLY SCANNED THE ITEMS I KNEW WOULD GIVE US SUCH A WARNING. EVERYTHING APPEARED TO BE IN THE PROPER POS. I DEPLOYED AND RESET THE SPD BRAKE LEVER AND ADVANCED THE THROTTLE WITHOUT GETTING A TKOF WARNING. THE TWR OPERATOR WANTED TO KNOW THE REASON FOR THE WARNING BECAUSE HIS SUPVR WOULD WANT TO KNOW. I TOLD HIM THAT THE SPD BRAKE LEVER DOWN DETENT HAD GIVEN THE FALSE WARNING. ONCE AGAIN WE WERE CLRED FOR TKOF. AS I TAXIED TO THE RWY, I PUSHED THE #3 SPD BRAKE TEST BUTTON ONLY TO GET ANOTHER TKOF WARNING. WE TAXIED CLR OF THE RWY ONCE AGAIN, AND CALLED OUR MAINT BASE. I NOTICED THAT THE LIGHTS ON THE OVERHEAD LEADING EDGE DEVICE ANNUNCIATOR PANEL WERE OUT AND THAT THE GREEN LEADING EDGE FLAPS EXTENDED LIGHT ON THE FORWARD INST PANEL WAS OUT AS WELL. (NOTE: I SUCCESSFULLY TESTED THE OVERHEAD PANEL ON MY PREFLT AND THE GREEN LIGHT WAS DEFINITELY ON WHEN WE READ THE SECOND ITEM ON THE BEFORE TKOF CHKLIST SHORTLY AFTER LEAVING THE GATE.) WE MOVED THE FLAP LEVER TO DIFFERENT POS WITHOUT CHANGING THESE INDICATIONS. CHKING FURTHER, WE FOUND THAT THE CIRCUIT BREAKER FOR THE LEADING EDGE POS INDICATOR HAD POPPED. WE RESET THE BREAKER AND RECEIVED THE PROPER INDICATIONS. WE COMPLETED THE FLT NORMALLY. AFTER ARRIVING IN DENVER, I DISCUSSED THIS SITUATION WITH DEN MAINT. WE DISCUSSED THE SPD BRAKE RESET FEATURE, WHICH APPARENTLY WAS NOT PART OF THE PROBLEM AND THE NATURE OF THE POPPED CIRCUIT BREAKER. SINCE THE CIRCUIT BREAKER IN QUESTION IS THE YELLOW- CAPPED ONE FOR THIS SYS, IT IS POSSIBLE THAT THE LATCHING MECHANISM HAS BEEN WEAKENED BY THE DAILY CYCLING OF THIS CIRCUIT BREAKER AND PERHAPS THE BREAKER WAS NOT SOLIDLY RESET DURING PREFLT EVEN THOUGH IT ALLOWED A SUCCESSFUL PREFLT AND BEFORE TKOF CHKLIST TO BE COMPLETED. WE AGREED THAT WE SHOULD WATCH AND SEE IF IT POPPED AGAIN BEFORE WRITING IT UP. THE NEXT 2 LEGS WERE COMPLETELY UNEVENTFUL AND THE CIRCUIT BREAKER STAYED IN THE ENTIRE TIME. A POSSIBLE FACTOR TO BE CONSIDERED IN THIS SITUATION IS THAT DIFFERENT ACFT CONFIGNS EXIST FOR THE TKOF WARNING SYS AND TEST. SOME ACFT MUST BE TESTED BY THE #3 SPD BRAKE BUTTON AND SOME BY ADVANCING THE THROTTLE. WHICH CONFIGN YOU HAVE CAN BE DETERMINED BY THE PRESENCE OF A STICKER MARKED 'TKOF' NEAR THE #3 BUTTON. THIS DIFFERENCE CONTRIBUTED TO MY FAILURE TO BE ABLE TO RULE OUT THE SPD BRAKE RESET AS THE CAUSE OF THE TKOF WARNING. EVEN THOUGH I TEST THE TKOF WARNING HORN ON PREFLT WITH THE THROTTLE OR WITH THE BUTTON AS THE ACFT CONFIGN DICTATES, THIS TIME AFTER RESETTING THE SPD BRAKE HANDLE, I MISTAKENLY RELIED ON ADVANCING THE THROTTLE TO TELL ME THAT THE SYS WAS WORKING. MY SEAT POS IS SUCH THAT THE 3 SPD BRAKE BUTTONS ARE NOT READILY VISIBLE TO ME UNLESS I DUCK MY HEAD TO LOOK UNDER THE GLARESHIELD. SINCE THE WARNING HORN WAS SILENT WITH THROTTLE MOVEMENT, I FELT THAT RESETTING THE SPD BRAKE HAD RESOLVED THE PROBLEM WHEN IT HAD NOT. ONLY WHEN I REMEMBERED TO USE THE TEST BUTTON DID I DISCOVER THAT WE HAD NOT YET IDENTED THE REAL PROBLEM CORRECTLY.

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.