Narrative:

Flight was my leg bos to bwi. All required checklists and procedures were accomplished normally before departure. We were cleared for takeoff on runway 22R. Thrust levers were put approximately 3/4' forward of idle to allow the engines to accelerate and stabilize at the initial thrust setting (approximately 40% N1) as per our current company policy in the pilots operating handbook. Once stabilized, I attempted to further advance the thrust lever to the takeoff thrust setting. As I did so,we got an intermittent takeoff warning horn. Captain reduced thrust levers to idle and we both checked the flap handle position, speed brake handle position and stabilizer trim position--all possible causes of the takeoff warning horn. All 3 were in their normal, correct position for takeoff. Captain attempted to advance the thrust levers again; we got the takeoff warning horn again. Captain reduced thrust levers to idle and told me to advise the tower we were rejecting our takeoff and no equipment was required. I did so. Our airspeed at this time had not moved off of the 60 KT peg. We taxied to the next convenient taxiway, turned off the runway and stopped. Captain informed the passenger and F/a's of our situation via the P/a, to relieve apprehension and preclude an unwanted evacuate/evacuation. Bos tower was informed that we rejected our takeoff for a takeoff warning horn, and we wanted to stay where we were and troubleshoot the problem. Permission was given to do that. We carefully checked the speed brake problem. We carefully checked the speed brake lever position, stabilizer trim position, trailing edge flaps position, and the leading edge devices by looking outside, but were unable to determine the reason for the takeoff warning horn. We were about to return to the gate when we noticed that the leading edge flap position indicator circuit breaker had popped. Captain told me to reset the circuit breaker. I did, and we no longer got the intermittent takeoff warning horn when the thrust levers were advanced. We then requested and got clearance to taxi to runway 22R. We completed both the after start and before takeoff checklists again, then took off and proceeded to bwi west/O further incident. It is unknown to either the captain or me when or why the leading edge flap position indicator circuit breaker popped. 'Circuit breaker's...checked' is on our originating and intermediate checklists, required on the first flight of the day or with a crew change, respectively. For us, that was 2 legs prior to this one and both of those takeoffs and flts were normal. In retrospect, this was an uneventful situation that transpired in a normal manner. The system, if you will, of following procedures, using checklists and having backup warnings worked as it should have. The actions of the captain and myself were as per company procedures, and the decisions made were correct, resulting in a safely completed flight.

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Original NASA ASRS Text

Title: ACR ABORTS TKOF WHEN TKOF WARNING HORN SOUNDS.

Narrative: FLT WAS MY LEG BOS TO BWI. ALL REQUIRED CHKLISTS AND PROCS WERE ACCOMPLISHED NORMALLY BEFORE DEP. WE WERE CLRED FOR TKOF ON RWY 22R. THRUST LEVERS WERE PUT APPROX 3/4' FORWARD OF IDLE TO ALLOW THE ENGS TO ACCELERATE AND STABILIZE AT THE INITIAL THRUST SETTING (APPROX 40% N1) AS PER OUR CURRENT COMPANY POLICY IN THE PLTS OPERATING HANDBOOK. ONCE STABILIZED, I ATTEMPTED TO FURTHER ADVANCE THE THRUST LEVER TO THE TKOF THRUST SETTING. AS I DID SO,WE GOT AN INTERMITTENT TKOF WARNING HORN. CAPT REDUCED THRUST LEVERS TO IDLE AND WE BOTH CHKED THE FLAP HANDLE POS, SPD BRAKE HANDLE POS AND STABILIZER TRIM POS--ALL POSSIBLE CAUSES OF THE TKOF WARNING HORN. ALL 3 WERE IN THEIR NORMAL, CORRECT POS FOR TKOF. CAPT ATTEMPTED TO ADVANCE THE THRUST LEVERS AGAIN; WE GOT THE TKOF WARNING HORN AGAIN. CAPT REDUCED THRUST LEVERS TO IDLE AND TOLD ME TO ADVISE THE TWR WE WERE REJECTING OUR TKOF AND NO EQUIP WAS REQUIRED. I DID SO. OUR AIRSPD AT THIS TIME HAD NOT MOVED OFF OF THE 60 KT PEG. WE TAXIED TO THE NEXT CONVENIENT TXWY, TURNED OFF THE RWY AND STOPPED. CAPT INFORMED THE PAX AND F/A'S OF OUR SITUATION VIA THE P/A, TO RELIEVE APPREHENSION AND PRECLUDE AN UNWANTED EVAC. BOS TWR WAS INFORMED THAT WE REJECTED OUR TKOF FOR A TKOF WARNING HORN, AND WE WANTED TO STAY WHERE WE WERE AND TROUBLESHOOT THE PROB. PERMISSION WAS GIVEN TO DO THAT. WE CAREFULLY CHKED THE SPD BRAKE PROB. WE CAREFULLY CHKED THE SPD BRAKE LEVER POS, STABILIZER TRIM POS, TRAILING EDGE FLAPS POS, AND THE LEADING EDGE DEVICES BY LOOKING OUTSIDE, BUT WERE UNABLE TO DETERMINE THE REASON FOR THE TKOF WARNING HORN. WE WERE ABOUT TO RETURN TO THE GATE WHEN WE NOTICED THAT THE LEADING EDGE FLAP POS INDICATOR CB HAD POPPED. CAPT TOLD ME TO RESET THE CB. I DID, AND WE NO LONGER GOT THE INTERMITTENT TKOF WARNING HORN WHEN THE THRUST LEVERS WERE ADVANCED. WE THEN REQUESTED AND GOT CLRNC TO TAXI TO RWY 22R. WE COMPLETED BOTH THE AFTER START AND BEFORE TKOF CHKLISTS AGAIN, THEN TOOK OFF AND PROCEEDED TO BWI W/O FURTHER INCIDENT. IT IS UNKNOWN TO EITHER THE CAPT OR ME WHEN OR WHY THE LEADING EDGE FLAP POS INDICATOR CB POPPED. 'CB'S...CHKED' IS ON OUR ORIGINATING AND INTERMEDIATE CHKLISTS, REQUIRED ON THE FIRST FLT OF THE DAY OR WITH A CREW CHANGE, RESPECTIVELY. FOR US, THAT WAS 2 LEGS PRIOR TO THIS ONE AND BOTH OF THOSE TKOFS AND FLTS WERE NORMAL. IN RETROSPECT, THIS WAS AN UNEVENTFUL SITUATION THAT TRANSPIRED IN A NORMAL MANNER. THE SYS, IF YOU WILL, OF FOLLOWING PROCS, USING CHKLISTS AND HAVING BACKUP WARNINGS WORKED AS IT SHOULD HAVE. THE ACTIONS OF THE CAPT AND MYSELF WERE AS PER COMPANY PROCS, AND THE DECISIONS MADE WERE CORRECT, RESULTING IN A SAFELY COMPLETED FLT.

Data retrieved from NASA's ASRS site as of August 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.