Narrative:

This was the first leg of a 3 day trip. We taxied out from gate to runway 4 on a VFR morning. As we were cleared to cross runway 31C en route to runway 4, there were 3 aircraft ahead of us in sequence. The tower cleared the other 2 aircraft for takeoff fairly rapidly. We were cleared into position to hold much sooner than we expected. We were probably about 3000 ft from the hold line when he cleared us onto hold. The captain called for the before takeoff checklist as we approached the runway. I assumed he had completed the throttle burst sometime during the taxi out, but I really don't know if he did or not. It was my takeoff and was briefed prior to taxi. We completed the checklist prior to entering the runway and were told by tower to be ready, there was an aircraft on final (3 or 4 mi, I think). I took control of the aircraft and was cleared for takeoff. When I pushed up the thrust levers, the takeoff warning horn sounded. I pulled the levers to idle. We both looked at confign, and saw the trim, flaps and speed brakes had the appropriate normal indications. He said push it up again, and again the horn went off. I began to pull back the throttles again, but he said 'everything is ok, go ahead and go.' I pushed the throttles up again and again the horn went off. I said set takeoff thrust and relinquished the throttles to the captain. He elected to continue the takeoff with the horn sounding until we lifted off. This entire event occurred very quickly with the aircraft never perceptibly slowing from the initial takeoff roll. I did not apply the brakes at any time. I had 2 thoughts in my mind during the sequence. The decision to abort rests with the captain and I was pretty sure the book said not to take off with a takeoff warning horn. As I looked back, I realized I could have applied the brakes and stopped the aircraft on the runway, but I was expecting the captain to make the abort decision. Once he committed to take off, I went along with his decision. I wish I had been more assertive and just stopped the airplane on the initial horn sounding, but I expected him to take the aircraft when I pulled the throttles back and taxi off the runway. My strong recommendation is to make the 'throttle burst' part of the before takeoff checklist. In this case with an extremely early clearance onto hold, we were rushed to the before takeoff check and missed the throttle burst before we got on the runway. Once on the runway, that insidious 'go mentality' got the best of us. I must assume that there was some sensor malfunction on this B-700, because we both saw flaps at 5 degrees, trim in the green and the speed brake stowed. The aircraft behaved normally for the rest of the day. I also know that pilots sometimes see what they expect to see and that's why the horn is there. We should have followed the procedures and troubleshot the problem on the taxiway after aborting the takeoff. We should also have written up a malfunctioning aircraft so some other crew isn't faced with this same preventable event. I will next time. Supplemental information from acn 634114: continued the takeoff by my command. Takeoff was normal. Double-checked the confign and both pilots agreed it was normal. As a note, this was my third false takeoff warning horn in the B-700 aircraft. Other two were high speed heavy weight warning sounded between 80 KTS and V1. If we are to obey the takeoff warning horn, we desperately need a dependable takeoff warning system. We were cleared very early for takeoff (still 2 aircraft on the taxiway ahead of us) and began the before takeoff checklist before we had a chance to do the throttle burst. If this was part of the before takeoff checklist, we would have found this false horn before we were cleared for takeoff.

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Original NASA ASRS Text

Title: A B737-700 FLT CREW CONTINUES THEIR TKOF AFTER RECEIVING AN ACFT CONFIGN WARNING HORN AFTER THROTTLE ADVANCEMENT AT MDW.

Narrative: THIS WAS THE FIRST LEG OF A 3 DAY TRIP. WE TAXIED OUT FROM GATE TO RWY 4 ON A VFR MORNING. AS WE WERE CLRED TO CROSS RWY 31C ENRTE TO RWY 4, THERE WERE 3 ACFT AHEAD OF US IN SEQUENCE. THE TWR CLRED THE OTHER 2 ACFT FOR TKOF FAIRLY RAPIDLY. WE WERE CLRED INTO POS TO HOLD MUCH SOONER THAN WE EXPECTED. WE WERE PROBABLY ABOUT 3000 FT FROM THE HOLD LINE WHEN HE CLRED US ONTO HOLD. THE CAPT CALLED FOR THE BEFORE TKOF CHKLIST AS WE APCHED THE RWY. I ASSUMED HE HAD COMPLETED THE THROTTLE BURST SOMETIME DURING THE TAXI OUT, BUT I REALLY DON'T KNOW IF HE DID OR NOT. IT WAS MY TKOF AND WAS BRIEFED PRIOR TO TAXI. WE COMPLETED THE CHKLIST PRIOR TO ENTERING THE RWY AND WERE TOLD BY TWR TO BE READY, THERE WAS AN ACFT ON FINAL (3 OR 4 MI, I THINK). I TOOK CTL OF THE ACFT AND WAS CLRED FOR TKOF. WHEN I PUSHED UP THE THRUST LEVERS, THE TKOF WARNING HORN SOUNDED. I PULLED THE LEVERS TO IDLE. WE BOTH LOOKED AT CONFIGN, AND SAW THE TRIM, FLAPS AND SPD BRAKES HAD THE APPROPRIATE NORMAL INDICATIONS. HE SAID PUSH IT UP AGAIN, AND AGAIN THE HORN WENT OFF. I BEGAN TO PULL BACK THE THROTTLES AGAIN, BUT HE SAID 'EVERYTHING IS OK, GO AHEAD AND GO.' I PUSHED THE THROTTLES UP AGAIN AND AGAIN THE HORN WENT OFF. I SAID SET TKOF THRUST AND RELINQUISHED THE THROTTLES TO THE CAPT. HE ELECTED TO CONTINUE THE TKOF WITH THE HORN SOUNDING UNTIL WE LIFTED OFF. THIS ENTIRE EVENT OCCURRED VERY QUICKLY WITH THE ACFT NEVER PERCEPTIBLY SLOWING FROM THE INITIAL TKOF ROLL. I DID NOT APPLY THE BRAKES AT ANY TIME. I HAD 2 THOUGHTS IN MY MIND DURING THE SEQUENCE. THE DECISION TO ABORT RESTS WITH THE CAPT AND I WAS PRETTY SURE THE BOOK SAID NOT TO TAKE OFF WITH A TKOF WARNING HORN. AS I LOOKED BACK, I REALIZED I COULD HAVE APPLIED THE BRAKES AND STOPPED THE ACFT ON THE RWY, BUT I WAS EXPECTING THE CAPT TO MAKE THE ABORT DECISION. ONCE HE COMMITTED TO TAKE OFF, I WENT ALONG WITH HIS DECISION. I WISH I HAD BEEN MORE ASSERTIVE AND JUST STOPPED THE AIRPLANE ON THE INITIAL HORN SOUNDING, BUT I EXPECTED HIM TO TAKE THE ACFT WHEN I PULLED THE THROTTLES BACK AND TAXI OFF THE RWY. MY STRONG RECOMMENDATION IS TO MAKE THE 'THROTTLE BURST' PART OF THE BEFORE TKOF CHKLIST. IN THIS CASE WITH AN EXTREMELY EARLY CLRNC ONTO HOLD, WE WERE RUSHED TO THE BEFORE TKOF CHK AND MISSED THE THROTTLE BURST BEFORE WE GOT ON THE RWY. ONCE ON THE RWY, THAT INSIDIOUS 'GO MENTALITY' GOT THE BEST OF US. I MUST ASSUME THAT THERE WAS SOME SENSOR MALFUNCTION ON THIS B-700, BECAUSE WE BOTH SAW FLAPS AT 5 DEGS, TRIM IN THE GREEN AND THE SPD BRAKE STOWED. THE ACFT BEHAVED NORMALLY FOR THE REST OF THE DAY. I ALSO KNOW THAT PLTS SOMETIMES SEE WHAT THEY EXPECT TO SEE AND THAT'S WHY THE HORN IS THERE. WE SHOULD HAVE FOLLOWED THE PROCS AND TROUBLESHOT THE PROB ON THE TXWY AFTER ABORTING THE TKOF. WE SHOULD ALSO HAVE WRITTEN UP A MALFUNCTIONING ACFT SO SOME OTHER CREW ISN'T FACED WITH THIS SAME PREVENTABLE EVENT. I WILL NEXT TIME. SUPPLEMENTAL INFO FROM ACN 634114: CONTINUED THE TKOF BY MY COMMAND. TKOF WAS NORMAL. DOUBLE-CHKED THE CONFIGN AND BOTH PLTS AGREED IT WAS NORMAL. AS A NOTE, THIS WAS MY THIRD FALSE TKOF WARNING HORN IN THE B-700 ACFT. OTHER TWO WERE HIGH SPD HVY WT WARNING SOUNDED BTWN 80 KTS AND V1. IF WE ARE TO OBEY THE TKOF WARNING HORN, WE DESPERATELY NEED A DEPENDABLE TKOF WARNING SYS. WE WERE CLRED VERY EARLY FOR TKOF (STILL 2 ACFT ON THE TXWY AHEAD OF US) AND BEGAN THE BEFORE TKOF CHKLIST BEFORE WE HAD A CHANCE TO DO THE THROTTLE BURST. IF THIS WAS PART OF THE BEFORE TKOF CHKLIST, WE WOULD HAVE FOUND THIS FALSE HORN BEFORE WE WERE CLRED FOR TKOF.

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.