ACR LGT ABORTED TKOF WHEN WARNING HORN ACTIVATED AT 80 KTS.

Narrative

ACFT WAS DEICED BTWN XA50 AND XB05 LCL. DEPARTED GATE AT XB14 LCL AND TAXIED TO RWY (APPROX 5-6 MIN TAXI). LOWERED FLAPS TO 5 DEGS AND CHKED TKOF WARNING HORN OPERATION WITH BYPASS AND SPEEDBRAKE PER OUR (AIRLINES) NORMAL PROC. WHILE TAKING RWY FOR TKOF; WARNING HORN SOUNDED AS INITIAL SPOOL UP PWR WAS APPLIED. FLAP POS WAS DOUBLE CHKED AT 5 DEGS; SPD BRAKE WAS CHKED IN FULL FORWARD DETENT; AND TRIM WAS CHKED IN TKOF GREEN BAND. ALL INDICATIONS WERE NORMAL AND CORRECT WITH WARNING HORN STILL SOUNDING. FLAPS WERE MOVED TO 15 DEGS AND WARNING HORN STOPPED. FLAPS WERE MOVED BACK TO 5 DEGS WITH NO RESULTANT HORN. WHILE ACCOMPLISHING ALL THE ABOVE; THE ACFT HAD BEEN POSITIONED AT A POS AND HOLD ON THE RWY AND PWR REDUCED TO IDLE. TKOF PWR WAS NOW APPLIED (FLAPS 5 DEGS) AND TKOF ROLL COMMENCED WITH NO HORN. AT APPROX 80 KTS AIRSPD; TKOF WARNING HORN AGAIN SOUNDED. TKOF WAS IMMEDIATELY ABORTED AND ACFT WAS TAXIED TO AN ADJACENT TXWY. FLAPS WERE POSITIONED TO 15 DEGS AND THROTTLES AGAIN ADVANCED WITH NO HORN. ACFT RECONFIGURED (FLAPS AND TRIM) FOR 15 DEG FLAP TKOF. DURING 15 DEG FLAP TKOF; NO TKOF WARNING HORN WAS EXPERIENCED. WHEN ACFT ARRIVED IN HOUSTON; ENTIRE FLAP POS WARNING SYS WAS CHKED BY MAINT. NO DEFECTS WERE FOUND AND SYS CHKED NORMALLY. SUSPECT DEICE FLUID MAY HAVE CONTRIBUTED TO MALFUNCTION BY ENTERING CANNON PLUG OR MICROSWITCH IN 5 DEG FLAP POS SENSING SYS. ALL PROCS AND ACTIONS TAKEN BY CREW WERE PER PUBLISHED PROCS.