TKOF WARNING HORN ACCOUNT FLAP PROBLEM. TKOF ABORT.

Narrative

WE WERE CLRED FOR TKOF AT WASHINGTON NATL ARPT; DCA. CONDITIONS WERE NIGHT VMC; GOOD CEILING AND VISIBILITY. ALL CHKLISTS WERE COMPLETED. TYPE ACFT WAS MLG. AFTER BEING CLRED FOR TKOF I MOVED THE THROTTLES FULL THROW FORWARD AND AFT TO CHK THAT ALL CONFIGN AND TRIM SETTINGS WERE PROPERLY SET FOR THE TKOF. AFTER REVIEWING ALL CONFIGN OF FLAPS/TRIM/SLATS AND AUTOFLT; I ONCE AGAIN TOOK A FINAL LOOK AT THE WT SHEET. WITH EVERYTHING SET CORRECTLY I TURNED CTL OF THE ACFT OVER TO THE FO. HE ADVANCED THE PWR AND I READ OFF THE N1 SETTINGS ONCE THE PWR WAS SET. THE ACFT ACCELERATED DOWN THE RWY NORMALLY UP TO APPROX 105 KTS. AT THAT TIME THE AURAL 'FLAPS; FLAPS' AUDIO WAS HEARD. I CHKED FLAP AND SLAT CONFIGN AND ALL WAS NORMAL AND SET CORRECTLY FOR TKOF. NOT KNOWING THE PROBLEM I ORDERED THE ABORT. THE FO ABORTED THE TKOF AND I NOTIFIED THE TWR. I ASSUMED CTL OF THE ACFT AT TAXI SPD AND CLRED THE RWY WITH NO PROBLEM. I HAD THE FO ADVISE THE FLT ATTENDANTS AND MAKE A SHORT PA TO THE PAX. WE REVIEWED THE FLT MANUAL PROCS FOR AND ABORTED TKOF AND THEN COMPLETED THE AFTER LNDG. I RETURNED THE ACFT TO THE GATE AND TURNED IT OVER TO MAINT. MAINT FOUND A LOT OF DEBRIS IN THE FLAP SELECT DETENT AREA. THE AREA IN THE CONSOLE NEEDED TO BE CLEANED BADLY. THE CAUSE OF THE PROBLEM AS MAINT TOLD US WAS THE FLAP DETENT IN THE DIAL A FLAP POS WAS FULL OF DEBRIS AND WOULD NOT ALLOW THE FLAP SETTING PIN TO FULLY SLIP INTO THE DETENT POS. AFTER THIS AREA WAS CLEANED AND ALL FLAP POS INDICATORS WERE CHKED AND SIGNED OFF BY MAINT WE MADE ANOTHER TKOF WITHOUT ANY PROBLEM. RECOMMENDATION: CONSOLE AREA OF ALL ACFT; NOT ONLY THE MLG; SHOULD BE CHKED AND CLEANED OCCASIONALLY FOR SUCH DEBRIS.