AN LTT CREW SELECTED THEIR ANTI-SKID TO 'TEST' VICE 'OFF.' THIS TURNED OFF THE BRAKES ALLOWING THE ACFT TO GO OFF THE END OF THE RWY.

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CLBED TO 7500 FT VFR AND PROCEEDED TO ILM AND CONTACTED ZDC FOR TFC AND WX. AT APPROX XY15Z WASHINGTON GAVE US THE XY50Z ILM WX AS CLR AND 7. WE ELECTED A VISUAL APCH TO RWY 17 AND HAD VISUAL CONTACT SEVERAL MI OUT. AGAIN; ON SHORT FINAL; FOG WAS ENCOUNTERED AND PWR APPLIED FOR A GAR. BEFORE SPOOL-UP; VISUAL CONDITIONS WERE REACHED AND THE PWR REDUCED FOR A LNDG. TOUCHDOWN WAS APPROX. MIDFIELD WHICH SHOULD HAVE BEEN ADEQUATE FOR A SAFE STOP. HOWEVER; WITH SPDBRAKES EXTENDED; THRUST REVERSERS EXTENDED; AND BRAKES APPLIED; IT BECAME APPARENT THAT WE WERE NOT STOPPING. THE ANTI-SKID WAS CYCLING RAPIDLY AND I DECIDED TO TURN THE ANTI-SKID OFF. THE 3 POS SWITCH (ON-OFF-TEST) WAS MOVED INADVERTENTLY TO THE TEST POS FOR AN INSTANT; WHICH CAUSES COMPLETE LOSS OF BRAKING; AND THEN BACK TO OFF. AT THIS POINT; WITHOUT ANTI-SKID PROTECTION; THE WHEELS LOCKED UP AND BLEW THE L MAIN TIRE. A COMPLETE STOP WAS NOT ACCOMPLISHED UNTIL APPROX 100 FT PAST THE END OF RWY 17. THERE WAS NO DAMAGE OTHER THAN THE TIRES; AND 1 RWY LIGHT; AND NO INJURIES. SUPPLEMENTAL INFO FROM ACN 220679: IT APPEARED THAT WE HAD AMPLE RWY AS WE FLARED. ACFT FLOATED BRIEFLY; THEN TOUCHED DOWN. CAPT DEPLOYED THRUST REVERSERS AND BRAKES WHILE I DEPLOYED SPDBRAKES. BRAKING ACTION APPEARED POOR TO ME; AND I OBSERVED CAPT REACHING FOR ANTI-SKID SWITCH. DURING GND SCHOOL AT WICHITA; GND INSTRUCTOR HAD INFORMED US THAT ON SOME OCCASIONS; ANTI-SKID HAD PERFORMED INCORRECTLY DUE TO COMPUTER GLITCHES IN WHEEL SPD SENSORS. HE SAID THAT ONE OPTION WOULD BE TO DISABLE OR TURN ANTI-SKID OFF.