A DASSAULT FALCON 20 ON LANDING ROLL OUT EXECUTED A GAR DUE TO #1 AND #2 BRAKE SYSTEM MALFUNCTION. CAUSED BY THE BRAKE HANDLE DETENT LOCK FAILURE.

Narrative

SHORTLY AFTER TOUCHDOWN AT ZZZ (APPROX 2-3 SECS) THE BRAKE HANDLE RELEASED TO A POSITION THAT WAS BTWN BRAKES #1 AND (BRAKES #2 -NO ANTI-SKID); THEREBY REMOVING ANY AND ALL BRAKING ACTION. AT THAT TIME I (CAPT) TOOK CTL OF THE ACFT; ASSUMING WE HAD A COMPLETE BRAKE FAILURE AND INITIATED A GAR LIFTING OFF AT THE RWYS EDGE. ONCE AIRBORNE ON THE MISSED WE REALIZED THE NATURE OF THE PROBS; CORRECTED BRAKE HANDLE AND RECEIVED RADAR VECTORS TO THE ILS AT ZZZ. INBOUND ON THE ILS TWR NOTIFIED US THAT VISIBILITY HAD DROPPED BELOW MINIMUM (3/4 MILE) WE THEN DIVERTED TO ZZA AND HAD AN UNEVENTFUL LANDING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THE BRAKE HANDLE IS LOCATED ON THE CENTER GLARESHIELD AND SELECTS EITHER #1 SYSTEM NORMAL BRAKING WITH ANTI-SKID OP OR #2 SYSTEM ALTERNATE BRAKE SYSTEM WITH NO ANTI-SKID. THE RPTR SAID #1 SYSTEM WAS SELECTED AND AFTER DISCOVERY OF NO BRAKING ON LANDING ROLL A GAR WAS EXECUTED. THE RPTR STATED IN FLIGHT IT WAS FOUND THE BRAKE HANDLE WAS RELEASED FROM THE #1 DETENT AND MOVED TO A POSITION BTWN #1 SYSTEM AND #2 SYSTEM RESULTING IN A NO BRAKE CONDITION. THE RPTR SAID THE CAUSE OF THE HANDLE BEING DISPLACED WAS A WORN DETENT LOCK LEVER. THE RPTR SAID THE LOCK LEVER WAS MADE OF PLASTIC AND OVER YRS IN SERVICE WAS WORN TO THE POINT WHERE IT WOULD NOT LOCK THE HANDLE.