LOSS OF ACFT CTL LNDG ROLLOUT.

Narrative

AFTER A NORMAL LNDG AND ROLLOUT AT APPROX 70 KTS; THE ACFT; AN LTT; BEGAN TO DEPART THE RWY CTRLINE TO THE L. UP TO THIS POINT THRUST REVERSE AND NORMAL BRAKING WERE IN EFFECT. REVERSE WAS SLOWLY BEING BROUGHT TO IDLE WHEN ACFT BEGAN TO DEVIATE TO L. R RUDDER UP TO FULL INPUT AND HVY R BRAKE PRESSURE HAD NO EFFECT. R NOSEWHEEL STEERING (ELECTRIC) AND AN ATTEMPT AT R DIFFERENTIAL THRUST REVERSE ALSO HAD NO EFFECT. ALL THIS OCCURRED IN A MATTER OF SECONDS; AND AT THE TIME; WITH NO APPARENT REASON AS TO WHY. THE LNDG HAD BEEN MADE AFTER EXECUTION OF THE ILS TO RWY 27R AT FLL (9000 FT) UNDER VFR CONDITIONS WITH LIGHT WIND; (320 DEGS AT 4 KTS) AND A DRY RWY. AT APPROX 4000 FT FROM APCH END OF RWY; THE ACFT WAS DEVIATING TO THE L AT APPROX 30 DEGS FROM RWY CTRLINE. AT THIS TIME; MAX BRAKING AND FULL REVERSE THRUST WERE BEING APPLIED IN AN ATTEMPT TO STOP THE ACFT. THE ACFT DEVIATED THROUGH A GRASSY AREA AND CAME TO A STOP ON A HARD SURFACE TXWY S OF RWY 27R. THERE WERE NO INJURIES; NO DAMAGE TO ARPT PROPERTY; AND NO SUBSTANTIAL DAMAGE TO THE ACFT. THE ACFT IS IN MAINT AND SO FAR; IT HAS BEEN FOUND THAT R PWR BRAKE VALVE HAD BROKEN. A ROD WHICH PUSHES ON THE PISTON HAD SHEARED AND WEDGED ITSELF BTWN THE R PWR BRAKE ASSEMBLY AND THE LEVER WHICH IS LINKED TO THE RUDDER PEDAL. THIS IS WHY THE R BRAKE PEDAL NEVER WENT FLAT (TO THE FLOOR) AND WHY I HAD NO INDICATION THAT THERE WAS NO R BRAKE. (I FELT RESISTANCE ON THE R SIDE; AS IF I HAD R BRAKE). MANUFACTURER HAS BEEN NOTIFIED AND A RPT IS BEING SENT TO THEM SO THAT ANY ACTION OR MAINT CHANGES TO LTT CAN BE RESEARCHED.