DURING THE TAKEOFF ROLL, THE AIRPLANE BEGAN TO VEER LEFT OF THE RUNWAY CENTERLINE. THE PILOT APPLIED THE RIGHT BRAKE AND GOT NO RESPONSE. HE TRIED TO REGAIN CONTROL OF THE AIRPLANE BY APPLYING THROTTLE TO GET TAIL RUDDER CONTROL, BUT THIS ACTION WAS INEFFECTIVE. THE AIRPLANE CONTINUED TO VEER OFF THE RUNWAY AND DOWN THE AN EMBANKMENT. AS THE AIRPLANE TIPPED DOWN OVER THE EMBANKMENT, THE PILOT'S KNEE PUSHED THE THROTTLE FORWARD, WHICH GAVE THE ENGINE A BURST OF POWER. THE AIRPLANE CONTINUED DOWN THE EMBANKMENT AND NOSED OVER. THE ON SCENE INVESTIGATION DETERMINED THERE WAS NO BRAKE FLUID IN THE RIGHT BRAKE RESERVOIR AND THERE WERE NO SIGNS OF FLUID LEAKAGE THROUGHOUT THE BRAKE SYSTEM. EXAMINATION OF THE RAKE SYSTEM DID NOT REVEAL ANY ANOMALIES. THE PILOT STATED HE ACCOMPLISHED A BRAKE CHECK PRIOR TO TAKEOFF AND DID NOT OBSERVE ANY MALFUNCTION. THE AIRPLANE WAS OPERATED 153 HOURS SINCE THE LAST ANNUAL INSPECTION 11 MONTHS EARLIER.