What was found
DURING THE TAKEOFF ROLL, WHILE INDICATING 40 KIAS, THE PILOT DISARMED THE NOSEWHEEL STEERING IAW THE AFM. UPON APPROACHING 95 KIAS THE AIRCRAFT BEGAN TO STEER LEFT. THE PILOT PUT IN RIGHT RUDDER AND RIGHT BRAKE WITH NO EFFECT. THE TAKE OFF WAS ABORTED BUT THE AIRCRAFT CONTINUED LEFT DEPARTING THE RUNWAY AND CONTINUING TO TURN LEFT UNTIL IT CAME TO A STOP. UPON INVESTIGATION IT WAS DISCOVERED THAT THE ARMING VALVE HAD ALLOWED HYDRAULIC PRESSURE TO ENTER THE STEERING MANIFOLD AND PASS THROUGH THE SERVO VALVE TO THE LEFT CYLINDER OF THE ACTUATOR.