RWY EXCURSION.

Narrative

I SET THE PARKING BRAKES AND DID THE RUNUP. WAS CLRED FOR TKOF WITH USUAL INSTRUCTIONS BY TWR FOR IFR FLT. TO THIS POINT ALL WAS UNREMARKABLE. RELEASED PARKING BRAKES AND TAXIED ONTO RWY 05. IN POS AT THE END OF THE RWY HELD THE FOOT BRAKES UNTIL THE TURBO CHARGES 'KICKED IN' AT 35 PLUS INCHES -- MANIFOLD PRESSURE. RELEASED FOOT BRAKES AND BEGAN TKOF ROLL. THE PLANE STARTED DRIFTING TO THE L. BOTH ENGS WERE AT FULL PWR AND BOTH PROPS AT FULL RPM. I ADDED MORE (LULL) R RUDDER AND AILERON. IT APPEARED AT THIS POINT THERE WAS MORE XWIND THAN EXPECTED (ENGS FINE AND NO SUGGESTION OF TIRE PROBS). ACFT CONTINUED TO THE L AT GREATER RATE OF DRIFT AND WENT OFF THE RWY. I GAINED DIRECTIONAL CTL ON THE GRASS AND BROUGHT THE PLANE BACK TO RWY. A RWY LIGHT WAS STRUCK BY ONE BLADE OF EACH PROP WITH THE TIP OF THE R BLADE THROWN THROUGH THE FUSELAGE. I WAS UNABLE TO EXPLAIN WHAT OCCURRED UNTIL I FOUND THE PLANE WOULD NOT MOVE WHEN TRYING TO PUT IT BACK IN THE HANGAR WITH THE TOW. I HAD USED THE BRAKE AGAIN TO STOP AT THE HANGAR. I FOUND THE PARKING BRAKE LEVER HALF WAY OUT. AFTER PUSHING THIS IN; THE PLANE MOVED EASILY. I FOUND THAT WITH THE PARKING BRAKES SET THE PARKING BRAKE LEVER BINDS AT THE MIDWAY POS AS ONE PUSHES IT IN TO RELEASE THE BRAKES. IT NEVER DID THIS PREVIOUSLY. ON THE BARON THE LEVER IS UNDER THE INST PANEL AND DIFFICULT TO SEE. IN MY BARON WITH TWIN YOKES; THE CTL COLUMNS ALSO HIDES THE LEVER. IT FELT AS IF THE LEVER WERE COMPLETELY RELEASED. THE MECH WHO WILL REPAIR THE PLANE AND I INVESTIGATED THIS A COUPLE DAYS AGO AND FOUND THAT IN ONE PARTICULAR LOCATION OF THE PARKING BRAKE LEVER. THE L BRAKE IS ON AND THE R BRAKE IS OFF OR RELEASED. A 1/16 INCH MORE BOTH BRAKES ARE ON; A 1/16 INCH LESS; BOTH BRAKES ARE OFF. I HAD THE MISFORTUNE OF DISCOVERING THIS RELEASING THE BRAKES (R ONLY) AT FULL THROTTLE AND LOSING DIRECTIONAL CTL TEMPORARILY -- LONG ENOUGH TO GO OFF THE RWY. THE PARKING BRAKE SYS WILL BE REPAIRED TO CORRECT THE ANOMALY. WILL MAKE A SPECIAL EFFORT TO VISUALLY CHK POS OF LEVER.