What was found
DURING TAKEOFF ROLL AT ROTATION SPEED, AIRCRAFT LANDING GEARS RETRACTED WHILE THE GEAR LEVER WAS IN THE 'DOWN' POSITION. PROPELLER TIPS STRUCK PAVEMENT AND PILOT RETARDED THROTTLES CAUSING THE AIRCRAFT TO SKID ON ITS LOWER FUSELAGE UNTIL IT CAME TO A STOP AT THE END OF THE RUNWAY. RECOMMEND THAT CAM ASSY ON GEAR LEVER SHAFT BE DRILLED AND A ROLL PIN INSTALLED TO PREVENT CAM FROM COMING LOOSE ON SHAFT. IN THIS CASE, THE CAM CAME LOOSE AND ALLOWED THE MICROSWITCH TO STAY IN THE 'UP' POSITION ALLOWING GEARS TO RETRACT.