AFTER DEPARTING THE AIRSTRIP, THE AIRPLANE MADE TWO LEFT CLIMBING TURNS TO A DOWNWIND LEG AND THEN LEVELED OFF AT APPROXIMATELY 150 FEET AGL. A WITNESS HEARD A HIGH PITCH SOUND, THEN OBSERVED THE RIGHT WING DROP APPROXIMATELY 60 DEGEES, AND THEN RETURN TO A WINGS-LEVEL ATTITUDE WITHOUT AN ALTITUDE LOSS. THE NOSE THEN PITCHED DOWNWARD, AND THE AIRPLANE DESCENDED VERTICALLY TO IMPACT IN AN OPEN PLOWED FIELD. THERE WAS EVIDENCE OF ROTATIONAL DAMAGE THROUGHOUT THE ENGINE. THE PROPELLER WAS FOUND TO BE AT A HIGH PITCH ANGLE AT IMPACT COMPARED TO THAT EXPECTED FOR A NORMAL TAKEOFF POWER SETTING. THE ENGINE DID NOT MEET THE APPROVED DATA PLATE CONFIGURATION DUE TO NONCONFORMANCE OF THE PROPELLER PITCH CONTROL AND THE SECOND STAGE STATOR ASSEMBLY. THE PROPELLER PITCH CONTROL CAM WAS OF UNKNOWN TYPE AND IDENTIFICATION. THE ENGINE HAD NOT BEEN OVERHAULED AS REQUIRED, AND AN AIRWORTHINESS DIRECTIVE REGARDING THE ENGINE TORQUE SENSOR HAD NOT BEEN ACCOMPLISHED AS REQUIRED.