THE PILOT AND PILOT RATED PASSENGER WERE ON A LOCAL FLIGHT. THE PASSENGER STATED AFTER THE ACCIDENT THAT WHILE APPROACHING THE AIRPORT, THE PILOT DID NOT TURN TOWARD THE RUNWAY AND BEGAN DESCENDING INTO THE TREES. THE PASSENGER ADDED 1/2 POWER BUT THE PILOT REDUCED THE POWER. THE PASSENGER THEN ATTEMPTED TO GAIN CONTROL USING THE CONTROL STICK, HOWEVER, IT WAS 'NOT FREE' AND THE AIRPLANE STRUCK TREES. POST MORTEM EXAMINATION OF THE PILOT REVEALED EVIDENCE OF CORONARY ARTERIOSCLEROSIS.