Accident Narrative
According to the pilot's statement, the engine began to run rough during flight and then started vibrating excessively. He attempted to land at Phillips Army Airfield, but the airport was closed and the runway lights were not illuminated. By the time he saw the runway, the aircraft was not in a position to land, so he maneuvered toward an open area on the airport. However, the aircraft collided with trees and crashed.
Engine Examination
An examination of the engine revealed that the number 3 exhaust valve pushrod was bent and the number 1 intake valve was broken.
Operational Changes
Following the accident, the owner/operator (Civil Air Patrol) stopped using Phillips XC2 engine oil due to possible problems associated with its use, which included sticking valves.