N5963F

The 445-hour private pilot reported that while on the base leg of a traffic pattern at a non-towered airport, the engine lost power. During the forced landing, the pilot was unable to maintain altitude and collided with trees near the approach end of runway 17. An examination of the single-engine airplane revealed no mechanical anomalies. Both wing fuel tanks were breached and the firewall was wrinkled. The 160-horsepower engine was test ran on the airframe. The engine started immediately and ran at various power settings without interruption. The reason for the reported loss of engine power could not be determined.