19980314003469A

Approximately ten minutes into the flight the pilot reported that the engine developed a rough running condition. The pilot tried suveral power settings in an effort to reduce the condition, but no action on his part resolved the rough running condition. Since the pilot could not maintain altitude, then he selected an adjacent field for an emergency landing. The pilot said that landing surface was rough and uneven. Examination of the engine assemble disclosed that the right magneto cover was not secure and that the five screws that secure the cover to the magneto assemble were missing. The visual examination of the internal components of the magneto assembly showed evidence of water stains on the magneto block. Internal component continuity was established when the engine was rotated completely through. Low compression was also noted on all cylinders. (-23) shortly after takeoff, pilot experienced rough running engine followed by backfiring, popping sound and subsequent power loss. Pilot went to full power but could not maintain altitude so he accomplished a forced landing to a cow pasture. He landed faster than normal and started braking immedi ately after touchdown. The aircraft hit some ruts and became airborne so the pilot forced it back down causing the propeller to impact the ground. Subsequently, the engine hit the ground and dug in. The aircraft pivoted on its nose, flipped over and came to rest inverted. The aircraft sustained substantial damage but the pilot was not injured.