What happened
During the initial climb phase following takeoff, the airplane failed to accelerate or climb, operating at a gross weight approximately 50 pounds above the maximum allowable limit. After the pilot executed a crosswind turn at 250 feet AGL, roughly one-half mile beyond the end of the runway, the engine RPM began to decrease steadily.
Because the pilot was unable to restore the engine RPM, a forced landing was conducted in a nearby pasture. During the landing sequence, the aircraft collided with a fence and a ditch, which caused the plane to nose over. The impact resulted in an aircraft fire.
The investigation
An examination of the engine was performed to determine the cause of the power loss. Investigators discovered that the spark plugs were fouled and the magneto impulse coupling was weak. Additionally, the inspection revealed rust and evidence of detonation within the cylinders and on the piston domes, findings which contributed to the degradation of available power.