What happened
While operating in cruise flight, the pilot of a homebuilt replica aircraft heard several popping sounds. Although no drops in oil pressure or temperature were noted on the gauges, the engine subsequently seized and the propeller stopped rotating.
Recognizing that the destination airport was unreachable, the pilot searched for an alternative landing site. Due to the presence of power lines and vehicles in the area, options were limited. The pilot eventually identified a flat road clear of cars and power lines, though the area contained natural desert vegetation. Upon touchdown, the left wing struck a tree, causing the aircraft to ground loop. The pilot was not injured.
The investigation
The engine, a 1929 Wright Whirlwind R540A, was inspected following the accident. Investigators discovered a large hole on the right side of the engine case. Examination of the internal components revealed that damage to the other cylinders and connecting rods resulted from the separation of the number 3 articulating rod, which began moving erratically inside the engine. The engine seizure occurred when the number 3 articulating rod bent the number 4 articulating rod and subsequently moved into the bottom of the number 5 cylinder, forcing itself between the piston and the master rod.