What happened
During the initial climb phase, the pilot reported that no discrepancies were noted during taxi, run-up, or the takeoff roll. The aircraft initially climbed at approximately 20 degrees nose-up before beginning a left bank. At an altitude of about 200 feet above the ground, the pilot and passenger heard a loud bang, after which the aircraft continued to roll to the left. The aircraft then entered a right spin and impacted a wooded area in a nose-down attitude. There were 2 occupants on board.
The investigation
Examination of the wreckage revealed that a portion of the wooden propeller was almost entirely embedded in a tree branch approximately 3 inches in diameter. Investigators found that the number nine front spark plug had been ejected from the engine, and a burned torch mark was located on the underside of the cowling near the number nine cylinder. Additionally, three other spark plugs were found loose within their cylinders.
Maintenance records indicated that an annual inspection had been performed on the aircraft approximately one month before the accident. During that inspection, the spark plugs had been cleaned, gapped, and rotated. The aircraft had flown for approximately 30 minutes since that maintenance event.