Accident Summary
On July 22, 2022, at about 1647 central daylight time, a Van's Aircraft RV-10 airplane, registration N4400K, sustained substantial damage during an off-airport landing near Beaver Dam, Wisconsin. The aircraft was being operated as a personal flight under Title 14 Code of Federal Regulations Part 91. The pilot and one passenger were not injured, while one passenger received minor injuries.
The pilot reported that after takeoff from Dodge County Airport (UNU) in Juneau, Wisconsin, he heard a “very loud pop” from the experimental engine. Smoke entered the cockpit but later cleared, and the smoke did not inhibit his visual functions. The pilot decided to perform an off-airport landing in a field. During the landing approach, he added power to avoid power lines. After touchdown, the right wing struck a soccer goal post. The airplane continued its rollout and impacted a streetlight and a portable toilet before coming to rest upright. All three occupants egressed without further incident. Substantial damage was noted to the fuselage and the right wing. The pilot later stated that the engine was operating after the pop, but he did not confirm this with cockpit gauges or attempt to maintain level flight.
Postaccident Examination
A postaccident examination of the engine revealed that the lower spark plug wire boot for the No. 6 cylinder was disconnected from the spark plug. The rubber boot showed burn signatures on the outside of its 90° bend and at the end where it likely contacted an exhaust pipe. The boot was burned sufficiently to allow the electrode to contact the exhaust pipe. No other areas of the engine exhibited signs of burning. Airframe-to-engine control continuity was confirmed. Except for the burned spark plug wire boot, no preimpact mechanical malfunctions or failures were found that would have prevented normal engine operation.
Maintenance Background
Review of maintenance records indicated that a condition inspection was performed on the airplane on March 22, 2022. During that inspection, a mechanic satisfactorily performed a compression check on the engine. The inspection entries stated that the work was carried out in accordance with 14 CFR Part 43 and the manufacturer’s maintenance and inspection procedures. According to the pilot, the engine had accumulated 79.7 hours since that inspection.