Accident Overview
On February 5, 2023, at 1255 central standard time, a Piper PA-28-180, registration N9770J, was destroyed when it was involved in an accident near Eau Claire, Wisconsin. The commercial pilot and two passengers were uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight.
Pilot Actions and Start Attempts
The pilot reported that he last flew the airplane on December 4, 2022, during which it started and flew without any anomalies. On December 25, 2022, he was unable to start the airplane, which he attributed to the outside air temperature of -7°F. On the day of the accident, the pilot attempted approximately six engine starts before the battery died. After recharging the battery, he attempted an additional six engine starts before ceasing further attempts. During each start attempt, he applied the engine primer three times and pumped the throttle control two times, with the throttle positioned about ¼ inch forward. At times during the start attempts, he placed the mixture control into idle cutoff and ran the engine starter. After stopping his start attempts, he decided to contact an aircraft mechanic.
Fire and Examination Details
After the pilot and passengers exited the airplane, one of the passengers observed a small flame inside the engine cowl. The pilot instructed the remaining passenger to move the mixture control to idle cutoff. The fuel selector was not turned to the off position. The flames continued to spread, and the airplane was destroyed by the fire. A photograph taken during the accident showed flames in two areas: the first was beneath the engine, and the second was near the right aft top side of the engine by the right forward fuselage.
Examination of the engine compartment in the first area revealed that the carburetor airbox assembly and the carburetor heat assembly were consumed by fire. The fuel line leading to the carburetor was intact. The area above the carburetor exhibited soot consistent with lower combustion temperatures above a hotter area, which lacked soot and was around the carburetor bowl. Examination of the second area revealed a separated and thermally damaged engine primer line for the No. 3 cylinder. The remainder of the engine primer lines were intact. The area near the separated primer line did not contain a comparable amount of soot as that of the area further from the separated primer line. Fire damage precluded determination of the fuel and ignition sources of the fire.