What happened
On October 16, 2016, a Cessna 150, registration N7948F, was performing a takeoff from Berry Hill Airport (7GA7) in Stockbridge, Georgia, when it experienced a loss of performance. The flight was a personal trip intended for Cherokee County Airport (CNI) in Canton, Georgia.
Prior to departure, the pilot had refueled the aircraft and performed a normal engine runup. During the takeoff roll on runway 11, the pilot rotated the aircraft approximately halfway down the 3,000-foot runway. Shortly after rotation, the pilot noticed the airplane was not climbing normally and became concerned about clearing the tree line located about 500 feet beyond the runway end. The pilot attempted to steer the aircraft toward the shortest trees to facilitate a controlled landing in a nearby field. The aircraft subsequently impacted the ground, resulting in 2 serious injuries to the pilot and passenger.
The investigation
An examination of the wreckage showed the aircraft came to rest approximately 800 feet past the end of the runway. The damage, which included aftward crushing of the nose and the leading edges of both wings, was consistent with a nose-low impact following an aerodynamic stall.
A witness at the scene reported hearing "popping" sounds coming from the engine during the climb, though the pilot did not notice any engine abnormalities due to the use of noise-canceling headsets.
Mechanical analysis of the engine revealed that the exhaust valve in the No. 4 cylinder was stuck in the fully open position and was coated with a carbon-type material. While the other cylinders showed compression and valve train continuity, the No. 4 cylinder's stuck valve was a significant finding. Additionally, the carburetor had separated from the engine due to impact, and the carburetor heat control was found in a fixed center position. The oil screen contained a small amount of carbon deposits, and no fuel screen was installed in the system.