CEN22FA211

The pilot had been observed flying in the area over a period of several weeks at a low altitude and while performing “ag-type maneuvers” over the fields, as he aspired to become an agricultural pilot. There were no witnesses to the accident; the airplane wreckage was discovered in a field by a local farmer. Examination revealed that the airplane impacted terrain in a nose- and right-wing-low attitude, and the orientation of the wreckage was consistent with an aerodynamic stall/spin. There was no evidence of mechanical malfunctions or anomalies of the airframe or engine that would have precluded normal operation. Based on the available information, it is likely that the pilot exceeded the airplane’s critical angle of attack while maneuvering, possibly at low altitude, which resulted in an aerodynamic stall/spin, a loss of control, and impact with terrain.

The Federal Aviation Administration (FAA) publication H-8083-25A, Pilot's Handbook of Aeronautical Knowledge, stated that an aerodynamic stall results from a rapid decrease in lift caused by the separation of airflow from the wing's surface brought on by exceeding the critical angle of attack (AOA). AOA is defined as the acute angle between the chord line of the airfoil and the direction of the relative wind. An aerodynamic stall can occur when the airplane flies too slowly, or when higher wing loads are imposed due to maneuvers such as pull-ups or banked flight. According to the Federal Aviation Administration Airplane Flying Handbook (FAA-H-8083-3C): At the same gross weight, airplane configuration, CG location, power setting, and environmental conditions, a given airplane consistently stalls at the same indicated airspeed provided the airplane is at +1G (i.e., steady-state unaccelerated flight). However, the airplane can also stall at a higher indicated airspeed when the airplane is subject to an acceleration greater than +1G, such as when turning, pulling up, or other abrupt changes in flightpath. Stalls encountered any time the G-load exceeds +1G are called “accelerated maneuver stalls.” The accelerated stall would most frequently occur inadvertently during improperly executed turns, stall and spin recoveries, pullouts from steep dives, or when overshooting a base to final turn. An accelerated stall is typically demonstrated during steep turns. On May 24, 2022, about 0700, a Piper PA-12 airplane, N78466, was destroyed when it was involved in an accident near Seagraves, Texas. The pilot sustained fatal injuries. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. According to local authorities and family acquaintances, the pilot had been flying in the local area over a period of several weeks with aspirations to become an agricultural pilot. During those weeks, the airplane had been observed by several people to be flying at low altitude while performing “ag-type maneuvers” over the fields. The airplane wreckage was located by a farmer about 1150, and there were no witnesses to the accident. Postaccident examination of the accident site revealed that the airplane impacted terrain in a nose- and right-wing low attitude. The initial ground scar was consistent with the propeller, engine, forward fuselage, and wings. The airplane sustained substantial damage to the fuselage, wings, and empennage. The vertical stabilizer was pointed to the right, consistent with a clockwise stall/spin at impact (see Figure 1). Figure 1. Accident airplane Flight control continuity was established from the cockpit to all flight control surfaces. The engine remained partially attached to the firewall and could not be manually rotated due to damage to the engine crankcase. The propeller blades displayed forward twisting deformation. Examination of the airframe and engine revealed no evidence of mechanical malfunctions orfailures that would have precluded normal operation.