On July 27, 2002, an Air Tractor AT-502 (registration N293JK) was involved in an aviation accident near San Manuel, AZ. Investigators recorded the probable cause as: the pilot's failure to maintain adequate airspeed while maneuvering in a box canyon, which resulted in a stall/mush. A factor in the accident was downdraft conditions that led to an uncontrolled decent. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
While seeding a fire-damaged forest area, an airplane stalled and collided with mountainous terrain after encountering an unexpected loss of altitude during a turn in a box canyon. The pilot reported no mechanical issues.
Incident Overview
The airplane was conducting a seeding flight over a fire-devastated portion of a National Forest. The pilot had flown into the same box canyon several times on previous days to apply seed. On the accident flight, after completing a seed run near the closed end of the canyon, the pilot initiated a course reversal turn.
Maneuver and Collision
Approximately halfway through the turn, the airplane experienced a rapid loss of altitude. The pilot determined that the airplane would not be able to complete the turn and leveled the wings. Subsequently, the airplane stalled and collided with flat terrain on the side of the mountain.
Pilot Observations
The pilot attributed the loss of altitude to mountain downdrafts. He reported no preimpact mechanical malfunctions or failures with the airplane. The purpose of the flight was to seed the burned area within the National Forest. The area of operations was a box canyon, and the collision occurred while maneuvering in that terrain.