Accident Overview
On July 17, 2024, at about 1500 central daylight time, an Air Tractor AT-602 airplane, registration N622AW, was substantially damaged in an accident near Oakland, Nebraska. The airplane was operating as a Title 14 Code of Federal Regulations Part 137 agricultural flight. The pilot reported a loss of engine power while the airplane was in an aerial-application spray turn. During the subsequent forced landing in a cornfield, the aft fuselage sustained substantial damage. The pilot was not injured.
Fuel Imbalance Analysis
A postaccident review of the airplane's digital engine monitor revealed a fuel load imbalance before departure. The left-wing fuel tank contained about 105 gallons and the right-wing fuel tank about 75 gallons, totaling approximately 180 gallons. After departure, but before the pilot began aerial-application spray passes, the fuel imbalance decreased to about 10 gallons between the tanks. However, during spray passes, the right-wing fuel tank showed a net decrease, while the left-wing fuel tank had minimal decrease. About 1 hour and 4 minutes into the flight, the right-wing fuel tank quantity decreased to zero gallons. Approximately 6 minutes later, a sudden loss of fuel flow occurred, leading to a loss of engine power.
Further review of engine monitor data from the previous three flights indicated a history of fuel imbalance during aerial-application operations. During those flights, fuel quantity in each tank fluctuated at least ±10 gallons per spray pass. However, unlike the accident flight, after an initial decrease in fuel quantity from one tank, there was a measured increase in that same tank later. This observation occurred for both left and right tanks during separate portions of those flights. When one wing tank decreased, the opposite wing tank either showed minimal decrease or net increase as the flight progressed. Nonuniform fuel depletion was primarily observed during spray passes, while flying to or from a field tended to balance the fuel load.
Aircraft Fuel System
The Air Tractor AT-602 fuel system consists of two 108-gallon wing fuel tanks interconnected by a 2-gallon header tank. The airplane is not equipped with a fuel tank selector; only a fuel system shutoff valve is located downstream of the header tank.
The airplane wreckage was retained for further examination.