What happened
The pilot was conducting agricultural operations, specifically spraying a rice field, in formation with another airplane. During this phase of the flight, the aircraft encountered an in-flight upset. The cause of this upset was identified as propwash, or wake turbulence, generated by the companion aircraft flying nearby.
Following the upset, the aircraft's landing gear struck a rice levee. The impact force sheared the landing gear off the airframe. The aircraft then bounced from the levee and subsequently nosed over upon final impact with the ground.
The investigation
The investigation focused on the sequence of events leading to the accident. It was determined that the formation flying maneuver created aerodynamic interference between the two aircraft. This interference resulted in a sudden loss of control or stability for the affected aircraft due to the turbulent air mass left by the other plane's propeller.
Findings
The primary factor contributing to the accident was the encounter with wake turbulence from the adjacent aircraft during close formation agricultural operations. The structural failure of the landing gear was a direct result of striking the levee at an abnormal angle and speed following the aerodynamic upset.