What happened
The pilot was conducting an agricultural application flight, specifically a swath run intended to deliver chemical treatments to a farm field. While navigating the terrain, the aircraft approached a hill within the field boundaries. As the pilot crested the top of the hill, visibility of the immediate ground level was compromised by the natural contour of the land.
Upon reaching the summit, the pilot identified a tree situated on the edge of the field. However, due to the perspective created by the hill's crest, this obstacle visually merged with another tree located further behind it. This optical illusion caused the pilot to significantly underestimate the proximity of the first tree. Upon realizing the danger, the pilot attempted to pull up to avoid the collision. The aircraft stalled shortly after this maneuver was initiated.
The investigation
The investigation focused on the pilot's account of the event and the physical evidence of the impact. The pilot stated that the tree blended in with another tree behind it, making it appear closer than it actually was until the last moment. The mechanical condition of the aircraft was consistent with a stall-induced impact.
Findings
The primary factor contributing to the accident was the pilot's failure to maintain adequate terrain clearance during low-level agricultural operations. The visual blending of obstacles due to the hill's crest led to a critical misjudgment of distance. The subsequent attempt to recover from the imminent collision resulted in an aerodynamic stall, leading to the loss of control and impact with the tree.
Safety message
Pilots conducting low-altitude agricultural operations must be aware that terrain features such as hills can create visual illusions regarding obstacle proximity. Careful assessment of the environment is required to avoid misjudging distances between trees and other hazards.