What happened
During an agricultural spraying mission, a pilot departed from a valley-based airstrip located within hilly terrain. The aircraft, a loaded spreader, was transporting a full payload of superphosphate to a nearby property. Prior to the flight, the pilot had inspected the intended flight path and the destination site, planning a route that involved ascending through a valley and crossing a low ridge.
Upon takeoff, the pilot configured the aircraft for climb by adjusting flaps and power settings. While navigating toward the ridge, the pilot observed that the aircraft's altitude appeared to be decreasing despite the climb configuration. In an attempt to maintain clearance from obstacles, the pilot performed a partial dump of the fertilizer and increased flap deployment to avoid a cluster of trees. This maneuver caused the airspeed to drop from 70 knots to 60 knots, as the pilot failed to increase engine power.
As the flight continued, the pilot executed a second partial dump to clear another tree. Shortly after, a third partial dump was performed alongside a right-hand turn intended to avoid the rising terrain. During this maneuver, the right wing dropped, leading to an aerodynamic stall. The aircraft struck the ground on its right wing and cartwheeled approximately 50 metres from the initial point of impact.
Findings
An investigation by the company's chief pilot identified that the pilot was subject to a false horizon effect caused by the surrounding hills, which created the illusion of flying over level ground when the terrain was actually rising at a 5-degree incline. Additionally, it was determined that the aircraft's weight prevented it from clearing the ridge using only cruise power settings.