What happened
On July 17, 2013, at approximately 08:06 UTC, a Z-37A agricultural aircraft, registration OK-HJF, crashed into a water reservoir near the village of Žlunice. The aircraft was performing aerial spraying operations for Air Special, a.s., targeting cornfields.
After taking off from the Sběř working area, the pilot was conducting agricultural tasks at a low altitude, typically around 5 meters. Witnesses observed the aircraft flying from a cornfield toward the edge of a residential area before performing a sharp right turn at a very low airspeed. The aircraft then disappeared behind a line of trees and struck the water. The impact destroyed the nose of the aircraft and tore parts of the wing away. The pilot sustained severe injuries and was trapped in the deformed cockpit, partially submerged in the water, until rescuers extracted him.
The investigation
The ÚZPLN investigation examined the aircraft, the pilot's experience, and the environmental conditions. The aircraft was found to be in a valid state of airworthiness, and the engine was functioning at the time of impact. There was no evidence of mechanical failure prior to the crash.
The investigation also reviewed the pilot's background, noting he was a highly experienced professional with over 5,900 total flight hours and extensive experience specifically with the Z-37A type. Investigators also analyzed the terrain, which included high-voltage power lines and trees, as well as the potential for thermal turbulence caused by temperature contrasts between the fields and the water reservoir.
Findings
- The aircraft was within its maximum takeoff weight and had sufficient fuel for the mission.
- The pilot was performing a working turn, likely attempting to climb over obstacles such as trees or power lines.
- A combination of pilot error during a working turn and sudden thermal turbulence likely caused the aircraft to exceed the critical angle of attack.
- The aircraft entered a spiral dive at a low altitude, leaving the pilot with insufficient height to recover the aircraft by reducing load or adjusting controls.
- The destruction of the aircraft was the direct result of the high-angle impact with the water surface and the reservoir bottom.