What happened
On June 22, 2023, at approximately 04:05 UTC, a Zlín Z-37T agricultural aircraft, registration OK-MFM, was performing crop spraying operations near the village of Domoradice. The pilot was conducting the third flight of the day, specifically targeting a rapeseed field.
During a working turn intended to reposition the aircraft for the next pass, the aircraft struck high-voltage power lines. The impact caused the wires to break. One of the severed lines fell onto a road leading from Domoradice to Vysoké Mýto, where it struck a passing passenger vehicle. The impact with the wire damaged the vehicle's front bumper and pulled an insulator from the ground. The incident also caused a small grass fire in a roadside ditch. The pilot, who was alone on board, was uninjured and successfully returned the aircraft to the operating site at Řepníky.
The investigation
The ÚZPLN investigation focused on the flight execution, the aircraft's condition, and the operator's procedures. The investigation established that the pilot had performed a reconnaissance flight prior to the spraying mission to identify obstacles. However, the pilot noted that while the power lines were expected along the roadside, a diagonal section of the wires crossing the corner of the field was not visible from the air because the wires were positioned between trees and lacked sufficient contrast against the field.
Investigators also reviewed the operator's manual, which dictates that reconnaissance flights should be conducted with an empty aircraft. In this instance, the pilot performed the reconnaissance while the aircraft was already loaded with the spraying agent. Furthermore, the investigation found that the organization's risk assessment did not specifically address the risk of insufficient obstacle identification during reconnaissance.
Findings
- The primary cause of the incident was an inadequate flight preparation procedure, which resulted in an incomplete understanding of the environment where the spraying was to take place.
- The pilot's reconnaissance was performed from the air only, and the wires were not sufficiently visible from that altitude due to the lack of visual contrast and the placement of the lines near trees.
- The pilot conducted the reconnaissance flight with the aircraft loaded with spraying agent, which deviated from the company's established procedures.
- The operator's risk register failed to adequately address the risk of encountering obstacles due to improper reconnaissance.
- The aircraft sustained minor damage to the landing gear and the spraying equipment.