Summary
On 24 September 2022, a Robinson R44 Raven II helicopter, registration OK-STK, experienced an incident shortly after takeoff from a grassy area at the southeast edge of the former deep mine Lazy. The pilot felt an impact to the rear of the helicopter but continued the planned flight due to no control limitations. After landing back at the departure point, damage to the tail rotor blade was discovered. The pilot was uninjured.
Factual Information
The pilot, a private helicopter pilot with a valid PPL(H), had conducted two earlier flights that day. The incident flight, according to analysis of a SkyDemon recording, began around 11:59 UTC. The helicopter was operated by a legal entity and owned by a private individual. Weather conditions were suitable for visual flight rules, with scattered cumulus clouds, good visibility, and light winds. The aircraft had no recorded technical malfunctions.
Investigation Findings
The investigation, conducted by the Czech Air Accidents Investigation Institute (ÚZPLN) in cooperation with the Police of the Czech Republic, analyzed GPS data from the SkyDemon app, photographs, and statements. The grass surface at the takeoff site showed no visible foreign objects before the flight. The tail rotor blade exhibited damage consistent with contact with a hard, non-metallic object. No evidence of a collision with a UAV or other aircraft was found, contrary to the initial report. The helicopter's systems functioned normally, and the pilot's actions were appropriate.
Probable Cause
The immediate cause of the incident was contact of the tail rotor blade with an unknown object. The incident occurred as a result of an undetected object on the grassy surface at the takeoff point.