Incident Overview
On 1 July 2019 at 11:50 local time, a Robinson R22 helicopter, registered as HB-XZN, was involved in a serious incident during a training flight near Kaltbach, in the municipality of Mauensee, Canton Lucerne, Switzerland. The helicopter was operated by Airport Helicopter AHB AG, based in Neudorf. The flight was conducted under visual flight rules (VFR) and was a training session for a student pilot working toward a Private Pilot Licence for Helicopters (PPL(H)).
Sequence of Events
The training flight focused on practicing autorotations. Prior to the exercise, the designated landing area—a field located about 500 meters southwest of Kaltbach—was inspected during a reconnaissance flight to identify any obstacles. The student pilot then performed an autorotation approach to the field. At an altitude of approximately 3 to 5 meters above ground, the flight instructor initiated a go-around. The area appeared free of obstructions except for a pole approximately 4 meters high located diagonally ahead along the flight path. As the instructor attempted to point out this pole to the student, a light impact was felt. The helicopter was approximately abeam the pole at the time. Initially suspecting a bird strike, the instructor immediately took over controls, landed the helicopter on a nearby field, and shut down the engine.
Damage and Injuries
Both pilots remained uninjured. The helicopter sustained scratches to the main rotor mast cover, control rods, and the front windshield on both sides. The aircraft was classified as lightly damaged.
Findings
Subsequent inspection revealed that a thin agricultural wire (Viehüterdraht) had been strung across the landing field at a height of about 4 meters. Such wires are commonly installed to allow continued access for agricultural vehicles while preventing livestock from crossing. The weather conditions at the time were calm winds, 25 °C, and good visibility, suitable for visual flight.
Analysis and Conclusions
The cultivation of fields with thin wires at several meters above ground is a common agricultural practice. However, these wires pose a significant hazard for external landings, as they are difficult to detect even during a reconnaissance flight.
Probable Cause
The investigation report does not specify a probable cause for the incident.