What happened
On June 20, 2023, at approximately 15:30 local time, an Airbus Helicopters AS 350 B3, registered HB-ZMK, was conducting a commercial transport flight from Alp Nera to Thusis. The aircraft was flying under Visual Flight Rules (VFR) at an altitude of approximately 1,700 meters (roughly 4,800 ft AMSL) with a ground speed of about 140 knots. The pilot had intentionally reduced cruise speed due to gusty wind conditions.
While navigating the region between Lohn and Zillis, the pilot spotted a bird of prey ahead. Despite an attempt to maneuver the aircraft to avoid a collision, a hawk weighing approximately 800g struck the right side of the windshield. The impact was forceful enough to shatter the acrylic windscreen, sending fragments into the cockpit. The bird then struck the rear of the instrument console, causing head injuries to the pilot. The task specialist seated in the rear remained unharmed. Following the impact, the pilot experienced a momentary loss of visibility and a change in aircraft attitude but managed to stabilize the flight and reduce speed. The pilot successfully performed an emergency landing in the Zillis area.
The investigation
Investigators from the SUST examined the wreckage and the cockpit environment. They confirmed that the right windscreen was destroyed, with acrylic fragments scattered inside the cabin. While traces of a bird strike were found on one main rotor blade, no structural damage to the rotor was identified. The investigation also noted that the pilot was not wearing a protective helmet at the time of the incident.
Findings
- The collision involved a hawk weighing approximately 800g.
- The lack of a protective helmet with a closed visor was a significant factor, as wearing such equipment would likely have prevented the pilot's head injuries.
- Under current EASA certification specifications for small rotorcraft (those with up to five passengers), there are no mandatory structural requirements for bird strike protection. In contrast, larger helicopters with six or more seats must be designed to ensure a safe landing after a 1.0 kg bird strike.
- The incident occurred at an altitude below 3,500 ft AGL and at a speed exceeding 80 knots, which aligns with statistical trends for helicopter bird strikes.
Safety action
To mitigate the risk of future bird strikes, the investigation suggests that pilots may adopt adjusted flight tactics, such as maintaining higher altitudes or further reducing flight speeds. Additionally, the use of protective helmets with integrated closed visors is recommended to prevent head injuries during such impacts.