What happened
On December 22, 2014, at approximately 10:30 local time, a Robinson R44 II, registration HB-ZMQ, was preparing for departure from Heliport West at Zurich Airport. The aircraft was operating under Visual Flight Rules (VFR) for private purposes. During the pre-takeoff phase, the pilot increased rotor RPM while awaiting clearance from the tower. To prevent the windows from fogging, the occupants were intermittently opening one of the doors to allow for ventilation.
After receiving takeoff clearance, the pilot transitioned the helicopter into a hover. During this maneuver, the pilot-side door opened unexpectedly. In an attempt to land the aircraft briefly to secure the door, the pilot momentarily released the cyclic pitch control. This action led to a rapid and unexpected loss of stability. The main rotor struck the ground, causing the helicopter to tip sideways.
The investigation
The investigation focused on the sequence of events leading to the instability and the physical impact of the rotor with the ground. The inquiry examined the cockpit environment, specifically the state of the door and the pilot's control inputs during the transition to hover. The investigation also assessed the condition of the aircraft and the impact on the surrounding environment, noting that the ground was contaminated by spilled substances during the accident.
Findings
- The aircraft sustained significant damage.
- The incident resulted in one person seriously injured and three people with light or no injuries.
- A primary contributing factor was the unintended release of the cyclic pitch control during a critical phase of flight.
- It is probable that the collective pitch lever was not fully lowered at the moment the pilot released the controls, contributing to the sudden instability.
- The unexpected opening of the pilot-side door prompted the pilot's decision to descend, which preceded the loss of control.