Background
On 22 June 2014, an AgustaWestland AW109SP helicopter, registration HB-ZRU, operated by the Swiss Air Rescue Guard (Guardia aerea svizzera di soccorso), was involved in a serious incident near Cortaccio, in the municipality of Brissago, Switzerland. The helicopter was crewed by a pilot, a Helicopter Emergency Medical Services crew member, and a doctor.
Sequence of Events
During a steep descent with rapidly increasing speed in a right turn, the pilot applied pedal inputs for directional control about the vertical axis. The available pedal travel became insufficient to maintain control. In combination with an inappropriate control correction, the helicopter temporarily became uncontrollable. As a consequence, the maximum permissible rotor speed was exceeded.
Contributing Factors
The investigation determined that the helicopter was being flown near or possibly outside the certified flight envelope at the time of the incident.
Cause
The serious incident was caused by insufficient pedal travel for directional control about the vertical axis during a steep descent with rapidly increasing speed in a right turn, combined with an inappropriate control input, leading to temporary loss of control. Subsequently, the maximum permissible rotor speed was exceeded. A contributing factor was that the helicopter was flown near or possibly outside the certified flight envelope.