What happened
On November 24, 2007, an AgustaWestland A100S, registration I-REMJ, was conducting a night VFR medical mission from Grosseto to Isola del Giglio. The crew, consisting of two pilots, a doctor, and a nurse, was responding to an urgent medical request.
During the final approach to the heliport, approximately 0.8 NM from the landing pad, the aircraft began to vibrate violently and lose altitude rapidly. The pilot attempted to maintain control by applying full collective pitch to limit the descent rate. The helicopter impacted the sea surface with a slight nose-down and right-side attitude. All four occupants managed to exit the aircraft before it sank to a depth of approximately 105 meters. While the crew survived, the doctor sustained serious injuries, and the pilot sustained serious injuries.
The investigation
The ANSV investigation examined the flight data, wreckage, and environmental conditions. Analysis of the wreckage by the Italian Air Force Experimental Flight Center confirmed that all structural deformations and component failures, including the separation of the main transmission and rotor, were caused by the impact with the sea rather than progressive in-flight failure.
Investigators also looked into the difficulty the crew faced when attempting to exit the aircraft. It was discovered that the cockpit doors were difficult to release; the left door was found detached, while the right door remained stuck on its hinges despite the emergency handle being pulled. A technical bulletin regarding similar door hinge interference had been issued by the manufacturer five days after this accident. Additionally, the investigation found that the emergency floats had not been armed prior to impact, which prevented them from inflating and would have likely mitigated the sinking of the airframe.
Findings
- The primary cause of the accident was the onset of a vortex ring state (anello vorticoso), triggered by low translational airspeed, a high rate of descent, and a tailwind component.
- The crew experienced a loss of situational awareness due to the suddenness of the descent and a lack of external visual references during the night approach.
- The low altitude at which the aerodynamic phenomenon occurred left insufficient time for recovery.
- The emergency floats were not armed, preventing the aircraft from maintaining buoyancy.
- The crew had not undergone specific underwater escape training, which was later made mandatory by regulatory changes following this event.