What happened
On December 27, 2020, at 15:40 UTC, an AW139 helicopter, registration I-OLBI, was performing a Helicopter Emergency Medical Service (HEMS) mission near Baunei, Italy. The crew was engaged in a winch operation to deploy an alpine rescue technician to a target site. To maintain stability against local 15-knot southwest winds and to optimize power margins for a potential one-engine inoperative scenario, the pilot had elected to fly with the aircraft's nose into the wind, positioning the rock wall to the right and rear of the helicopter.
As the rescue technician approached the target, the main rotor blades made contact with the rock face. The crew immediately aborted the deployment, recovered the technician, and moved the aircraft away from the obstacle. Upon landing nearby to assess the damage, it was determined that the extreme tips of all five rotor blades had been damaged, necessitating their replacement and an extensive inspection of various components. No injuries were reported.
The investigation
The ANSV investigation utilized Cockpit Voice Recorder (CVR) and Flight Data Recorder (Foliage) data to reconstruct the final moments of the flight. The FDR confirmed that the impact occurred at 15:40:10 UTC, showing minimal variations in torque and engine RPM, which aligned with the pilot's testimony that control inputs were minimal and primarily forward just before the strike.
Investigators examined the crew's communication and the aircraft's configuration. The investigation found that the pilot had intentionally lightened the aircraft by offloading the co-pilot and a nurse to increase power performance. However, this decision placed the burden of obstacle monitoring on the Helicopter Crew Member (HCM), as the co-pilot's position provided no better visibility of the obstacle than the pilot's. The CVR transcripts revealed critical communication breakdowns; specifically, the pilot requested the HCM to monitor the rotor's distance from the right-side obstacle, but the HCM responded regarding the tail position, leading to a misunderstanding that the pilot did not correct.
Furthermore, the aircraft was equipped with an Obstacle Proximity LIDAR System (OPLS) designed to alert the crew to nearby obstructions. However, the system was not utilized because the pilot had not received specific training on its use, and the operator's manual had not yet been updated to include procedures for this equipment due to training delays caused by the COVID-19 pandemic.
Findings
- The primary cause of the incident was the contact between the main rotor blades and the rock wall during a hover maneuver performed at a very close distance to the obstacle.
- The decision to adopt a heading that placed the obstacle to the right and rear of the aircraft prevented the pilot from maintaining a direct line of sight to the hazard.
- Ineffective and non-assertive communication between the pilot and the HCM led to a failure in monitoring the rotor's proximity to the wall.
- The absence of specific operator procedures requiring the Pilot Flying to directly monitor obstacles in such configurations contributed to the event.
- The lack of operational training and formal procedures for the onboard OPLS system meant a vital safety tool was unavailable to the crew.