What happened
On August 28, 1999, an SA315B Lama, registration HB-XXS, was engaged in a commercial external load operation near Corippo, Alpe del Corgell. The mission involved recovering a large wooden cross that had fallen down a steep slope. After an initial reconnaissance flight, the pilot landed at Alpe Corgell to allow a flight assistant to prepare the load.
The flight assistant climbed onto a rocky outcrop to attach a sling to the aircraft's cargo hook. During the approach, the pilot positioned the helicopter with the nose facing uphill and the tail downhill, moving close to the rock face to assist the assistant. While the pilot was checking the underside of the aircraft via a ventral mirror, the helicopter drifted forward slightly. This movement caused the main rotor blades to strike the rock wall.
The impact caused the helicopter to enter counter-rotation and strike the cliff with its fuselage. The aircraft flipped forward and came to rest precariously balanced on a rocky spur. The pilot, who was wearing a helmet and secured by his seatbelt, remained suspended in his harness. However, the two passengers, who were not wearing seatbelances, were thrown from their seats during the impact. The flight assistant managed to jump from the rock ledge and landed safely below.
The investigation
SUST examined the operational procedures and the physical circumstances of the site. The investigation confirmed that the aircraft was in a valid maintenance status and that the pilot was fully licensed for the type and qualified for mountain operations. The investigation also noted that while the pilot used contact lenses to satisfy a medical requirement for corrective lenses, there was no evidence of physical impairment or alcohol consumption.
Investigators reviewed the company's Flight Operation Manual (FOM), noting that while the manual required all occupants to be belted during takeoff and landing, the passengers in this instance were not secured. Furthermore, the investigation looked into the communication between the crew and the lack of specific procedures for mixed operations involving both passengers and external loads.
Findings
- The primary cause of the accident was the loss of control following the collision of the main rotor blades with the rock wall.
- The operation was characterized by insufficient preparation for the specific recovery task.
- A lack of effective coordination and communication between the pilot and the flight assistant contributed to the incident.
- The pilot's decision to approach the steep terrain closely, combined with a momentary loss of visual contact with the rotor blades while checking the ventral mirror, facilitated the strike.
- The presence of unbelted passengers increased the risk of injury during the impact.
Safety action
- It is recommended that the attachment of loads directly to the cargo hook should be restricted to areas free of obstacles.
- The significant responsibilities assigned to flight assistants should be supported by thorough, specialized training.
- Operators should evaluate the necessity of prohibiting passengers from remaining on board during external load operations.