What happened
On February 9, 2005, an Eurocopter Alouette 3 Lama, registration F-GIBK, was performing sling load operations in the Cirque de Mafate. The mission involved transporting supplies to mountain refuges, and the aircraft was performing its final rotation of the day. The crew, consisting of a pilot and an assistant, had just landed on a platform to collect empty nets. After the assistant secured the cargo, the pilot initiated a hover and then began a transition to forward flight.
During this transition, the aircraft's flight path drifted unexpectedly to the right. The pilot was unable to correct this deviation and attempted to release the load by activating both the automatic and manual release mechanisms of the cargo hook. Despite these efforts, the aircraft continued off course and struck trees approximately 300 meters from the takeoff point near a ravine. The impact resulted in two minor injuries and the total destruction of the helicopter.
The investigation
Investigators examined the cargo hook and the sling assembly following the crash. The cargo hook was found to be in working order and was in the open position at the time of the accident. The investigation focused on the movement of the aircraft during the initial stages of the takeoff and the interaction between the sling and the helicopter's structure.
Findings
- The investigation established that the sling likely became entangled with the rear of the right skid during the pilot's initial backward movement to inspect the load.
- As the pilot transitioned into forward flight, the tension applied to the sling caused a significant imbalance in the aircraft.
- Because the sling was pulled toward the rear, it became wedged in the jaw of the cargo hook, preventing the load from being released even when the release mechanisms were activated.
- The primary cause of the accident was the use of an inappropriate takeoff procedure.
- According to the Special Activities Manual, when handling a sling load, the pilot should first increase altitude above the load and perform a vertical takeoff to tension the cables before attempting to transition into forward flight.