What happened
During a fuel delivery operation at a remote tent camp, a Bell 206B helicopter was performing a sling-load task, transporting barrels from a beach to a generator shed. As the pilot attempted to place two fuel barrels on the ground, the aircraft suddenly lost tail rotor authority. The helicopter began a violent rightward rotation, spinning approximately three times before striking the ground upright and rolling onto its right side.
At the time of the failure, a ground assistant was positioned directly beneath the aircraft to secure the load. To avoid striking the assistant or the generator shed, the pilot lifted the collective and maneuvered the aircraft away, though the unreleased sling load and the low altitude prevented a successful autorotation. The impact caused substantial damage to the helicopter, including the separation of the skid cross tubes and the severing of the tail boom by the main rotor. The pilot sustained minor injuries, while the ground assistant remained uninjured.
The investigation
Investigators examined the mechanical integrity of the tail rotor drive system and the aircraft's maintenance history. The investigation focused on the aft short tail rotor drive shaft, which had previously operated for approximately 19,000 hours in a highly corrosive, saltwater environment in the Arabian Gulf.
Technical analysis of the shaft revealed that the internal wall had been compromised by scratches from a past improper rework. These scratches allowed corrosive elements—including sodium, chlorine, and sulfur—to penetrate the interior of the shaft. Because the shaft is hollow and the corrosion was located on the internal bore, the degradation was not visible during standard external inspections.