What happened
On 16 September 2015, a Bell 206 helicopter, registration ZS-HGO, was conducting a commercial external-load operation near Worcester, Western Cape. The mission, part of a power line maintenance project, involved transporting a 25m cargo sling to a maintenance team.
After lifting off from a confined area near a vineyard, the pilot began transitioning from a hover to forward flight. During this maneuver, the empty cargo sling snagged on grapevine bushes. The tension caused the sling to release violently, at which point it became wrapped around the aircraft's tail rotor. The pilot reported hearing the sound of breaking metal as the force of the entanglement exerted extreme pressure on the tail boom. The helicopter subsequently yawed clockwise and entered a rapid descent, striking the ground with significant force. While the aircraft suffered substantial damage to the tail boom, skids, and lower fuselage, the pilot escaped without injury.
The investigation
An investigation by the SACAA AIID examined the sequence of events, the operational legality, and the mechanical state of the aircraft. Investigators confirmed that the pilot was highly experienced and the aircraft was well-maintained by an approved organization. However, the inquiry uncovered significant regulatory discrepancies.
It was established that the flight was unauthorized, as the external operating certificate had expired the previous day. Furthermore, the investigation found that the operational arrangement between the aircraft owner, Civair, and the operator, Chopper Worx, lacked a legal leasing agreement and involved misleading the authority regarding the Air Operator Certificate (AOC) to facilitate the operation. Additionally, the aircraft was found to be uninsured for the commercial activities being performed.
Findings
- The primary cause of the accident was the cargo sling entangling in the tail rotor, which damaged the tail boom during the transition to flight.
- The sling snagged on vineyard branches and released with enough force to wrap around the rotating tail rotor.
- The pilot failed to confirm with ground personnel that the sling was clear of all obstacles before initiating forward flight.
- The operation was conducted without a valid operating certificate, as the agreement had expired.
- There were significant regulatory breaches regarding the use of the AOC and the lack of a formal, approved lease agreement between the parties.