What happened
On 4 January 2014, a Eurocopter AS-365N2 helicopter, registration ZS-HOS, was performing a commercial cargo slinging operation near Cape Town. The mission involved transporting a 485kg load from a vessel, the Al Jabriyah2, to the Black River Helistop.
After lifting the load from the ship's deck, the pilot-in-command initiated a climb. Once the aircraft reached an altitude of approximately 200 to 300 feet above mean sea level, the pilot handed control of the aircraft to the First Officer. While the helicopter was executing a coordinated left turn at roughly 80 knots, the crew felt the load depart the aircraft. A crew member acting as winchman visually confirmed that the cargo had been lost. The helicopter returned safely to the helistop without sustaining any damage, and there were no injuries to the crew.
The investigation
SACAA AIID investigators examined the cargo hook system and the rigging used during the flight. While the aircraft was found to be airworthy and the crew was properly licensed, the investigation identified several procedural discrepancies. It was noted that the company's internal external load operations procedures and documentation protocols were not strictly followed. Specifically, the weight and balance records submitted by the operator contained inaccuracies, with some dates being manually altered due to technical issues with the electronic calculation system.
Testing conducted after the incident could not replicate the uncommanded release. However, the investigation focused on the interface between the cargo and the hook.
Findings
- The primary contributing factor was the roll out/jamming phenomenon of the shackle used on the cargo hook.
- A load ring with an inner diameter larger than the manufacturer's specified limit for that specific hook was utilized.
- This allowed the load-bearing ring to move over the hook's tongue and keeper, leading to an unintended release.
- The company's internal procedures for external load operations and aircraft documentation were not fully adhered to.
- Discrepancies were found in the weight and balance load sheets provided by the operator.