Eurocopter AS 350 B3 Cargo Hook Release Incident at Lanseria Airport (ZS-RWB)

Incident Overview On 6 February 2002, a Eurocopter AS 350 B3 helicopter, registration ZS-RWB, was operating a commercial test flight for Spectrum Air. The aircraft departed from and was intended to land at Lanseria Airport (FALA). The pilot-in-command held an ALTP license and had 10,200 total flying hours, including 300 hours on type. ## Operational Details The helicopter was tasked with flying a “HEM bird” on a test line west of Krugersdorp. Weather conditions were fine, with a 10-knot wind from the north and a temperature of +22°C. The HEM bird was prepared and hooked up at Lanseria Airport under the supervision of Spectrum Air personnel. ## Incident Sequence During the transit flight, the HEM bird was monitored frequently with an onboard camera, and no instability or out-of-position conditions were observed. The required test functions were performed at 1,000 feet above ground level (AGL). Approximately 20 minutes into the flight, the helicopter was maneuvered to intercept the survey line at 250 feet and 40 knots. About 100 meters from intercepting the line, the HEM bird was last monitored with the onboard camera. Although the bird had moved slightly in the turn, it was considered normal. Approximately 10 seconds later, while flying straight and level, the pilot felt the load releasing underneath the helicopter. After landing, the helicopter and cargo hook assembly were inspected, and everything appeared normal, suggesting an accidental release. The aircraft was then flown to Eurocopter’s facility at Lanseria Airport for further inspection of the cargo hook assembly. ## Probable Cause The inadvertent or accidental release of the cargo hook could be attributed to one or a combination of the following: 1. Overload condition due to improper or incorrect installation of the cargo swing/sling assembly. 2. Incorrect adjustment and/or installation of the mechanical/manual cargo sling release cable. 3. Accidental release by the pilot, either via the electrical operated release button located on the cyclic control stick or the manual release lever located on the collective pitch lever.