2001-03-06: The Aerospatiale AS350
-B2 helicopter was being utilized to move bags containing seismic recording equipment. The pilot had just released the last bag off of the carousel rack and was climbing and turning to return to the staging area. During the turn the carousel and longline released uncommanded from the helicopter. The carousel impacted the ground from a height of approximately 120 feet and sustained damage to two non-structural legs. The pilot immediately landed the helicopter in a field near the carousel. No personnel were injured and the helicopter was not damaged. The helicopter was fitted with a SIREN belly hook, part number S1609. On this hook a sheath encloses the manual release cable, like the coating on a bicycle brake cable, and is required to be attached to the body of the hook. Maintenance examination determined that when the hook was swung to the extreme position, the sheath covering the manual release cable would separate from the body of the hook. In the extreme position the hook could pinch the sheath against the cable and freeze the cable. When the hook moved back to its central position, the hook release mechanism could activate and release the load. The operator indicated that there may have been other similar occurrences. The operator has advised the helicopter manufacturer of this incident.