Nowadays the majority of the transportation of materials is done using this optional equipment. At the beginning this technique was used only when there were large quantities of material to be transported. In these cases usually two wood platforms were erected one parallel to the other with a space between of about 1.50 m. Then the helicopter landed on them and the cargo was set in position and fixed to the barycentric hook.
Photo 1, taken in Ambrì in February 1955 during the “St. Gotthard operation”, shows Leo Kunz at the controls of the Bell 47G HB-XAE as he lands on the specially designed platform. An oil drum on the ground is ready to be transported to the St. Gotthard massif, where workers were repairing an electric power line damaged by an avalanche.
The Bell 47G was fitted with a “Siren” cargo sling attached to the centre frame, close to the helicopter’s centre of gravity, with a manual release system. A ground crew member guided Kunz with hand signals, as radio communication between pilots and ground crews was not yet available. Early walkie-talkies were expensive, heavy and had a limited range, while radio equipment was often removed to save weight.
That same year, Heliswiss developed a lightweight aluminium-tube device attached to the undercarriage to prevent suspended loads from rotating during flight.
On the photo 2 taken in Summer 1955 this equipment is visible on the Bell 47G HB-XAK while it transports some wood panels used for the costruction of a hut in the Linthtal/GL. This equipment was however soon abandoned.
Much later to observe the hook and unhook manoeuvres the pilots asked their mechanics to install a rear view mirror in front of the cabin.
Nowadays helicopters are equipped with digital weight scale that indicate the weight suspended on the barycentric hook.
HAB 12/2009