What happened
On May 24, 2010, an emergency medical response was initiated in the Chaltbrunnental region to assist an exhausted jogger. Because the terrain prevented vehicle access, medical personnel and the patient's family had to approach the site on foot. To facilitate the rescue, a REGA helicopter arrived at approximately 18:20 local time to perform a winch operation.
Due to the inability to land directly at the patient's location, the pilot hovered over a nearby clearing to lower a physician via hoist. The physician was lowered to a distance of 72 meters. While the physician was being deployed, a group of people—including the patient's family and a paramedic—remained near the patient at the base of a nearby cliff, approximately 16 meters from the helicopter's hoist site.
During the hover, the powerful downwash from the Eurocopter MBB-BK 117 C-2 caused a large, rotten beech branch to snap from a tree positioned above a rock wall. The branch, weighing approximately 25 kg, fell onto the group of people below, knocking them to the ground. The incident resulted in one serious injury to a paramedic and one minor injury to the patient's daughter.
The investigation
The investigation examined the sequence of the winch operation and the environmental conditions at the site. Investigators analyzed the physical state of the fallen branch, which was found to be a 4-meter-long section of beech that appeared healthy externally but was rotten at the break point.
Technical inspections of the HB-ZRE revealed no pre-existing mechanical defects that could have contributed to the accident. The investigation also reviewed the training of the medical personnel, noting that while basic training covers the dangers of downwash, specific training regarding helicopter operations was infrequent within the paramedic's organization due to the rarity of such missions.