Accident Summary
On 22 October 1988, a SA 315B "Lama" helicopter, registration HB-XPM, operated by Air Grischa Helikopter AG, crashed during a firefighting demonstration in the Rossboden area of Chur, Switzerland. The pilot, a Swiss national born in 1943 with a professional helicopter license and 6365 total flight hours (160 on type), was fatally injured. The helicopter was destroyed.
Sequence of Events
The helicopter was participating in a fire brigade exercise attended by approximately 1500 spectators. After landing on a cordoned-off gravel parking lot, a firefighter and two companions attached a "Bamby Bucket" water container to the cargo hook. The pilot lifted off, hovered to a nearby water basin, and submerged the bucket to fill it with about 750 liters of water. Two attempts to release the water over a demonstration fire were unsuccessful, so the pilot landed again.
During the landing, the pilot first set the filled bucket on the ground, then positioned the helicopter immediately left and behind it, with the bucket near the right front skid. With the turbine running but the main rotor stopped, the pilot exited to inspect the electrical connections and suspension. After signaling readiness, he reboarded and engaged the rotor.
On takeoff, the right front skid caught one of the eight 4-mm suspension cables. The helicopter hovered about 1 meter above the ground with the load still on the ground. As it climbed, it tilted sharply to the right, inverted, and crashed into a cornfield approximately 100 meters away.
Weather Conditions
Weather at the time was influenced by a high-pressure system with high fog in the lowlands. At the accident site, cloud cover was 1-2 oktas with a base around 3000 meters, visibility exceeding 10 km, wind from northeast at 5-10 knots with gusts to 20 knots, temperature 10°C, dew point 6°C, and QNH 1021 hPa.
Findings
Examination revealed that the mission switch, which enables electrical release of the cargo hook, was off. The mechanical cable for emergency release was in the pulled (open) position. The right front skid tube had been broken and showed clear indentation marks consistent with a steel cable. The helicopter's center of gravity was well outside the approved lateral forward envelope due to the cable caught on the skid. The bucket remained properly attached to the cargo hook.
Cause
The investigation determined the accident was caused by improper lifting and takeoff with an external load. Contributing factors included insufficient ground crew support and pressure from the demonstration.