What happened
On September 9, 2018, a Robinson R66 helicopter, registration HB-ZPK, was conducting a private flight near Speck airfield (LSZK). At approximately 11:03 AM, the helicopter was cruising at an altitude of roughly 3,000 ft AMSL, approaching the airfield from the south. At the same time, a Cessna 208 was operating skydive missions, transporting 15 jumpers per flight.
While the helicopter pilot was aware of potential skydiving activity due to a published NOTAM and receiving alerts from a Flarm collision warning system, the aircraft entered the active "Para-Box" zone while skydivers were in the air. Some jumpers had already deployed their parachutes, while others were still in freefall. Although the helicopter crew believed no dangerous proximity occurred, a ground observer estimated the minimum distance between the helicopter and a skydiver to be as little as 5</strong> 50 meters. Ground personnel attempted to contact the helicopter crew on the airfield frequency to warn them of the active jumping zone, but these attempts were unsuccessful.
The investigation
The SUST investigation examined the circumstances surrounding the flight path and the effectiveness of existing warnings. The investigation noted that the pilot was in contact with "Zurich Information" and was monitoring Flarm technology, which provides explicit warnings for active parachute drop zones. The investigation also reviewed the operational risks associated with flying over airfields during skydiving operations, noting that the high vertical speeds and unpredictable trajectories of modern, smaller parachutes make the "see and avoid" principle extremely difficult to execute.
Findings
- The primary cause of the near-miss was the failure to adhere to established procedures and safety recommendations regarding uncontrolled airfields.
- Pilots are advised to avoid using uncontrolled airfields as waypoints in flight planning due to the high likelihood of unexpected traffic, such as skydivers, glider winch launches, or aerobatic aircraft.
- The investigation highlighted that pilots often prioritize horizontal airspace monitoring, making them less likely to detect threats approaching from a vertical direction, such as descending skydivers.
- While the pilot was aware of the NOTAM, the flight path through the active zone created a high-risk situation.