What happened
On April 28, 2012, a Robinson R44 Raven II helicopter was conducting a charter flight from Bonn-Hangelar toward Bergneustadt. During the flight, a passenger experienced physical discomfort, prompting the pilot to perform an unscheduled landing on a meadow near Spieckern to allow for a break. Following the landing, two additional passengers joined the flight.
During the subsequent takeoff from the meadow, the helicopter struck a 10-kV overhead power line. The impact caused the aircraft to strike a tree and crash to the ground. The helicopter was destroyed in the accident. The pilot sustained serious injuries, while the three passengers suffered minor injuries. All occupants were able to exit the wreckage, though one passenger was briefly trapped.
The investigation
The BFU investigation examined the aircraft's condition, the flight parameters, and the environmental factors at the landing site. The investigation established that the helicopter was operating at its maximum allowable takeoff mass. Due to the high ambient temperature of approximately 27 °C and the density altitude, the aircraft was at its performance limits.
Technical examination of the wreckage revealed no evidence of mechanical failure. The investigation also noted that the aircraft was not equipped with a flight data recorder or cockpit voice recorder. The takeoff site was found to be sloped, and the power lines were positioned such that they were visually aligned with houses in the background from the perspective of the takeoff path.
Findings
- The pilot was focused on cockpit performance instruments due to experiencing lift issues during the takeoff roll.
- This concentration on instruments resulted in a failure to detect the overhead power lines.
- The aircraft's center of gravity was at the edge of the permissible range.
- Under the prevailing high density altitude and maximum takeoff weight, an out-of-ground-effect (OGE) hover was not possible.
- The aircraft lacked a cable-cutting system to mitigate the impact of wire strikes.