What happened
On November 19, 2013, at approximately 11:47 AM, a Robinson R44 Raven II helicopter departed from the Donaueschingen airfield (EDTD) for a training flight. The flight, involving a flight instructor and a student pilot, was intended to perform radio navigation exercises with a planned destination of the Neuhausen ob Eck landing site (EDSN).
Initially, the aircraft climbed to approximately FL65, flying above a solid cloud layer. Radar tracking indicates that at around 12:30 PM, the aircraft began descending from FL65 to 5,000 ft AMSL. Shortly thereafter, the flight path changed toward the south and then abruptly toward the northeast. During this period, the helicopter began a rapid descent accompanied by a significant loss of airspeed. Radar data recorded a very tight, autorotation-like descending turn with a diameter of only about 70 meters.
At approximately 12:34 PM, the radar track ended about 78 meters from the crash site at an altitude of roughly 500 ft AGL. The aircraft struck trees in a forested area near the B5933 road, resulting in the fatal injuries of both the flight instructor and the student pilot. The helicopter was destroyed, and damage was caused to the surrounding forest.
The investigation
The BFU investigation examined the aircraft's technical condition, weather reports, and radar/GPS data. The investigation found that the engine, main gearbox, and tail rotor drive components showed no signs of mechanical failure or internal damage. The engine showed evidence that the crankshaft was rotating during the impact.
Weather analysis revealed that the area was experiencing a deep inversion with low-level stratus clouds and fog, significantly reducing visibility. While some areas had a cloud break, the flight conditions were classified as marginal for VFR operations. The investigation also reviewed the flight crew's communications and the aircraft's navigation equipment, noting that the crew had access to GPS and artificial horizon instrumentation.