What happened
On September 9, 2012, during a biennial flight event at the Roßfeld glider airfield, a pilot was performing a series of demonstration maneuvers in an Eurocopter EC 120B. The flight began with the pilot taking off from a designated parking area and transitioning into a hover. After an initial 180-degree turn, the helicopter entered a lateral hover at an extremely low altitude, approximately 50 cm above the ground, moving toward the south.
During this lateral movement, the helicopter''s altitude began to decrease. The rear of the left skid made contact with the ground, followed by the right skid and the tail boom. This triggered a rapid rollover to the right. The entire sequence, from takeoff to the impact, lasted approximately 21 seconds. The impact caused the main rotor blades to disintegrate, sending debris and internal rotor weights flying into the crowd. The accident resulted in one fatality among the spectators, two serious injuries, and two light injuries among the spectators, while the pilot and passenger sustained light injuries.
The investigation
The BFU examined video footage of the accident, which showed the sequence of the rollover. The investigation also included an analysis of the aircraft's Engine Multifunction Display (VEMD). While the system recorded engine speed fluctuations and discrepancies following the impact, the manufacturer confirmed these were expected consequences of the broken drive shaft after the rotor hit the ground.
The investigation also reviewed the airfield's topography, noting that the terrain at Roßfeld is significantly undulating, which can make maintaining a constant altitude difficult. The pilot's experience, the aircraft's maintenance history, and the weather conditions—which were clear and calm—were all evaluated. The investigation also looked into the positioning of the spectators and the aircraft's takeoff area relative to the crowd.
Findings
- The primary cause of the accident was a dynamic rollover caused by an unintentionally low hover altitude.
- The pilot likely failed to realize the low altitude over the sloping terrain during the lateral hover.
- The unevenness of the airfield terrain, which lacks a consistent horizontal horizon, contributed to the difficulty in maintaining altitude.
- The disintegration of the rotor blades released heavy internal weights that struck spectators, leading to the fatal injury.
- The pilot's orientation toward the sun during the maneuver may have caused temporary glare, potentially affecting visual references.