What happened
On December 5, 2012, an Eurocopter AS 350BA helicopter was performing a ferry flight from Lübeck, Germany, to Halmstad, Sweden, for a Norwegian operator. The flight was intended to conclude a series of laser-scanning missions in Northern Europe. During the flight, the aircraft entered the airspace near the Neustädter Bucht, where the pilot was advised by Bremen Information to avoid a temporary flight restriction zone near Sierksdorf.
While maneuvering to bypass the restricted area, the aircraft's transponder signal disappeared from radar. At 13:57 local time, the pilot transmitted an unintelligable message via radio, after which all communication was lost. Radar tracking by the German military recorded the last primary target contact at 13:57:47, heading 084° in the middle of the Neustädter Bucht. Following a search operation, the wreckage and the bodies of the two fatalities (the pilot and the system operator) were located on the seabed in approximately 20 meters of water on December 13, 2012.
The investigation
The BFU investigation examined the aircraft's technical condition, the flight planning, and the survival circumstances. Investigators analyzed radio transcripts, radar data, and surveillance footage from Lübeck Airport. The investigation also included a chemical analysis of fuel samples and an examination of the aircraft's weight and balance. The investigation noted that the aircraft was not equipped with a Flight Data Recorder (FDR) or Cockpit Voice Recorder (CVR), which limited the ability to reconstruct the final moments of the flight.
Findings
Technical analysis suggested that the engine suffered a loss of power, which prevented the crew from maintaining altitude and reaching the shoreline. While the exact cause of the engine disturbance could not be definitively confirmed, investigators found evidence of fuel starvation. This was likely caused by a combination of a missing fuel filter element and an excessive concentration of anti-ice additive in the fuel, which created a gel-like substance that restricted fuel flow through the engine control unit (FCU) inlet filter.
Furthermore, the investigation found that the helicopter was likely operating in an overloaded state. The weight of the specialized Saab TopEye TM equipment, combined with a full fuel load and other onboard items, pushed the aircraft's mass to approximately 2,110 kg, leaving very little margin for error. The aircraft was also found to be technically unairworthy due to the missing filter and an expired fuel control unit component.
Regarding the fatalities, the investigation determined that the crew died from hypothermia and drowning. Contributing factors to the severity of the accident included the lack of required survival equipment—such as life jackets, immersion suits, and life rafts—as well as delays in the commencement of rescue operations caused by the ambiguous nature of the final radio transmission and the loss of radar contact.