What happened
On February 28, 2014, an Airbus BK117 C-1 helicopter was conducting a night-time winch training exercise near a rescue cruiser in the Baltic Sea, approximately 3 NM north of Prerow. The flight was conducted under Visual Flight Rules (VFR) at night.
After departing from Rügen airfield, the crew proceeded toward the Baltic 1 offshore wind farm before changing course to rendezvous with the rescue vessel. During the approach, the crew attempted to locate the ship using radar. After an initial aborted approach, the crew attempted a second approach. During this maneuver, the helicopter began a descent before reaching the final approach phase and before the crew had established visual contact with the vessel. The aircraft struck the water surface and sank.
The investigation
The BFU investigation focused on the flight sequence, crew performance, and organizational procedures. Investigators analyzed radar data, the Cockpit Voice Recorder (CVML), and Flight Data Recorder (FDR) to reconstruct the descent. The investigation also examined the company's operational manuals, training programs, and the regulatory oversight provided by the relevant aviation authority regarding offshore operations.
Findings
Three fatalities and one minor injury occurred during the accident. The investigation identified several contributing factors:
- The crew lacked sufficient experience regarding specific procedures for night operations over the sea.
- The approach deviated from the established procedures.
- The approach was not stabilized in terms of altitude, airspeed, or descent rate.
- The descent was initiated without visual contact with the target vessel.
- There was inadequate monitoring of flight instruments and a loss of situational awareness.
- The crew failed to react to altitude warnings from the radar altimeter.
Systemic issues were also identified, including inadequate task descriptions for crew coordination during offshore missions, a lack of defined criteria for aborting unstabilized approaches, and insufficient company guidelines regarding the use of autopilot stability functions during sea-based maneuvers.