What happened
On December 28, 2010, an MD 600N helicopter was performing specialized utility flights near Jena-Isserstedt, Germany. The mission involved assessing snow loads on flat roofs and using the helicopter's rotor downwash to clear snow from rooftops. After completing tasks in the Gera and Hermsdorf areas, the crew refueled at Jena-Schöngleina before proceeding to a local hardware store to pick up a passenger and evaluate another roof.
The crew landed in a cleared roadside bay approximately 120 meters southwest of the hardware store. During the landing and subsequent takeoff, the rotor downwash kicked up large clouds of snow. After the passenger boarded, the pilot performed a vertical takeoff to avoid flying directly over bystanders. At approximately 1/100 ft above ground level, while the aircraft was at a low forward airspeed, the engine failed. The crew attempted an autorotative landing on the road in front of the aircraft, but the helicopter struck the ground with a high sink rate, resulting in the destruction of the aircraft. The two pilots sustained serious injuries, while the passenger suffered minor injuries.
The investigation
The BFU investigation examined the aircraft's engine, the flight data from a nearby surveillance camera, and the operational history of the day. Investigators discovered that the aircraft had already experienced an engine failure earlier that same day during a similar snow-clearing task near Hermsdorf. The crew had restarted the engine and continued the mission without informing the company management.
Technical analysis of the Rolls-Royce 250-C47M engine was conducted by the manufacturer in the United States. While the engine showed no mechanical defects during ground testing, investigators found damage to a compressor blade. The investigation also noted that the helicopter was equipped with a standard grid air intake rather than a particle separator, which is an optional feature designed to protect the engine from foreign object ingestion.
Findings
- The primary cause of the accident was an engine failure caused by the ingestion of ice.
- The engine failure occurred during a flight phase (low altitude and low airspeed) that was unsuitable for a successful autorotative landing.
- The use of a standard grid air intake instead of a particle separator increased the vulnerability of the engine to snow and ice ingestion.
- The crew's decision to continue operations after an earlier engine failure without notifying management prevented the company from implementing necessary safety precautions.
- The landing site in the roadside bay was not secured or cordoned off, and the presence of high snow banks limited the available space for an emergency maneuver.