History of the Flight
The helicopter, a model 369E with registration SE-JVM, was conducting a power line inspection flight. It was the second flight of the day, following a refueling stop at Enköping/Långtora Airport in Uppsala County. The crew consisted of a pilot and a system operator. The helicopter was parked on a grassy area outside a hangar with its nose pointing east. The take-off weight was 2,811 lbs.
After engine start, the helicopter hovered to just above ground level. During the hover, it began to rotate clockwise. The pilot applied full pedal travel but could not stop the rotation. The helicopter continued rotating while ascending to approximately 15 meters, then descended while rotating and struck the ground.
Injuries and Damage
The crew exited the helicopter with assistance from witnesses at the scene. Both occupants sustained minor injuries and were transported to a hospital for examination and treatment. Rescue services, police, ambulance, and an ambulance helicopter were called to the scene. The aircraft sustained damage, but the extent is not specified in the source.
Meteorological and Environmental Information
The weather at the time was clear and sunny, with a south-westerly wind. The source states that the relative wind came from the rear on the right side during the take-off and hover, although the pilot perceived the wind as coming from the front. No other meteorological details were provided.
Technical Examination
A thorough technical investigation of the helicopter was conducted. No faults were identified that could have contributed to the accident. The crew reported no unusual sounds, warnings, or malfunctions before the rotation began. An examination of the engine and a fractographic examination of parts were performed, with no anomalies found.
Causes of the Accident
The investigation states that during take-off, the helicopter operated at high power output and a relatively high take-off weight. The relative wind was coming from the rear on the right side, which contributed to the helicopter's fin acting like a wind vane, causing a loss of tail rotor effectiveness and unanticipated yaw. This led to the loss of control.