Final report after main rotor separation
Jul 07, 2014
The Swedish Accident Investigation Board (Statens Haverikommission, SHK) has published its final report following an accident that occurred in Porjus on 8 November 2012.
The aircraft, a Swedish Bell 206B Jet Ranger with the registration SE-HOM, was engaged in a periodic operator’s proficiency check in the vicinity of the Porjus village, carrying one pilot and an instructor on board. The experienced crew had just performed an autorotation landing, when a loud noise and vibrations that corresponded to the rotor RPM suddenly evolved. Moments later, the whole main rotor separated from the helicopter and it landed in the snow approximately 10 meters to the left of the airframe. The helicopter remained upright with no injuries to the occupants.
The SHK concludes that the fracture on the main rotor driveshaft was caused by a design flaw in the freewheel unit’s lubrication system that allowed for possible debris to obstruct the oil flow to the unit. The possible debris where considered to be in such size that they could be present in a PART 145 maintenance shop. SHK recommends EASA and Transport Canada to work for a reduction of the lubrication system's vulnerability to debris and to inform operators of advices how to avoid possible contamination of the oil in the freewheel unit.