Serious incident to the helicopter Alouette 3 registered HB-XXM on 28/04/2017 at Steffisburg [Investigation led by STSB / Switzerland]

Preliminary data based on the notification from the authorities of Switzerland :

After the completion of the proficiency check flight, the crew flew back to Wilderswil. in the region of Steffisburg at an altitude of about 3500 ft, the pilots heard a bang. The flight instructor took over the control of the helicopter and initiated an autorotation despite strong vibrations, the flight instructor could land the helicopter on a meadow without damage. On the ground, the crew found that the tail rotor control cable was broken.