Tail rotor struck a cable while on a reconaissance flight. Two occupants thrown clear of the helicopter and two trapped inside. Piloting the helicopter was Jacques Fouque, an experienced pilot and mountain guide, the engineering director of the Emosson dam Regis Desmus, Jean-Marc Mermillod, from IG3M a company specialising in lifts and cable work and Sebastien Brun, the helicopter mechanic and son of CMBH director Pascal Brun.