Abstract: A method and configuration to optimize an entire traction system available on a helicopter including an auxiliary engine by allowing the engine to provide non-propulsive and/or propulsive power during flight. The auxiliary engine is coupled to participate directly in providing mechanical or electrical propulsive power and electrical non-propulsive power to the aircraft. An architecture configuration includes an on-board power supply network, two main engines, and a system for converting mechanical energy into electrical energy between a main gearbox to the propulsion members and a mechanism receiving electrical energy including the on-board network and power electronics in conjunction with starters of the main engines. An auxiliary power engine provides electrical energy to the mechanism for receiving electrical energy via the energy conversion system and a mechanism for mechanical coupling between the auxiliary engine and at least one propulsion member.