A propulsion
assembly (100) comprising: first and second engines (1, 2) each having a
gas generator (12, 22) and a free
turbine (11, 21); a main rotor (62) coupled to the free
turbine (11, 21); the engines (1, 2) each comprise: a first
electric machine (30, 40) coupled only to the
gas generator (12, 22); and a second
electric machine (32, 42) coupled to the
gas generator (12, 22) by means of first
coupling means (34, 44) when rotating in a first direction and coupled to the free
turbine (11, 21) by means of second
coupling means (36, 46) when rotating in a second direction, the first
electric machine (30, 40) selectively operating in a motor mode or a generator mode, the second electric
machine (32, 42) being coupled to the gas generator (12, 22) by means of first
coupling means (34, 44) when rotating in a first direction and to the free turbine (11, 21) by means of second coupling means (36, 46) when rotating in a second direction. The second electric
machine (32, 42) operates in a motor mode when rotated in a first direction and selectively operates in a motor mode or a generator mode when rotated in a second direction.