A piloting assistance device for a hybrid helicopter is provided with a rotary wing, two half-wings (8′, 8″) provided respectively with first and second propellers (6′, 6″), and an engine installation continuously driving the rotary wing (100) and the propellers by meshing with a mechanical interconnection system. Furthermore, the device is provided with computer element (40) for determining maximum mean pitch (max) applicable to the first and second propellers without exceeding the power available for the propellers, the computer element determining the maximum mean pitch (max) as a function of the current mean pitch of the blades of the first and second propellers as measured in real time, of a maximum power that can be delivered by the engine installation, of a current power being delivered by the engine installation, and of a relationship determining a power gradient (GRD) as a function of pitch for the first and second propellers.