A method of managing a power demand to assure the operation of a pilotless aircraft. The aircraft includes an internal combustion engine supplying a maximum principal power which can vary. The management method is particularly suitable for a rotary wing pilotless aircraft. It guarantees the storage of an amount of electrical energy at least equal to a recovery energy of the aircraft in the event of failure of the internal combustion engine. This recovery energy enables the control of autorotation and landing of the aircraft.