The purpose of this paper is to present and describe a hybrid electrical network for an aircraft in emergency operation. The principle of this network is to hybridize, through a bidirectional DC/DC converter, a high speed turbine (Ram Air turbine – RAT) with an electrochemical storage. Some experiments on a lab test bench have allowed validating the principle of the hybridization and several energy management strategies have been tested with a low voltage lithium ion battery. A design study of DC/DC power converters, according to the voltage of that storage device, has been done. This study tries to be as exhaustive as possible in view of determining the best voltage connection in terms of mass and efficiency. This study has led to the design and sizing of a medium-voltage battery from which future tests will be carried out on the lab test bench.