One of the ongoing challenges in aeronautics is to reduce the weight of the aircraft, in terms both of the structure and the onboard systems in order to maintain the payload, that is to say both the fuel and the payload properly speaking (freight or passengers on commercial aircraft). One of the means envisaged by the aircraft manufacturers is, as it happens, to save weight on the hydraulic part. Rather than delivering large quantities of hydraulic fluid from the motors over a long distance, the principle adopted consists of locally generating whatever is needed to operate a particular system. Entirely hydraulic systems have been replaced by electro-hydraulic systems, activated by an electro-pump, known as an EHA (Electro Hydrostatic Actuator), which is itself driven by an electric motor situated in the immediate area of the system.
In other words, the principle of centralised hydraulic generation common to all the systems has been replaced by decentralised hydraulics. However, decentralised hydraulics may be used to supply several actuators in the same system (for example, several brake rings on the same landing gear boogie).
Apart from the weight gains, obtained by doing away with useless, heavy lengths of piping, this solution has other advantages: a reduction in costs, notably operating costs as maintenance is less onerous, and improved safety, resulting from the increased diffuseness and segregation of the circuits.
