The Fly By Wire (FBW) technology requires monitoring functions of flight control critical system based on dedicated failure detection techniques. One of the main failure cases of interest is the Oscillatory Failure Case (OFC) which directly impacts the structural design of the aircraft. A robust analytical redundancy diagnosis technique, based on a hydraulic actuator non linear model, is currently implemented in A380 flight control computer for detecting this failure. This paper presents new fault detection architecture, dedicated to other kind of actuators, based on linear model with a feedback loop including a dynamic filter in order to increase fault detection efficiency in a specific bandwidth. This scheme uses a second-order linear model, corresponding to an Electro-Hydrostatic Actuator (EHA). The feedback loop filter is then designed by H∞ synthesis using weighting functions according to frequency specification objectives. The efficiency of the proposed approach is illustrated by some simulation results using real A380 flight test data corresponding to an EHA actuator