This paper addresses the problem of Oscillatory Failure Cases (OFC) detection in the Electrical Flight Control System (EFCS) of the Airbus airplanes. OFC lead to strong interactions with loads and aero-elasticity and consequently are to be detected very early in time. The work describes the status of on going research activity undertaken within a collaborative project between Bordeaux University (France) and Airbus. An hydraulic actuator model is currently used as the basis for a robust analytical redundancy-based technique implemented in A380 Flight Control Computer (FCC) for detecting unauthorized oscillatory events. For upcoming and future generation A/C (Aircraft), it could be required to detect OFC with less important amplitude. The method presented here is based on nonlinear state space modeling, associated with the same decision test as used by in-service Airbus A/C. It is shown that the model quality could be improved significantly by reliable estimating of some physical parameters. The fault indicating signals are compared on the same data set obtained from A380 computers during flight tests.