Robust and early detection of Oscillatory Failure Case (OFC) in the Electrical Flight Control System (EFCS) of new generation aircrafts (A/C) appears to be a challenging problem. OFC leads to strong interactions with loads and aero-elasticity and consequently must be detected in time. A robust analytical redundancy-based technique implemented in A380 Flight Control Computer (FCC) is used for detecting such unauthorized oscillatory events. The technique has been successfully validated and provides a complete OFC coverage without false alarms in the A380 EFCS. However, for upcoming and future generation A/C, it could be required to detect OFC with less important amplitude. To meet this requirement, it becomes necessary to get more sensitive fault indicating signals. It is shown that the model quality can be significantly improved by reliable estimating of some physical parameters. The fault indicating signals are compared to those obtained from A380 computers during flight tests. The results are quite encouraging and suggest that OFC with less important amplitude could be successfully detected by the new strategy.