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This paper presents on line sensor fault detection, isolation (FDI) and the associated fault tolerant control (FTC) algorithm for a tactical aerospace vehicle. A study on the analytical redundancy and a sensor fault detection scheme (FDI ) into a flight control system has been performed for a tactical aerospace vehicle using the longitudinal model. There are various methods available in the academic literature to apply FDI and FTC schemes to control systems and some have already been applied to real applications. Among these, observer-based approaches have arisen as one of the most widespread. The basic ideas behind observer-based FDI schemes are the generation of residuals, and the use of an optimal threshold function to differentiate faults from disturbances. Generally, the residuals, also known as diagnostic signals, are generated from estimates of the system's measurements obtained by a Luenberger observer or a Kalman filter. The threshold function is then used to 'detect' the fault by separating the residuals from false faults and disturbances. The change in residual signal is used to detect and isolate the fault and corresponding fault tolerant control action is taken to arrest the failure of the aerospace vehicle. A closed-loop simulation with nonlinear 6-degree of freedom (6-DoF) model shows that the above FDI and FTC scheme will be able to reduce the probability of mission failure due to the fault in one of the sensors.