The false alarm of a fault detection module in aircraft will interfere with flight. If there is a time-offset between the inertial navigation system (INS) and air data system (ADS), the probability of a false alarm (PFA) of the fault detection module will increase, which is ignored in existing approaches. To address the problem, a fault detection approach is proposed applied to INS/ADS with a time-offset. An INS/ADS fault detection model based on kinematic equations is developed, and we combine

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... an unscented Kalman filter (UKF) with Runge-Kutta to deal with the non-linear and discretisation problem. A timeoffset estimator is designed and the observability of time-offset is analysed, showing that time-offset is observable only in the manoeuvre phase. A fault detection architecture applied to INS/ADS with a time-offset is designed, which solves the problem of the high PFA of INS/ADS fault detection under a time-offset. Simulation results show that under multiple time-offset scenarios, the root mean square error of the proposed approach can reach 0.0134 s minimally, and after time alignment, the PFA of the fault detection can be reduced to 1.8%.