Abstract: Analytical redundancy of the advanced sensor failure detection isolation and fault sensor output reconstruction obviously enhance the reliability of aircraft engine controls.The Bayesian multiple hypothesis testing is applied to detection isolation and accommodation of the hard failure.The hypothesis conditioned errors,the covariance matrices of the cost function and the optimal estimate are obtained from a bank of Kalman filters.The example using the microcomputer based simulation indicates that the detective rate,the accuracy of output reconstruction and the detectable minimum range and so on has the advantage over the Kalman filter residual in hard failure.