In this paper, we propose to monitor the Fuel Metering Valve (FMV) of a jet engine, subsystem controlling the fuel flow. The proposed control strategy aims to design a virtual sensor based on robust on-line estimation for LPV systems using Takagi-Sugeno formalism. The purpose of the original approach is to provide performances required in the specifications in spite of occurrence of an unexpected fault during the operation. The robustness is guaranteed by a Neural Kalman Filter accommodating, in real time, the model prediction. In the proposed methodology, an off-line closed-loop identification scheme is first used to elaborate multi local linear state space models, after that a multi-model observer based on Linear Matrix Inequalities (LMI) optimization is used to build the virtual sensor. The NEKF is added to circumvent online model accuracy problems.The efficiency and limit of the approach are shown and discussed through simulations on a complete numerical engine test bench.