This paper presents a new approach to co-design of state feedback and dynamic proportional observer for a class of uncertain linear systems with disturbances and faults. Our objective is to simultaneously estimate the state, the faults. The system is controlled with the state estimate. An H∞ index is used in order to minimize the effect of the disturbance input on the state and fault estimation errors. The state feedback and observer gains are obtained by solving an optimization problem under LMI constraints. The procedure is applied to the dynamics of a 2DOF helicopter. It shows its ability to well handle the system.