A simple nonlinear controller for a low-power gas turbine based on direct passivation is proposed in this paper. It uses a nonlinear state space model of the gas turbine in input-affine form based on first engineering principles. It is found by standard nonlinear analysis that the developed model is reachable and observable in the whole application domain and stable in a small neighborhood of an operating point. Accordingly, the control aim is to guarantee the asymptotic stability of every operating points in the whole application domain and to provide suitable disturbance rejection. The proposed nonlinear controller is based on a prescribed quadratic Lyapunov-function and it is able to solve the protection of the gas turbine. The robustness of the closed-loop system with respect to the time-varying parameters is also investigated.