This paper is devoted to a consistent numerical method for Optimal Control Problems (OCPs) associated with a specific class of nonlinear systems. We study dynamic models equipped with the piecewise constant (fixed-level) control inputs. The presented formalism also includes some switched dynamic models. We develop an implementable control algorithm for the above-mentioned classes of switched-type OCPs, study convexity characteristics and discuss some key properties of the proposed numeric scheme. We also consider a computational example. The computational scheme we propose is based on the Armijo-type projected gradient methodology.