In this article we present a simple control procedure for a quadrotor that ensures convergence to a required altitude and attitude set-points under conditions of unknown physical parameters. The quadrotor model is highly nonlinear. The altitude set-point strategy is based on a two-mode control strategy: coarse and the fine motion modes and a sort of huristic process. In the first control mode we apply piecewise control functions. In the attitude regulation the design procedure is based on the passivity-based approach and in particular the controller is independent of the system physical parameters. The considered control strategy might be useful in various aerial missions in which stable hovering is required as for example in reconnaissance and aerial photography flights. The control design complies with the system structure which restricts the thrust force to act in one direction. Simulation results demonstrate the controller performance.