The paper deals with the problem of ultra-light and light aircraft structural health monitoring. The phenomenological basis and engineering decisions for methods to monitor accumulated fatigue damage and to register overstress of aircraft principal structural elements have been shown. The proposed fatigue indicator is lightweight and autonomous; the output information of the indicator reflects the inhering feature of the fatigue damage – appearance and growth of surface extrusions and intrusions. The overstress indicator simplicity and correctness of the information is provided by “fuse” principle of the design.