Security evaluation of nose wheel steering systems based on GSPN methods

To solve the problem of how to evaluate the safety of a system without relative statistical data, the generalized stochastic petri nets (GSPN) and classical evaluating method were hung together. Taking a certain type of airplane's nose wheel steering system, which was still at the stage of design, as an example, the failure modes and effects analysis (FMEA) list was set up by analyzing system's function structure figure. The failure rate, maintenance rate, the mean time between failure and the mean time of the maintenance were calculated by the experiential formula. According to these parameters and the nose wheel steering system's GSPN model, the steady failure probabilities were calculated by the TimeNET software package. The safety of the nose wheel steering system was evaluated with the experiential formula and the risk matrix. After the evaluation, this nose wheel steering system conforms to the design demands.