Exploring how to ensure reliability of lock system of retracting-lowering landing gear

Up to now, to our best knowledge, there is no paper in the open aerospace literature on ensuring reliability of lock system of retracting-lowering landing gear; we give and analyze 16 actual accidents of aircraft landing gear that occurred at home and abroad. We analyze one accident in much detail; we give a brief description of this accident; the downlock is opened spontaneously, caused by the improper mesh of locking detent and lock hook. The failure mode effect analysis of retracting-lowering lock system with different kinds of conditions is explained. And the typical fault tree analysis is presented. The method of reliability analysis for the failure of these lock systems is presented. The failure types of some aircraft landing gear are analyzed. In our analysis, we assume that the allowance value of improper mesh includes manufacture error, rude filing and beating, and structural distortion. Based on our analysis, we summarize how to deal very carefully with nine problems to ensure the reliability of lock system of retracting-lowering landing gear: three problems in design of lock system, three problems in analyzing reliability of lock system, and three problems in testing of lock system.