Abstract: The steel cables used in an aircraft cockpit fractured during service. The steel cables were used to pull the canopy when it was opened or closed. The steel cables usually suffered from tensile force, however, it also suffered from vibration load during flight. Based on macro and micro appearance observation, EDS analysis, metallurgical structure inspection and hardness testing, the failure mode and cause of the cables were studied. The results show that the fracture of the steel cables is fatigue fracture and overload fracture. The fracture of the steel cables was caused by the relatively larger load. Besides, poor lubrication and wear promoted the fracture of the steel cables.