中文摘要：

飞机起落架的结构安全性对航空运输安全至关重要。针对某型飞机起落架折断事故，通过理论计算和断口微观形貌分析，探讨了造成事故的原因。研究表明：飞机前起落架下阻力臂因受压失稳而过载断裂，当拖把施加于飞机的拉力超过2.261×10^5N时下阻力臂就会发生压失稳断裂。研究结果对制定飞机地面安全技术规范有重要参考价值。

英文摘要：

It is crucial for the aviation transportation safety to assure the landing gear＇s structure reliability. The cause of the landing gear collapsing is studied through the fracture surface analysis and theoretic computation. The research indicated that the lower drag brace was buckled in compression and fractured by overload. When the tension load which the towbar applied in the aircraft surpassed 2. 261×10^5 N, the lower drag brace would be buckled in compression. The research result will be value to make the specification for the aircraft ground safety technology.