Abstract:

 A dynamics model of nose landing gear retracting system was developed to analyze the emergency lowering faults of an airplane. The landing gear loads were analyzed and calculated during emergency lowering under different modes, based on which the reasons the emergency lowering failed were analyzed in detail and two improved methods were discussed. The results show that, at the end of the emergency lowering, the beneficial torque mutation produced by the spring happens after the adverse torque mutation by the front door. Thus, the total torque will appear to be negative for some times, which will cause emergency lowering faults. The increase of the flight speed is harmful to emergency lowering. Based on analysis results, requirements of nose landing gear emergency lowering can be satisfied by changing the way of the front door retraction linkage.

Key words: nose landing gear, emergency lowering, dynamics, torque mutation, door linkage

摘要：

针对某客机前起落架应急放故障的问题，建立了起落架的收放系统动力学模型，对不同飞行工况下前起落架应急放的受载情况进行了分析计算，讨论了起落架应急放功能失效的原因及改进方案。研究结果表明：在起落架应急放下行程末端处，弹簧的有利力矩突变滞后于前舱门的不利力矩突变，起落架所受的外载总矩会出现负值段，导致前起落架应急放功能失效，并且飞行速度越大，越不利于前起落架的应急放。基于分析结果，通过改变前舱门收放的联动方式可以实现前起落架的应急放功能要求。

关键词: 前起落架, 应急放, 动力学, 力矩突变, 舱门联动