低空风切变系统建模及其对直升机飞行安全威胁定性分析

系统地建立了含湍流的三维低空风切变模型,并综合分析了其对直升机飞行安全的威胁。建立了微下击暴流风场及大气湍流场组合的风切变模型,在不增加计算量的前提下,选取特征点发展直升机飞行动力学模型,有效捕捉了风切变的切变特性,提高了在风场中的动态响应计算精度。模型配备姿态保持功能的控制增稳系统已符合一般直升机的飞行状态,并改善机体响应。根据风速分布的特点,选取不同飞行速度、不同风场位置进行飞行仿真,定性地对比分析状态量变化与风场对应关系,并且以垂向通道为例,从动力学角度分析验证了响应的理论计算表达式。结果表明：湍流主要导致高频姿态角响应,风切变对飞行状态量变化占主导作用,且垂向风是引起威胁的主要因素,据此提出危险风场规避建议。

Systematical modelling of low-altitude windshear and its qualitative threat analysis to helicopter flight safety

The model of three-dimensional low-altitude windshear with turbulence is systematically established, its threat to helicopter flight safety is comprehensively analyzed. A windshear model composed of microburst and atmosphere turbulence is developed. Without increasing the amount of calculation, a helicopter flight dynamic model integrated with wind velocity and windshear items is proposed, which optimizes the simulation precision of helicopter dynamic response through the windshear. Then a flight control system with attitude holding is synthesized into this model to correspond to the general helicopter flight state and to improve the response performance of helicopter. Following this, based on the characteristics of the windfield model, various flight velocities and windfield positions are selected and analyzed their relation between state changes and windfield. From the aspect of dynamics, the formula of response is derived theoretically with the vertical channel as the example. The results show that the turbulence mainly induces high frequency attitude response, while the windshear plays a dominant role in flight state influence, and the vertical downwind is the main inducement of threat. Based on the results, suggestions to avoid the windfiled threat are proposed.