考虑因素异质影响的直升机事故严重性分析

Analyzing Heterogenous Effects of Contributing Factors Affecting Injury Severity of Helicopter Accidents

提取美国国家运输安全委员会(National Transportation Safety Board, NTSB)数据库1241起直升机事故记录的关键信息,分析通用航空直升机事故后果严重性的影响因素及其影响异质性问题。首先,将事故记录中各项信息梳理为时间、飞行过程、飞行员、直升机和气象条件类因素,同时,采用卡方检验分析各因素在无伤事故、轻伤事故和重伤死亡事故分类下的分布差异;而后,基于不同先验概率分布的随机系数构建若干混合Logit模型,拟合事故严重性;最后,通过对比不同模型的拟合效果,根据最优模型的参数估计,分析不同事故严重性对应因素的影响机理和影响的异质性问题。结果表明:直升机事故严重性的统计建模存在明显的因素影响异质性问题;基于独立正态和多元正态分布的相关随机系数混合Logit模型拟合效果优于其他模型;影响因素中,出现仪表气象条件、空中失去控制、燃油问题、低空运行及挂载(含撞线/树)、运动及作业、进近、老年驾驶员、飞行员具有直升机仪表能力以及直升机起火爆炸等因素时,将显著增加重伤死亡事故的概率;异质性分析中,周末、老年飞行员和三点式座椅安全带等因素存在显著的影响异质性。

The study explores the contributing factors affecting the injury severity of helicopter accidents based on the modeling exercises that capture unobserved heterogeneity.The data include 1241 helicopter accident records collected from the National Transportation Safety Board(NTSB)database,categorizing the accident information into temporal,flight,pilot,helicopter,and meteorological factors.Afterward,the study uses Chi-square tests to examine the statistical differences of factors'probability distributions across injury severities(property-damage-only,minor injury,and serious injury or fatal).Several mixed Logit models are developed to model the injury severity,which set the random parameters with diverse priori densities.Through a meticulous comparison,the optimal model is selected based on data-fitting metrics.Further,the estimates of this model are used to analyze the effects of the contributing factors on injury severities and their heterogenous effects.The results indicate that unobserved heterogeneity can be found in modeling the injury severity of helicopter accidents.The mixed Logit model with independent normal and multivariate normal random parameters outperformances others in data-fitting.Among the factors,encountering IMC,loss of control in flight,fuel issues,low altitude operation or external loading(including contact with powerlines or trees),maneuvering or operation,approaching,elder pilots,pilots with helicopter instrument qualification,and accidents involving fire or explosion significantly increase the probability of serious injuries or fatalities.For the factor's heterogenous effects,the coefficients of weekend flight,elder pilots,and the use of 3-point restraints can be modeled as random parameters.