基于故障树-蒙特卡罗模拟的航空发动机控制系统适航审定安全性分析方法

Airworthiness Compliance Validation Safety Assessment Method of Aero-engine Control System Based on Fault Tree-Monte Carlo Simulation

为航空发动机控制系统(FADEC系统)初始适航审定安全性分析提供一种方法.通过将FADEC系统出现故障导致发动机LOTC事件作为系统的失效状态,分析FADEC系统导致LOTC事件的系统单元,建立FADEC系统单元之间的可靠性模型,求出系统失效状态的最小割集,然后在时域内模拟系统状态的随机游走;通过计算机仿真来实现利用蒙特卡罗模拟对系统状态之间的转移时间和转移结果进行抽样来得到大量具体的系统状态,系统失效的概率用抽样得到的系统失效的频率来估计。计算单元修复率为1次/h、0. 8次/h和0. 5次/h三种情况下的FADEC系统瞬时LOTC率和平均LOTC率。结果表明单元修复率为0. 5次/h FADEC系统不满足适航要求的平均LOTC率水平,但其他情况均可以满足要求。可见该方法计算得到的保留故障要求与航空器MMEL适航文件一致。

In order to provide a safety assessment method for the aero-engine control system (FADEC system) in the initial airworthiness certification phase.The failure of the FADEC system was taken as the failure state of the engine LOTC event,and then the FADEC system units that caused the event of LOTC were analyzed.The reliability model was established between FADEC system units.The minimum cut sets of the system failure state were calculated,and then the random walk of the system state was simulated in the time domain.Through the computer simulation,The Monte Carlo simulation was used to sample the transfer time and transfer result among the system state to get a large number of specific system state.The system failure probability was estimated with the system failure frequency.Instantaneous LOTC and average LOTC rates for FADEC systems with unit repair rates of 1 h^-1, 0.8 h^-1 and 0.5 h^-1 were calculated.The results show that the FADEC system does not meet the average LOTC level of airworthiness requirements at a unit repair rate of 0.5 h^-1.But other cases,the requirements can be met.It is concluded that the deferred fault requirements obtained by this method are consistent with the airworthiness documents of the aircraft MMEL.