Identifying High-Risk Occurrence Chains in Helicopter Operations from Accident Data

摘要

In this paper, we present a method to identify high-risk occurrence chains using historical accident data. The National Transpiration Safety Board (NTSB) defines an occurrence as a distinct major event of relative significance that leads to an accident or incident. We analyzed 5051 helicopter accidents between 1982 and 2008, and obtained the high-risk occurrence chains. We rank occurrence chains based on (1) frequentist approach-that is, how often a chain resulted in accidents, and (2) impact model, which accounts for the level of injury and damage, and the frequency of occurrence chains that resulted in accidents. Between 1982 and 2008, we identified 366 different occurrence chains. The loss of control (LOC) occurrence chain resulted in 13.1% of the helicopter accidents, and had a 13.8% probability of resulting in a fatal accident-the highest probability among all occurrence chains. Three of the top-five occurrence chains resulting in serious accidents involved engine failure. The impact model demonstrates that a high-frequency occurrence chain need not translate to a high-impact chain by, for example, relegating "200S: Hard landing" from sixth to 13th position while "240: inflight encounter with weather", ranked 13th based on frequency, moved to fourth position. Similarly, considering only fatal accidents when seeking risk reduction strategies may lead to missing potentially effective strategies. For example, "250-220: loss of control-inflight followed by inflight collision with object" is ranked 30th when only fatal accidents are considered; however, the impact model ranks this chain at 19th.