Research On Risk Assessment Methods Of Civil Aircraft Operational Occurrence

The aircraft must be ensured that all operation conditions are constantly maintained in anairworthy state in accordance with type design character during its operational process, which can beinterpreted as continuing airworthiness. To identify, analyze, and assess the occurrence risk duringoperation and maintenance process effectively is essential in maintaining continuing airworthiness. Itis also a main concern for both aircraft designer and airworthiness authority. In such circumstances,this thesis investigates the risk assessment methods and process of operational occurrence of civilaircraft based on risk management theory, system safety theory, and the relevant international anddomestic regulations.This thesis studied relevant theory of civil aircraft operational occurrence. The occurrencedefinition and characteristics are investigated from the point view of airworthiness, the occurrencessources are analyzed and its classification was presented based on occurrence severity and causes. Thecriterion of the unsafe occurrence was provided. The process of occurrence treatment was established.An integrated risk assessment system for operational occurrence was established based on riskmanagement theory. The risk assessment process was comprised of hazard identification, preliminaryrisk analysis, detailed risk analysis and risk evaluation. Besides, the appropriate methods for each partwere provided; the characteristic and applicability were studied, which guided risk assessmentmethods selection.The risk assessment methods for operational occurrence of civil aircraft were studied. Thequalitative risk assessment method was established by risk matrix based on occurrence severity andprobability index, which methods were proposed. The quantitative occurrence estimation for aircraftand fleet was provided based on the observation rate. The probabilistic risk assessment process wasintroduced into operational occurrence analysis for the first time. The aircraft hydraulic oil leakageoccurrence was analyzed by the probabilistic risk assessment method.The civil aircraft occurrence risk assessments process and methods established in this thesis canefficiently maintain and improve the reliability and safety of the in-service aircrafts.