Implication of mishaps to preliminary hazard analysis of hypersonic vehicles

To highlight the safety-critical areas of hypersonic vehicles through data-driven analysis, this paper applies the hazardous factors of the Preliminary Hazard Analysis (PHA) method recommended in the advisory circular AC- 431.35-2A to review 99 mishap flights of hypersonic vehicles. Mishaps with complex processes are modeled and analyzed using a new graphic method for aviation accident analysis named accident tree (AcciTree). Unsafe factors identified are then examined statistically to highlight the safety-critical zones and to identify possible new hazardous factors for the PHA list. The results indicate that the first-level categories of the PHA list have been defined extensive enough by the method to cover all hazardous factors examined in the 99 mishaps; and six factors are newly identified as supplements to the second-level categories to address the hypersonic features. The top six hazardous factors are system malfunction, hazardous component, protective system, system compatibility, undesired state, and human error; and the six systems with top high occurrence frequencies are propulsion, heat protection, flight control, brake, environment control, and landing gear.