STPA for continuous controls: A flight testing study of aircraft crosswind takeoffs

A light aircraft crosswind takeoff is a risky operation. The purpose of this paper is to demonstrate the feasibility of applying STPA (Systems-Theoretic Process Analysis) to closed-loop continuous controls, identifying the hazards of crosswind takeoffs with light aircraft and the mitigating actions that could make its execution safer. The paper analyzes the variables that affect the response of the aircraft when subjected to severe crosswind, considering how aircraft characteristics affect its stability. The hazard analysis technique STPA is a tool based on the conceptual accident causality model called STAMP (System-Theoretic Accident Model and Processes), which in turn is based on systems theory. To deal with closed-loop actions on continuous control systems, a new approach to STPA was developed and effectively used to analyze data collected on a crosswind flight test campaign. This campaign, conducted by the Flight Test and Research Institute, led to a flight envelope extension of the Embraer's training aircraft Super Tucano. The demonstration analysis showed the need for new, previously unidentified mitigating measures to be assigned to aircraft manufacturers, operators or owners, and their pilots.