As engineering designs become increasingly more sophisticated, the responsibility of maintaining a balance between process standardisation and navigating the overwhelming complexity of engineering tasks typically falls to the organisation's chief engineer. This research examines the socio-technical interactions that shape the chief engineer's risk-based decisions within complex engineering systems. It takes into account previous studies that considered the development of an engineer's identity, the positivist and constructivist paradigms, and the need for effective communication of technical problems. The purpose of this study seeks to understand the factors that shape the chief engineers' approach to risk-based decision-making, using a collaborative ethnomethodological informed thematic approach. [...]