Distributed Control Systems for Aero Gas Turbine Engines: A wicked problem for systems engineering?

Present day jet engines are controlled and monitored by a series of hydraulic, fueldraulic, electrical and pneumatic sub-systems known as the Full Authority Digital Engine Controller (FADEC). At the heart of the FADEC lies a centralised Electronic Engine Controller (EEC) responsible for control and safety of the wider engine system. It has long been postulated that a distributed EEC would contribute to improvements in control system performance and life-cycle costs which the aerospace industry demands. Despite an extensile list of potential benefits and the belief that the obtrusion of distributed control systems is inevitable, such systems have yet to become commonplace in large civil gas turbine engines. This paper proposes that distributed control system development is complex problem with difficulties well beyond the challenge of designing, implementing and proving technology. Distributed systems hosting present day functionality are unlikely to contribute the life-cycle savings necessary to overcome these risks; their role as a platform for new technologies which may increase fuel efficiency and engine ‘intelligence’ complicates viability assessment. Beyond commercial factors, the technical design problem is inherently complex. The flexibility and scalability of distributed systems are undoubtedly major benefits, yet such flexibility presents a vast range of design options that complicates design, realisation and assessment of optimal solutions. This paper presents a framework for the design and analysis of distributed control system for gas turbine control. The understanding behind the framework was derived form an analysis of distributed control system design as a wicked problem.