Aviation as a system of systems: Preface to the special issue of human factors in aviation

Aviation is a system of systems. Maier (1998) characterised a ‘system of systems’ as possessing five basic traits: operational independence of elements; managerial independence of elements; evolutionary development; possessing emergent behaviour; having a geographical distribution of elements. In the context of aviation, these systems have distinct operational independence (aircraft operations; maintenance; air traffic management/control) and each of these aspects has managerial independence (they are offered by independent companies or national providers); however, they are bound by a set of common operating principles and international regulations for design and operation. All aspects of aviation encompass technical, human and organisational aspects. It is a sociotechnical ‘system of systems’ encompassing critical human factors considerations such as usability, training, design, maintenance, safety, procedures, communications, workload and automation. It is fair to say, though, that the aviation ‘system of systems’ was never designed, it is a legacy system that has evolved over the past century. All the components in aviation are themselves open systems (i.e. they must interact with their environment). Open Systems Theory is derived from General Systems Theory (von Berthalanfry 1956); however, these organisations are only selectively open, in that they interact with their environment but also need boundaries in order to exist. For example, civil airlines operate into a wide range of airports (none of which they own), aircraft maintenance is often provided by third parties, aircraft ramp servicing is almost invariably provided by a range of external suppliers and air traffic management/ air traffic control (ATC) is provided by the air traffic service providers from the countries into which they either operate or overfly. In the operation of civil aircraft, there are a great number of interand intraorganisational boundaries that information and resources must cross in this system of systems. Leveson (2002, 2004) has proposed that the nature by which systems of systems remain in a dynamic equilibrium is via the control and communication of constraints. In Systems-Theoretical Accident Model and Processes, accidents are considered to result from inadequate control or enforcement of safety-related constraints (occurring during the design, development or operation of the system) and not from individual or component failures. Safety is a product of control structures embedded in an adaptive socio-technical system. Accidents are viewed as control failures. The papers in this special issue of Ergonomics address all aspects of the aviation system. Some adopt a macro-ergonomics approach investigating system-wide issues in the safe operation of aircraft. Other papers are much more focused in their aims and objectives, addressing a very specific issue in human performance. However, all papers can be viewed from a wider, socio-technical system perspective.