SHELL MODEL

HUMAN FACTORS

(SHELL MODEL)

What is the shell model?

The SHELL Model is one of the tools used by psychologists to study the interaction between individuals, the systems in which they function, and the environment which influences those activities.  This model, whose major components include software, liveware (humans), and hardware, is used extensively by multi-disciplinary design teams as follows:

Systems designers have three types of resources to employ:

·         Hardware → (The interface between people and hardware) The Air Traffic Control suites, their configuration, controls and surfaces, displays and functional systems // Physical property, tangible items such as buildings, vehicles, equipment, materials, and so forth.

·         Software → (The interface between people and software) Rules, regulations, orders, policies, standing operating procedures, customs, practices, habits and so forth, all of which administratively govern the manner in which the system operates, and perhaps, the organizational structure of its people and information.

·         Liveware → (The interface between people and other people) The human beings - the controller with other controllers, flight crews, engineers and maintenance personnel, management and administration people - within in the system.

·         Enviroment → (The interface between people and the environment) The situation in which the L-H-S system must function, the social and economic climate as well as the natural environment.

Each of these components must interact with each of the others in an environment which will potentially influence any or all of the individual resources.  These external factors which affect the performance of a system or its components, but over which the system designers have no influence, are termed environmental factors.  This system may be simplistically illustrated as follows:

For human factors researchers, the most important interactions are those that involve the people, or liveware.  This includes:  L-H, L-S, and L-L interfaces.  In real world application the relationships of course are not limited to two dimensions, but must be thought of and planned in three dimensions.  This occurs for example, when both the cockpit and cabin crewmembers interactions with each other and the myriad of hardware and software interfaces encountered in the course of a normal air carrier flight are considered.