Location within a site. Arrangement into 16 suites. Small group of workers per suite (2 controllers, 2 assistants, 1 sector chief), co-location at a suite. Ability to oversee and overhear one another. Focus on the use and reconciliation of two types of representations:
1. Public display and arrangement of a series of flight strips on one wall.
2. Radar screens.
Various artefacts for achieving control are important. Particular attention is given to the 'flight progress strips'. These are paper strips that are printed off a computer that contain information about specific flights, for example flight level, destination, radio code and planned flight path. Many changes are made to flights dependant on emerging contingencies dictated in the airspace and accordingly the fight strips are amended and annotated by hand. These flight strips are placed centrally on a wall and represent the flow and organisation of the airspace. Strips on one part of the wall rack represent planes about to enter a particular area of airspace, those on another are within that area and when an aircraft exits the airspace the strip is removed. This representation not just on individual strips but in the arrangement of them on the wall allows the controller to plan and manage the airspace over time. The amount of aircraft in the airspace and about to enter it provides a resource in which a configuration of flight paths for any given time is decided. 'The orderliness of the strips stands proxy for the orderliness of the skies; and ordering the strips is a means to creating order in the sky'. The different facets of the airstrips and their placement and configuration are clearly crucial for control, however, they provide only some of the resources for this work to be achieved. Radar screens too are crucially important as when considered in conjunction with the strips. While the strips are about organising and planning the radar provides a at-a-glance 'here and now' representation of what is actually happening in the skies, how busy they are, in what areas and whether two planes meant to pass 2000 feet apart are actually going to do so. The different representations are suited to different aspects of the work. An awareness of the full situation is provided by the reconciliation of the perspectives by the workers. While the strips are the most important representations, radar, maps and so forth as also employed.
Radar is used for visualising the here and now while flight strips are used for planning and ordering.
Coordination is achieved both through the artefacts themselves and the individually accountable amendments to them and through individual and group interaction with them. Individual workers may notice something on the radar, for example, and this may stimulate interaction with others and result in changes to flight paths and therefore the flight progress strips. Amongst the group coordination is required to reconcile and compare the different representations of activity that may be monitored, created and so on by different co-workers.
Inter-organisational group of workers in an air traffic control room.