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Buffering and Efficacy – The Management of Goal States

Buffering describes the range of behaviours the system can cope with. If we consider goal states in relation to CPs, we can identify situations where events become compressed or the attainment of the goal state is deferred. Figure 5.5 illustrates some of the possible relationships between the goal states and CP. Failing to achieve the appropriate status by the CP will complicate subsequent activity but will not necessarily lead to breaching the boundary. However, in situations such as these, the workload will increase and both load shedding and forgetting will increase the risk.

Because of the dynamic nature of both atmospheric processes and the operating environment, pilots must continually verify the validity of the goal state. Changes in the circumstance will alter the values of certain attributes, and this will, in turn, affect the extent to which the constraint set can be satisfied. It may even render the desire goal state illegal. For example, on an approach to a runway in winter, a report of runway braking action made by an aircraft landing ahead of you may contain new information that could trigger a change in your plan. Changes in a goal state, therefore, may require additional activities in order to satisfy any updated constraints or even the selection of a new goal state. Buffering also reflects the adaptive capacity of the system.

Possible conditions

FIGURE 5.5 Possible conditions.

Efficacy describes the degree to which interventions will satisfy goal constraints within the margin available and lies at the heart of CRM. Efficacy is sustained by effective collaboration, but it is a reflection of the contribution of individuals. It involves us in continually comparing the current status, in part captured by the device sensors and displayed to the pilot, with the desired goal state to verify convergence or congruence. Unfortunately, here we have several potential problems. First, reflecting on the experience of the Saab 340 crew in Chapter 3, the interface between the aircraft and the crew can be remarkably opaque. Second, the system status is a construct based on the relationship between the condition of the actual world and the operator’s understanding of the world. The problem is that, as we will see in the next section, the individual’s view of the current state is often based on a plausible interpretation of available information rather than an absolute version of reality (Weick, 1995; Hutchins, 1995). Operators work with representations of the world around them, not with absolute truths. The degree to which operators can construct valid representations is, in part, a function of the feedback received from the system and the environment.

Pilots can modify the trajectory by bringing forward, deferring, deleting or inserting new task elements. Buffering will reflect the capacity of the system to cope with these task modifications, especially improvisations, whereas efficacy reflects the fitness of the chosen action. Task management skills include the array of techniques to sustain or recover the desired trajectory, the processes by which all team members maintain a shared view of the task and the techniques used to resolve the implications of task modifications, all underpinned by fundamental knowledge of the performance and system’s behaviour. In the next section, we will look at how individuals make sense of the work and organise work. The signals we use to confirm that a constraint has been satisfied will vary in significance and salience. Expertise is a measure of the richness of our constraint sets, and our ability to detect the cues that suggest that constraints will not be satisfied.

Goal States and Resilience

In order to negotiate a successful path through the various goal states comprising the aircraft’s trajectory, individuals must construct an understanding of the prevailing state of the world, but, as was stated above, we often work with approximations of reality. Returning to the B-777 landing at Heathrow described earlier, the notional plan for the last few seconds is illustrated in Figure 5.6. Unfortunately, events unfolded rather differently, and the revised approximate sequence is illustrated in Figure 5.7.

Heathrow revised trajectory

FIGURE 5.7 Heathrow revised trajectory.

These two representations illustrate how the space occupied by the activity can be both concrete and abstract. Under normal circumstances, the transition from the descent to touchdown is concrete. It can be witnessed, and the implications of a failure to manage the transition are known. The set of abnormal goals illustrated in Figure 5.7 are largely abstract, and they are attempts to resolve ambiguity or to increase the probability of the desired outcome, ‘reach the airfield’, for example. This latter goal points to the nature of the action. By intervening, the captain changed the status of both the aircraft and the world, as it was presented to him. His action was to reduce the flap setting in order to reduce drag. Because of the condition of the aircraft, which was established by the inputs of the FO to the controls, both the drag states, the path of the aircraft and the point of touchdown, were modified. The captain now' had a different view' of the world and, as a result, could anticipate a different set of outcomes. The point I want to make here is that the world is not a static entity to which individuals respond. Action shapes the world thereby offering changed sets of possibilities. This concept will be important when we come to explore sense-making.

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