F ACTORS A FFECTING 2
2.2 Challenges in Coping with Abnormal Situations
Controllers have to make vital decisions pertaining to aviation safety in situations of time pressure, uncertainty and minimal error toler-ance. Although flight crews take credit for their skills in managing abnormal events—as they are the actors who face grave and imminent danger—it is also widely established that controllers play a significant role in the prevention of the incident trajectory and the recovery from disasters. There are ample cases where controllers timely and accu-rately mitigated or prevented disasters, although they did not receive the same publication from mass media as other cases of mishandling and poor judgment.
Emergencies are critical situations close to the margins of safety that present many challenges to controllers, requiring competence in problem-detection and replanning. As soon as the relevant cues are detected, a problem is formulated and the need to replan for the situ-ation becomes critical. In the evolution of an occurrence, new threats may appear while current ones may change their demands. This amplifies the need for gathering new information to fill in gaps, clar-ify assumptions and correct explanations. All this calls for cognitive strategies for how to assess new demands, how to manage uncertainty, and when to engage other team members in the situation.
On another level, team performance is also challenged because emergencies require teamwork strategies such as synchronization of activities, exchange of critical information, and reallocation of roles as new tasks are added and priorities are altered. Furthermore, emer-gencies are not tolerant of errors and require competence in managing error detection and correction. Taskwork and teamwork strategies are important elements of effective human performance in air traffic con-trol (ATC) that are elaborated in Chapter 4.
Even in everyday situations, controllers encounter various normal threats that have the potential to increase work complexity, such as:
• Adverse weather conditions
• Degradation of CNS systems
• Distractions in the operations room
FACTORS AFFECTING ATM PERFORMANCE 41
• High-complexity traffic
• Military exercise areas affecting the area of responsibility
• Special handling traffic
• Diversion of flights
• Air traffic flow and capacity management (ATFCM) failures that result in over deliveries of flights and high workload
Everyday threats can combine in different ways, escalate in steep patterns, or become difficult to anticipate, hence making it difficult to manage them.
In the beginning of the twenty-first century, two fatal accidents that were attributed to human error (the Linate runway collision and the Ueberlingen midair collision) triggered considerable interest in ATM safety. Plane crashes are by their nature high-profile events that attract extensive media coverage that eventually has an impact on air transportation policies. The active involvement of controllers in the causation of accidents is usually pointed out by an ever-present blame culture. In hindsight, it is easy to attribute blame to control-lers since all the information about a mishap is revealed after the fact, although it was possibly unavailable in the actual course of events.
Furthermore, media intervention and blame attribution may lead directly to extreme actions as manifested in the assassination of the controller involved in the Ueberlingen accident. In contrast, limited media coverage is devoted to everyday operations where controllers successfully manage to avert numerous hazards and adverse events.
The ATC units are responsible for the provision of alerting ser-vices in their area of responsibility (AoR). An alerting service aims at notifying appropriate clusters of aircraft in need of search and rescue.
In general, an alerting service is provided through the declaration of three emergency phases as follows (ICAO 2007a):
1. The uncertainty phase where uncertainty exists as to the safety of the aircraft and the passengers.
2. The alert phase where apprehension exists as to the nature of the emergency, which allows more units to be called in the situation.
3. The distress phase where there is reasonable certainty that an aircraft is threatened by grave and imminent danger or requires immediate assistance.
4 2 COGNITIVE ENGINEERING AND SAFETY ORGANIZATION
In the most straightforward case, flight crews may declare an emer-gency to the ATC units by directly stating the exact nature of the problem (e.g., explosive decompression) and their intention to act (e.g., immedi-ate landing). In this case, it is obvious that a distress phase is declared directly and the aircraft in emergency is compelled to land at the nearest airport. Normally there is no precise guidance to the transition from one phase to the other apart from generic rules in the operational manu-als. ICAO (2007a) has explicitly acknowledged that the wide range of circumstances surrounding an emergency precludes the establishment of detailed instructions for how to respond in the operating procedures.
The constant demand for greater traffic capacity has increased the range of possible emergencies and created more possibilities for new classes of complicated emergencies. Although complex occurrences may be less frequent than typical or textbook emergencies, the con-sequences of human mishandlings could be extremely important.
Controllers are expected not only to handle everyday traffic efficiently, but also to manage complex emergencies that may occur unexpectedly and follow a steep escalation pattern.
Official investigation reports and field observations of practitioners have shown that controllers employ a range of cognitive strategies to meet their work demands successfully by relying on their professional knowledge, acquired skills, and trained competencies. Cognitive strategies—such as decision-making, sensemaking, replanning, and adaptation—are the building blocks of cognition that are elaborated in Parts II and III. Mainstream ATM research has focused mainly on methods, tools, and taxonomies of errors that can assist the inves-tigation of mishaps and the design of automated support tools. With respect to training, most aviation organizations have devoted their resources to technical skill training so that practitioners acquire and perfect their skills in the full range of tasks. Although operational teams are the basic functional blocks of the ATC system, a relatively small appreciation has been made for training controllers as effective team members. Only recently, we have witnessed courses on team resource management (TRM) introduced in the development phase of training. There is, however, an increasing recognition that team decision-making should become an integral part of ATC training, together with other conventional knowledge and technical skills in the management of abnormal situations.
FACTORS AFFECTING ATM PERFORMANCE 4 3 2.3 Work Demands and Stress in the Operating Environment
The operating environment of flight crews and controllers exposes them to numerous work demands, ranging from physical stress (e.g., noise, heat, cold, vibration, and altitude) to time pressure, workload, and negative feedback on performance. The perception of practitio-ners of the imbalance between work demands and coping abilities is an important factor in the incidence of stress (Cox 1987). Figure 2.1 shows a transactional model where stress is viewed as a process by which certain work demands evoke an appraisal process in which perceived demands exceed coping resources and result in undesirable physiological, emotional, cognitive and social changes.
This section looks at the work demands of the ATM environment and the sort of stressors that are likely to degrade the performance of aviation practitioners. It is interesting to note that the reaction to stress is not always dysfunctional since experienced people can manage to adapt their priorities as they start to perceive an imbalance between demands and resources. This matter is treated more thoroughly in the examination of models of human performance (Chapter 4) and in the management of work complexity (Chapter 9).
Work demands
Appraisal process
Perceived work demands
Perceived control and coping resources
Moderators Experience, Interface design,
System design
Moderators Experience, Teamwork, Procedures Coping strategies
and adaptation
Figure 2.1 A transactional model of stress.
4 4 COGNITIVE ENGINEERING AND SAFETY ORGANIZATION
Early approaches to stress at work have focused on the character-istics of the technical environment that could have a high potential for causing stress (e.g., noise, heat, cold, vibration, and altitude). The introduction of new technology has shifted the focus to work demands at the task level such as time pressure, workload, information uncer-tainty and negative feedback on performance. With the increas-ing recognition of the importance of the balance between resources and demands has come an awareness of a range of team-level fac-tors that could act either as stressors or as stress-moderafac-tors. Team characteristics—such as cohesion, communication, supervision, and allocation of roles—could affect our perception of resources and may either exacerbate or alleviate the effects of task-level stressors. A similar argument can be made for what Ivancevich and Matteson (1980) called
“organizational-level factors” that derive from the general climate and the organizational processes. Table 2.1 shows examples of a range of stressors that seem to have general applicability to the ATM domain (Kontogiannis 1999a).
Table 2.1 also provides a useful context for examining the role of technology either as a source of stress or as a moderator of stress. On
Table 2.1 Work Stressors at Different Levels in the ATM System
WORK ENVIRONMENT TECHNICAL LEVEL INDIVIDUAL OR TASK LEVEL
TEAM AND ORGANIZATIONAL
LEVEL Data overload, noise Emergencies and
abnormal situations
Threat/high error consequences
Lack of team cohesion
Humidity conditions Complexity and traffic volume
Time pressure/
Workload
Intra and inter team conflicts
Low visibility Adverse weather conditions
Uncertainty Shift work/night shifts
Lighting conditions Traffic that requires special handling
Inexperience Role ambiguity
Interruptions in the operations room
Malfunctions/
limitations/
degradations of CNS systems
Incomplete knowledge
Insufficient/
ambiguous/missing SOPs/LoAs, contingency plans Design inefficiencies Airspace structural
complexity
Incomplete mental modes
Occupational stress
Tower cabin windows (dirty, spots, etc.)
Automated handoff failures
Illness Communication
difficulties
FACTORS AFFECTING ATM PERFORMANCE 4 5
the one hand, technology can give rise to many stressors ranging from environmental to team-level stressors. Poor organization of alarms, for instance, can increase noise levels while unfriendly interfaces can increase information uncertainty and workload in navigating through the computer screens. The design of technology may also reduce the
“horizon of observation” (Hopkin 1995) by restricting access to the work of other colleagues. On the other hand, the design and use of technology can function as moderators of stress. Prioritization of alarms and logging devices, for instance, can minimize noise levels while user-friendly interfaces can minimize diversion of attention to secondary tasks. In addition, error-tolerant technologies may increase the response time and provide opportunities for error recovery. At the team level, appropriate design of technologies can facilitate distrib-uted cognition and enable timely hand-over of tasks to other work shifts.
The work demands or stressors in Table 2.1 can be used to define a set of work characteristics in the ATM system as follows:
• Rapidly escalating situations: The transition between normal and high tempo operations can be rapid. In an explosive decompression, for example, the crew may initiate a rapid descent (e.g., 5000–6000 feet per min) from its cruising level that could affect many other aircraft without any prior notice.
• Multiple information resources: ATC operations rooms are information rich environments but can also be noisy at other times. There are multiple sources of information including radar screens, CNS systems, pilot communications, and other adjacent traffic units.
• Uncertainty: Weaknesses in the presentation of information can increase uncertainty (i.e., missing data, unreliable data, and inconsistent data).
• Severe time pressure: Available time for decision-making and coordination may be severely constrained; in cases of loss of separation, for instance, an avoiding action must be issued within seconds.
• Errors with high consequences: Errors may have disastrous effects especially in cases where safety nets may be mal-functioning. For example, a loss of separation may lead to a
4 6 COGNITIVE ENGINEERING AND SAFETY ORGANIZATION
mid-air collision simply because the traffic alert and collision avoidance system (TCAS) may be malfunctioning while weather conditions may prevent visual maneuvering.
• Multifaceted decisions and conflicting goals: The goals of safe, orderly, and expeditious traffic may be in conflict and their consequences could cascade into the tactical level. Expediting traffic implies working close to separation minima which, in turn, could erode safety margins.
• Multiple stakeholders: Airlines, airport operators, government agencies, and other organizations can interact in complex ways with the ATC system. For example, an airline may reroute a flight to avoid an overcrowded sector but may saturate a previ-ously unaffected sector that was not in the initial flight plan.
• Physiological stressors: ATC operations require 24 hours of service, seven days a week, resulting in long and unsocial hours of work. Working in shifts may desynchronize human biological and circadian rhythms, hence causing some physi-ological stress.
The transactional approach to stress has gained wider recognition with its emphasis on the appraisal process of work demands and stress coping strategies (Salas et al. 1996). Confidence in one’s own coping resources, experience with handling other emergencies, team support and availability of procedures may influence one’s perception of the ability to cope and, hence, the appraisal of the situation. This implies that training for emergency responses should both specify the condi-tions that optimize coping resources and increase confidence in man-aging emergencies.
The experimental literature has documented many disorganiz-ing effects of stress on human performance (Kontogiannis 1999a).
It can be generally said that stress narrows the perceptive field, decreases vigilance, reduces the capacity of working memory, causes premature closure of options, and may result in task shedding.
However, there is little evidence that these dysfunctional reactions observed in laboratory tasks could transfer to real-life emergencies that involve highly experienced teams. In fact, field research within the paradigm of naturalistic decision-making (Klein et al. 1993;
Zsambok and Klein 1997; Flin et al. 1997) claims that the reactions
FACTORS AFFECTING ATM PERFORMANCE 47
of experienced practitioners are adaptive rather than dysfunctional.
Perceptual narrowing, for instance, may support a more selective use of cues when there is insufficient time to examine all infor-mation; especially for experienced practitioners with the skill to prioritize cues, narrowing of attention would seem to make sense.
The same holds true for task shedding since some tasks may have to be deferred under time pressure; recognizing high priority tasks to start with could make task shedding a quick and efficient response.
In the same sense, premature closure of options may not be so dysfunctional since delays in making decisions could be proved a graver problem. Moreover, taking precautions for some predictable side effects could alleviate any problems due to premature closure of options.
Field studies have shown that experienced people can maintain performance under stress by establishing priorities, adapting their decision strategies, and changing their communication patterns (Serfaty et al. 1993; Cohen et al. 1996; Lipshitz 1997; Xiao et al. 1997).
For example, with the Federal Aviation Administration (FAA) man-date for grounding all traffic due to U.S. airspace closure following the 9/11 terrorist attacks, controllers managed to redirect and safely land an enormous volume of en-route traffic. They were faced with the unthinkable scenario of a complete closure of the U.S. airspace and the pressing goal of redirecting and landing of en-route traffic at a short notice. Dozens of aircraft over-flying the Atlantic Ocean inbound to the United States were redirected to other airports while others were in critical fuel conditions. Controllers responded to this stressful sce-nario by effectively managing traffic without any accidents.
Further research in coping with stress and complexity is reviewed in Chapter 9, showing that performance can decline gracefully when controllers work under stress. In fact, controllers adapt their criteria of performance, their plans, and their coordination patterns in ways that they manage a complex situation satisfactorily. Under stress, for instance, controllers may give priority to safety over efficiency, may develop plans that are looser and increase chances of error recovery, or may become more sensitive and supportive to the needs of their teams. Of course, these skills in stress management require extensive experience and specialized training. Chapter 9 describes a study that recorded several complexity-mitigation strategies.
4 8 COGNITIVE ENGINEERING AND SAFETY ORGANIZATION