Stress, Workload and Arousal
Stress and arousal
Stress is the body's response to demand. Short-term stress can sharpen performance, but prolonged stress impairs judgement, sleep and health. The Yerkes-Dodson curve relates arousal to performance: too little arousal causes complacency, too much causes narrowing of attention and errors. The optimum lies in the middle and is narrower for complex tasks.
Workload
Workload is the demand placed on limited mental resources. It can be too high (overload) or too low (underload, leading to boredom and complacency). Mental workload rises with unfamiliarity, poor displays, time pressure and fatigue. Good design, checklists, automation and crew coordination manage workload. Stressors include noise, vibration, heat, hunger, illness and interpersonal conflict.
Traps in questions
Candidates often assume all stress is bad; some stress is useful. They also confuse workload with stress: workload is the demand, stress is the response. Another trap is thinking that low workload is always safe; underload causes vigilance decrements. Remember that arousal and performance are not linear.
Worked example
During a busy approach, a pilot becomes fixated on one task and misses a call. This is high arousal narrowing attention. Rule of thumb: when workload rises, prioritise, delegate and use checklists, and watch for the narrowing of attention.
Human Error and Threat and Error Management
Error models
Reason's model separates slips and lapses (skill-based), mistakes (rule- and knowledge-based) and violations. Errors are normal and inevitable; safety comes from managing them. The error chain idea shows that accidents usually follow a sequence of small failures. Error management aims to trap errors before they become undesirable states.
Threat and Error Management (TEM)
TEM has three layers: threats (external events such as weather, traffic or aircraft malfunction), errors (crew actions that deviate from intention) and undesirable aircraft states (e.g. unstabilised approach, wrong altitude). The crew counters threats, traps errors and recovers from states. Countermeasures include briefings, cross-checks, callouts, standard operating procedures and monitoring. The goal is not zero error but resilience.
Traps in questions
A common trap is treating a violation as an error; violations are deliberate. Another is forgetting the third TEM layer, the undesirable state. Examiners also test whether TEM applies only to pilots: it applies to all crew and to the whole operation. Remember that threats can be anticipated and briefed.
Worked example
On approach, a thunderstorm (threat) leads the crew to accept a tailwind, producing an unstabilised approach (undesirable state). The crew recognises the state and goes around. Rule of thumb: brief the threats, trap the errors early, and recover from states before landing.
Crew Resource Management
What CRM covers
CRM is the effective use of all available resources - people, equipment and information - to achieve safe and efficient flight. It includes communication, leadership and followership, teamwork, situational awareness, decision-making, workload management and the management of automation. It arose because most accidents involved human and crew factors rather than technical failure.
Communication and leadership
Good communication is closed-loop: the sender states the message, the receiver acknowledges and confirms. Assertiveness matters: a junior crew member must be able to speak up, and the captain must invite challenge. Leadership styles range from autocratic to laissez-faire; the effective style is flexible and situation-dependent. Briefings set expectations and clarify roles. Barriers include hierarchy, fatigue, noise and language.
Traps in questions
A frequent trap is thinking CRM is only about 'being nice'; it is about performance and safety. Another is confusing assertiveness with aggression. Examiners also test the difference between leadership and command: command is authority, leadership is influence. Remember that CRM applies to single-pilot operations too, through resource management and decision-making.
Worked example
A first officer notices a wrong altimeter setting but hesitates to speak. The captain invites challenge and the error is corrected. Rule of thumb: use closed-loop communication and speak up early; a challenge is a gift to safety.
Decision Making, Situational Awareness, Automation, Health and Fitness
Decision making and situational awareness
Aeronautical decision making is a systematic approach to choosing among options. Models include the DECIDE loop (detect, estimate, choose, identify, do, evaluate) and the recognition-primed model used by experts. Situational awareness has three levels: perception, comprehension and projection. Loss of situational awareness often follows fixation, ambiguity, unpredicted change or fatigue.
Automation and health
Automation reduces workload but introduces complacency, mode confusion and skill decay. Pilots must monitor the automation and understand its modes. Health and fitness affect performance: alcohol, drugs, fatigue, illness and dehydration all degrade judgement. The IMSAFE checklist (illness, medication, stress, alcohol, fatigue, emotion) is a practical pre-flight self-check.
Traps in questions
Examiners test the levels of situational awareness and the difference between complacency and boredom. They also test automation traps: automation bias (trusting the machine over evidence) and mode confusion. Another trap is assuming fitness is only physical; mental fitness matters. Remember that DECIDE is a guide, not a guarantee.
Worked example
A pilot becomes absorbed in reprogramming the flight-management system and fails to notice a level-off clearance. This is fixation and loss of projection. Rule of thumb: use IMSAFE before flight, monitor the automation, and share situational awareness with the crew.