Human Factors in Safety: Preventing Errors and Optimizing Performance

Understanding Circadian Rhythms and Their Impact

Circadian rhythms are 24-hour biological rhythms that regulate various physiological processes in living organisms, such as sleep, body temperature, and the propensity for human error. These internal clocks follow a consistent 24-hour pattern.

Circadian rhythms play a crucial role in regulating sleep patterns. Chemical changes occur in the body as it prepares for sleep, typically around 8 PM. Body temperature reaches its lowest point around 3 AM and then gradually increases throughout the day until natural awakening.

Challenges for Night Shift Workers

Night shift workers often operate against their natural circadian rhythm. Regular night shift workers frequently experience a strong desire to sleep during the night and may struggle to achieve restful sleep during the day.

The Window of Circadian Low (WOCL)

The Window of Circadian Low (WOCL) is a critical period, typically between 2 AM and 5 AM, when individuals would normally be asleep. This timeframe is recognized as a high-risk period for human error due to reduced alertness and cognitive function.

Strategies for Mitigating WOCL Risks

• Avoid performing the most safety-critical tasks during the WOCL.
• Maintain good lighting and a slightly cool temperature in the workspace.
• Avoid monotonous or tedious tasks during this period.
• Ask a colleague to check your work for accuracy.
• Stretch, walk around, and get some fresh air to stay alert.
• If possible, take a brief nap (a few minutes) to refresh.
• Use caffeine carefully; excessive use may make it more difficult to sleep when you get home.

Managing Risks from Repetitive Tasks

Repetitive tasks are simple tasks performed consistently across all shifts. While seemingly straightforward, they pose unique safety challenges.

Examples of Repetitive Tasks

• Inspecting passenger life jackets.
• Rivet inspections on aircraft structures.
• Opening inspections of passenger oxygen masks.

Dangers Associated with Repetitive Tasks

A significant danger is that technicians may neglect to consult the manual, potentially missing crucial updates or changes to a task. Attention can also wane when inspecting items that are rarely found to be wrong, damaged, or out of tolerance, especially during visual inspections.

Preventing Errors in Repetitive Tasks

To mitigate these dangers, technicians should vary their tasks to prevent complacency and consistently follow all procedures and manuals for each task. This proactive approach helps maintain vigilance and ensures adherence to current standards.

Understanding Unintended Errors

Unintended errors occur when an individual has no intention of making a mistake. These errors typically arise when our attention is distracted or divided.

Two Types of Unintended Errors

• Slips: Occur when we perform an action differently than intended. For example, pressing the wrong switch or entering an incorrect value during refueling.
• Lapses: Involve forgetting to complete an intended action. For example, leaving a tool inside the aircraft or failing to close an airplane manhole cover.