Human Factors in a Night Shift Maintenance Error
During a night shift at Bahrain International Airport, a licensed AME is tasked with replacing a fuel pump on an Airbus A320. The shift started at 22:00, and the AME has already worked 10 hours. The replacement procedure requires disconnecting fuel lines, and the AME is fatigued. The AME's colleague, who was supposed to assist, called in sick, so the AME is working alone. The AME rushes the job to finish before the end of the shift at 06:00. After the replacement, the AME signs off the task but forgets to torque one of the fuel line fittings to the specified 25 Nm. The aircraft is scheduled for a test flight in the morning. During the pre-flight inspection, a fuel leak is detected from the fitting. The AME is called to investigate.
1. Identify the human factors that contributed to the error and explain how they interacted.
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The primary human factors are fatigue, time pressure, and lack of teamwork. Fatigue from working 10 hours and during the night shift impairs cognitive function, vigilance, and decision-making. Time pressure to finish before shift end led to rushing and skipping steps. The absence of the colleague meant no cross-check or independent inspection, increasing the likelihood of omission. Additionally, the AME may have experienced complacency due to routine task repetition. These factors interacted: fatigue reduced attention, time pressure encouraged shortcuts, and the lack of a second person removed a safety barrier. The error was forgetting to torque the fitting, a critical step. The organization also contributed by understaffing and not managing fatigue risk.
2. What corrective actions should be taken at the individual and organizational levels to prevent recurrence?
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At the individual level, the AME should be retrained on torque procedures and the importance of using a checklist. The AME should also receive fatigue management training. At the organizational level, the maintenance provider should review shift scheduling to ensure adequate rest periods and avoid excessive overtime. Implement a fatigue risk management system (FRMS). Ensure that critical tasks are not performed by a single person; require independent inspection or dual sign-off for fuel system work. Provide adequate staffing to cover sick leave. Introduce a just culture where errors are reported without fear, and use the incident for learning. Additionally, enforce the use of torque wrenches with calibration and sign-off, and consider installing a physical warning system. The CAA may require a report under the mandatory occurrence reporting scheme.