Effective Shift Handover and Human Error in Aviation Maintenance

Effective Shift Handover

Effective communication between outgoing and incoming personnel is extremely important in maintenance. Individuals must assume personal ownership and responsibility for their tasks. Information should be transmitted in written, spoken, and gestured (nonverbal) forms. Using multiple communication methods (redundancy) reduces risk.

When an experienced person hands over to an inexperienced one, the former must assume the latter lacks the same knowledge and will need more time for the handover. For example, a brief, spoken-only handover (lack of redundancy) resulted in missing screws during installation. The next shift, believing all screws were installed, released the airplane for service.

The Dirty Dozen

The Dirty Dozen refers to twelve common human error preconditions that can lead to accidents or incidents. These factors influence people to make mistakes:

1. Lack of Communication
2. Distraction
3. Lack of Resources
4. Stress
5. Complacency
6. Lack of Teamwork
7. Pressure
8. Lack of Awareness
9. Lack of Knowledge
10. Fatigue
11. Lack of Assertiveness
12. Norms

Case Study: Failure to pressurize after outflow valve left open. A technician left the outflow valve selector in manual (open) position for a test. During flight, the valve remained open, causing hypoxia. The AMM (Aircraft Maintenance Manual) stated, "put the airplane in normal conditions," but didn't specify setting the outflow valve to auto. This illustrates lack of knowledge and lack of resources (vague AMM).

Types of Errors in Maintenance Tasks

Unintended Errors

Slips

Slips occur when a routine action is performed out of place, often due to distraction. Example: writing the previous year's date in January.

Lapses

A lapse is forgetting to complete an intended action, often due to interruption. Example: forgetting to resume a task after being interrupted.

Intended Errors

Mistakes

Mistakes are errors in thinking, not doing.

Rule-Based Mistakes

Occur in familiar situations where a pre-existing "rule" is misapplied. Example: not checking flight controls before applying AC power.

Knowledge-Based Mistakes

Reflect a lack of knowledge or awareness of where to find information. Example: spraying solvent with AC power on.

Violations

Intentional deviations from procedures, often to get the job done.

Routine Violations

Everyday deviations for efficiency. Example: not using a torque wrench.

Exceptional Violations

Well-intentioned deviations due to problems like missing documents or parts. The AMT knows they are deviating but may justify it, considering the risk minimal.