Human Error Types

Types of Human Error in Aviation

Human error types are classified to help identify, manage, and mitigate risks in flight operations. The main categories are:

• Slips: These occur when the intended action is correct, but its execution is flawed. For example, a pilot may mean to raise the landing gear but accidentally selects the flaps instead. Slips are usually detected quickly because the intention was sound.

• Lapses: These are failures to carry out an intended action, often due to memory failure or loss of attention. An example is forgetting to lower the landing gear before landing. Lapses are typically linked to temporary forgetfulness.

• Mistakes: Here, the action is carried out as intended, but the plan or decision itself is incorrect. For instance, shutting down an engine for a minor vibration when reducing power would have sufficed. Mistakes often go unnoticed because the process is logical, even if the outcome is wrong.

• Violations: These are deliberate deviations from rules or procedures, such as intentionally flying below minimum safe altitude. Violations are conscious choices to break established protocols.

Behavioural Levels and Error Sources

• Skill-based errors happen during routine, automatic actions (motor programmes). Two specific errors here are action slips (wrong action, right intention) and environmental capture (habitual actions triggered by familiar cues, even if inappropriate).
• Rule-based errors involve misapplying procedures or rules to familiar situations.
• Knowledge-based errors arise in novel situations where reasoning or problem-solving is required, often due to incomplete or incorrect knowledge.

Internal and External Error Generation

• Internal factors include overconfidence, insufficient care, improper technique, motivation, personality, and emotional state.
• External factors in the cockpit include poor ergonomics, distractions, and inadequate procedures or communication.

The Error Chain

Errors rarely occur in isolation. The 'error chain' describes how a sequence of small mistakes, omissions, or violations can combine to create a serious incident or accident. Breaking any link in this chain can prevent escalation.

Error Prevention and Management

Modern aviation focuses on reducing error frequency and limiting the consequences when errors do occur. This includes robust procedures, effective crew resource management, and designing systems that are tolerant to inevitable human mistakes.