Human Error and Reliability, Error Models and Threat and Error Management
What the domain tests
You must classify errors, place them in a model and apply Threat and Error Management (TEM), rather than stopping at 'human error'.
Core rules
- An error is an unintended deviation from intention or standard; a violation is a deliberate deviation, though not necessarily reckless.
- Skill-based slips are wrong actions; lapses are omitted actions. Rule-based and knowledge-based mistakes are wrong plans. Violations may be routine, situational or exceptional.
- Reason: active failures at the sharp end, latent conditions upstream, with defences that can align like Swiss cheese.
- HFACS uses four levels: unsafe acts, preconditions, unsafe supervision and organisational influences.
- TEM: threats are external events, errors are crew actions, and undesired aircraft states are the result. Countermeasures avoid, trap or mitigate.
- Reliability is probabilistic; even good pilots err. Normalisation of deviance turns repeated small violations into accepted practice.
Worked example
A crew takes off with the wrong altimeter setting because the first officer misheard the ATIS and the captain did not challenge. Classification: a perceptual/communication mistake at the unsafe-act level; precondition, high workload and authority gradient; organisational, no cross-check policy. TEM countermeasure: challenge and response, then cross-check against the ATIS.
Traps
Do not call every bad outcome an error - hindsight bias. Do not classify a violation as a slip. Do not use 'pilot error' as the final cause. Do not confuse threats with errors.