9.8 Human Error - Error Models Flashcards
what 4 models are used to describe human error?
- swiss cheese model
- shell model
- pear model
- error chain
how are errors categorised?
- design versus operator-induced errors
- variable versus constant errors
- reversible versus irreversible errors
- slips, lapses and mistakes
- skill, rule and knowledge-based behaviours and associated errors
what are means of SHELL?
and what are there meanings?
s = software (procedures, manuals, checklist layouts)
h = hardware ( tools, test equipment, structure of aircraft, flight deck design)
e = environment (physical environment, hangar condition, work patterns)
l = live-ware (the people at the centre of the model)
how can shell be negative?
s = misinterpretation of procedures, poorly written manuals etc
h = not enough tools, inappropriate equipment etc
e = uncomfortable workplace, inadequate hangar space
l = relationships with other people, manpower shortage etc
human beings are intrinsically unreliable, how is this overcome?
by providing good training, procedures, tools and duplicate inspections
what is the pear model?
it is used to recall the four considerations for assessing and mitigating human factors
what is the 4 considerations of the pear model?
p = people (the humans)
e = environment (physical workplace)
a = actions (actions required to complete the task )
r = resources (resources requited to complete the task
in the pear model, what is meant by people?
the humans.
their capabilities and limitations, vision, hearing, memory, communication etc.
in the pear model, what is meant by environment?
physical working environment (lighting, space, temperature, noise, time of day)
and
organisational environment (supervision, pressures, safety culture, norms)
in the pear model, what is meant by actions?
consideration is taken from the actions that people must perform to complete a job efficiently and safely
what is jta?
job task analysis
human factors approach to identify knowledge, skills and attitudes to perform a task.
instructions, tools and other resources
in the pear model, what is meant by resources?
anything that a mechanic requires to get the job done,
could anything from qualifications to the tooling and lift access required
what is an error chain?
a chain where any link that is broken causes incidents.
can be prevented if measures are built in at each stage
other than crew, engineers and ATC, what else may have made an error if the aircraft has been sufficiently maintained and operated correctly?
the manufacturer by design has a flaw in it
or
company procedures for maintenance, crew
which type of error is easier to identify and predict?
constant errors
what does a constant error show?
that there is a consistent, systematic pattern
variable error random in nature
how may an error be reversible or irreversible?
reversible is one that you can recover from (drilled wrong rivet out but can be replaced)
irreversible is one that cannot be recovered from (over pressure fuselage and ruptures)
how could any error made by an engineer be reversible?
by having a well designed system or procedures
what is a slip?
actions not carried out as intended or planned
ie. getting the order of steps in a procedure wrong
what is a lapse?
missed actions or omissions
ie, failed to do something due to lapses of memory or attention
what is a mistake?
specific type of error brought about by a faulty plan/intention
ie. someone did something believing it was correct when it wasn’t
what is a violation?
differ from slips, lapses and mistakes as they are deliberate illegal actions
ie. failing to follow proper procedures
how can the behaviour of engineers be catergorised?
-skill based
-rule-based
-knowledge based
what is skill based behaviours?
actions that rely on stored routines or motor programmes that have been learned with practised and can be executed without conscious thought
what skill based behaviour errors may occur?
-action slips (same as slips)
-environmental capture (making an adjustment on 1 aeroplane and doing it on another although not required.)
-reversion (when a skill cannot be unlearned when no longer appropriate, ie procedure that has recently been revised)
what is rule-based behaviour errors?
for which a routine or procedure has been learned
how may rule-based errors occur?
when the wrong rule or procedure has been applied
what is knowledge based errors?
for when no procedure has been established
how may knowledge based errors occur?
when incomplete or incorrect knowledge has been applied or interpreting the situation incorrectly
what is the swiss cheese model?
the layers of swiss cheese are defense layers, ie, duplicate checks, preflight functional checks, check lists, once these all line up, an incident will occur
in the swiss cheese model, how are failures designated?
latent failure (procedure failure, at design of an aircraft)
active failure (errors made by front line personnel)
