9.8 Human Error - Error Models

Question 1

what 4 models are used to describe human error?

Answer 1

1. swiss cheese model
2. shell model
3. pear model
4. error chain

Question 2

how are errors categorised?

Answer 2

1. design versus operator-induced errors
2. variable versus constant errors
3. reversible versus irreversible errors
4. slips, lapses and mistakes
5. skill, rule and knowledge-based behaviours and associated errors

Question 3

what are means of SHELL?

and what are there meanings?

Answer 3

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)

Question 4

how can shell be negative?

Answer 4

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

Question 5

human beings are intrinsically unreliable, how is this overcome?

Answer 5

by providing good training, procedures, tools and duplicate inspections

Question 6

what is the pear model?

Answer 6

it is used to recall the four considerations for assessing and mitigating human factors

Question 7

what is the 4 considerations of the pear model?

Answer 7

p = people (the humans)
e = environment (physical workplace)
a = actions (actions required to complete the task )
r = resources (resources requited to complete the task

Question 8

in the pear model, what is meant by people?

Answer 8

the humans.
their capabilities and limitations, vision, hearing, memory, communication etc.

Question 9

in the pear model, what is meant by environment?

Answer 9

physical working environment (lighting, space, temperature, noise, time of day)
and
organisational environment (supervision, pressures, safety culture, norms)

Question 10

in the pear model, what is meant by actions?

Answer 10

consideration is taken from the actions that people must perform to complete a job efficiently and safely

Question 11

what is jta?

Answer 11

job task analysis

human factors approach to identify knowledge, skills and attitudes to perform a task.

instructions, tools and other resources

Question 12

in the pear model, what is meant by resources?

Answer 12

anything that a mechanic requires to get the job done,

could anything from qualifications to the tooling and lift access required

Question 13

what is an error chain?

Answer 13

a chain where any link that is broken causes incidents.

can be prevented if measures are built in at each stage

Question 14

other than crew, engineers and ATC, what else may have made an error if the aircraft has been sufficiently maintained and operated correctly?

Answer 14

the manufacturer by design has a flaw in it
or
company procedures for maintenance, crew

Question 15

which type of error is easier to identify and predict?

Answer 15

constant errors

Question 16

what does a constant error show?

Answer 16

that there is a consistent, systematic pattern

variable error random in nature

Question 17

how may an error be reversible or irreversible?

Answer 17

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)

Question 18

how could any error made by an engineer be reversible?

Answer 18

by having a well designed system or procedures

Question 19

what is a slip?

Answer 19

actions not carried out as intended or planned
ie. getting the order of steps in a procedure wrong

Question 20

what is a lapse?

Answer 20

missed actions or omissions
ie, failed to do something due to lapses of memory or attention

Question 21

what is a mistake?

Answer 21

specific type of error brought about by a faulty plan/intention

ie. someone did something believing it was correct when it wasn’t

Question 22

what is a violation?

Answer 22

differ from slips, lapses and mistakes as they are deliberate illegal actions

ie. failing to follow proper procedures

Question 23

how can the behaviour of engineers be catergorised?

Answer 23

-skill based
-rule-based
-knowledge based

Question 24

what is skill based behaviours?

Answer 24

actions that rely on stored routines or motor programmes that have been learned with practised and can be executed without conscious thought

Question 25

what skill based behaviour errors may occur?

Answer 25

-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)

Question 26

what is rule-based behaviour errors?

Answer 26

for which a routine or procedure has been learned

Question 27

how may rule-based errors occur?

Answer 27

when the wrong rule or procedure has been applied

Question 28

what is knowledge based errors?

Answer 28

for when no procedure has been established

Question 29

how may knowledge based errors occur?

Answer 29

when incomplete or incorrect knowledge has been applied or interpreting the situation incorrectly

Question 30

what is the swiss cheese model?

Answer 30

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

Question 31

in the swiss cheese model, how are failures designated?

Answer 31

latent failure (procedure failure, at design of an aircraft)
active failure (errors made by front line personnel)