Week 7 p 2

Question 1

What is the current ICAO investigation process in 4 steps ?

Answer 1

1. Gathering and
2. Analysis of info
3. Drawing conclusions including determination of causes and where appropriate
4. Making safety recommendations

Assumes linear sequence

Question 2

What is the sequential model approach to accidents ?

Answer 2

Cause-to-effect concept
One root cause leads to another event which leads to another etc until final state or top event reached

Question 3

How can the sequential approach be modified to account for more complex accidents which can’t be explained by simple sequential models ?

Answer 3

Multiple sequential models
Event trees where events and factors are arranged in a hierarchical and directed network with top event considered a result of sequence of several combinations of other factors as events

Question 4

What are advantages of the sequential approach?

Answer 4

Describes events as outcome of series of individual steps in a unique order of occurrence which follows reasoning
Easily graphically represented

Question 5

What are the disadvantages of the sequential approach?

Answer 5

First event of sequence not always well defined - arbitrary stopping point
Assumes a simple and deterministic cause and effect relation between successive events

Question 6

For more complex systems with more complex accidents which accident model developed from the sequential approach?

Answer 6

The epidemiological accident model

Allows for deeper analysis and considers latent conditions behind each failure

Question 7

What does the epidemic analogy compare the accident to?

Answer 7

A disease which can thrive only if:
Several factors associated with host (living being), agent (virus), and environment where host remains manifest in a specific way

Question 8

What does the epidemiological accident model assume?

Answer 8

Any system has developed and maintains specific defences against failure
Safety barriers deflect or minimise consequences of events
Thus the model identifies the failure of barriers and possible latent conditions responsible for this

Question 9

What is the Swiss Cheese model?

Answer 9

The model which suggests safety barriers have initial deficiencies
Barrier failures, occurring one after another, permit a trajectory of accident opportunity

Question 10

What do the hole sizes and positions symbolise in the Swiss cheese model?

Answer 10

Each barrier’s deficiencies and weaknesses

Question 11

The Swiss Cheese model opens up discussion on latent factors whose effects are not easily observed and measurable. It considers the general health of the system and can provide insight on possible performance deviations. True or false?

Answer 11

True

Question 12

If the context behind the performance deviations in the Swiss cheese model is understood what can be achieved ?

Answer 12

Remedial actions to correct root cause of problem: preventing latent conditions or improving barrier efficiency

Question 13

What are disadvantages of the Swiss Cheese model?

Answer 13

The added complexity to explain the accident causation path can make the model harder to spell out, and graphical representations are more complex - less easy to understand

Question 14

What is an advantage of the Swiss Cheese model? Who uses it?

Answer 14

It’s very powerful as a model and used by the ICAO in international safety management and investigation manuals

Question 15

What is the historic Safety I approach?

Answer 15

The state in which the possibility of harm is reduced to and maintained at or below an acceptable level through hazard identification and safety management

Question 16

What is the current Safety-II approach?

Answer 16

The ability of the system to succeed under varying conditions so the number of intended and acceptable outcomes is as high as possible

Question 17

What is the definition of safety for S1 and S2?

Answer 17

S1 - as few as possible things go wrong
S2 - as many things as possible go right

Question 18

What is the safety management principle for S1 and S2?

Answer 18

S1 - reactive
S2 - proactive

Question 19

What is the view of the human factor in safety management in S1 and S2?

Answer 19

S1 - humans seen as liability
S2- humans seen as resource needed for system resilience

Question 20

How is the role of performance variability seen in S1 and S2?

Answer 20

S1 - harmful and should be prevented
S2- inevitable but useful, should be monitored and managed

Question 21

How is accident investigation seen in S1 and S2?

Answer 21

S1- accidents due to failure and malfunction, investigation should find what
S2- understand how things usually go right as basis for explaining how things go wrong

Question 22

What are the four cheese blocks which must fail simultaneously to allow a trajectory from exposure to accidents?

Answer 22

Organisational influences
Unsafe supervision
Preconditions of unsafe acts
Unsafe acts

Question 23

What is the marine pyramid ?

Answer 23

Near miss
Innocuous incidents
Less serious incidents
Serious incidents