4. Economic & political climate
Cascading influences
Top-level management decisions
Culture
Culture
Line management implementation
Error-producing conditions in the
team and workplace
Unsafe acts at sharp end
Exceedances
Incidents & near misses
Accidents
5. Errors need to be managed at
all levels of the system
Everyone’s blunt end is someone
else’s sharp end.
(Karlene Roberts)
6. Reaching ever higher for the fruit
Systemic factors
Social factors
Individual factors
7. Milestones
• From 1917: Psychometric testing
• 1940s: Cambridge Cockpit; Applied
Psychology Unit; centres at Ohio State &
University of Illinois; ERS (UK)
• 1950s: HFS (US); ‘Human Factors in Air
Transportation’ (Ross McFarland)
• 1960s: Manned space flight; cockpit
ergonomics; command instruments
• 1970s: ALPA accident investigation course;
IATA human factors committee; SHEL(L)
• 1980s: CRM; ASRS; cognitive and systemic
factors; interaction of many causal factors
• 1990s: Organizational and cultural factors
8. Sentinel events
• Tenerife runway collision
• Mt Erebus and the Mahon Report
• Manchester runway fire
• Dryden and the Moshansky Report
• BASI reports on the Monarch and
Seaview accidents
• NTSB Report on Embraer 120 accident
at Eagle Lake, Texas (Lauber dissent)
• Challenger (Vaughan) and Columbia
Accident Investigation Board Report
9. Individual factors
• Pilot aptitude measures
• Psychomotor performance
• Sensory and perceptual factors
• Fatigue and stress
• Vigilance decrement
• Cockpit ergonomics
• ‘Ironies of automation’
• Cognitive issues
10. Predictive value of WW2 AAF
test battery
(from Ross McFarland, 1953)
Decrease in
elimination rates
with increase in
stanine scores
indicates value of
properly weighted
battery of tests.
11. Social and team factors
• Crew resource management
• LOFT and behavioural markers
• Cabin evacuation studies
• Maintenance teams
• Air traffic controllers
• Ramp workers
• Naturalistic decision making
• Procedural non-compliance
12. The high-hanging fruit
• Targeting error traps and recurrent
accidents (e.g. CFIT, maintenance
omissions, etc.)
• Resolving goal conflicts: production vs
protection
• Combating the ‘normalization of
deviance’
• Striving for system resilience (high
reliability)
13. ICAO Annex 13 (8 Ed., 1994) th
1.17. Management information. Accident reports
should include pertinent information concerning
the organisations and their management involved
in influencing the operation of the aircraft. The
organisations include . . . the operator, air traffic
services, airway, aerodrome and weather service
agencies; and the regulatory authority. Information
could include organisational structure and functions,
resources, economic status, management policies
and practices . . .
14. Ever-widening search for
the ‘upstream’ factors
Individuals
Workplace
Organisation
Regulators
Society at large
15. Echoed in many hazardous
domains
Piper Alpha Challenger
Young, NSW
Dryden
Barings Zeebrugge
King’s X Chernobyl
Clapham Columbia
16. CAIB Report (August, 2003)
‘In our view, the NASA organizational
culture had as much to do with this
accident as the foam.’
‘When the determinations of the causal
chain are limited to the technical flaw
and individual failure, typically the actions
taken to prevent a similar event in the
future are also limited . . .’
17. But has the pendulum swung
too far?
Collective Individual
responsibility responsibility
18. Mr Justice Moshansky on
the Dryden F-28 crash
Had the system operated operated effectively,
each of the (causal) factors might have been
identified and corrected before it took on
significance . . . this accident was the result of
a failure of the air transportation system as a
whole.
19. Academician Valeri Legasov
on the Chernobyl disaster
After being at Chernobyl, I drew the
unequivocal conclusion that the Chernobyl
accident was . . . the summit of all the
incorrect running of the economy which
had been going on in our country for
many years.
(pre-suicide tapes, 1988)
20. CAIB Report (Ch. 5)
‘The causal roots of the accident can
be traced, in part, to the turbulent post-
Cold War policy environment in which
NASA functioned during most of the
years between the destruction of
Challenger and the loss of Columbia.’
21. Remote factors: some concerns
• They have little causal specificity.
• They are outside the control of system
managers, and mostly intractable.
• Their impact is shared by many systems.
• The more exhaustive the inquiry, the more
likely it is to identify remote factors.
• Their presence does not discriminate
between normal states and accidents; only
more proximal factors do that.
22. Revisiting Poisson
• Poisson counted number of kicks received
by cavalrymen over a given period.
• Developed a model for determining the
chance probability of a low frequency/high
opportunity event among people sharing
equal exposure to hazard.
• How many people would one expect to have
0, 1, 2, 3, 4, 5, etc. events over a given
period when there is no known reason why
one person should have more than any
other?
23. Unequal liability: common finding
No. of exceedances by fleet pilots (John Savage)
More people
N have zero events
than predicted
A few people have
have more events than
would be expected
by chance alone
0 1 2 3 4 5 6 7 8
Number of events sustained in a given period
24. Interpreting pilot-related data
• Repeated events are associated with
particular conditions. Suggests the need
for specific retraining.
• Repeated events are not associated with
particular conditions:
Bunched in a given time period. Suggests
influence of local life events. Counselling?
Scattered over time. Suggests some
enduring problem. Promote to management?
26. Conclusions
• Widening the search for error-shaping factors
has brought great benefits in understanding
accidents.
• But maybe we are reaching the point of
diminishing returns with regard to prevention.
• Perhaps we should revisit the individual (the
heroic as well as the hazardous acts).
• History shows we did that rather well.
