Post on 20-Aug-2020
In-depth Incident Investigation Linking Contexts and Causes
Nicola Jordan, Anne Isaac
NATS, UK
Munich, 22nd October 2009
Overview
» Background
» Incident investigation
» Day to Day Safety Survey
» Case study 1: en-route
» Trends in the detail from investigations of en-route losses of separation
» Case study 2: aerodrome
» Developing a matrix for linking errors and contexts for runway incursions
» Summary
Background: Incident investigation
» Incident investigation
» structured techniques for identifying the sequence of events that led to the incident (e.g. HERA- JANUS technique, NATS common causal factors scheme)
» error types
» details and mechanisms of the human contribution
» contextual conditions
» Benefits
» widen the area of ‘focus’ for the investigation
» ensure that thorough consideration is given to the facts and information that have been ascertained
» lead to more effective and targeted recommendations
» enhance the view of unit management to the way that controllers work and the impact of the ATC environment on their tasks [1]
[1] Anne Isaac, Paul Engelen, Martin Polman (2005), Human Factors Impacts in Air Traffic Management,Chapter 4: Human Error in European Air Traffic Management: from Theory to Practice, Ashgate
Background: Typical trend analysis
Sep-07
Oct-07
Nov-07
Dec-07
Jan-08
Feb-08
Mar-08
Apr-08
May-08
Jun-08
Jul-08
Aug-08
Sep-08
Oct-08
Nov-08
Dec-08
Jan-09
Feb-09
Mar-09
Apr-09
May-09
Jun-09
Jul-09
Aug-09
Number of Human Performance Reports
Safety event Other report
Not see
Incorrect decision / plan
Misjudge
Transmit / record no
information
Transmit / record incorrect
information
Inaccurate/no recall from
working memory
Mis-perceive auditory
information
Causal factor
Number of Reports
Causal Aggravating Situational
Tracking trends over time
Identifying frequently occurring causal factors
Background: Day to Day Safety Survey
» Observation based technique, in a non-threatening and non-judgemental way, a controller doing their daily task
» record the employment of the agreed and observable techniques
» over time, capture trends in the occurrence of them
» gain more understanding of what it is we do to keep it safe
» help to answer the question “How safe are we?”
» focus is on the positive behaviours and techniques that operational staff employ to keep things safe
» specifically those that prevent/mitigate the top causal factors
Incident
investigation
Open reporting
Day to Day safety survey
Measures events that go wrong
Measures positive things
people do
Incident
investigation
Open reporting
Day to Day safety survey
Measures events that go wrong
Measures positive things
people do
Case study 1: En-route
Trends in the detail from investigations of en-route losses of separation
Case study 1: Methodology
» Information used:
» en-route ATC centre, 2007
» all losses of separation that had an ATC attributable element
» Analysis undertaken:
» specifics of all of the errors tabulated
» e.g. for each of the ‘Not See’ perception errors, what was ‘Not Seen’?
» details of the contextual conditions
» e.g. any contextual conditions associated with the ‘Not See’ errors were identified for cross-referencing.
» information consolidated and common themes identified
» consideration given to trends in the findings by sector type andgeographic location
Case study 1: Findings
» Perception and decision errors most prevalent
» Common themes (perception errors)
» not seeing/mis-perceiving the location of a particular aircraft,
» not seeing/mis-perceiving the detection of a conflict through not referring adequately to strips or the radar display
Mis hear
3%Not hear
3%
No detection of
information
28%
Not see
32%
Mis see
9%
Mis-perceive
visual information
25%
Perception errors
Case Study 1: Findings
» Day to day observations:
» strip management behaviours demonstrated less frequently at thisunit compared to other En-Route units.
Strip Management Behaviours
0
10
20
30
40
50
60
70
80
90
100
FPS Moved Tactile Methods Highlights Removed
Wei
gh
ted
Sco
re
Baseline score
Unit score
Case study 1: Findings
» Decision errors centred around reliance on, or expectation of, aircraft performance. » majority involved at least one aircraft climbing or descending (and frequently both)
» majority were where the aircraft were crossing laterally
» Other themes» misjudging the effect of wind on aircraft turns
» not checking the strip bay/radar display before issuing a clearance
» not taking into account conflicting traffic (e.g. military traffic or when operating close to a sector boundary)
Decision errors
Incorrect decision
/ plan
29%
Insufficient
decision / plan
47%
Misjudge
21%
Late decision /
plan
3%
Case study 1: Findings
» The following contextual conditions commonly occurred: » distraction (almost always job related)
» time pressure
» on the job training
» handover/takeover
» Distractions:» cause operational staff to juggle too many tasks with a resultant increase in
workload.
» taking over the tasks of other controllers for a short period,
» taking phone calls whilst checking other information,
» doing tasks in rest breaks which can interfere with the next operational session.
» Half of the incidents where a decision error occurred involved some type of distraction; decision making appeared to suffer the biggest impact from
distractions (followed by visual perception).
» Self-induced time pressure: » to execute a plan early and to ‘keep traffic moving’
» to provide a good service to the aircraft by keeping a climb or descent going
» to help out other colleagues when they see problems, despite their own workload
Case study 1: Applications
» Provided insight to safety managers at the unit
» Informed ‘continual professional development’ (CPD) for operational controllers
» include modules on aircraft performance
» decision making on a sector-specific basis
» Observations have been customised to include individual sector characteristics
» On the job training (OJT)
» Bespoke observation criteria to explore OJT technique developed and under trial.
Case study 2: Aerodrome
Developing a matrix for linking errors and contexts for runway incursions
Case Study 2: Methodology
» Runway incursions (when an aircraft or vehicle enters an active runway without clearance) are significant safety issue at airfields
» Information used:
» all runway incursion reports where a human error (ATC / pilot / driver) was cited, 2006-2008
» 173 reports
» Analysis undertaken:
» matrix devised to enable the contextual conditions to be cross-referenced with the associated errors
Case Study 2: Findings
61Rule breaking / conformance
4113Distraction/interruption
14Inadequate CRM
343Inadequate TRM
621Fatigue & stress
311Incorrect airport signage
263Inadequate experience on position
1111Conditional clearance
Incorrect decision/plan
Not hear/ mishear
Not / mis-seen / seen late
ATC errors
HP issues/ Contextual issues
» Clear link between aural perception errors (not hear/mis-hear) and two contextual conditions:
» conditional clearances
» distractions / interruptions
Case study 2: Applications
» Conditional clearances trial undertaken
» Perception of participating controllers:
» use of conditional clearances gives more flexibility to the controller as to the timing of their instruction and:
» reduce workload
» reduce of R/T load
» increase capacity
» Analysis of objective data:
» the level of traffic managed exceeded the slotted demand
» no decrease in departure rates or increase in gaps between departures and arrivals
» no increase in delays
» no increase in communications load
» Following this trial, conditional clearances are now only permitted for use at the airfield in particular scenarios
Case study 2: Applications
» Distractions:
» understanding the nature of operational distractions though day to day safety observations:
» how often do controllers signal others to stand-by whilst paying attention to other information?
» how often do controllers defer a telephone call whilst listening to a readback?
» Clear, unambiguous communication:
» implementing activities that embrace active listening techniques(following findings from day to day safety observations):
» awareness campaigns
» readback/hearback exercises in Training for Unusual Circumstances and Emergencies (TRUCE)
Most common incident causal factors
Day to day safety survey results
Incident investigation and day to day safety survey
» Excellent agreement between causal factors and day to day safety survey findings
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Scanning Cycles Extra Monitoring Conflicting Traffic Phone Calls
Deferred
Standby Standard
Phraseology
Incomplete
Readbacks
Percentage of responses
Always Sometimes Never Not Applicable
Mis-Hear
Transmit / record incorrect information
UNKNOWN (Memoryx3, Perceptionx1)
Forget planned action
Misjudge
Mis-perceive auditory information
Mis-perceive visual information
Transmit / record no information
Incorrect decision / plan
Not see
Timing error
Transmit / record unclear information
Summary
» Incident investigation process essential to establishing the causes and contextual conditions
» promotes lesson learning
» identifies recommendations to prevent/mitigate a re-occurrence
» Examples of where deeper insight and understanding of the contextual conditions can be gained:
» trends and recurring themes can be identified in the underlying causes and contexts
» local safety improvement activities and technological developments can be informed
» Day to day safety survey observations complement incident investigation findings and provide a pro-active means of understanding how safe we are.