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.