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Key Dismukes, Loukia Loukopoulos, Immanuel BarshiHuman Factors Research and Technology Division
NASA-Ames Research Center
and
U.S. Navy Aerospace Experimental Psychology
November 2003
FSF IASS, Washington D.C.
Concurrent Task Demands and Pilot Error in
Airport Surface Operations
Consequences of Inadvertent Procedural Omissions
• LaGuardia (1994): MD-82 ran off runway end after high-speed rejected take-off– NTSB: Anomalous airspeed indications caused by failure to turn on
pitot heat
• Detroit (1987): DC-9 crashed shortly after take-off – NTSB: Crew failed to set flaps/slats to take-off position
• Dallas (1988): B-727 crashed shortly after take-off– NTSB: Crew failed to set flaps/slats to take-off position ------------------------------------------------------------------------
• Houston (1996): DC-9 landed gear-up– NTSB: Hydraulic boost pump not set to high position
Were These Accidents Unique?
• Rejected take-offs– Anomalous airspeed indications (pitot heat not on)– Configuration warning (flaps or trim not set)
Not according to recent ASRS reports:
– Departed with inadequate fuel– APU left running during takeoff -- fire– Packs failed in cruise– Took-off without PDC– Deviated from speed or altitude
restriction– Nose gear failed to retract– etc.
• Other consequences of overlooked procedural steps– Runway incursions– Broken tow-bars– Taxi into ditch– Engine flame-out– Overtemp engine– Flew wrong departure route– Go-around
Unnecessary costs and delaysBut for luck any of these incidents might have become accidents
Why?
• Why would experienced crews forget a procedural step they normally perform day in and day out?
• Why fail to catch omissions with checklists?
An Ongoing NASA Research Project
• “Carelessness” not an adequate explanation
• Crews vulnerable to omissions when:– Interrupted or preoccupied with one of several concurrent tasks (Young, Dismukes, & Sumwalt, 1998).
– Deferring tasks out of normal sequence (Loukopoulos, Dismukes, & Barshi, 2003).
• Vulnerability to error among experienced pilots largely driven by:– Characteristics of tasks performed
– Demands tasks place on human cognitive processes
– Operating environment
– Norms for actual line operations
Jumpseat Observation Study(Loukopoulos, Dismukes, & Barshi, 2003)
• Reviewed FOMs, observed line operations, analyzed ASRS, NTSB reports.– All phases of flight — focus today on preflight and taxi
• Discovered disconnect between FOM/training and actual line operations in area of task management.
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICERPreflight - In theory (FOM)
Obtain ATIS
Obtain clearance
Review paperwork
Prepare/review charts
(Passenger count)
(Load Sheet)
Program FMC
Begin checklist
Checklist complete
Begin checklistChecklist complete
ENGINE START & PUSHBACK
Review paperwork
Sign flight release
Prepare/review charts
Review Load Schedule
Review FMC
Takeoff brief
Ask for checklist
•Ask for checklist
CLEARANCE
procedure
procedure
checklist
checklist
Cabin Attendant
Gate Agent
ACARs / OPC
Interphone
Ground/Company/Dispatch
Frequencies
Depiction of Cockpit Task Management in FOM/Training
• Linear: task A task B task C in a fixed sequence.
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICERPreflight - In theory (FOM)
Obtain ATIS
Obtain clearance
Review paperwork
Prepare/review charts
(Passenger count)
(Load Sheet)
Program FMC
Begin checklist
Checklist complete
Begin checklistChecklist complete
ENGINE START & PUSHBACK
Review paperwork
Sign flight release
Prepare/review charts
Review Load Schedule
Review FMC
Takeoff brief
Ask for checklist
•Ask for checklist
CLEARANCE
procedure
procedure
checklist
Cabin Attendant
Gate Agent
ACARs / OPC
Interphone
Ground/Company/Dispatch
Frequencies
checklist
Depiction of Cockpit Task Management in FOM/Training
• Linear: task A task B task C in a fixed sequence.
• Controllable: tasks are initiated by crew at their discretion.
• Predictable:– Information available to crew when needed.– Individuals can communicate as needed.
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICERPreflight - In theory (FOM)
Obtain ATIS
Obtain clearance
Review paperwork
Prepare/review charts
(Passenger count)
(Load Sheet)
Program FMC
Begin checklist
Checklist complete
Begin checklistChecklist complete
ENGINE START & PUSHBACK
Review paperwork
Sign flight release
Prepare/review charts
Review Load Schedule
Review FMC
Takeoff brief
Ask for checklist
•Ask for checklist
CLEARANCE
procedure
procedure
checklist
Cabin Attendant
Gate Agent
ACARs / OPC
Interphone
Ground/Company/Dispatch
Frequencies
checklist
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICERFirst Officer
Receive taxi clearance
Start checklist
Checklist complete
Receive takeoff clearance
Start checklist
Checklist complete
Captain
Start taxiing
Ask for checklist
Receive takeoff clearance
Ask for checklist
Line up with runway
Taxi Clearance
MONITORGround
Company
Takeoff Clearance
MONITOR Ground
Company/Dispatch
MONITOR Captain taxiing
TAKEOFF
Taxi-out - In theory (FOM)
Depiction of Cockpit Task Management in FOM/Training
• Linear: task A task B task C in a fixed sequence.
• Controllable: tasks are initiated by crew at their discretion.
• Predictable:– Information available to crew when needed.– Individuals can communicate as needed.
• Overall picture: flight operations are pilot- driven and under moment-to-moment control of crew.
Obtain ATIS
Obtain clearance
Review paperwork
Prepare/review charts
(Passenger count)
(Load Sheet)
Program FMC
Begin checklist
Checklist complete
Begin checklistChecklist complete
ENGINE START & PUSHBACK
Review paperworkSign flight releasePrepare/review charts
Review Load Schedule
Review FMC
Takeoff brief
Ask for checklist
Ask for checklist
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICER
CLEARANCE
procedure
Cabin Attendant
Gate Agent
ACARs / OPC
Interphone
Ground/Company/Dispatch
Frequencies
Preflight - the reality
Interruption
FO busy
Interruption
busy frequencyKeep trying
Ask for checklist
Resume flow
Inoperative item
Time pressure
Inoperative item
Flight release still not picked up
no time, familiarity
Interruption
Delay at gate
Ramp and/or Ground?
Flight plan/Departure runway change
Conduct exterior walk-around
no time, familiarity
New PDC
Still refueling
Data unavailable
Passenger count unavailable
Call maintenance
Look for ops/gate agent
Double-check charts
Resume checklist
Confirm Mx responded
Confirm Mx departed
Confirm resolution
Confirm logbook on board
Check charts
Defer programming FMC
Communicate with companyCompute new performance #s
Re-program FMS
Re-program FMC
Check fuel quantity and pumps
Re-brief
Re-flow trim & other settings
New flight release/PDC?Re-set MCP
Takeoff brief
Request passenger count
procedure
procedure
checklist
checklist
Obtain ATIS
Obtain clearance
Review paperwork
Prepare/review charts
(Passenger count)
(Load Sheet)
Program FMC
Begin checklist
Checklist complete
Begin checklistChecklist complete
ENGINE START & PUSHBACK
Review paperworkSign flight releasePrepare/review charts
Review Load Schedule
Review FMC
Takeoff brief
Ask for checklist
Ask for checklist
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICER
CLEARANCE
procedure
Cabin Attendant
Gate Agent
ACARs / OPC
Interphone
Ground/Company/Dispatch
Frequencies
Preflight - the reality
Interruption
FO busy
Interruption
busy frequencyKeep trying
Ask for checklist
Resume flow
Inoperative item
Time pressure
Inoperative item
Flight release still not picked up
no time, familiarity
Interruption
Delay at gate
Ramp and/or Ground?
Flight plan/Departure runway change
Conduct exterior walk-around
no time, familiarity
New PDC
Still refueling
Data unavailable
Passenger count unavailable
Call maintenance
Look for ops/gate agent
Double-check charts
Resume checklist
Confirm Mx responded
Confirm Mx departed
Confirm resolution
Confirm logbook on board
Check charts
Defer programming FMC
Communicate with companyCompute new performance #s
Re-program FMS
Re-program FMC
Check fuel quantity and pumps
Re-brief
Re-flow trim & other settings
New flight release/PDC?Re-set MCP
Takeoff brief
Request passenger count
procedure
procedure
checklist
checklist
TAKEOFF
Receive taxi clearance
Start checklist
Checklist complete
Receive takeoff clearance
Start checklist
Checklist complete
Start taxiing
Ask for checklist
Receive takeoff clearance
Ask for checklist
Line up with runway
Taxi Clearance
MONITORGround/Company
Takeoff Clearance
MONITOR Captain taxiing
Taxi-out - the realityMONITOR
Ground//Dispatch
Acknowledge clearance
Form mental picture of taxi routeConfirm CA’s understanding
Remember taxi instructionsId taxiways and turns
Remember to follow aircraftIdentify aircraft to follow
Remember to hold shortId correct place to hold short
New/ Additional taxi instructions
Unfamiliarity with airport
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICER
Strobes
LandinglightsRadar?
“Clear” ramp areaConsult charts
Shoulder harnesses
FMC update
“Clear” runway
APU off for 2 min before off-loading
Keep head up/ outside
Calculate & reset Performance data
Inform Company (new #s, delays)
Cross check with CA
FMC: program/verify
Keep trying
MONITORaircraft position on chart
MONITORTower frequency
MONITOR airport traffic
Acknowledge clearanceConfirm CA’s understanding
Defer takeoff flaps
Defer checklist
Restart engineRepeat checklists
Brief new runway
Check charts
De-icing Checklist
APU? Packs?
Repeat Checklist Take control of aircraft while finishing checklist
Accept new runway?
Consult charts
Keep trying
Consult charts
Before/After StartChecklist
Form mental picture of route
Resume checklist
Just-in or new load data
busy frequency
Interruption
Ice/Snow
Ice/Snow
traffic, FO busy
Change in takeoff runway
Change in takeoff sequence FO’s leg
Ramp and/or Ground?
Extended taxi delay
Busy airport/ departure rush
Unfamiliarity with airport
Delayed engine start
busy frequency
– Each pilot must juggle several tasks concurrently.– Crews are frequently interrupted.– External demands arrive at unpredictable moments.– Conditions sometimes force task elements to be performed out of
normal sequence.
Line Observations Reveal a Different Story
• Normal line operations are quite dynamic:
– Each pilot must juggle several tasks concurrently.
– Crews are frequently interrupted.
– External demands arrive at unpredictable moments.
– Conditions sometimes force task elements to be performed out of normal sequence.
Line Observations Reveal a Different Story
• Normal line operations are quite dynamic:
• Crews must at times struggle to maintain control of the timing and sequence of their work tasks.
– Little guidance or training.
Conflict Between Theory and Reality
• FOM is a powerful tool for safety by providing:
• Operational reality disrupts ideal execution of procedures
– Explicit description of how each task is to be performed
– Standardization across crews
– Checklists and checking procedures
So What?
• Pilots become accustomed to concurrent task demands, interruptions, distractions and disruptions.
• However these situations substantially increase vulnerability to error, especially omission of critical procedural steps.
•
Obtain ATIS
Obtain clearance
Review paperwork
Prepare/review charts
(Passenger count)
(Load Sheet)g
Program FMC
Begin checklist
Checklist complete
Begin checklistChecklist completeENGINE START & PUSHBACK
Review paperwork
Sign flight release
Prepare/review charts
Review FMC
Takeoff brief
Ask for checklist
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICER
CLEARANCE
Sample of Preflight errors
Omitted review of (SID) charts - distractions - speed violation on departure
Failed to program new departure - interruptions during preflight - discover after takeoff
Forgot to request updated PDC - distractions; misled because preflight already complete - take off with expired PDC
Skipped checklist item - interruption - push back with Seat Belt signs off
Omit requesting Load sheet - defer during preflight; ACARS inoperative - takeoff without load sheet
Omitted check of circuit breakers - busy with preflight; rushing - unable to start engine after pushback
Never finished review of maintenance log - interruptions - aircraft flown with “open” item in logbook
Checklist item read but not verified - interruption - pushback with emergency door slides armed
Entered wrong weight into FMS - tail strike at takeoff
Missed checking main tank fuel quantity - distractions - departed with insufficient fuel
Neglected to add MEL to flight release - multiple distractions, busy with preflight - discovered en route
Skipped over checklist item - interruption - departed without lobgook
Skipped over checklist item - interruptions - discover insufficient fuel after pushback
Omitted flow and checklist items - interruptions; delay; change in departure runway - discover insufficient fuel at 12000 ft
Forgot to call maintenance - distractions - depart with hatch installed backwards
Forgot to request PDC - deferred when instructed to request by voice, not ACARS - discover after takeoff
Forgot to complete preflight flow - interruption - took off with APU running
Missed aircraft not refueled - checklist interrupted - return to airport after taking off
Skipped over checklist item - fuel pumps deferred during preflight because refueling - engine starvation in flight
Improper setting of pressurization during preflight flow - interruptions - cabin altitude warning light in cruise
Read but not verify checklist item - distractions - pushback with throttles open, damage to aircraft
Forgot logbook at ramp - kept deferring to check it; distractions; busy with preflight - discovered en route
Receive taxi clearance
Start checklist
• TAKEOFF
Start taxiing
Ask for checklist
Receive takeoff clearance
Ask for checklist
Line up with runway
Failed to start engine #-2 - distracted while discussing special operations for destination; omitted checklists - delay takeoff
Omitted call for flaps -rushed to clear ramp/gate area for arriving aircraft -aborted takeoff
Omitted flaps - crew discussing problem with APU, delayed flaps due to snow - aborted takeoff
Flaps incorrectly set, missed noticing during checklist - crew busy with fuel problem, runway changes, programming FMC - aborted takeoff
Omit above-line Checklist - running late, checklist interrupted by Tower, unexpected clearance for takeoff - abort takeoff
FO failed to monitor CA - busy checking and correcting calculations of load data - taxi past hold short line
FO failed to monitor CA – busy with flow; night taxi – taxi in wrong direction
CA taxied without having fully understood instructions - busy looking at other aircraft on taxiway and ramp - ground controller issued warning
FO failed to monitor CA - busy with pre-takeoff preparations - aircraft crossed hold short line
Flaps incorrectly set - late paperwork ; runway change; programming FMC; short taxi; rushed to accept takeoff clearance- aborted takeoff
Started taxi without clearance - trouble-shooting problem with engine start - nearly hit ground handler
Started taxi without clearance - crew discussing taxi instructions - struck pushback tug
Omitted flaps - checklist interrupted by Tower; crew rushed to accept takeoff clearance - aborted takeoff
Omitted flaps - checklist interrupted by thrust reverser light; crew busy troubleshooting - aborted takeoff
Misunderstood Tower instruction - new FO on IOE, CA coaching FO - taxi onto runway w/o clearance
Confuse own position on taxiway diagram - new terminal; studying NOTAMs; runway change – taxied into ditch
Started taxi without clearance – rushed by other aircraft waiting to pull into gate; radio congestion; marshaller’s headset inoperative – query by ground controller
Omitted checking reason for bleed air indicator light-busy with delayed engine start and checklists - takeoff without troubleshooting
Fail to confirm flap position - evaluating heavy rain showers; rushed to accept takeoff clearance - aborted takeoff
Neglected to set flaps -preoccupied with new departure clearance and packs-off operation -aborted takeoff
FO failed to monitor CA -runway change; busy reprogramming FMC -taxied past intended taxiway
Omitted checklist - busy with delayed engine start and checklists; rushed to accept takeoff clearance - flaps not set, aborted takeoff
Incorrect trim setting - checklist interrupted after item had been read but not verified - aborted takeoff
CAPTAINCAPTAIN FIRST OFFICER FIRST OFFICERSample of Taxi-out errors
Why So Vulnerable to These Errors?
• Brain has two ways of processing information to perform tasks:
• Cockpit tasks vary from requiring mainly controlled processing to being largely automatic.
Why So Vulnerable to These Errors?
1) “Controlled” processing– Corresponds to conscious
attention
– Slow, serial, and effortful: low capacity
– Required for tasks with novel aspects
2) Automatic processing– Fast, minimal effort, high
capacity
– Develops with extensive practice of habitual procedure
– Requires minimal conscious supervision
Automatic processing has enormous advantages but also
has serious vulnerabilities
Aft Overhead
Logbook/Gear Pins
PREFLIGHT Flow (B737-300 - as trained)
**
*
*
**
*
**
*
***
*
*
*
*
Aft Electronic
Center Instrument
Mode Control Panel
CaptainInstrument
First OfficerInstrument
Forward Overhead
Forward Electronic
ControlStand
Logbook/Gear Pins
**
* *
*
* *
*
*
*
**
*
Aft Overhead
First OfficerInstrument
ATISSlakfj aslkfj890Slkdfj 3409589Slkafj f095j 019Sa;lskdfjlLskd
LOADSlakfj aslkfj890Slkdfj 3409589Slkafj f095j 019Sa;lskdfjlLskd
Slkf9 9oy99SlkdfjA;slkg eri kgj skj 9
FLIGHT PLANSlakfj aslkfj890Slkdfj 3409589Slkafj f095j 019Sa;lskdfjlLskd SFAS ALSKFJ
XLKAF ALKDFJJ;AL
PAX CT107, 22, 53 WH
FUEL107, 22, 53 WHPDC
Slakfj aslkfj890Slkdfj 3409589Slkafj f095j 019Sa;lskdfjlLskd
Slkf9 9oy99SlkdfjA;slkg eri kgj skj 9
JEPP107, 22, 5
• •x
Forward Overhead
CaptainInstrument
Center Instrument
Forward Electronic
ControlStand
Aft Electronic
Mode Control Panel
CA flow FO flow
* Checklist item
Vulnerabilities of Automatic Processing
• If procedural flow is interrupted, chain is broken.– Pause prevents one step from triggering the next.
• Initiation of automatic process depends on receiving signal or noticing a cue in the cockpit environment.– If signal does not occur, individual is not prompted to initiate
procedure.
Vulnerabilities of Automatic Processing
• If procedural flow is interrupted, chain is broken.– Pause prevents one step from triggering the next.
• Initiation of automatic process depends on receiving signal or noticing a cue in the cockpit environment.– If signal does not occur, individual is not prompted to initiate
procedure.
• Highly practiced procedures and checklists tend to develop “look without seeing” automatic responses.
• High workload and/or rushing prevent conscious supervision of automatic processes — exacerbates vulnerability.
Vulnerability to Errors of Omission Can Be Reduced
1) Actions airline operations and training departments can take
2) Actions individual pilots can take
Ways airlines Can Reduce Vulnerabilities
• Analyze actual line ops write procedures to minimize opportunities for disruptions.
• Avoid “floating” procedural items allowed to be performed at varying times.– Anchor critical items (e.g., setting takeoff flaps) to distinct
step that cannot be forgotten (e.g., before start of taxi).
Ways airlines Can Reduce Vulnerabilities
• Analyze actual line ops write procedures to minimize opportunities for disruptions.
• Avoid “floating” procedural items allowed to be performed at varying times.– Anchor critical items (e.g., setting takeoff flaps) to distinct
step that cannot be forgotten (e.g., pushback).
• Analyze actual fleet “norms” for how checklists are executed and bottom-lines observed.– LOSA
Ways airlines Can Reduce Vulnerabilities
• Analyze actual line ops write procedures to minimize opportunities for disruptions.
• Avoid “floating” procedural items allowed to be performed at varying times.– Anchor critical items (e.g., setting takeoff flaps) to distinct
step that cannot be forgotten (e.g., pushback).
• Analyze actual fleet “norms” for how checklists are executed and bottom-lines observed.– LOSA
• Train with realistic concurrent task demands
Ways Pilots Can Reduce Vulnerability• Being aware of vulnerability reduces threat.
– Especially vulnerable when head-down, communicating, searching for traffic, or managing abnormals.
• When interrupted or deferring a task:– Pause to encode intention to resume – Create conspicuous cue as reminder
• Develop habit of deliberate execution of procedures and checklists to allow controlled supervision of habitual responses.
• Avoid rushing.
Ways Pilots Can Reduce Vulnerability• Being aware of vulnerability reduces threat.
– Especially vulnerable when head-down, communicating, searching for traffic, or managing abnormals.
• When interrupted or deferring a task:– Pause to encode intention to resume – Create conspicuous cue as reminder
• Develop habit of deliberate execution of procedures and checklists to allow controlled supervision of habitual responses.
• Avoid rushing.• Pause at critical junctures to review.
• Schedule / reschedule activities to minimize concurrent task demands (e.g., brief before TOD).
• Treat monitoring as essential task (Sumwalt).
For further information:http://human-factors.arc.nasa.gov/ihs/flightcognition/
This work is supported by NASA’s Airspace Systems Program and by the FAA (AFS-230), Dr. Eleana Edens, program manager.