CONCURRENT TASK DEMANDS IN THE COCKPIT: CHALLENGES AND VULNERABILITIES Loukia D. Loukopoulos R. Key Dismukes Immanuel Barshi NASA Ames Research Center.

CONCURRENT TASK DEMANDS IN THE COCKPIT: CHALLENGES AND VULNERABILITIES

Loukia D. LoukopoulosR. Key DismukesImmanuel Barshi

NASA Ames Research CenterMoffett Field, CA

ALPA Training CouncilMarch 2003

2

MOTIVATION• Complex operating environments

• number• timing• and interaction of tasks

flows, checklists procedures, phase of flight structure

automaticity habit

? ?

• Characterize nature of interaction• Characterize demand such interaction places on cognition

• Qualitative approach• Jumpseat observation of routine flights

• Boeing 737; 2 air carriers; 1-4 hours per leg; nation-wide• notes; informal interviews

• Training (initial, transition/upgrade)• Written materials (manufacturer and carrier FOMs)• Incident reports (ASRS, NTSB, ASAP)

• Work applies to all phases of flight: use Preflight and Taxi-out for illustration

3

real

• Idealmanufacturer perspective (manuals)

ideal

assumed

LAYERING

• Assumedcarrier perspective (FOMs, training)

• Errors pilot perspective (ASRS reports)

• Real

observer perspective (jumpseating)

4

Manufacturer’s representation? (ideal)

5

PREFLIGHT - ideal (manufacturer)

• Goals:• Pre-check systems operating properly• Configure aircraft for engine start and push-back (next phase of flight)

• Configure for takeoff• Configure for flight

• Considerations:• Safe operation of aircraft• Optimal performance of aircraft

PANEL OFF light --- Extinguished Set panel --- As desired WARNING: Do not key HF radio while airplane is being fueled. Injury to personnel or fire may result

FLIGHT ALTITUDE indicator --- cruise altitudeLANDING ALTITUDE indicator --- destination field elevationPressurization mode selector --- AUTO AUTOMATIC FAIL light --- Extinguished

PreflightB737 Ops Manual

BEFORE START checklist

L I S T

(24 items)

Preflight - ideal (manufacturer)

FLIGHT DECK PREPARATION procedure

F

L

O

W

(17 items)

Finish PREPARATION procedure

FINAL PREPARATION procedure (2 items)

Start checklist

checklist complete

Start checklist

checklist complete

ENGINE START & PUSHBACK


F

L

O

W

(57 items)


FINAL PREPARATION procedure

(2 items)

Ask for BEFORE START checklist (down to the line)

Ask for BEFORE START checklist (below the line)

CAPTAIN FIRST OFFICER

CLEARED FOR START


L I S T (4 items)

8

•Linear, stable flow of events

•Checklist is “meeting point”

•Independent tasks

•Independent operators

•Reliance on habit (B always follows A) and triggers (F prompts G)

BOEINGFinal Flight Deck Preparation (down to the line)

Challenge ResponseFlight deck preparation CompletedLight test CheckedOxygen and interphone CheckedYaw damper OnNavigation transfer and display switches AUTO & NO RMALFuel _ lbs. & pumps OnGalley power OnEmergency exit lights ArmedPassenger signs SetWindow heat OnHydraulics NormalAir conditioning and pressurization _ pack(s), bleeds On, setAutopilots DisengagedInstruments Cross-checkedAutobrake RTOSpeed brake Down detentParking brake SetStabilizer trim cutout switches NormalWheel well fire warning CheckedRadios, radar, transponder, and HUD SetRudder and aileron trim Free & zeroPapers AboardFMC/CDU SetN1 and IAS bugs set

BOEINGFinal Flight Deck Preparation (below the line)

Challenge ResponseDoors ClosedFlight deck windows LockedAir conditioning pack switches OffAnti collision light switch On

PHASE OF FLIGHT - ideal (manufacturer)


9

Carrier’s representation? (assumed)

10

PREFLIGHT - assumed (carrier)

• Goals:• Pre-check systems operating properly• Configure aircraft for engine start and push-back (next phase of flight)

• Configure for takeoff• Configure for flight

• Considerations:• Safety• Performance of aircraft

+ Carrier (additional) considerations + Priorities (fuel, time, passenger comfort)+ Type of operations (short/long-haul, turn-arounds,

regions/airports, fleet)+ Philosophy (safety, efficiency)+ New technologies (ACARS, on-board performance computer)+ Coordination with agents (dispatch, maintenance, company)

11

(be watching for w) *

PHASE OF FLIGHT - assumed (carrier)


•Complexity added but at pre-determined, predictable points in time

•Some dependency of task but in non-explicit ways

•Some interaction between operators

•But still fundamentally linear flow of events

PILOT-driven operation

BOEINGFinal Flight Deck Preparation (down to the line)

Challenge ResponseFlight deck preparation CompletedLight test CheckedOxygen and interphone CheckedYaw damper OnNavigation transfer and display switches AUTO & NORMALFuel _ lbs. & pumps OnGalley power OnEmergency exit lights ArmedPassenger signs SetWindow heat OnHydraulics NormalAir conditioning and pressurization _ pack(s), bleeds On, setAutopilots DisengagedInstruments Cross-checkedAutobrake RTOSpeed brake Down detentParking brake SetStabilizer trim cutout switches NormalWheel well fire warning CheckedRadios, radar, transponder, and HUD SetRudder and aileron trim Free & zeroPapers AboardFMC/CDU SetN1 and IAS bugs set

BOEINGFinal Flight Deck Preparation (below the line)

Challenge ResponseDoors ClosedFlight deck windows LockedAir conditioning pack switches OffAnti collision light switch On


L

I

S

T

Preflight - assumed (carrier)

Obtain ATIS

Obtain clearance

Review paperwork

Prepare/review charts


F

L

O

W


(Passenger count)

(Load Sheet)

Program FMC

Start BEFORE START checklist

BEFORE START checklist complete

Review paperwork

Sign flight release



F

L

O

W


Review Load Schedule

Review FMC

Takeoff brief

Ask for BEFORE START checklist


Cabin Attendant

Gate Agent

ACARs/OPC

MONITOR Interphone

MONITOR Ground frequency

Company/Dispatch frequency

ENGINE START & PUSHBACK

13

… and so it should all work as expected…

… or maybe not?

Captain’s ASRS Report # 425357 (edited)“The aircraft we had for this flight had an inoperative fuel gauge, and an inoperative APU… DFW was in the midst of a departure rush. Since we had to do a crossbleed start, we did not do the After Start checklist immediately...

TAXI-OUT -real

There were many distractions leading up to this incident which should have been warning signals.•There was a time pressure element, we were running late and knew we had an airplane change in a short ground time in Denver before our next flight. •The APU and the necessity for the crossbleed start precluded the normal flow of calling for flaps and the before takeoff checklist as we taxi from the gate. •I was distracted by calling for taxi, so ground control knew we were ready to move. •Immediately after that call we were given a complicated taxi route with hold short and follow instructions and we were concentrating on finding the taxiways in the dark…”

We got clearance to taxi and requested a spot to do the start. We stopped ... as instructed and completed the start. As we were finishing, ground control was giving instructions to aircraft taxiing mentioning us in reference. We heard this, completed the after start checklist, and told ground we were ready to taxi.

We were given instructions to hold short of taxiway WJ, give way to opposite direction traffic, then proceed N to taxiway Z to taxiway HY to taxiway Y across the bridge to taxiway J to taxiway EF for takeoff on runway 17R, follow an ACR aircraft. With all the above, taxiing to a new and unfamiliar runway (for this crew) in the dark, we didn't complete the before takeoff checklist. As we were cleared for takeoff and applied power, the takeoff warning horn sounded and we immediately realized that the flaps had not been extended for takeoff.

15

Line representation (real)

Obtain ATIS

Obtain clearance

Review paperwork




(Passenger count)

(Load Sheet)

Program FMC



Review paperwork

Sign flight release





Review FMC

Takeoff brief


CAPTAIN FIRST OFFICERPREFLIGHT errors attributed to “distractions” (incident reports)

ENGINE START & PUSH-BACK

Improper setting of pressurization during preflight flow - interruptions - cabin altitude warning light in cruise

Missed aircraft not refueled - checklist interrupted - return to airport after taking off

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

Omitted review of (SID) charts - distractions - speed violation on departure

Skipped over checklist item - fuel pumps deferred during preflight because refueling - engine starvation in flight

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 inop - 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

Set flaps

Request taxi clearance

Monitor radios

Receive taxi clearance

Acknowledge taxi clearance

Form mental picture of taxi route

Check for obstacles

Perform PRE-TAKEOFF flow

(above line)

Start PRE-TAKEOFF checklist

Monitor radios

Monitor traffic

Monitor position on airport chart

Checklist complete

Monitor aircraft movement

Switch to Tower and monitor

Receive clearance

Acknowledge takeoff clearance

Perform PRE-TAKEOFF flow (below line)

Start checklist

Checklist complete

Ask for flaps

Ask for taxi clearance

Monitor radios



Check for obstacles

Start taxiing

Perform PRE-TAKEOFF flow (above line)

Ask for PRE-TAKEOFF checklist

Monitor radios

Monitor traffic

Maintain positional and situational awareness

Monitor Tower

Receive clearance



Line up with runwayTAKEOFF

Failed to start engine #-2 - distracted while discussing special operations for destination; omitted checklists - delay takeoffNeglected to set flaps -preoccupied with new departure clearance and packs-off operation -aborted takeoff

Omitted call for flaps -rushed to clear ramp/gate area for arriving aircraft -aborted takeoff

Omitted checking reason for bleed air indicator light-busy with delayed engine start and checklists - takeoff without troubleshooting

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

Fail to confirm flap position - evaluating heavy rain showers; rushed to accept takeoff clearance - aborted takeoff

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

TAXI-OUT errors attributed to “distractions” (ASRS incidents)CAPTAIN FIRST OFFICER

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

FO failed to monitor CA -runway change; busy reprogramming FMC -taxied past intended taxiway

Incorrect trim setting - checklist interrupted after item had been read but not verified - aborted takeoff

Omitted checklist - busy with delayed engine start and checklists; rushed to accept takeoff clearance - flaps not set, aborted takeoff

18

•Wide range of outcomes

•Large number of omissions not caught by later checklist

•Consequences spill into all phases

•$$$ ramp mishaps

•$$$ taxiway/runway incursions

•$$$ rejected takeoffs

•$$$ time, fuel

19

XY

PHASE OF FLIGHT - real


*monitor for Z3

Z1Z2Z3Z4Z5

w

*Wait for w

•Complexity •Inter-dependency of tasks•Interaction between operators and

between operators and agents

•Dynamic flow of events

•Impossible to predict interactions

•Impossible to pre-determine their timing

ENVIRONMENT-driven operation

Obtain ATIS

Obtain clearance

Review paperwork




(Passenger count)

(Load Sheet)

Program FMC



Review paperwork

Sign flight release





Review FMC

Takeoff brief



ENGINE START & PUSH-BACK


L

I

S

T

MONITOR Flight Interphone

MONITOR Ground frequency

Company/Dispatch frequency

Preflight - real (compiled observations)

PDC unavailable

Inoperative item

Passenger count unavailableFlight release still not picked up

no time, familiarity

Interruption

Interruption

Delay at gate

Ramp and/or Ground?

busy frequency

Flight plan/Departure runway change

Conduct exterior walk-around

no time, familiarity

New PDC

Still refueling

FO busy

Load sheet unavailable

Interruption

Inoperative item

FO busy

Time pressure

Request passenger count

Call maintenance

Look for ops/gate agent

APU off for 2 min before off-loading

Defer programming FMC

Double-check charts

Resume checklist

Confirm Mx responded

Confirm Mx departed

Confirm resolution

Confirm logbook on board

Keep trying

Check charts

Communicate with company

Compute new performance #s

Re-program FMS

Re-program FMC

Check fuel quantity and pumps

Ask forChecklist

Re-brief

Re-flow trim & other settings

New flight release/PDC?Re-set MCP

Resume flow

Defer programming FMC

Takeoff brief

PRE-TAKEOFF checklist

(above line)

L

I

S

T

Set flaps

Request taxi clearance

Monitor radios


Acknowledge taxi clearance


Check for obstacles

Perform PRE-TAKEOFF flow

(above line)

Start PRE-TAKEOFF checklist

Monitor radios

Monitor traffic

Monitor position on airport chart

Checklist complete

Monitor aircraft movement

Switch to Tower and monitor

Receive clearance

Acknowledge takeoff clearance


Start checklist

Checklist complete

Ask for flaps

Ask for taxi clearance

Monitor radios



Check for obstacles

Start taxiing

Perform PRE-TAKEOFF flow (above line)


Monitor radios

Monitor traffic

Maintain positional and situational awareness

Monitor Tower

Receive clearance



Line up with runwayTAKEOFF


PRE-TAKEOFF checklist

(below line)

L

I

S

T

Taxi-out - real (compiled observations)

busy frequency

Delayed engine startDe-icing pad

Environmental conditions

no time

no time

no time, familiarity no time, familiarity

short taxi, no time

short taxi, no time

New/ Additional taxi instructions

Interruption

Ramp and/or Ground?

busy frequency

traffic, FO busy)

Takeoff Brief: no time, familiarity

Change in takeoff runway

Just-in or new load data

Change in takeoff sequence

FMC: Program, set, verify

Extended taxi delay

Before/After Start Checklist

APU?

De-icing Checklist

Flaps before takeoff

Landinglights

Remember taxi instructionsId taxiways and turns

Remember to follow aircraftIdentify aircraft to follow

Remember to hold shortId correct place to hold short

Resume checklist

Double-check charts

Keep trying

Defer checklist

Consult charts

Keep head up/ outside

Calculate & reset Performance data

Inform Company (new #s, delays)

Resume checklist

Shoulderharness

Strobes

Check charts

Restart engine

Repeat checklists

RepeatChecklist?

FMC updateShoulderharness

Radar?

Cross check with CA

Stow OPC

Accept/Plan/Requestnew runway

Brief new runway

22

Challenge 1

• Pilots are constantly being interrupted• Interruptions demand attention and action• Such demands are unpredictable both in timing and in nature

(e.g., Ground controller announces change in planned departure while crew involved in preflight procedures at the gate)

Observed event : the FO received a call from Ground control notifying the crew of a change to their flight plan regarding the initial climb altitude in their departure. At that time, she was involved in setting the Pressurization panel as part of the Preparation flow … She suspended that activity and reached over to dial in the new altitude in the Mode Control Panel (MCP) altitude window while glancing over at the CA. She knew she had to verbally inform him of the change and to point out that she had already updated the MCP. She noticed that the CA was busy coordinating a luggage loading issue with the baggage handlers and Company, so she maintained the information in memory and formed an intention to carry out those actions at a later time. The FO resumed her flow, but monitored the CA’s activity. As soon as the luggage issue was resolved and the CA became available and able to redirect his attention to her again, she proceeded to inform him of the initial climb altitude change and the update to the MCP.

23

Challenge 2• Pilots must often perform >1 tasks concurrently

(e.g., captain doing preflight flow, looking for chart,

first officer asks for load sheet,

flight attendant reports item in galley needing service)

Observed event : A request from the FO asking for the Load sheet that the CA had just finished reviewing a moment ago interrupted the CA in the process of looking through his binder for the relevant departure chart in the binder. The chart was obviously misplaced because the CA had trouble locating it. The CA closed the binder but used his finger as a bookmark pointing to the pages he had just looked through. While sifting through some papers on his left in search of the Load sheet, a Flight Attendant entered the cockpit to let the CA know he had identified a problem in the galley, had placed a call to the service crew, and would be informing him upon their departure and resolution of the problem. The CA momentarily directed his attention to the FA standing at the door behind him and acknowledged the situation. Upon redirecting his attention inside the cockpit and to his own activities he became re-engaged with the issue of the misplaced departure chart and went back to his binder. The FO’s second request for the Load Sheet reminded him he had neglected to locate it and he re-interrupted the search for the chart to find and hand the chart to the FO.

24

Challenge 3

• Pilots do not/cannot always initiate actions• circumstances may not be right for an action

(e.g., must not extend flaps if taxiing in snow/icy conditions)

• information/tool/agent may not be available for coordination (e.g., cannot proceed with checking final fuel load until refueling complete)

Observed event: the CA reached the point on his preflight flow calling for verification of sufficient fuel on board. The fact that he still did not have a refueling slip on board made him realize that refueling was still underway. Rather than wait, and hoping for an on-time departure, he proceeded with the next step in the preflight flow. He formed the intention to conduct the fuel quantity check later (he may have also relied on the ensuing checklist which would, by definition, ask for number of gallons of fuel on board). When the Gate Agent brought the fuel slip for him to sign a few minutes later, he remembered the deferred intention and checked the fuel quantity readings.

25

• Challenges are underestimated• Vulnerabilities to making errors when facing

such challenges are not appreciated

26

Vulnerabilities 1

Deferring activities (interrupted or new)• Must resume/start later

requires• Deliberate formation of an intention• Remembering the existence of an intention• Remembering the exact content of intention

(what was suspended & at which point/what needs to be done)

• Remembering at a time when it is appropriate to carry out intention

+ (prospective) memory for intentions is poor99% of memory errors in the cockpit involve PM (Nowinski, Holbrook, & Dismukes, 2003)

+ “triggers” for sequence of activities are disrupted and lost+ intentions fade from working memory/focus of attention with time+ other events continue to flow in habitual sequence and timing

27

Vulnerabilities 2Interleaving activities (habitual/novel)• Combine two activities in previously/never-before encountered ways• Attend to two or more activities intermittently

requires• Remembering each activity• Deciding when to check on progress of each activity• Remembering to check on progress of each activity

+ Monitoring+ Essentially, a continuous prospective memory demand + Monitoring schedule for own /others’ progress?+ “triggers” for sequence of activities are absent

28

Countermeasures• Acknowledge human fallibility• Vulnerable to interruptions

• Examine procedures and checklists• Content• Timing• Identify source and nature of interruptions in each phase of flight

• Apportion workload• Provide warning signs for pilots to look for• Establish triggers for items at risk (tie critical functions to fixed

reference points)

• Set traps (strict decision criteria not to cross unless all expected activities fulfilled)

• Monitoring is a critical task• Better guidance needed (Sumwalt, Thomas, Dismukes, 2002)

ALPA Training CouncilMarch 2003

30

“At this point the scheduled flight is about 1.5 hours behind schedule. Prior to our arrival… we experienced some problems with the autopilot system… my FO… contacted company operations, advised them of our time of arrival and called for fuel with an order for 1900 lbs…

…once on the ground…I went inside the terminal to call Maintenance… got the information I needed and headed back to the aircraft to complete the paperwork. The passengers were boarding the flight and the FO was at the back of the aircraft… as we both got into the cockpit the FO started the load manifest. I then completed the write-up in the Maintenance Log and during this time asked the FO if the Before Start checks were complete. He answered 'no.' I then started the Before Start checks myself but was distracted by the events of a final baggage and passenger count for the Load manifest.

…There (were) other flights on the ground and I had seen the fuel truck moving about… with the passengers and bags onboard and (the) doors closed, the engines were started and a call for taxi made...

...Construction has been going on at this airport on the main runway and we have been using a shorter runway… we were given taxi for runway 29. After a look at the takeoff data, winds and weights, we advised (Tower) we needed runway 22. The Tower then cleared us for takeoff on runway 22 but we had not completed the checklist and so we advised Tower and took the time to complete the checklist. Once completed we departed runway 22 … after climbing through 12000 ft MSL … I was scanning the instruments and noticed the fuel quantity only showed 980 lbs…

I feel there were many distractions that interrupted the flows on the checklist and items were skipped..“

PREFLIGHT - real (Captain’s ASRS Report # 335059)

CONCURRENT TASK DEMANDS IN THE COCKPIT: CHALLENGES AND VULNERABILITIES Loukia D. Loukopoulos R. Key Dismukes Immanuel Barshi NASA Ames Research Center.

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