CONCURRENT TASK DEMANDS IN THE COCKPIT: CHALLENGES AND VULNERABILITIES Loukia D. Loukopoulos R. Key...
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Transcript of CONCURRENT TASK DEMANDS IN THE COCKPIT: CHALLENGES AND VULNERABILITIES Loukia D. Loukopoulos R. Key...
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
FLIGHT DECK PREPARATION procedure
F
L
O
W
(57 items)
Finish PREPARATION procedure
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
BEFORE START checklist
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)
CAPTAIN FIRST OFFICER
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)
CAPTAIN FIRST OFFICER
•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
BEFORE START checklist
L
I
S
T
Preflight - assumed (carrier)
Obtain ATIS
Obtain clearance
Review paperwork
Prepare/review charts
FLIGHT DECK PREPARATION procedure
F
L
O
W
Finish PREPARATION procedure
(Passenger count)
(Load Sheet)
Program FMC
Start BEFORE START checklist
BEFORE START checklist complete
Review paperwork
Sign flight release
Prepare/review charts
FLIGHT DECK PREPARATION procedure
F
L
O
W
Finish PREPARATION procedure
Review Load Schedule
Review FMC
Takeoff brief
Ask for BEFORE START checklist
CAPTAIN FIRST OFFICER
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
Prepare/review charts
FLIGHT DECK PREPARATION procedure
Finish PREPARATION procedure
(Passenger count)
(Load Sheet)
Program FMC
Start BEFORE START checklist
BEFORE START checklist complete
Review paperwork
Sign flight release
Prepare/review charts
FLIGHT DECK PREPARATION procedure
Finish PREPARATION procedure
Review Load Schedule
Review FMC
Takeoff brief
Ask for BEFORE START checklist
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
Receive taxi clearance
Form mental picture of taxi route
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
Perform PRE-TAKEOFF flow (below line)
Ask for PRE-TAKEOFF checklist
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
CAPTAIN FIRST OFFICER
*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
Prepare/review charts
FLIGHT DECK PREPARATION procedure
Finish PREPARATION procedure
(Passenger count)
(Load Sheet)
Program FMC
Start BEFORE START checklist
BEFORE START checklist complete
Review paperwork
Sign flight release
Prepare/review charts
FLIGHT DECK PREPARATION procedure
Finish PREPARATION procedure
Review Load Schedule
Review FMC
Takeoff brief
Ask for BEFORE START checklist
CAPTAIN FIRST OFFICER
ENGINE START & PUSH-BACK
BEFORE START checklist
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
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
Receive taxi clearance
Form mental picture of taxi route
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
Perform PRE-TAKEOFF flow (below line)
Ask for PRE-TAKEOFF checklist
Line up with runwayTAKEOFF
CAPTAIN FIRST OFFICER
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)