This presentation describes the results of a medium fidelity piloted flight deck simulation of future surface operations.

1. Piloted Simulation of NextGen Time-based
Taxi Clearances and Tailored Departures
David C. Foyle, PhD
NASA Ames Research Center
Becky L. Hooey, MSc
C st a
Christina L. Kunkle, BA
u e,
Martin F.J. Schwirzke, MA
Deborah L. Bakowski, MA
San Jose State University Foundation at
NASA Ames Research Center
ICNS 2009
http://humansystems.arc.nasa.gov/groups/HCSL/

2. Outline
• S f
Surface operations
ti
• 4-D (time-based) taxi clearances
• Surface Traffic Management (STM) system
characteristics
• Simulation Experiment
• Results
• Conclusions

3. Surface Operations
• Airport surface congestion results in the largest delay cost in US
p g g y
airspace system (Glass & Gawdiak, 1997)
• Delays are caused by competition for resources
Solutions
• Increase taxi efficiency and improve runway coordination (Cheng, Sharma,
& Foyle, 2001)
• Coordinated runway crossings can potentially increase traffic throughput
of airports
(Cheng, Sharma, & Foyle, 2001; Hooey, 2005)
• Surface Traffic Management
Systems (STMs)
– Utilize dynamic algorithms
– Precise surface coordination
– 4-D (time-based) taxi clearances

4. Pilot Requirements for 4D Taxi Clearances
Problem: Integrating surface
traffic management
system 4D taxi clearances
with flight deck
information requirements
Advanced surface traffic management systems
and ConOps must incorporate pilot Human factors pilot-in-the-loop studies to
operating requirements determine pilot operating requirements
- Ability to comply with speed requests - Speed conformance
- A/C variance of route and time conformance - Route and time conformance
- Conceptual development (e.g., form of taxi
(e g - Conceptual (ConOps) development
clearances - continuous, updates, etc.) - Pilot workload, Situation awareness (SA)
- Pilot/Aircraft non-conformance - Safety impacts due to time pressure
- Rerouting
4D Taxi Navigation Issues
4D Concepts
- Continuous-coupled 4D commands
- Progressive taxi/route updates
- Endpoint-only 4D commands (push-back, departure queue)
4D Taxi Clearance Display Formats
- Speed vs. time displays
- C ti
Continuous vs. non-continuous command displays
ti d di l
- Bandwidth of command updates (pilot display and ATC concept)
Pilot Performance Metrics
- Variance of speed, time-of-arrival error
- SA, workload impacts

5. Development of Time-based STMs
(Surface Traffic Management (STM) Systems)
Defining Characteristics
• ATC/STM - Number of Traffic Flow Points
• ATC/STM - Flow Point Time Constraint
• ATC/STM - Refresh/reoptimization (due to traffic changes, pilot
performance)
• Flight Deck - Onboard "display" algorithms (e g error nulling)
display (e.g.,
• Flight Deck - Display Bandwidth Speed (bounding conditions)
• Speed (bounding conditions)
STM
Pilot A/C
Algorithms Performance

6. Development of Time-based STMs
(Surface Traffic Management (STM) Systems)
Defining Characteristics
• ATC/STM - Number of Traffic Flow Points
• ATC/STM - Flow Point Time Constraint
• ATC/STM - Refresh/reoptimization (due to traffic changes, pilot
performance)
• Flight Deck - Onboard "display" algorithms (e g error nulling)
display (e.g.,
• Flight Deck - Display Bandwidth Speed (bounding conditions)
• Speed (bounding conditions)
STM
Pilot A/C
Algorithms Performance

7. Taxi-out Departure

8. Taxi-out Departure
“Departure is currently the highest
workload phase of flight”
- Richard L Newman Phd
L. Newman,
Formerly FAA
Human Factors Specialist,
Commercial Transport
p
NextGen Operations
- Dynamic, Tightly Coupled
- Potential for High Workload & Errors

9. Simulation
Medium Fidelity Part-task Simulator
Part-
• Human-Centered Systems
Human-
Laboratory (HCSL)
L b t
• NASA Ames Research Center
• Previously validated
Dallas-
Dallas-Fort Worth (DFW) airport
Visibility: Clear, distant haze
Simple B737 aircraft model
Controls: Tiller, throttle, toe brakes,
rudder pedals
Pilots: 16 commercial transport
Age: 25-63 yrs (M=45 5 yrs)
25- (M=45.5
Flight hours: 1,000-20,000 (M=5,586)
1,000-

10. Experiment Overview
Pilot Tasks
• Taxi (with speed/time)
• Verify departure clearance
• Maintain checklist
• Traffic separation
Traffic Flow Points
Independent Variables Limited NextGen:
• N tG Implementation (between)
NextGen I l t ti (b t ) Speed Change
S C
- Limited, Advanced Advanced NextGen:
• Traffic Flow Points (within)
Speed Change &
- 1, 3, or 5
• Ta i Speeds (within)
Taxi ( ithin) TND Checkpoint
- 10, 14, 18, 22 kts
Same traffic locations and speeds for
Limited NextGen vs. Advanced NextGen
conditions
Final
Dependent Measures
Departure
• Time of Arrival (TOA) error (at traffic
flow points & RWY)
Clearance
• Departure Clearance Verification
(Errors and Latency)

11. DFW Routes
12 Unique DFW Routes
• 14,300’ length (avg.)
• Repeated 2x
- Different traffic flow points
- Other traffic Traffic Flow Points
• Final Departure Clearance
p
given 25-75% into route
Trials
• 4 Familiarization trials
(no data collection, ~1 hr)
collection 1
• 24 NextGen nominal Final
• 2 Departure clearance Departure
mismatches Clearance
• 1 “Current-day” taxi

12. NextGen Conditions and Displays
Primary Flight Display (
y g p y (PFD)
) Taxi Navigation Display (TND)
g p y( )
Limited NextGen
• ATC: Speed commands at traffic
flow points
• Pilots: Maintain commanded
speed (avg.) – 15 kts turn max.
• PFD: Current, commanded
speed
• TND: Route, Traffic

13. NextGen Conditions and Displays
Primary Flight Display (
y g p y (PFD)
) Taxi Navigation Display (TND)
g p y( )
Limited NextGen
• ATC: Speed commands at traffic
flow points
• Pilots: Maintain commanded
speed (avg.) – 15 kts turn
• PFD: Current, commanded
speed
• TND: Route, Traffic
Advanced NextGen
• ATC: Speed commands at traffic
flow points
• Pilots: Maintain commanded
speed (dynamic) – 15 kts turn
• PFD: Current, commanded
speed, Required Time of Arrival
(RTA), Elapsed Time, Error-nulling
algorithm (for RTA)
• TND: Route, Traffic, Traffic flow
point

14. NextGen Conditions and Displays
Limited NextGen
• ATC: Speed commands at traffic
flow points
Error-nulling
Error nulling algorithm (for RTA):
• Pilots: Maintain commanded
speed (avg.) – 15 kts turn max.
• PFD: Current, commanded
speed Remaining Distance
g
Current commanded speed =
C
• TND: Route, Traffic
Remaining Time
Advanced NextGen
• ATC: Speed commands at traffic
flow points
• Pilots: Maintain commanded
speed (dynamic) – 15 kts turn
• PFD: Current, commanded
speed, Required Time of Arrival
(RTA), Elapsed Time, Error-nulling
algorithm (for RTA)
• TND: Route, Traffic, Traffic flow
point

15. Checklist, Datalink, Nav Display
Taxi Navigation Display (TND)
Datalink Text
Pre-trial
• TND overview mode
Departure Clearance
Window
• At DFW ramp spot
• ATC verbal route clearance Checklist Window
• Navigation Display (ND): Pre-
loaded predeparture clearance
Navigation Di l
N i ti Display (ND)
• Pilot: “Ready to taxi”
Taxi trial
• TND: Track-up, perspective
• Checklist scan task (~2 min)
• Datalink text departure
clearance: Predeparture
clearance
• Navigation Display (ND): Pre-
loaded predeparture clearance

16. Departure Clearance Verification Task
NOMINAL
Pending
• Departure clearance sent 25-
75% into route
• Chi
Chime, ACCEPT/REJECT
flashing
• Pilot must verify match
between:
1) D t li k t t and
Datalink text, d
2) ND
- Route ID number
- Last leg direction

17. Departure Clearance Verification Task
NOMINAL
Pending
• Departure clearance sent 25-
75% into route
• Chi
Chime, ACCEPT/REJECT
flashing
• Pilot must verify match
between:
1) D t li k t t and
Datalink text, d
2) ND
- Route ID number
- Last leg direction
Accepted
• Accept or Reject clearance
(button press)
• Loads into FMS/ND
• If incorrectly rejected,
ATC re-sent

18. Departure Clearance Verification Task
OFF-NOMINAL
2 Mismatch Trials
• 1st – ID number and route
direction
• 2 d – ID number
2nd b
• If incorrectly accepted –
loaded
• If correctly rejected – correct
clearance sent

19. Departure Clearance Verification Task
OFF-NOMINAL
2 Mismatch Trials
• 1st – ID number and route
direction
• 2 d – ID number
2nd b
Rejected
• If incorrectly accepted –
loaded
• If correctly rejected –
correct clearance sent

20. Time of Arrival (TOA) Error
TOA error calculation
• Actual TOA - Required TOA (RTA)
p=.001 • Limited NextGen: No explicit RTA
(Calculated using segment length and
ATC-commanded speed)
Late
TOA error results
Early
1. Limited vs. Advanced NextGen (3-way, p<.01)
Advanced NextGen (speed error-nulling avionics)
( p g )
allows reduced TOA error for all speeds and
number of traffic flow points
2. Limited NextGen (Quadratic x Linear, p<.01)
Speed commands only (without speed error error-
nulling avionics):
p=.01 • Increase number of traffic flow points yields
exponential reduction in TOA error
• 14 kts best (turns typical taxi speed)
(turns,
• Replicated Williams, Hooey, & Foyle, 2006
Late
3. Advanced NextGen (Linear x Linear, p=.058)
Early
Speed error-nulling avionics:
p g
• Overall reduction in TOA error
• 14 kts best (turns, typical taxi speed)
• Linear improvement with more traffic flow points

21. TOA Error Distributions
TOA error distribution results
Advanced NextGen (error-nulling avionics) much
less variable TOA error than Limited NextGen
(speed commands)

22. Departure Clearance Verification Errors
Departure clearance verification results
Incorrect rejections: 3 / 400 nominal clearances, p(error)=.008
p(error) .008
- Likely due to heading text readout (N vs. NE)
Incorrect acceptances: 2 / 32 off-nominal (mismatched), p(error)=.06
- Both 2nd mismatch, 1 in each NextGen implementation
May be indicative of increased workload with time-based taxi clearances

23. Departure Clearance Verification Latency
Limited NextGen vs. Advanced
NextGen (interaction, p=.005)
p=.005
Correct = “Accept” Correct = “Accept” Correct = “Reject”

24. Departure Clearance Verification Latency
Limited NextGen – Speed commands *
only, no error-nulling avionics:
(overall, p<.05) *= Significant *
Advanced NextGen – Error-nulling
*
avionics: (overall, p<.001) n.s. *
Correct = “Accept” Correct = “Accept” Correct = “Reject”

25. Departure Clearance Verification Latency
Compared to “current-day” baseline
taxi,
Advanced NextGen (error-nulling
avionics) had longer latencies to:
- Correctly accept correct clearances
- Correctly reject incorrect clearances
Compared to Limited NextGen (speed
commands only),
Advanced NextGen (error-nulling
avionics) had longer latencies to:
- Correctly reject incorrect clearances
May be indicative of increased
workload in Advanced NextGen Correct = “Accept” Correct = “Accept” Correct = “Reject”
implementation

26. Post-study Questions
How many ‘speed changes’ (Limited
NextGen) or ‘traffic flow points’
(Advanced NextGen) per route
are acceptable?
All: “2-3”
Were there too many ‘speed changes’
(Limited NextGen) or ‘traffic flow
traffic
points’ (Advanced NextGen)? (1,
3, or 5)
Limited NextGen: 0% “yes”
Advanced NextGen: 88% “yes”
yes
(p<.001)

27. Post-Study Structured Interviews
1.5 hr Post-study Structured Interview Findings
Time-based Taxi Clearances
• Improve airport efficiency
• Pilot acceptance likely (efficiency gains)
• Some concern for safety (“eyes in”)
• Ground speed on PFD reasonable
• Suggestions for TND to show nearby traffic and taxi holds
• Possible increase in crew coordination – need for speed “callouts”
callouts
NextGen Tailored Departures (Datalinked flexible 4-D departures)
• Improve system-level efficiency (routing)
p y y( g)
• Improve individual aircraft efficiency (fuel, time)
• Decrease flight deck workload (direct upload of clearances into FMS)
• General acceptance of concept
- Terrain/traffic cleared by ATC
y
- No issue with unique routes (may help with complacency)
- Cross-check of datalink and route loaded required; Reasonable as implemented
• Some concern about how to “back up” unique complex routes
- Pre-departure briefings (
p g (how do y describe to each other, manually fly?)
you , y y )
- Emergency or off-nominal fall-back procedures (avionics failure, engine out)
- Requires future research

28. Conclusions
Commanded Speed
• TOA compliance most accurate with moderate taxi
- Arrive early for slower speeds; Late for faster speeds
Segment Distance
• TOA error largest with single (long) route segments
NextGen Taxi Implementation
• Requirement for Advanced NextGen error-nulling avionics
q g
- Limited NextGen speed commands TOA error too high/variable (could limit
optimization by STMs)
- Advanced NextGen error-nulling avionics substantially improves TOA
compliance
• However, Advanced NextGen error-nulling avionics:
- May induce increased flight deck workload
- Need to investigate procedures and aids to offset
- Required conformance levels of speed and TOA ‘windows’
NextGen Tailored Departures
• No major concept issues
• Need for cross-check, verification
• How to ‘back up’ unique complex routes (for briefing, emergency, off-nominal)

29. Piloted Simulation of NextGen Time-based
Taxi Clearances and Tailored Departures
David C. Foyle, PhD
NASA Ames Research Center
Becky L. Hooey, MSc
C st a
Christina L. Kunkle, BA
u e,
Martin F.J. Schwirzke, MA
Deborah L. Bakowski, MA
San Jose State University Foundation at
NASA Ames Research Center
ICNS 2009
http://humansystems.arc.nasa.gov/groups/HCSL/