Incredible Challenges of the Air Traffic Control System Modeling, Control and Optimization in the National Airspace System

1
Incredible Challenges of the Air Traffic Control
SystemModeling, Control and Optimization in
the National Airspace System

• Dr. Banavar Sridhar
• NASA Ames Research Center
• Moffett Field, CA 94035
• Banavar.Sridhar_at_nasa.gov

UCSC Seminar May 27, 2004
2
Outline

• What is the National Airspace System (NAS)?
• Scope
• Influence on the economy
• Transformation
• Comparison with other networks
• Technology Research in Traffic Flow Management
  (TFM)
• Strategic flow models
• FACET simulation and modeling capability
• Transformation of the NAS
• Questions?

3
Visualization of Air Traffic Data
4
(No Transcript)
5
Hierarchy in TFM

• Centralized command and control structure
• Command Center, Herndon, VA
• 20 Centers
• 830 high and low-altitude sectors

6
Time-Scales in Air Traffic Management
Ref Boeing/Aslaug Haraldsdottir
7
Inter-Center Traffic Flow
ZBW
ZLC
ZSE
ZOB
ZMP
ZNY
ZAU
ZDV
ZKC
ZID
ZDC
ZOA
ZME
ZAB
ZFW
ZLA
ZTL
ZJX
ZHU
ZMA
8
TFM problem

• Capacity
• Theoretical maximum flow rate supported by the
  separation standard
• Throughput
• Rate of flow realized in operation
• Efficiency
• How close is throughput to capacity?
• Objective
• Maximize flow rate to meet traffic demand

9
Types of Control (TFM actions)

• Ground Delay Program
• Controlling aircraft departure time to manage
  aircraft arrival rates
• Metering (Miles-in-Trail)
• Controlling flow of aircraft into a center by
  imposing flow restrictions on aircraft one or
  more centers away
• Reroutes
• Congested En-route area
• Weather
• Special Use Airspace
• Playbook
• Effort to provide a common understanding of
  re-routing strategy under previously defined
  situations

10
Transforming the NAS
11
September 11, 2001 Chronology of events

• 845 a.m. A large plane crashes into World Trade
  Center north tower.
• 903 a.m. A second plane crashes into World Trade
  Center south tower.
• 917 a.m. FAA shuts down all New York City area
  airports.
• 940 a.m. FAA grounds civilian flights
• 1024 a.m. FAA reports that all inbound
  transatlantic aircraft flying into the United
  States are being diverted to Canada.
• 1230 p.m. The FAA says 50 flights are in U.S.
  airspace, but none are reporting any problems.

12
(No Transcript)
13
Commercial Transport Enplanements
800.0
700.0
Large Air Carrier Passenger Enplanements
(Millions)
600.0
500.0
400.0
Forecast
Actual
300.0
200.0
100.0
0.0
05
06
07
08
09
10
11
12
13
14
95
96
97
98
99
00
01
02
03
04
Calendar Year
Source 1990-2002 U.S. Air Carriers, Form 41,
U.S. DOT 2003-2014 FAA Forecasts
14
System Reaching Saturation
Target Year
Source LMI, Alternatives for Improving
Transportation Throughput and Performance, March
2002
15
What is at stake in air transportation?

• Lost growth and output from air transportation
  due to demand outstripping capacity
• Unserved demand of 180 billion Revenue Passenger
  Miles (RPMs) resulting lost annual economic
  output of 23 billion by 2015 (23B does not
  include additional impact of lost user
  productivity)
• Major policy / operational alternatives within
  the current air transportation architecture
  recaptures only a small fraction of unserved
  demand and economic output
• Large, continuing security costs to protect the
  system from acts of terrorism
• Difficult to measure efficacy

Rising costs, rising frustrations, lost
opportunities
Source LMI, Alternatives for Improving
Transportation Throughput and Performance, March
2002
16
What makes NAS different?

• Safety is paramount
• Human-in-the-loop decision making at all levels
• System capacity limits established by human
  performance
• Changes need to be done while the system is in
  operation
• Difficulty in modeling user reaction to events
• Availability/absence/uncertainty of information
• Need to get consensus among various parties FAA,
  unions, airlines, aircraft manufacturers, etc.
• Status of automation/decision support tools

17
Strategic Flow Models
18
Outline

• Strategic Flow Models
• Linear Time-variant Dynamic System representation
• Flow Matrix
• Forcing Function
• Example
• Bounds on the Model
• Concluding remarks

19
Traffic Flow Models
Detailed Aggregate
Deterministic CTAS, FACET, CRCT Flow models
Stochastic Sector Congestion Queuing models

• Detailed models
• Useful for developing algorithms affecting
  individual aircraft
• Controller/Traffic Manager decision support tools
• Aggregate models
• Useful for understanding the general behavior of
  the system
• Effectively address system uncertainties and long
  term behavior

20
Traffic Flow
Different Centers
Atlanta Center on different days
21
Linear Time-Varying Dynamic Traffic Flow Model
22
A Matrix (May 6, 2003 6 hour average, 5-11P.M,
PST)
23
Variation of A Matrix
Daily Variation May 6,7,8 2003 5-11 P.M
Variation during May 6 11P.M- 5A.M, 5-11 A.M,
11A.M-5 P.M
24
Variation of A Matrix During May 6, 2003 5-11 P.M
Hourly Variation
Two-Hour Variation
25
Modeling A(k) Constant for different time
intervals
26
Normalized mean and standard deviation of Error
27
Modeling of the forcing function (BuCw)
Departure Counts (May 6, 2003 Every 10 Minutes)
28
Effect of using A from previous days
Atlanta Center (ZTL) Traffic Counts for May 8,
2003 predicted using May 7 and May 6 flow
matrices
29
Departure Counts (May 6-8, 2003 Every 10 Minutes)
May 6
May 7
May 8
30
Modeling departures using mean value
31
Error Bounds for Model
32
Modeling departure errors as gaussian
33
Concluding Remarks

• Described linear time varying models to represent
  traffic flow for developing strategic TFM
  decisions.
• Linear dynamic traffic flow system model with a
  slowly varying transition matrix and Gaussian
  departure representation adequately represents
  traffic behavior at the Center-level.
• Error bounds around nominal traffic counts in the
  Centers was described.
• Numerical examples presented using actual
  traffic data from four different days to
  demonstrate the model characteristics.
• Advantages
• Unlike trajectory-based models, these models are
  less susceptible to uncertainties in the system,
• The model order is reduced by several orders of
  magnitude from 5000 aircraft trajectories to 23
  states at any given time
• Tools and techniques of modern system theory can
  be applied to this model because of its form.
• Capabilities of this class of models for
  strategic traffic flow management will be
  explored in the future.

34
Future ATM Concepts Evaluation Tool (FACET)
35
Future ATM Concepts Evaluation Tool (FACET)

• Environment for exploring advanced ATM concepts
• Balance between fidelity and flexibility
• Model airspace operations at U.S. national level
  (10,000 aircraft)
• Modular architecture for flexibility
• Software written in C and Java programming
  languages
• Easily adaptable to different computer platforms
• Runs on Sun, PC and Macintosh computers
• 3 Operational Modes Playback, Simulation, Hybrid
• Used for visualization, off-line analysis and
  real-time planning applications

36
FACET Architecture
Winds
Applications Air and Space Traffic
Integration Airborne Self-Separation Data
Visualization Direct-To Analysis Dynamic
Density System-Level Optimization Traffic Flow
Management
Flight plans Positions
Route Parser Trajectory Predictor
Climb Cruise Descent
Centers Sectors Airways Airports
37
FACET Displays
Traffic
Winds
3-D
Convective Weather
38
ATL Arrivals (Purple) and Departures (Green)
39
FACET Display
16
17
40
Severe Weather Playbook Reroutes(Eastbound
Traffic over Watertown)
41
Alternative effects of TFM actions
42
Integrated traffic counts in ZMP Sector 16
A Nominal Counts, B Playbook Reroute, C
Playbook MIT, D Playbook MITLocal Reroute.
43
EWR and LGA Delay Contours
44
FACET for AOC Applications

• March 2001 request by Aircraft Dispatchers
  Federation (ADF) team to increase NASA research
• FACET modified to work with Aircraft Situation
  Display to Industry (ASDI) data
• Developed a version of FACET for AOC use

• Enable efficient operations planning by AOC
• Risk analysis
• Departure planning and congestion assessment
• Integration with weather
• Commercial Technology Office to license the
  software to Flight Explorer (FACET release in FE
  6.0, October 2004)

45
Comments from Airline Dispatchers

• I usually (almost always) plan for the worst
  case scenario. The ability to tailor fuel uplift
  to individual flights with a very high degree of
  confidence in the probability of en route delay
  is worth tens of millions of dollars to the
  airlines. It costs me about 400,000 a year to
  carry one additional minute of fuel on each
  flight. If I am carrying an average of 35
  minutes, and I really only need a system-wide
  average of 15 minutes, that would be worth 8
  million per year to my airline alone.
• I would find the predictive data very helpful in
  planning routing and fuel load.
• The concept of alerting a dispatcher regarding
  ATC sector overload and inbound ATC reroutes is
  an excellent idea.
• To the dispatcher at the desk, I think it would
  give him a huge advantage to see, understand,
  plan, fuel and brief the crews on possible ATC
  initiatives based on volume issues.
• FACET would be great because when the Command
  Center says, or the ATC community says These are
  your three options, we could say You know, you
  might want to consider a fourth option here that
  we could game or model on FACET.
• Weve been asking for a common situation display
  for a long time. This may be the basis for it.

46
Transformation of the NAS
47
Commission on the Future of the United States
Aerospace Industry

• Recommendations
• 2 The Commission recommends transformation of
  the U.S. air transportation system as a national
  priority.
• Rapidly deploy a new highly automated ATM system
• 3 The Commission recommends that the U.S.
  create a space imperative.
• 9 The Commission recommends that the federal
  government significantly increase its investment
  in basic aerospace research, which enhances U.S.
  national security, enables breakthrough
  capabilities, and fosters an efficient, secure
  and safe aerospace transportation system.

48
Partners in Development ofNational Plan for the
Future NAS

• JPO develops and maintains National
  Transformational Plan which includes
• Associated policies, technology, processes
• Overall operational concepts
• Supporting research
• Implementation strategies
• Policy and implementation commitments

Strategic Plan Perf. Goals
Strategic Plan Perf. Goals
Strategic Plan Perf. Goals
RD Plan
Pgm. Plan
49
Capability
Time
50
Issues in the transformation of NAS

• Automation
• Need
• Impact
• Human Factors
• Policy
• Regulations
• Certification
• Equity
• Allocation of scarce resources
• Sharing of information
• Cost of equipment
• Integration with existing systems
• Software verification and validation