Dr. Banavar Sridhar NASA Ames Research Center Moffett Field, CA 94035 Banavar.Sridhar@nasa

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@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

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 • 8:45 a.m. A large plane crashes into World Trade Center north tower. • 9:03 a.m. A second plane crashes into World Trade Center south tower. • 9:17 a.m. FAA shuts down all New York City area airports. • 9:40 a.m. FAA grounds civilian flights • 10:24 a.m. FAA reports that all inbound transatlantic aircraft flying into the United States are being diverted to Canada. • 12:30 p.m.: The FAA says 50 flights are in U.S. airspace, but none are reporting any problems.

13. Commercial Transport Enplanements 800.0 700.0 Large Air Carrier Passenger Enplanements (Millions) 600.0 500.0 400.0 Actual Forecast 300.0 200.0 100.0 0.0 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 Calendar Year Source: 1990-2002: U.S. Air Carriers, Form 41, U.S. DOT; 2003-2014 FAA Forecasts

14. 180 160 Baseline Revenue Passenger Miles Lost 140 New Hubs Nighttime Operations 120 Schedule Smoothing 100 (Billions) Direct Service 80 Larger Aircraft 60 Aggressive New Technology 40 20 0 2005 2010 2015 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 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: (Bu+Cw) 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. Weather NOAA ETMS/ASDI User Interface Historical Database Aircraft Performance Data Traffic & Route Analyser Adaptation Data 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. Traffic Winds FACET Displays Convective Weather 3-D

38. ATL Arrivals (Purple) and Departures (Green)

39. FACET Display 16 17

40. Severe Weather Playbook Reroutes(Eastbound Traffic over Watertown)

41. Local Reroute Local Reroute C D B MIT Playbook A B Nominal Alternative effects of TFM actions

42. Integrated traffic counts in ZMP Sector 16 [A] Nominal Counts, [B] Playbook Reroute, [C] Playbook + MIT, [D] Playbook + MIT+Local Reroute.

43. EWR and LGA Delay Contours

44. FACET for AOC Applications • March 2001: request by Aircraft Dispatcher’s 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.” • “We’ve 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. JPO develops and maintains National Transformational Plan which includes: Associated policies, technology, processes Overall operational concepts Supporting research Implementation strategies Policy and implementation commitments Executive Board Aviation System Joint Program Office National Plan FAA NASA DoD DHS Strategic Plan & Perf. Goals R&D Plan R&D Plan R&D Plan OEP CIP Infra. Plan As Required As Required As Required Partners in Development ofNational Plan for the Future NAS Strategic Plan & Perf. Goals Strategic Plan & Perf. Goals Strategic Plan & Perf. Goals R&D Plan Pgm. Plan

49. Defining a Transformational System Future NAS (initial design space) Future NAS Transition-2 NAS Transition space Transition-1 NAS Current NAS 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