NASA Research Results for “4D-ASAS” Applications

1. NASA Research Results for“4D-ASAS” Applications Presented by David Wing (david.wing@nasa.gov)Bryan Barmore (bryan.barmore@nasa.gov)NASA Langley Research Center ASAS Thematic Network 2 Third Workshop, Glasgow, Scotland 11-13 September 2006

2. FlightCrew • Information • Decision making • Responsibility AeronauticalOperationalControl Air Traffic ServiceProvider Research Premise: Distributing ATM Functions Results in Scalable ATM System Distributed 4D Trajectory Management ATSP sets strategic trajectory constraints Operator manages trajectory to meet them Strategic functions: ATSP Traffic flow management, resource scheduling Local functions: 4D-ASAS-capable operator Flight safety, ATSP-issued constraint conformance, trajectory optimization Distributed Air Ground Traffic Management Changes impacting NAS resource usage are coordinated strategically Local situations and “no impact” changes are implemented by 4D-ASAS aircraft RTA unchanged Example local situation Presentation is on Two DAG-TM “4D-ASAS” Concepts En-Route: Autonomous Flight ManagementTerminal Arrival: Airborne Precision Spacing Modified 4D trajectory, same strategic constraints Original 4D trajectory ATSP: Air Traffic Service Provider RTA: Required Time of Arrival 4D-ASAS: Four Dimensional Airborne Separation Assistance Systems

3. Autonomous Flight Rules(AFR) Aircraft Special Use Airspaceavoidance Instrument Flight Rules (IFR) Aircraft Air Traffic Service Provider Autonomous Flight Management An En-Route/Transition 4D-ASAS Concept $+J • Integrated Operational Principles • Performance-based operations • 4D trajectory operations • Non-segregated operations Q Cost control Passenger comfort Q IFRpriority Q Q Distributed separationassurance Q Q Q Q Q Hazard avoidance Q Fleet management Q AFR-managed trajectories Q Priority rules IFR trajectorymanagement Q Q Q Q Q Q Q Maneuver restrictions Q Q Q Q Q Q Terminal areaentry constraints Levels of 4D-ASAS performance IFR and AFR traffic flow management Q Terminal area David Wing NASA Langley Research Center david.wing@nasa.gov

4. AFM Research Accomplishments • NASA project-level accomplishments • Operational concept description • Feasibility assessment of airborne and integrated air/ground operations • Feasibility assessment of ATSP operations • Human factors assessment • Life-cycle cost-benefit analysis • Safety impact assessment • Flight deck technology for autonomous operations • ATSP decision support technology • Experimental evaluation of integrated air/ground operations • Langley contribution highlights • Developed flight-deck decision support toolset and supporting flight deck systems-- Autonomous Operations Planner (AOP) • Conducted 3 HITL simulation experiments • Performed 36-issue assessment of concept feasibility -- application of research analysis and domain expertise

5. Autonomous Operations Planner NASA’s Research Prototype of 4D-ASAS En-Route Toolset Principal Functions • Strategic & tactical conflict detection & resolution • Conflict-free maneuvering support • Flow constraint conformance • Airspace restriction avoidance Crew inputs AOP Priority rules Command conflicts Ownship intent Planning conflicts Attributes Intent-based conflict detection Conflict resolution and trajectory planning • Working software prototype w/ ARINC 429 data-bus & 702a FMS integration • CD&R alerting is RTCA SC186 ACM-WG compliant • Simultaneously meets traffic, airspace, user, and flow management constraints (RTA) • Performs trajectory optimization as part of conflict resolution • Works within and ‘across’ normal autoflight modes, and within aircraft performance limits Traffic intent Conflict alerts and information Provisional (FMS/MCP) conflicts Maneuver restriction information Ownship state State-based conflict detection Blunder protection and collision data Traffic state ATC flow management constraints and airspace constraints

6. Pilot-Only Simulation Experiments: Study of Tools, Procedures, Hazards Scenario Design Conventional traffic conflicts • Lateral & vertical • State & intent Unconventional traffic conflicts • Blunders • Pop-up separation loss • Meter-fix conflicts Constraints • ADS-B surveillance limitations • Airspace restrictions • Required Time of Arrival Variables studied • Traffic density • Use of intent data • Conflict resolution method • Lateral separation standard • Airspace restrictions • Priority rules Studies resulted in significant gains in understanding of AFR operations feasibility, operational sensitivities, human factors design, and requirements for tools & procedures

7. missed one missed multiple No priority rules With priority rules met all 100% Goal Goal 80% 60% Constraint Conformance 40% Result: Better predictability 20% 0% Left aircraft Right aircraft Left aircraft Right aircraft 59 data runs No Events Result: Dominoeffect prevented Resolution method Pilot-Only Simulation Experiments: Sample Results Aircraft B Aircraft A SUA Over-Constrained Trajectories SUA SUA SUA Crossing Assignment RTA <30 seconds Altitude < 500 ft Position < 2.5 nm Identical crossing assignments Planned conflict ConflictPropagation Second generation conflict Resolution Method Tactical: open loop Strategic: closed loop Modified: pilot override

8. Integrated Air-Ground Experiment: Langley-Ames Experimental Evaluation Addressed 2 key feasibility issues: • Mixed Operations: Investigate safety and efficiency in high density sectors compared to all managed operations • Scalability: Investigate ability to safely increase total aircraft beyond controller manageable levels. Number of managed aircraft remains at or below current high-density levels. 4 test conditions 3 traffic levels Autonomous Managed L3 L2 T1 L1 L1 T0 C1 C2 C3 C4 • T0: ≈ current monitor alert parameter • T1: approximate threshold above which managed only operations will definitely fail (determined by Ames study) • Only overflights were increased (arrivals held constant) • 22 commercial airline pilots (20 single pilots + 2 pilot crew in high fidelity simulator) • 5 professional air traffic controllers (1 per sector + 1 tracker)

9. Increasing Traffic Langley Aircraft and Ames ControllerSample Results Controller workload assessment Meter fix conformance for arrivals High Low • Pilots mainly able to meet constraints • Some pilot entry error (RTA into FMS) • No apparent performance degradation as traffic level increased • Lower workload for all mixed conditions • Traffic levels at C3 and C4 not considered manageable if all aircraft IFR

10. AFM Feasibility Assessment Activity • Team analysis of 36 feasibility questions • Distributed operations, air/ground integration, strategic & local TFM, flight crew responsibilities, airborne equipage, CNS • Evaluations based on literature search, research results, operational experience and judgment • Sample questions: • Is the distributed AFR network vulnerable to system-level or cascading component failures? • Within what limits do AFR aircraft have the ability to adapt to changes in the airport acceptance? • Can airborne conflict management be performed in all ownship flight guidance modes? • Can AFR operations accommodate a range of RNP capabilities? • Conclusion: • Feasible at the integrated-system / laboratory-simulation maturity level • Further technical progress requirements identified • Sample challenges: Accommodating prediction uncertainties Flow-constrained descents Convective weather interaction Failure modes Traffic complexity management Complex AFR/IFR interactions

11. Airborne Precision Spacing A Terminal Arrival 4D-ASAS Concept Dr. Bryan Barmore NASA Langley Research Center bryan.barmore@nasa.gov

12. Airborne Precision Spacing ADS-B-enabled operation in which the ATSP assigns speed management for spacing to the aircraft Goal is to increase runwaycapacity by increasing the precision and predictability of runway arrivals ATSP manages traffic flow, ensures separation and determines the landing sequence Pilots precisely fly their aircraft to achieve ATSP-specified spacing goal A single strategic clearance reduces radio congestion and workload for both ATSP and pilots

13. Computes relative ETA at threshold Provides speed guidance to achieve desired relative ETA Safe merging is a consequence of beginning spacing operations early Spacing interval can be customized pair-wise to account for wake vortex hazard and other constraints Adjusts for dissimilar final approach speeds Corrects speed if necessary to prevent separation violations Gain scheduling to enhance stability of a aircraft stream Respects aircraft configuration limits for speed changes Lead:time to go = 22:15 APS Flight Deck Automation 30 seconds early at threshold  Slow down 5 knots Target: 90 secs Ownship:time to go = 23:15

14. Human-in-the-Loop Evaluation of APS Medium fidelity simulation results • Chicago O’Hare Flight Evaluation • Three equipped aircraft including NASA B757 • Wind shifts of 230º or more seen on base and final • Flight performance – 8 sec • Simulation performance – 2 sec • Medium fidelity simulation • Merging and in-trail operations • 9 aircraft stream (6 subject pilots) • No dependence on airspace design, type of operation or location in stream • 15-20 minute flight times

15. Fast-time Simulations DFW airspace with three merging streams Each data run had a stream of 100 aircraft / 40 repetitions per condition Wide range of aircraft types and performance (BADA model) Precision of approximately 2 sec under nominal conditions Challenges for significant initial spacing deviation; wind forecast errors and limited ADS-B range Knowing final approach speed gives significant improvement in spacing precision Improvements being made for wind updating and setting initial spacing requirements

16. CDA with Spacing Continuous Descent Approaches offer a fuel and time efficient descent while reducing ground noise and environmental pollutants However, ATSP must be largely “hands-off” resulting in loss of capacity to maintain safety By including airborne spacing we can realize the majority of the CDA benefits while maintaining capacity levels The ability to make only minor speed adjustments during the procedure allows the flight crew to stay close to the optimal CDA while maintaining spacing with other aircraft NASA is currently working with the FAA, other research organizations, a major airline and avionics vender to develop and implement merging & spacing This is seen as a first step to implementing airborne spacing in large, complex terminal environments

17. Preliminary Merging and Spacing Simulation Results Four CDA routes into DFW 350 nm routes Merges at cruise, downwind, base Nominal winds, initial spacing deviation Studied several disruptive events (not presented here) Results for nominal case: 0.21.3 sec for disturbances: -0.94.3 sec Separation at merge point

18. Current and Future NASA ResearchRelated to 4D-ASAS • Safety assessments of distributed airborne separation • Batch study on distributed strategic conflict management • Traffic complexity management through distributed control of trajectory flexibility • Development of flexibility metric, preservation function • Trajectory constraint minimization • Early implementation applications • Oceanic In Trail Procedure • Merging and spacing with continuous descents • Airborne Precision Spacing in super-density terminal arrival operations

19. Thanks for your attention. (Back-up charts follow)

20. En-RouteSafety Impact Assessment • Study performed by Volpe National Transportation Systems Center, Oct. 2004 • To provide NASA with information on potential safety impacts and risks that can be addressed during concept development, simulation, and testing • Approach: (1) Task-based analysis and (2) Simulation results analysis • Findings • Identified no safety showstoppers, several positive safety impacts, and several safety issues recommended for further research • Concept at early stages of R&D, too soon to determine safety relative to the current system • Ultimate assessment requires iterative safety analyses, determination of safety and performance requirements for systems and operators, and extensive testing • Safety Issues Recommended for Further Research (highlights) • Roll of automation: Need stringent criteria for availability, integrity, and accuracy • Unambiguous identification (air & ground) of AFR vs. IFR status • Determine need for ATSP awareness of AFR traffic, AFR-IFR conflicts • AFR awareness of AFR-IFR conflicts; AFR/ATSP coordination for short-term alerts • Upper limit of distributed authorities (AFR) for safe operations – complexity management* • AFR-to-IFR transition in non-normal situations; significant rates of metering non-conformance • Impact of degraded or erroneous intent information • Flight crew workload in descent • Preclusion of conflict propagation* * New R&D activities currently in progressor planned to address these issues

21. Safety DesignAOP’s Layered Approach to Distributed Separation Assurance Level 1 (L1) alert(low level alert) Pre-alert L2 alert(conflict alert) L3 alert(NMAC alert) ACAS Implicit coordination Strategic & tactical CR L3 alert(NMAC alert) Right-of-way rules Continuous surveillance X Display filtering Conflict preventionFlexibility preservation L2 alert(conflict alert) X Nearby aircraft L1 alert(low level alert) Maneuver restriction alerting L0 alert(traffic point out) Additional Protective Factors • Long look-ahead time horizon • On-condition intent-change broadcast • Intent-based automated conflict detection • Alert-based procedures • Rapid-update state surveillance • Human/automation redundancy Pre-alert Protection layers

22. 4D-ASAS Issues of ConcernFor Discussion and Possible Study • Socio-political acceptability • Social acceptance that a distributed-authority system is safe regardless of technical proof? • Political resistance to implementation of distributed system (users and service providers)? • Destabilization from gaming • Can this be mitigated using slot management? • Performance-achievement incentive • Is there sufficient incentive for users to always want to equip for higher ATM performance? • Short-distance flight benefits • Are there sufficient degrees of freedom? • Departure constraints impact on performance • Will users have sufficient departure-time control to achieve benefits? • Retrofit potential • Does forward-fitting meet the demand? • Are retrofit options technically feasible, cost-effective, and beneficial? • Mandate impact • What is the user cost/benefit impact if 4D-ASAS is mandated?