1. ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 Autonomous Aircraft Operations and the Resolution of ‘Over-constrained’ Conflicts David J. Wing * Dr. Karthik Krishnamurthy † Richard Barhydt * Dr. Bryan Barmore * * NASA Langley Research Center, Hampton VA USA † Titan Corporation, Hampton VA USA

2. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 2/18 Outline DAG-TM Concept Element 5 Overview ‘Over-Constrained’ Metering Scenario and Objective Experimental Approach and Setup Results and Summary Planned Joint Simulation of Air-Ground Integration in DAG-TM

3. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 3/18 DAG-TM CE-5 “En Route Free Maneuvering” Concept Overview

4. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 4/18 Arrival Metering of Autonomous Aircraft Design considerations to make constraints ‘achievable’ –What is the minimum metering interval consistent with airborne separation while converging to the fix? –How close to the fix can aircraft adjust to schedule changes? Nominal procedure: –ATS Provider establishes an arrival flow schedule to meet but not exceed airport capacity, and issues terminal entry clearances consisting of ‘Required Time of Arrival’ (RTA) and crossing restrictions at assigned terminal entry fixes. –Autonomous aircraft fly self-selected trajectories to meet the constraints while maintaining separation from traffic. Metering interval Schedule is set              Metering fix Separation zone To Airport

5. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 5/18 What about non-achievable constraints? –Constraints are often unrelated to each other, and could therefore be incompatible (e.g.,TFM, separation, weather/SUA, a/c perf., company prefs.) –Incompatibility could arise through failures in communication, data entry, or coordination –Example scenario of an over-constrained situation: separation loss at metering fix due to scheduling error –Result of significant system failure –“It would never happen” –Maybe, but studying extraordinary situations like this can help qualify inherent operational safety and stability characteristics of the basic concept An assessment of robustness to such failures is important to assessing concept feasibility –CE5 assumption: controller does not monitor autonomous aircraft separation –If monitoring is needed, this may seriously impact workload and procedures, and therefore cripple a key concept benefit – accommodating significant traffic growth Over-Constrained Situations

6. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 6/18 How robust are autonomous (distributed) operations in an over-constrained situation with no explicit coordination or centralized monitor (e.g., ATC)? Is a priority system needed to safely ensure the separation prevails over other constraints? Identical time and crossing altitude assignments Aircraft B Aircraft A SUA Experiment Research Issues and Scenario

7. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 7/18 Lab for investigating multi-aircraft operations (no ATC positions) Up to 8 interacting single-pilot stations using networked desktop simulators ADS-B modeling of message set, range, rate Aircraft simulation includes research prototype decision support tool for AFR operations Primary Flight Display Navigation / Traffic Display FMS / CDU Display and Glareshield Control Panels Pilot and Researcher Stations in NASA Air Traffic Operations Lab NASA Air Traffic Operations Lab Langley Research Center

8. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 8/18 Strategic FMS resolution Intent-based conflict alert State-based conflict alert Tactical GCP resolution Conflict prevention band Research Prototype Decision Support System for Airborne Conflict Management Time to Loss of Separation 10 min 5 min2 min0 min Intent Only Intent and State StrategicStrategic & TacticalTactical Detection: Resolution:

9. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 9/18 Priority Implemented Through Staggered Alerting Colors and implication based on MD-11 alerting conventions Alert level 0Traffic point out Conflict: Action optional Conflict: Action required Implication LoS Aircraft priority* Higher Lower 52 Minutes to Loss of Separation (LoS) 10 Symbology 1 2 * Modified VFR rule set used

10. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 10/18 Experiment Approach No priority rules Priority rules 1 2a Odd numbered pilots have priority All pilots have equal priority Even numbered pilots have priority 2b Pilot instructions –(#1) maintain separation; (#2) achieve waypoint constraints within tolerances –Receive an award for performing both most consistently (incentive) –If unable #2, ‘notify’ ATC at earliest time using ‘unable’ buttons –Perform secondary task: answering trivia questions when prompted (~90 sec.) 16 airline pilots (MD-11 or Airbus 319+) –6 hours training –Total of 10 data runs (includes Barmore and Barhydt data runs) –Questionnaires and debriefs ‘Unable’ buttons

11. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 11/18 Pilot Perspectives on Safety Pilot rankings –77% of the pilots rated the level of safety above neutral –36% of the pilots found the scenario completely safe –‘Less than neutral’ feedback Frustration at false alert Conflicts with no resolution guidance Unexpected simulation autoflight behavior Misunderstanding of separation requirements Frustration with finding conflict at RTA waypoint “Not at all safe” “Neutral” “Completely safe” “Considering the complete start-to-end scenario, including the conflicts and your resolution actions, what was the level of safety?”

12. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 12/18 Loss of Separation (LoS) Case 1 Initial descent to solve earlier conflict Pilot climbed on seeing other aircraft pass behind him First alert @ 10 minutes to conflict Alert terminated when pilot changed heading Brief LoS Aircraft A Aircraft B Premature climb by Aircraft B after observing Aircraft A pass behind his wing. Probable Cause of LoS Pass-behind counted as LoS in this simulation. Aircraft B declared ‘unable ALT’. Normally ATC would have assigned new altitude, precluding the climb. Relevant Factors Aircraft B’s path relative to Aircraft A Closest Point of Approach: 4.67 nm, 979 ft.

13. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 13/18 Initial descent to solve a different conflict First alert @ 5 minutes to conflict Pilot returned to FL 345, since other aircraft stayed high First alert @ 10 minutes to conflict Pilot climbs to FL355 to resolve Alert @ 5 minutes To conflict Erroneous descent by autoflight system Brief LoS Aircraft A Aircraft B Loss of Separation (LoS) Case 2 Simulation error: Unexpected descent by Aircraft A’s autoflight system below altitude limit set by pilot. Probable Cause of LoS Important Lesson Learned Fix the simulation errors Link the autoflight system to the conflict management tools, and use the ‘command’ trajectory for primary alerts. Aircraft A’s path relative to Aircraft B Closest Point of Approach : 1.92 nm, 998 ft.

14. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 14/18 Who Met Constraints Over-constrained conflicts –Setup: At least 1 pilot in each pair had to miss at least 1 constraint, by experiment design Key Findings –(1) All data runs: One-third of pilots met all constraints regardless of priority rules –(2) No priority rules: RH aircraft met all constraints more often than LH aircraft –(3) Priority rules: Only privileged aircraft met all constraints – increased predictability But still 1/3 of these did not False alerts and unnecessary maneuvering due to receiving traffic trajectory constraints (assigned RTA and altitude) in ADS-B message rather than the commanded trajectory Assigned Constraints: RTA <30 seconds Altitude < 500 ft Position < 2.5 nm

15. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 15/18 Who First Yielded Right-of-way Priority-based alerting –Objective: Reduce the probability of both aircraft moving simultaneously to resolve conflicts Key Findings –No priority rules: RH and LH aircraft were equally likely to maneuver first –Priority rules: Low priority aircraft was always first to maneuver – increased predictability Priority-based alerting successfully introduced a bias governing which aircraft would yield –Technique is suitable for complex priority rule sets LoS Aircraft priority Higher Lower 52 Minutes to Loss of Separation (LoS) 10

16. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 16/18 Experiment Summary Autonomous (distributed) operations was robust in this simulation of an over-constrained conflict scenario (potential hazard) –The absence of centralized monitoring and/or explicit coordination were not observed to be liabilities in protecting safety Priority rules were not observed to increase or decrease separation risks –Broadcasting state/intent information was sufficient coordination for airborne separation –Priority rules did increase predictability Broadcast of ‘command’ trajectory would reduce undesired maneuvering due to false alerts –Broadcasting assigned constraints was a factor in 1 of 2 separation loss events, and contributed to unnecessary disruption to traffic flow Implementation of priority system through staggered alerts was effective –Technique is suitable for complex priority rule sets, if needed

17. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 17/18 Planned Joint Simulation in Spring 2004 Objectives: –To investigate the feasibility of integrated (non-segregated) Managed (IFR) and Autonomous (AFR) operations –To test new CE5 roles/procedures for minimizing air/ground interaction in en-route and terminal transition –To test terminal arrival procedures related to CE11 merging and in-trail spacing Approach: Connect 2 NASA ATM research labs for real-time HITL simulation –Langley Air Traffic Operations Lab – joint sim focus is AFR operations –Ames Airspace Operations Lab – joint sim focus is ATC operations for mixed IFR/AFR traffic environment, and airborne human factors Environment: En-route, transition, and terminal arrival traffic flows –ZAB/ZFW Centers and DFW TRACON –~5 subject controllers, ~20 subject pilots (+ pseudo-pilots and automated traffic) –En-route / transition CD&R (including AFR/IFR conflicts) –Metering of AFR/IFR arrivals (including disruptions) –Merging and in-trail spacing in TRACON (DAG-TM Concept Element 11)

18. 5 th USA/Europe Air Traffic Management R&D Seminar Budapest June 2003 ADVANCED AIR TRANSPORTATION TECHNOLOGIES DISTRIBUTED AIR/GROUND-TRAFFIC MANAGEMENT David J. Wing, NASA Langley Research Center 18/18 New CE-5 Roles & Procedures for Air/Ground Interaction  Maintains separation from all* aircraft »Extra separation margin given to IFR aircraft where feasible to minimize impact on ATS Provider »Ensures no near-term conflicts are created by maneuvering or changing intent  Selects and flies user-preferred trajectory »Maneuvers by AFR aircraft do not require clearance from ATS Provider (similar to VFR) »Trajectories selected to meet flight safety, fuel efficiency, performance limitations, and company preferences »Includes avoiding convective weather and maximizing passenger comfort »Unrestricted route & altitude except SUA’s established by ATS Provider  Conforms to TFM constraints »Adjusts path and speed to meet Required Time of Arrival (RTA) received from ATS Provider »Notifies ATS Provider if unable to meet RTA or crossing restrictions; request new assignment or alternative »Conformance required to gain terminal area access Air Traffic Service (ATS) ProviderAutonomous Flight Rules (AFR) Aircraft  Separates IFR aircraft only* and monitors IFR conformance to flow/airspace constraints »Uses advanced tools and data link for enhancing IFR operations efficiency and tightening TFM tolerances  Establishes flow & airspace constraints for system-wide & local TFM »Meters AFR and IFR arrivals by assigning RTA’s (AFR) and speeds/vectors or data link trajectories (IFR) »Provides AFR aircraft an IFR clearance to enter terminal area (at which time AFR becomes IFR)  Not responsible for monitoring AFR ops* »Exception: Avoids creating near-term conflicts between AFR/IFR aircraft when maneuvering IFR aircraft »AFR aircraft treated much like VFR aircraft; relies on AFR aircraft to separate from IFR aircraft »Not responsible for ensuring AFR aircraft meet RTA *Key changes