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Modeling Requirements to Support Assessment of NextGen Mid-Term Performance

Victor H. L. Cheng*, Gregory D. Sweriduk†, S. Sai Vaddi†, Monish D. Tandale†, and Anthony Y. Seo‡

Optimal Synthesis Inc., Los Altos, CA 94022

Paul D. Abramson§

PDA Associates, Wayland, MA 01778

Edmund J. Koenke**

Genasys Consulting Services, Mays Landing, NJ 08330

The Next Generation Air Transportation System (NextGen) Concept of Operations addresses air transportation operations in the 2025 timeframe. Although NextGen is expected to include revolutionary solutions for handling the anticipated increase in demand in the National Airspace System (NAS) in this timeframe, implementation of the new systems and procedures will still have to evolve over time. Assessment of NextGen performance needs to address the target timeframe of 2025, as well as reasonably defined intermediate time points to understand its progression. The FAA has released its NextGen Implementation Plan (NGIP) to address the FAA’s portion of the work needed to realize NextGen, covering the FAA’s plan through the mid-term period of 2018. This NGIP serves as a good source of information to assess the NextGen mid-term performance as a transitional step towards the envisioned 2025-timeframe NextGen. This paper describes a study to establish the mid-term NextGen performance for defining scenarios for analyses of integrated concepts, technologies, and procedures under development in NASA’s Airspace Systems Program amidst projected FAA infrastructure development. The study involves a two-step process: it starts with a careful analysis of the NGIP documents in conjunction with an extensive literature search to identify research results applicable to NextGen to sort out the concepts, activities, and technologies, resulting in a proposed subset of these items; the process then focuses on the selected NGIP items to recommend modeling options to support simulation assessment of NextGen mid-term performance.

I. Introductionhe FAA Joint Planning and Development Office (JPDO) has developed a Concept of Operations (ConOps) for the Next Generation Air Transportation System1 (NextGen). The ConOps provides an overall, integrated view

of NextGen operations in the 2025 timeframe. In collaboration with the FAA and other agencies, NASA has organized NextGen projects2,3 to explore and develop integrated solutions involving ground and air automation concepts and technologies to allow NextGen to handle the anticipated increase in demand in the National Airspace System (NAS). With new operational concepts involving new procedures and technologies being developed, the research projects also have the responsibility to develop and apply system design and analysis methodologies, and simulation tools, for comprehensive assessment of the various design alternatives.

In the mean time, the FAA is accelerating the implementation of NextGen in the pursuit of a safer and more efficient NAS. The release of the FAA’s NextGen Implementation Plan4 (NGIP) in 2008 reflects a shift in focus from concept definition to tangible execution planning with a name change of its management plan from the “Operational Evolution Partnership” (OEP). The NGIP is meant to address the FAA’s portion of the work needed to * Principal Scientist, 95 First Street, Suite 240, and AIAA Associate Fellow. † Research Scientist, 95 First Street, Suite 240, and AIAA Member. ‡ Research Engineer, 95 First Street, Suite 240. § 4 Hampshire Road, and AIAA Senior Member. ** 420 Highland Drive.

T

9th AIAA Aviation Technology, Integration, and Operations Conference (ATIO) <br>and <br>Air21 - 23 September 2009, Hilton Head, South Carolina

AIAA 2009-6976

Copyright © 2009 by Optimal Synthesis Inc. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

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realize NextGen. Both the 2008 NGIP and the subsequent 2009 version5 cover the FAA’s plan through the mid-term period of 2012–2018, with the 2009 version showing a shift in focus to address the planned infrastructures to help stakeholders plan for their investments. It is important that any assessment of the NextGen system-level ConOps accounts for the progression of NextGen development, and the FAA’s NGIP serves as a useful source of information for identifying the mid-term NextGen capabilities. This paper documents an effort to develop modeling options for simulation assessment of NextGen mid-term performance in a two-step process, by (i) performing a careful analysis of NGIP and combining that with an extensive literature search to sort out and select the NextGen concepts, activities, and technologies with significant capacity benefits expected by 2018, followed by (ii) focusing on the selected NGIP items to research their expected benefits in mid-term NextGen and produce recommendations for their modeling. The results from these two steps are described in the two following sections, with more details captured in a couple of separate reports6,7.

II. Identification and Selection of NextGen Concepts, Activities, and Technologies

A. Decomposition of the NextGen Implementation Plan Two versions of NGIP currently exist, respectively from 20084 and 20095. The 2008 NGIP includes more detail

of the concepts, activities, and technologies in the form of solution set smart sheets, whereas the 2009 version appears to restrict its focus on the planned infrastructures to help stakeholders plan for their investments. Since the 2008 NGIP provides a broader view of midterm NextGen that is not contradicted by the 2009 version, the current study is based primarily on the items discussed in the 2008 NGIP. The 2008 NGIP contains (i) a report on recent accomplishments and several pending NextGen concept demonstrations, and (ii) a management plan that discusses the research, policy and requirement developments, and other activities and proposed system changes expected to be delivered in the mid-term. Some of the mid-term capabilities have some near-term commitments to be delivered prior to 2012. Furthermore, the NGIP has grouped the mid-term operational capabilities into three separate domains:

Airport Development Domain Air Traffic Operations Domain Aircraft & Operator (A&O) Requirements Domain

Table 1 lists the items identified in NGIP, grouped according to the three domains (down the rows) and the timeframes (across the columns). For this table, all airport enhancements identified for the 35 OEP airports are considered a single item, and all such enhancements considered for the identified list of metropolitan areas are considered another single item. A total of 86 items are identified from the NGIP document. The approach for down-selecting the NGIP items is described in the following section.

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Table 1. Identification of NGIP Items Already Accomplished 2009–2011 2012–2018

Airport Center Taxiway at LAX Surface Automation Technology

Airport Surface Detection Equipment

OEP 35 Airports OEP Metropolitan Areas ASDE-X Deployments

Air Traffic Operations

Closer Simultaneous Landing Operations

RNAV & RNP WAAS OPD Airspace Design and Improvement

New York Initiatives Improved ILS RVR Landing Capabilities

Modernizing Traffic Management on Surface at JFK

AIRE and ASPIRE CDA Trials at Atlanta 3D PAM at Denver Tailored Arrivals at MIA Predictive Weather Demo at DAB

Oceanic Enhancements at MIA

Weather Advisory Info to the Flight Deck

Airspace Flow Program Time-Based Metering Procedures National Aviation Safety Policy National Standard for Safety Management

Initial System-Wide Integrated Assessments

Data Fusion Demonstration Data Fusion from all Sources Enabled

RNAV STAR-Based Optimized Profile Descents

Integrated Surface Data Vision Systems in Reduced Visibility Conditions

RNAV SIDS and STARS RNP SAARS LPV Approaches Reroute Impact Assessment and Automation

ATC Surveillance via ADS-B Full Implementation of Safety Management System

Execution of Flow Strategies Airspace Redesign Projects for New York, Houston, and Chicago

Expanded Traffic Advisory Service En Route Automation Modernization ERAM

Simultaneous Non-Interfering Operations

Airspace Procedures and Enhancements – Western Corridor & Nevada

Airspace Procedures and Enhancements – High Altitude Airspace Management

Category II Operations on Type I ILS

Terminal Automation Modernization- Replacement

Terminal Flight Data Management Collaborative Air Traffic Management

Aeronautical Information Management

NextGen Weather Processor

Flexible Airspace Management Increase Capacity and Efficiency Using RNAV and RNP

Delegated Responsibility for Separation Automation Support for Mixed Environments Initial Conflict Resolution Advisories Point-in-Space Metering Oceanic In-Trail Climb and Descent Flexible Entry Times for Oceanic Tracks Integrated Arrival/Departure Airspace Management Improved Operations to Closely-Spaced Parallel Runways

Time-Based Metering Using RNP and RNAV Route Assignments

Initial Surface Traffic Management Use Optimized Profile Descent Provide Full Surface Situation Information Wake Turbulence Mitigation for Departures Ground-Based Augmentation System (GBAS) Precision Approaches

Enhanced Surface Traffic Operations Trajectory Flight Data Management Provide Full Flight Plan Constraint Evaluation with Feedback

On-Demand NAS Information Traffic Management Initiatives with Flight Specific Trajectories (Go Button)

Continuous Flight Day Evaluation Improved Management of Airspace for Special Use Trajectory-Based Weather Impact Evaluation Safety Management System (SMS) Implementation

Safety Management Enterprise Services Aviation Safety and Information Analysis and Sharing (ASIAS)

Operational Security Capability for Threat Detection and Tracking, NAS Impact Analysis and Risk-Based Assessment

Shared Situational Awareness and Information Systems Security Integrated Incident Detection and Response

Information on System Security and Surveillance Integration/Protection

National Environmental Management System (EMS)

Enhanced Air Traffic Procedures, Improved Environmental Technologies and Sustainable Alternative Aviation Fuels, and Integrated Environmental Modeling

Integration, development, and operations analysis capability

NextGen Facilities Net-centric Virtual Facilities

A&O Aircraft and Operator Requirements

B. Selection of Items for Inclusion in Modeling Considerations The following approach is used to down-select from the 86 items of concepts, activities, and technologies

identified from the NGIP:

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The description of the individual NGIP items were gathered from the NGIP document itself and the numerous solution-set smart sheets8–12 accompanying the document, as well as other reference documents. Two subjective ratings were assigned to each item. The first dealt with the expected level of benefits that the item might deliver. This was assigned a rating of High, Medium, or Low. The second dealt with the presumed difficulty in modeling the item for inclusion in planned concept assessment simulations. Modeling and simulation of the concepts are expected to be performed using the Airspace Concept Evaluation System13,14 (ACES) developed by NASA, and so the measure of difficulty of modeling is based on the ACES functionality anticipated to be available for assessment in the near future. The levels of benefits are determined based on the expected contribution of a given item to improvements in the following capacity and efficiency metrics: (i) delay, (ii) capacity, (iii) throughput, and (iv) fuel consumption. Items that primarily focused on improving safety and reducing controller workload reduction are important in and of themselves, but their benefit on capacity may be small and they are deemed difficult to model. Therefore, such items are not recommended for inclusion for assessment considerations. Items whose benefits can be modeled using implicit modeling approach (by modifying input parameters) in ACES are assigned “low” for “difficulty of modeling.” Certain items are identified as enabling technologies; these items are not expected to directly contribute to increase in capacity or efficiency. Their benefits would be captured by other selected items that could have an impact on capacity or efficiency. In some cases, an enabling technology may be realized by the mid-term timeframe while the technology or concept that it enables may not be realized until sometime later. These items are not recommended for inclusion for NextGen mid-term assessment considerations. In some cases the scope of accomplished items and items scheduled for near-term frame is identified to be similar to certain mid-term items. The level of benefits, difficulty of modeling and recommendation for inclusion are deferred to the mid-term items that subsume these items.

Table 2 lays out the criteria used for selection of items for inclusion in modeling considerations based on the level of benefits and difficulty of model.

Table 2. Criteria for Selection of Concepts for Inclusion in Modeling Considerations

Difficulty of Modeling

High Medium Low

Level of Benefits

High Yes Yes Yes

Medium No Yes Yes

Low No No No

Listed in Table 3 are the 86 items identified from the NGIP document, their expected level of benefits, difficulty of modeling, and the recommendation for inclusion in modeling considerations. The symbols ‘L’, ‘H’, ‘M’ correspond to the Low, High, and Medium ratings of Table 2, and the symbols ‘Y’, ‘N’, and ‘S’ represent recommended for inclusion, not recommended for inclusion, and subsumed by another item, respectively. The criteria summarized above have helped to narrow down the number of NGIP items to 13 essential ones for further consideration for modeling to support the assessment of NextGen mid-term performance, and these items are emphasized with bold fonts in Table 3. As noted above, many of the items not selected are merely subsumed by other items, or their capacity-related benefits are not as significant relative to the other items; their non-selection by no means should be construed as a lack of benefits.

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Table 3. Assessment of NGIP Items

No NGIP Item

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1. Surface Automation Technology - - S Subsumed by items 62 & 64 2. Center Taxiway at LAX - - S Subsumed by item 18 3. ASDE-X - - S Subsumed by item 28 4. Closer Simultaneous Landing Operations - - S Subsumed by item 60 5. Area Navigation (RNAV) & Required Navigation

Performance (RNP) - - S Subsumed by item 52

6. Wide Area Augmentation System (WAAS) - - S Subsumed by item 66 7. Optimized Profile Descent (OPD) - - S Subsumed by item 63 8. Airspace Design and Improvement. - - S Subsumed by item 39 9. New York Initiatives - - S Subsumed by items 39, 60 10. Improved ILS Runway Visual Range (RVR)

Landing Capabilities - - S Subsumed by item 66

11. Modernizing Traffic Management on the Airport Surface: Demonstrations at John F. Kennedy International Airport (JFK), August 2008

- - S

Item not permanent infrastructure or new operating procedure

12. AIRE and ASPIRE: International partnerships for “greening” aviation L H N

Environmental item; does not contribute to capacity/efficiency; oceanic airspace not within the scope of ACES

13. Continuous Descent Arrivals Flight Trials at Hartsfield-Jackson Atlanta International Airport (ATL), May 2008; Flight Trials at Miami International Airport (MIA), June 2008

- - S

Item not permanent infrastructure or new operating procedure

14. Three-Dimensional Path Arrival Management Simulations, September 2008; Flight Trial at Denver International Airport (DEN), September 2009

- - S

Item not permanent infrastructure or new operating procedure

15. Tailored Arrivals Flight Trial at MIA, September 2008

- - S Item not permanent infrastructure or new operating procedure

16. Predictive Weather Demonstration FY09: Initial system concept demonstration at Daytona Beach International Airport (DAB)

- - S Item not permanent infrastructure or new operating procedure

17. Oceanic Enhancements Flight Trial at MIA, May 2008 - - S

Item not permanent infrastructure or new operating procedure

18. OEP 35 Airports H M Y Recommended 19. Metro Areas - - S Specific instances (NY, Chicago, Houston) are

covered by item 39 20. Weather Advisory Information to the Flight Deck via

Flight Information Services-Broadcast (FIS-B) L H N Enabling technology; difficult to model impact

on capacity/efficiency 21. Airspace Flow Programs H L Y Recommended 22. Time-Based Metering Procedures - - S Subsumed by items 56, 61 23. National Aviation Safety Policy

L H N Safety policy does not directly contribute to increase in capacity/efficiency

24. National Standard for Safety Management L H N

Safety standards do not directly contribute to increase in capacity/efficiency

25. Initial System-Wide Integrated Assessments L M N

Item not permanent infrastructure or new operating procedure

26. Data Fusion Demonstration - - S

Item not permanent infrastructure or new operating procedure

27. Data Fusion from All Sources Enabled L H N

Enabling technology; difficult to model impact on capacity/efficiency

28. ASDE-X Deployments L H N Enabling technology; difficult to model impact on capacity/efficiency

29. RNAV STAR-Based Optimized Profile Descents - - S Subsumed by item 63 30. Integrated Surface Data - - S Subsumed by item 64

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No NGIP Item

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31. Vision Systems in Reduced Visibility Conditions L H N

Item could have significant impact on capacity; however, it is not clear if the technology will be operational by mid-term

32. RNAV Standard Instrument Departures (SIDs) and Standard Terminal Arrival Routes (STARs) H L Y Recommended

33. RNP SAAARs H L Y Recommended 34. LPV approaches M H N Item will lower approach minima but will not

increase capacity 35. Reroute Impact Assessment and Automation M H N Enabling technology; difficult to model impact

on capacity/efficiency 36. Air Traffic Control Surveillance Service in Non-

Radar Areas via ADS-B L H N Enabling technology; difficult to model impact

on capacity/efficiency 37. Full Implementation of the Safety Management

System for FAA’s Air Traffic Organization L H N Safety management system does not directly

contribute to increase in capacity/efficiency 38. Execution of Flow Strategies L H N Enabling technology 39. Airspace Redesign Projects for New York,

Chicago, and Houston M M Y Recommended

40. Expanded Traffic Advisory Services. Using Digital Traffic Data via Traffic Information Services-Broadcast (TIS-B)

L H N Enabling technology; difficult to model impact on capacity/efficiency

41. En Route Automation Modernization (ERAM) L H N Enabling technology; difficult to model impact on capacity/efficiency

42. Simultaneous Non-interfering Operations L H N Item primarily focused on helicopter traffic 43. Airspace Procedures and Enhancements –

Western Corridor & Nevada L H N

Not enough details available for modeling

44. Airspace Procedures and Enhancements – High-Altitude Airspace Management - - S

Subsumed by 52

45. Category II Operations on Type 1 ILS L H N Difficult to model and limited impact 46. Terminal Automation Modernization - Replacement L H N Enabling technology; difficult to model impact

on capacity/efficiency 47. Terminal Flight Data Management L H N Difficult to model impact on capacity/efficiency 48. Collaborative Air Traffic Management - - S Subsumed by items 68–73 49. Aeronautical Information Management L H N Difficult to model impact on capacity/efficiency 50. NextGen Weather Processor L H N Enabling technology; difficult to model impact

on capacity/efficiency 51. Flexible Airspace Management H H Y Recommended 52. Increase Capacity and Efficiency Using RNAV

and RNP H H Y Recommended

53. Delegated Responsibility for Separation M H N Difficult to model impact on capacity/efficiency 54. Automation Support for Mixed Environments M H N Difficult to model impact on capacity/efficiency 55. Initial Conflict Resolution Advisories M H N Difficult to model impact on capacity/efficiency 56. Point-in-Space Metering - - S Item similar in content to 61 57. Oceanic In-Trail Climb and Descent M H N Oceanic airspace not within the scope of ACES 58. Flexible Entry Times for Oceanic Tracks M H N Oceanic airspace not within the scope of ACES 59. Integrated Arrival/Departure Airspace Management

- - S Specific instances (NY, Chicago, Houston) covered by 39

60. Improved Operations to Closely-Spaced Parallel Runways H L Y Recommended

61. Time-Based Metering Using RNP and RNAV Route Assignments M L Y Recommended

62. Initial Surface Traffic Management H L Y Recommended 63. Use Optimized Profile Descent H H Y Recommended 64. Provide Full Surface Situation Information M M Y Recommended 65. Wake Turbulence Mitigation for Departures M M Y Recommended 66. Ground-Based Augmentation System (GBAS)

Precision Approaches M H N Enabling technology; difficult to model impact

on capacity/efficiency 67. Enhanced Surface Traffic Operations M H N Enabling technology; difficult to model impact

on capacity/efficiency

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No NGIP Item

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68. Trajectory Flight Data Management L H N Enabling technology; difficult to model impact on capacity/efficiency

69. Provide Full Flight Plan Constraint Evaluation with Feedback

M H N Enabling technology; difficult to model impact on capacity/efficiency

70. On-Demand NAS Information L H N Enabling technology; difficult to model impact on capacity/efficiency

71. Traffic Management Initiatives with Flight Specific Trajectories (Go Button)

M H N Enabling technology; difficult to model impact on capacity/efficiency

72. Continuous Flight Day Evaluation L H N Enabling technology; difficult to model impact on capacity/efficiency

73. Improved Management of Airspace for Special Use M H N Benefits not applicable to generic NAS 74. Trajectory-Based Weather Impact Evaluation M H N Enabling technology 75. Safety Management System (SMS) Implementation L H N All these items primarily deal with safety and

security and do not directly contribute to increase in capacity and efficiency.

76. Safety Management Enterprise Services L H N 77. Aviation Safety and Information Analysis and

Sharing (ASIAS) L H N

78. Operational Security Capability for Threat Detection and Tracking, NAS Impact Analysis and Risk-Based Assessment

L H N

79. Shared Situational Awareness and Information Systems Security Integrated Incident Detection and Response

L H N

80. Information on System Security and Surveillance Integration/Protection L H N

81. National Environmental Management System (EMS) L H N

Environmental items; do not directly contribute to increase in capacity or efficiency

82. Enhanced Air Traffic Procedures, Improved Environmental Technologies and Sustainable Alternative Aviation Fuels, and Integrated Environmental Modeling

L H N

83. Integration, development, and operations analysis capability

L L N Test facility; does not directly contribute to increased capacity/efficiency

84. NextGen Facilities L L N

New facilities; does not directly contribute to increased capacity/efficiency

85. Net-centric Virtual Facilities L L N

Not expected to contribute to direct increase in capacity/efficiency

86. Aircraft and Operator Requirements L H N

Not expected to contribute to direct increase in capacity/efficiency

The 13 items selected for further modeling considerations are shown in Table 4, which groups these items according to the nature of the expected improvements. The benefit mechanism, benefitted NAS segment, and the weather conditions under which the benefits are applicable are also listed. This table has expanded the 13 items into 15 because (i) Area Navigation (RNAV) Standard Terminal Arrivals (STARs) and RNAV Departure Procedures (DPs) are treated as separate items to account for their different grouping, and (ii) the new runway constructions and new taxiway constructions of the OEP 35 airports are similarly treated as separate items. The aforementioned distinctions are made owing to the different benefit mechanism of these items. In addition, the item #52 “Increase Capacity and Efficiency Using RNAV and Required Navigation Performance (RNP)” in Table 3 has been renamed “En Route RNAV/RNP” in Table 4 to distinguish it from the Terminal items “RNAV STARs” and “RNAV DPs,” and item #61 “Time-Based Metering Using RNP and RNAV Route Assignments” of Table 3 has been renamed “Time-Based Metering” in Table 4.

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Table 4. Summary of NGIP Items Recommended for Inclusion in Modeling Recommendations

NGIP Item Item Grouping Benefit Mechanism Benefitted NAS Segment

PertinentWeather

Condition

A. Airspace Flow Programs

En Route Improvements

Advanced Ground Delay Program Reduced Overall Delay

En route,Terminal & Airport

En route Storms

B. Flexible Airspace Management Homogenous Distribution of Flights

Increased Effective Sector Capacity

En route All Conditions

C. En Route RNAV/RNP Shorter Flight Paths Reduced Flight

Times

En route All Conditions

D. Airspace Redesign Projects in NY-NJ-PHL, Chicago, and Houston

Terminal Area Efficiency Improvements

Reduced Terminal Area Delay

Terminal Area (Arrivals & Departures)

All Conditions

E. RNAV STARs Shorter TRACON Distances Reduced Terminal Area Time

Terminal Area (Arrivals)

All Conditions

F. Optimized Profile Descent Reduced Fuel Consumption

Terminal Area (Arrivals)

All Conditions

G. RNP SAAARs

Arrival/Departure Capacity/Throughput Improvements

Increased Arrival Capacity Under Low-Visibility Conditions

Terminal Area(Arrivals)

MVMC, IMC

H. Improved Operations to Closely Space Parallel Runway Operations

Increased Arrival Capacity Under Low-Visibility Conditions

Terminal Area(Arrivals)

MVMC, IMC

I. Time-Based Metering Reduced Congestion at Metering Fixes Increased Throughput

Terminal Area (Arrivals & Departures)

All Conditions

J. New Runways at OEP 35 Airports Increased Arrival/Departure Capacity

Runways (Arrivals & Departures)

All Conditions

K. RNAV DPs Increased Departure Capacity

Terminal Area (Departures)

All Conditions

L. Wake Turbulence Mitigation for Departures

Increased Departure Capacity

Runways ( Departures)

All Conditions

M. Initial Surface Traffic Management Departure SequencingIncreased Departure Throughput

Runways (Departures)

All Conditions

N. New Taxiways at OEP 35 Airports Taxi Time & Taxi Delay Improvements

Reduced Taxi Time Taxiways All Conditions

O. Provide Full Surface Information Reduced Taxi-Time and Delay

III. Modeling Recommendations for Selected Concepts, Activities, and Technologies

A. Description and Benefits of NGIP Items Recommended for Inclusion in Modeling Considerations This section provides the descriptions of the 15 selected items tabulated in Table 4 and identifies their benefits to

be considered for their modeling. The descriptions are extracted directly from the NGIP documents4,5, and the benefits are assembled from the NGIP documents as well as published results from other research and development efforts as noted.

1. Airspace Flow Programs

Description: An Airspace Flow Program (AFP) is a traffic management process that identifies constraints in the en route system, develops a real-time list of flights that are filed into the constrained area, and distributes expected departure clearance times (EDCT) to meter the demand through the area. The approach is to merge Ground Delay

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Program (GDP) rationing algorithms with Flow Constrained Area (FCA) airspace depiction and flight list generation. This allows for formal control times to be issued to flights traversing a congested volume of airspace while more accurately defining which flights need to be controlled. These tools reduce en route congestion due to weather by equitably managing departure times, achieved by assigning ground delays to a specific airspace volume (this item was a near-term commitment in the 2008 NGIP and does not appear in the 2009 NGIP). The principal goal for the initial deployment will be to provide enhanced en route traffic management during severe weather events. Benefits Identified: Airspace flow programs are expected to reduce delay under en route bad weather conditions. The FAA reports a 9% reduction in delays in the Northeast under bad weather conditions while implementing AFPs at seven airports15.

2. Flexible Airspace Management

Description: Today’s airspace configurations and sector boundaries are pre-determined based on historical flows and pre-defined boundaries. This imposes a capacity constraint on the system during periods of peak demand, airspace use restrictions, and convective weather. Currently, airspace management techniques are implemented by degrees: for example, flight data, other automation functions (e.g., automated handoff), and the controller’s map displaying changes when the airspace is reconfigured. In another example, only the map would display changes. Each of these implementations requires adaptation in advance of their use. They will be used to varying degrees by different facilities and individuals, according to standard and/or individual practices. ANSP automation supports reallocation of trajectory information, surveillance, communications, and display information to different positions or different facilities. It redistributes controller capacity to meet demand. Automation enhancements enable increased flexibility to change sector boundaries and airspace volume definitions in accordance with pre-defined configurations. The extent of flexibility has been limited due to limitations of automation, surveillance, and communication capabilities. Examples of these limitations include primary and secondary radar coverage, availability of radio frequencies, and ground-communication lines. New automated tools will define and support the assessment of alternate configurations as well as re-mapping of information (e.g., flight and radar) to the appropriate positions. Benefits Identified: Flexible airspace management is expected to reduce en route delays. Research developed towards a 2025 timeframe shows substantial delay reduction16. However, it is unclear what portion of these benefits applies to the 2018 timeframe.

3. En Route RNAV/RNP

Description: Traditional airways are based on a system of routes among ground-based navigational aids. These routes require significant separation buffers. The constraint of flying from one navigational aid to another generally increases user distance and time. It can also create choke points and limit access to NAS resources, e.g., when severe weather forces the closure of some airport arrival fixes. RNAV and RNP will permit the flexibility of point-to-point operations and allow for the development of routes, procedures, and approaches that are more efficient and free from the constraints and inefficiencies of the ground-based NAVAIDS. RNAV and RNP will enable safe and efficient procedures that address the complexities of terminal operation through repeatable and predictable navigation. These will include the ability to implement curved approaches. Advanced RNAV includes the ability to access a navigation database containing the points, routes, speeds and altitudes for a specific procedure. This data may be loaded into an aircraft flight management system (FMS) or instrument-flight-rule-certified GPS system creating a path that can be followed using the flight director or autopilot. This capability can also be combined with an Instrument Landing System (ILS) to improve the transition onto an ILS final approach and to provide a guided missed approach. RNP is RNAV with onboard navigation monitoring and alerting. RNP is a statement of navigation performance necessary for operation within a defined airspace. Benefits Identified: RNAV routes are expected to reduce flight distance, flight times, and fuel consumption in the en route segment. An FAA study in the Southeast Region (over 15% of the total NAS traffic) showed approximately 1.5% reduction in flight times, distances, and fuel burn17.

4. Airspace Redesign for NY-NJ-PHL, Chicago, Houston

Description: Implement integrated routes and airspace. Add routes, change ATC procedures to reduce congestion in the New York metropolitan area and Philadelphia, Chicago, and Houston. NYICC would control a large area using terminal separation rules with the higher-altitude portion operating with en route separation rules. The inefficiencies associated with transfer of control from one facility to another are minimized. Many new routes are available to NY departures. Arrivals are rearranged so that airspace constraints do not prevent use of dual approaches to Newark at times of heavy arrival demand.

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Benefits Identified: Airspace redesign projects are expected to reduce delays in NY-NJ-PHL terminal airspace (3 min18) and Houston terminal airspace (4.38 min19). Airspace redesign projects in Chicago terminal airspace are expected to reduce flight times by 6 min20.

5. RNAV STARs

Description: RNAV allows more flexibility in designing STARs and reduces uncertainties in flight paths. RNAV STARs also reduce communications between the cockpit and ATC. RNAV Standard Terminal Arrival procedures (STARs) take advantage of this capability. Benefits Identified: RNAV STARs are expected to reduce flight distances and flight times in the terminal area. Studies conducted at Las Vegas and Phoenix airports reported 1.3% and 0.8% reductions in flight distances, respectively21,22.

6. Use Optimized Profile Descent

Description: An Optimized Profile Descent (OPD), in its optimal form, is an arrival where aircraft is cleared to descend from cruise altitude to final approach using the most economical power setting at all times. Based on published arrival procedures at final approach, aircraft begin a continuous rate of descent using a window of predetermined height and distance. Thrust may be added to permit a safe, stabilized approach speed and flap configuration down a glide slope to the runway. As an initial step, conventional or RNAV STARs can be defined with vertical constraints incorporated as crossing restrictions. Careful selection of constraints allows most aircraft FMS VNAV systems to calculate a continuously descending flight path, although the flight path may require a slightly non-optimal power setting. In addition, static spacing guidance, based on weight class and winds, as well as speed commands for descending traffic, allows STARs to be used with minimal impact on airport throughput, although with a slight additional environmental penalty compared to the ideal STAR OPD. At busy airports, achieving full fuel/emissions/noise benefits will be difficult without impacting capacity, unless advanced avionics and/or ground capabilities, and perhaps larger-scale airspace redesign are added.

Benefits Identified: Predominantly, NAS-published arrival procedures contain combinations of descending and level segments when defining paths from cruise airspace to a runway-approach procedure. Level segments require the use of higher engine power settings, resulting in excess fuel consumption and noise. An OPD is an arrival procedure where aircraft is cleared to descend from cruise altitude to final approach using the most economical power setting at all times. OPDs will permit aircraft to remain at higher altitudes on arrival at the airport and use lower power settings during descent. OPD arrival procedures will provide for lower noise and more fuel-efficient operations. The ANSP procedures and automation to accommodate OPDs will be employed, when operationally advantageous. Optimized profile descents can result in significant fuel savings. The FAA estimates a saving of at least 50 gallons per OPD landing4.

7. RNP SAAARs

Description: Special authorization by the FAA is required to conduct RNP approaches. RNP Special Aircraft and Aircrew Authorization Required (SAAAR) is the first public implementation of RNP in the NAS. RNP SAAARs reduce delay and increase capacity in reduced visibility. Benefits Identified: According to a MITRE study the following three applications of RNP SAAARs are expected to contribute to increased arrival capacity under MVMC and IMC23: (i) RNP parallel approach and transition, (ii) RNP dual approaches, and (iii) simultaneous converging instrument approaches. According to the study, RNP dual approaches on closely-spaced parallel runways enabled by RNP SAAARs can increase arrival capacity under IMC at the following airports: ATL, DTW, JFK, PDX, SEA and STL. Simultaneous converging instrument approaches enabled by RNP SAAARs can increase arrival capacity under IMC at the following airports: DFW, IAD, MSP, ORD, PHL, and PIT.

8. Improved Operations to Closely-Spaced Parallel Runways

Description: Maintaining access to closely-spaced parallel runways in limited visibility conditions by integrating new aircraft technologies will ensure safety through precision navigation, aircraft-based monitoring of the aircraft on the parallel approach, and flight guidance to avoid wake vortex generated by parallel traffic. This capability will apply aircraft-based technologies to maintain access in Instrument Meteorological Conditions (IMC), as well as support a new IFR standard for runway spacing. A number of other intermediate concepts for maintaining access to parallel runways continue being explored (e.g., use of RNP approaches to define parallel approaches with adequate spacing and visual transition to the runway).

Benefits Identified: Currently, dependent (staggered) operations are allowed in IMC on parallel runways between 2500 ft and 4300 ft. Improved throughput is needed during ceiling and visibility conditions that are less than Visual

American Institute of Aeronautics and Astronautics 11

Meteorological Conditions (VMC) on these runways, as well as those more closely spaced than 2500 ft. Establishing criteria for closely-spaced runways will allow airports to include new runway construction plans compatible with long-term NextGen operations. Enhanced procedures (including cockpit and ground improvements) will allow improvements in operations to parallel runways. This will reduce the impact to airport/runway throughput in lower-visibility conditions.

9. Time-Based Metering

Description: RNAV, RNP, and time-based metering (TBM) provide efficient use of runways and airspace in high-density airport environments. RNAV and RNP provide users with more efficient and consistent arrival and departure routings and fuel-efficient operations. Metering automation will manage the flow of aircraft to meter fixes. This will provide more efficient use of runways and airspace.

Benefits Identified: The current airport environment requires additional capacity. In addition, orderly arrival-spacing of traffic is necessary if congestion, delays, and risky terminal area maneuvering are to be avoided. Currently, spacing is monitored through a series of vectors and speed changes, based on existing fixes. Building on increased capacity in terminal separation procedures, time-based metering will facilitate efficient arrival and departure flows. This will be accomplished using RNAV and RNP routings, coupled with meter-fix crossing times.

Vandevenne & Andrews show runway throughput is 38–39 flights/hr with TBM vs. 34 flights/hr (12%–15%) with MIT24.Hansen & Peterman found TBM raised throughput by 1.2 flights/15 min, arrival handling capability by 7.8% at LAX25.Knorr, et al.26 found TMA increased arrival rate by 0.4 flight/hr and operations rate by 2.5 ops/hr, and decreased flight distances by 4.8 nmi and 8.2 nmi under VMC and IMC, respectively. Idris, et al.27 found McTMA reduced average delay almost 50% with increased capacity and increased throughput from 2.1%–4.96%. The FAA claims capacity increases of 3%–5%28.The FAA claims flight times into EWR have been reduced by 4 min. Green, et al. show how TMA can reduce delays in merging traffic streams29.

10. New Runways Constructions at OEP 35 Airports

Description: New runways are planned for CLT (Charlotte Douglas), IAD (Washington Dulles), ORD (Chicago O’Hare), and SEA (Seattle-Tacoma).

Benefits Identified: The addition of runways has a direct impact on airport capacity. The following four OEP 35 airports are expected to have a significant capacity increase due to new runway constructions: CLT30 (20%), IAD31

(50%), ORD32 (30%), and SEA33 (64%).

11. RNAV DPs

Description: RNAV Departure Procedures (DPs) take advantage of RNAV capabilities. The benefits of RNAV DPs mainly derive from the ability to use alternating, diverging departures. The minimum ATC separation standard that applies most frequently to consecutively departing aircraft operating at major U.S. airports, i.e., radar separation, calls for an initial application of 3-nmi spacing between in-trail departures. If the same aircraft can be sequenced for diverging operations and Same Runway Separation standards can be applied, a subsequent departure can be authorized to start the takeoff roll if the preceding departure has gained a distance of 6,000 feet and has become airborne. Thus, applicable ATC minimum standards for diverging departure operations generally impose less stringent constraints and enable ATC to effectively reduce inter-operation times between aircraft departing on diverging courses.

Benefits Identified: Mayer & Sprong measured 10–11 more departures per hour for each airport, with the possibility of 20 more departures/hour at DFW34. From ASPM data35, the ATL 2005 average rate in VMC is 79 departures/hour, and the DFW 2005 average rate in VMC is 61 departures/hour, so the improvement is 12%–32%.

12. Wake Turbulence Mitigation for Departures

Description: Weather sensors and algorithms are used to predict stable wind conditions that allow reduced separations due to wake movement. Procedures are developed at applicable locations based on the results of analysis of wake measurements and safety analysis using wake modeling and visualization. During peak demand periods with favorable wind conditions, these procedures allow airports to maintain airport departure throughput. A staged implementation of changes in procedures and standards, as well as the implementation of new technology, will

American Institute of Aeronautics and Astronautics 12

safely reduce the impact of wake vortices on operations. This reduction applies to specific types of aircraft and is based on wind blowing an aircraft’s wake away from the parallel runway’s operating area. Procedures based on site-specific wake measurement and safety analysis will be developed.

Benefits Identified: Departure service is part of an integrated air traffic control approach and departure procedures provided for airports. These procedures have proved safe for airports with closely-spaced parallel runways (CSPR). They do, however, limit capacity and create significant delays associated with their application during times of heavy airport departure demand, making it difficult for air carriers to maintain scheduling integrity. CSPR departure capacity limitations created by wake vortex separation standards are a liability to the NAS. Mitigation measures described above address these limitations. Studies done by MITRE36 conclude the following increase in departure rates BOS (16%), DTW (18%), PHL (12.2%), and STL (10%) due to wake-vortex mitigation by favorable winds at those airports.

13. Initial Surface Traffic Management

Description: ANSP automated decision support tools integrate surveillance data with other important sources of data. These include weather data, departure queues, aircraft flight plan information, runway configuration, expected departure times, and gate assignments. Local collaboration between ANSP and airport stakeholders improves information flow to decision support as well as the ability for aircraft operators to meet their operational and business objectives. Departures are sequenced and staged to maintain throughput. ANSP automation will use departure-scheduling tools to flow surface traffic at high-density airports. Automation will provide surface sequencing and staging lists for departures and average departure delay (current and predicted).

Benefits Identified: Currently, air traffic demand exceeds NAS resources. Traffic-flow managers apply a variety of tools, particularly various types of traffic management initiatives (TMIs), to handle departure runways at high-density airports. These initiatives depend upon the capability of controllers. Managing surface traffic to enable aircraft to depart or land at airport runways within tightly scheduled time windows is a daunting task. There is an increasing demand for decision-support tools to assist controllers in accomplishing this daunting task. Appropriate surface data, when developed, will be shared with flight planners, flight operations centers (FOCs), as well as airport authorities.

Balakrishnan and Balachandran37 predict an increase of 6 departures per hour using departure scheduling. The concept is based on minimizing the average wake vortex separation by appropriately sequencing the aircraft. The benefits of this approach are dependent on the fleet mix and the number of spots an aircraft is permitted to slide by the sequencing algorithm.

14. New Taxiway Constructions at OEP 35 Airports

Description: Taxiway improvements are planned for BOS (Boston Logan), DFW (Dallas-Ft. Worth), FLL (Ft. Lauderdale-Hollywood), JFK (New York John F. Kennedy), LAX (Los Angeles), ORD (Chicago), and PHL (Philadelphia).

Benefits Identified: Taxiway improvements reduce taxi times and may improve throughput. An FAA study predicts DFW to experience 27% less taxi time for departures derived from the construction of a new perimeter taxiway38. Studies conducted at the following five airports predict reductions in taxi delays due to new taxiway constructions: BOS39 (30%), FLL40 (88%), JFK41 (2.5 min), LAX42 (12.78%), and ORD43 (80%).

15. Provide Full Surface Information

Description: Surface situation information will complement visual observation of the airport surface. Decision support system algorithms will use enhanced target data to support identification and alerting of those aircraft at risk of runway incursion. In addition, non-ANSP functions, such as airport (movement and non-movement areas) and security operations will benefit from information exchange and situational awareness of aircraft and equipped vehicle surface position and movement. This capability will be accomplished through the use of multiple ground-based receivers on the airport surface to capture aircraft transponder broadcasts. These sensors will be strategically placed on the airport surface for maximum surface coverage. The sensors will receive transponder signals and, with supporting automation, time-stamp and fuse this information with other sensor information to determine target positions, velocity, and identity. This information will be provided to the ANSP and the FOCs. This will extend the capability beyond the Airport Surface Detection Equipment Model X (ASDE-X) sites.

Benefits Identified: Service providers, FOCs, and equipped aircraft need an accurate real-time view of airport surface traffic and movement, as well as obstacle location to increase situational awareness of surface operations. Currently, this is difficult because of several factors, including (but not limited to): poor visibility caused by weather or nighttime conditions; poor sight lines; fast-moving surface traffic; no automated capability to predict movement

American Institute of Aeronautics and Astronautics 13

of surface traffic; limited conflict detection; and the volume of moving vehicles in a limited geographic area. Full surface information provided to the ground controllers is expected to result in improved taxiway operations and reduced taxi times. A EUROCONTROL study found taxi-out times would be reduced by 13%–18% (3.5–4.5 min) in VMC, 9%–15% (2–3 min) in IMC44.

B. ACES Modeling Considerations This study is tied to simulation assessments being planned to be conducted using NASA’s Airspace Concepts

Evaluation System (ACES) software13,14. ACES has been in continuous development for the past decade and provides a capability for simulating flights in the NAS from gate to gate. ACES not only simulates flight trajectories based on assigned flight plans, but includes agents for performing air traffic control functions both en route and terminal, as well as options for modeling the movement of surface traffic at airports. While the capabilities of ACES continue to be expanded, there are currently some limitations on what can be modeled which are a factor in determining which concepts are modeled, and how.

Shown in Table 5 are the most likely explicit and implicit modeling options in ACES for the NGIP items recommended to be included in the assessment. Explicit modeling options are more accurate; however, explicit modeling of all the 15 items could be an intensive effort. On the other hand, implicit modeling option offers a quick approach to simulate the benefit of the items. It is effective for items such as new runway constructions that directly increase the capacity of the airport without having side-effects on other NAS operations.

To compute the value of implicit modeling parameter that is representative of the projected scenario, the overall effect of multiple items under different meteorological conditions has to be considered. As an example, consider the problem of computing the overall effect of NGIP items on the arrival acceptance rate under VMC. The primary source of capacity improvements under VMC are the runway improvements. Time-based metering is another item that increases the throughput. Other items such as RNP SAAARs are applicable only for low-visibility conditions. RNAV STARs and airspace redesign projects are expected to reduce terminal transit times. Therefore, airport arrival capacity in 2018 is determined primarily by the combined influence of runway improvements and metering. Capacity improvements for airports with new runway constructions are described in Section III.A.10. Expected throughput increases from metering are presented in Section III.A.9 for airports LAX, MSP, PHL, EWR, JFK, and LGA. For other airports with no such results, an average value of the observed throughput increases at the abovementioned airports can be assumed for the following example to demonstrate the idea of determining combined benefits. The average throughput increase from the six airports is found to be 3.5%. Assuming the percentage increase in runway arrival capacity in is Cr and the percentage increase due to metering is Cm, the combined effect of metering and runway improvements can be expressed in percentage increase over current-day operations as C = (1+Cr)*(1+Cm) – 1. Shown in Table 6 are the NGIP items that affect airport arrival capacities under VMC and their overall effect on individual airports. The numbers are percentage increase over current-day capacities. The “-” marks indicate no effect of a particular item on the corresponding airport.

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Table 5. Suggested Modeling Options for Selected NGIP Items

Item Requirements for Explicit Modeling Parameters for Implicit Modeling

Airspace Flow Programs Interface to existing Airspace Flow Program software

Implicit Modeling Not Recommended

Flexible Airspace Management Re-sectorization Algorithms Implicit Modeling Not Recommended

En Route RNAV/RNP Actual RNAV Routes and TME†† Implicit Modeling Not Recommended

Airspace Redesign for NY-NJ-PHL, Chicago, Houston

Airspace Designs and TME Implicit Modeling Not Recommended

RNAV STARs Trajectories Associated with Actual RNAV STARs and TME

TRACON Transit Times

Use Optimized Profile Descents (OPD) Optimal Descent Trajectories, TME, and NASEIM

‡‡Implicit Modeling Not Recommended.

RNP SAAARs(RNP Dual Approaches, SCIA)

Aircraft Pairing Algorithms and TME Arrival Acceptance Rate

Improved Operations to Closely Spaced Parallel Runways

Aircraft Pairing Algorithms and TME Arrival Acceptance Rate

Time-Based Metering TMA§§

, McTMA*** Arrival Acceptance Rate

New Runway Constructions at OEP 35 Airports

New Runway Geometry and STLE††† Arrival Acceptance Rate/Departure

Acceptance Rate

RNAV DPs Trajectories Associated with Actual RNAV DPs

Departure Acceptance Rate

Wake Turbulence Mitigation for Departures

Wind Based Departure Sequencing Algorithms and TME

Departure Acceptance Rate

Initial Surface Traffic Management Departure Sequencing Algorithms Departure Acceptance Rate

New Taxiway Constructions at OEP 35 Airports

New Taxiway Geometry and STLE Taxi Time, Taxi Delay

Provide Full Surface Information Surface Information Model and STLE Taxi Time, Taxi Delay

†† TME (Terminal Model Enhancement) is an extension of ACES under development that explicitly models trajectories in the terminal area. ‡‡ NASEIM (National Airspace System Environmental Impact Model) is a software package for estimating fuel consumption and emissions from trajectories and aircraft data, produced by Metron Aviation. §§ TMA (Traffic Management Advisor) is a set of software tools developed by NASA that can produce advisories for conducting time-based metering operations, among others, within an ARTCC. *** McTMA (Multi-center TMA) is an extension of TMA§§ to handle flights across multiple control centers. ††† STLE (Surface Traffic Limitations Enhancement) is an extension of ACES that explicitly models taxiway and runway systems, including taxi paths in the ramp area.

American Institute of Aeronautics and Astronautics 15

Table 6. Effect of NGIP Items on OEP 35 Airport Arrival Capacities under VMC

OEP 35 Airports

Runway Improvements

Time-Based

Metering

Overall Effect

ATL - 3.5% 3.5%

BOS - 3.5% 3.5%

BWI - 3.5% 3.5%

CLE - 3.5% 3.5%

CLT 20% 3.5% 24.2%

CVG - 3.5% 3.5%

DCA - 3.5% 3.5%

DEN - 3.5% 3.5%

DFW - 3.5% 3.5%

DTW - 3.5% 3.5%

EWR - 2.61% 2.61%

FLL - 3.5% 3.5%

HNL - 3.5% 3.5%

IAD 50% 3.5% 55.25%

IAH - 3.5% 3.5%

JFK - 2.87% 2.87%

LAS - 3.5% 3.5%

LAX - 7.8% 7.8%

LGA - 2.10% 2.10%

MCO - 3.5% 3.5%

MDW - 3.5% 3.5%

MEM - 3.5% 3.5%

MIA - 3.5% 3.5%

MSP - 0.67% 0.67%

ORD 30% 3.5% 34.55%

PDX - 3.5% 3.5%

PHL - 4.96% 4.96%

PHX - 3.5% 3.5%

PIT - 3.5% 3.5%

SAN - 3.5% 3.5%

SEA 64% 3.5% 69.74%

SFO - 3.5% 3.5%

SLC - 3.5% 3.5%

STL - 3.5% 3.5%

TPA - 3.5% 3.5%

IV. Concluding Remarks The JPDO NextGen ConOps provides an overall, integrated view of NextGen operations in the 2025 timeframe.

The FAA’s NextGen Implementation Plan (NGIP) released in 2008, and revised in 2009, describes operational capabilities planned by the FAA with the potential to produce system-level benefits towards the realization of NextGen. NGIP provides a glimpse into the FAA’s management plan in the mid-term (2012–2018). This paper documents an initial effort in analyzing the capabilities envisioned by NGIP by taking a snapshot of the capabilities identified in NGIP for 2018 for assessment, with the understanding that such capabilities are merely part of an intermediate step towards the full realization of NextGen.

The assessment approaches the problem of identifying the modeling and simulation requirements for the evaluation of NGIP with a two-step process: (1) provide an initial analysis of NGIP to identify the NGIP items recommended for assessment, and (2) prepare initial modeling and simulation requirements by quantifying the NGIP items identified for assessment. Recommendations are based on the assumption that the assessment will be carried out using the Airspace Concept Evaluation System (ACES) simulation developed by NASA. The next step will be

American Institute of Aeronautics and Astronautics 16

the development of modeling details to support the assessment, followed by ACES experiments and post-simulation analyses.

Acknowledgments This work was performed under support from NASA Contract No. NNA08AF13C. The authors thank Dr. Jorge

Bardina and Mr. Rob Fong of the Ames Research Center for their support, and Mr. Michael Downs of Perot Systems for sharing his technical expertise.

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