NASA/TM-2012-xxxxxx
Air Traffic Management Technology
Demonstration-1 Concept of Operations
(ATD-1 ConOps)
Brian T. Baxley
Langley Research Center, Hampton, Virginia
Harry N. Swenson
Ames Research Center, Moffett Field, California
Todd J. Callentine
San Jose State University
Ames Research Center, Moffett Field, California
John Scardina, Michael Greene
Crown Counsulting, Arlington, Virginia
Month Year
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NASA/TM-2012-xxxxxx
Air Traffic Management Technology
Demonstration-1 Concept of Operations
(ATD-1 ConOps)
Brian T. Baxley
Langley Research Center, Hampton, Virginia
Harry N. Swenson
Ames Research Center, Moffett Field, California
Todd J. Callentine
San Jose State University
Ames Research Center, Moffett Field, California
John Scardina, Michael Greene
Crown Counsulting, Arlington, Virginia
National Aeronautics and
Space Administration
Langley Research Center
Hampton, Virginia 23681-2199
Month Year
Table of Contents
1.0 INTRODUCTION/SCOPE .................................................................................................... 1
1.1
1.2
1.3
1.4
1.5
1.6
BACKGROUND ..................................................................................................................................... 1
PROBLEM STATEMENT ....................................................................................................................... 2
IDENTIFICATION ................................................................................................................................. 2
OPERATIONAL NEED .......................................................................................................................... 3
CONCEPT OVERVIEW ......................................................................................................................... 4
INTEGRATION WITH ANSP GROUND SYSTEMS & AIRCRAFT SYSTEMS ......................................... 4
2.0 CURRENT OPERATIONS AND CAPABILITIES ............................................................ 5
2.1 DESCRIPTION OF CURRENT OPERATION .......................................................................................... 5
2.2 CURRENT SUPPORTING INFRASTRUCTURE ....................................................................................... 6
3.0 JUSTIFICATION AND DESCRIPTION OF CHANGES ................................................. 8
4.0 ATD-1 CONCEPT OF OPERATIONS ................................................................................ 9
4.1 INTRODUCTION ................................................................................................................................... 9
4.2 ASSUMPTIONS AND CONSTRAINTS ..................................................................................................... 9
4.3 OPERATIONAL ENVIRONMENT ........................................................................................................ 10
4.4 OPERATIONS ..................................................................................................................................... 11
4.4.1 TMA with Terminal Metering (TMA-TM)..................................................................................... 12
4.4.2 Controller-Managed Spacing (CMS) .............................................................................................. 13
4.4.3 Flight Deck Interval Management (FIM) ........................................................................................ 14
4.5 BENEFITS TO BE REALIZED .............................................................................................................. 15
4.5.1 Overall Benefits .............................................................................................................................. 15
4.5.2 Benefits to ANSP ............................................................................................................................ 16
4.5.3 Benefits to NAS User...................................................................................................................... 16
4.5.4 Benefits to Airport .......................................................................................................................... 16
5.0 OPERATIONAL SCENARIOS .......................................................................................... 17
5.1 ATD-1 NOMINAL SCENARIO ............................................................................................................ 17
5.2 ATD-1 NOMINAL SCENARIO VARIATIONS ...................................................................................... 25
5.2.1 ATC assigns a temporary speed change to an aircraft conducting IM ............................................ 25
5.2.2 ATC amends an IM clearance ......................................................................................................... 25
5.2.3 ATC issues an IM clearance to the FAF ......................................................................................... 25
5.3 ATD-1 OFF-NOMINAL SCENARIOS .................................................................................................. 25
5.3.1 ATC assigns a vector to either CMS or IM aircraft ........................................................................ 25
5.3.2 ATC terminates an IM clearance .................................................................................................... 25
5.3.3 Flight crew terminates an IM clearance .......................................................................................... 26
5.3.4 ATC issues a new IM clearance ...................................................................................................... 26
6.0 SUMMARY OF IMPACTS ................................................................................................. 27
7.0 REFERENCES ...................................................................................................................... 28
APPENDIX A: ACRONYMS AND DEFINITIONS ............................................................. A-1
APPENDIX B: PHRASEOLOGY ........................................................................................... B-1
APPENDIX C: SCHEDULING AND IM ALGORITHMS .................................................. C-1
APPENDIX D: OPERATIONAL ASSUMPTIONS AND REQUIREMENTS .................. D-1
APPENDIX E: INFORMATION FLOW ............................................................................... E-1
APPENDIX F: SAMPLE ATD-1 ARRIVAL AND APPROACH PROCEDURES ............F-1
1.0 Introduction/Scope
This document describes the Concept of Operations (ConOps) to be researched and
demonstrated in the Air Traffic Management (ATM) Technology Demonstration #1 (ATD-1).
ATD-1 is sponsored by the National Aeronautics and Space Administration (NASA) System
Analysis, Integration, and Evaluation (SAIE) Project (part of NASA’s Airspace Systems
Program). The goal of ATD-1 is to demonstrate the feasibility and value of the concept, and
transfer NASA-developed technology and procedures to stakeholders.
The ATD-1 ConOps will demonstrate IM-TAPSS, or Interval Management – Terminal Area
Precision Scheduling and Spacing, which integrates three NASA research efforts to achieve high
throughput, fuel-efficient arrival operations into busy terminal airspace [ref 1]. They are:
 TMA-TM: Traffic Management Advisor with Terminal Metering for precise timebased schedules to the runway and points within the terminal area
 CMS: “Controller-Managed Spacing” decision support tools for controllers to better
manage aircraft delay using speed control
 FIM: “Flight deck Interval Management” aircraft avionics and flight crew procedures
to conduct spacing operations
IM-TAPSS aligns with the Federal Aviation Administration’s (FAA) NextGen Mid-Term
ConOps [ref 2], draft Time-Based Flow Management (TBFM) ConOps [ref 3], and Arrival
Interval Management – Spacing (IM-S) Concept of Operations for the Mid-Term Timeframe [ref
4]. It is also consistent with the FAA’s expected National Airspace System Enterprise
Architecture Operational Improvements (OI) in the 2015-2018. In addition to the these FAA
ConOps, the IM-TAPSS capabilities are also intended to fully support NASA’s Integrated
Arrival, Departure, and Surface (IADS) concept for the Mid-Term [ref 5].
This ATD-1 ConOps and procedures for controllers and flight crew document follows FAA
guidance to derive concept-level requirements for supporting services, systems, technologies,
tools, procedures, and airspace changes [ref 6]. Scenarios and procedures to be used during the
2015 operational evaluation are the primary focus of this document. IM-TAPSS operations part
of the long-term vision, but outside the ATD-1 time frame, is generally not included (for
example, departure and oceanic operations).
1.1
Background
To prepare the National Airspace System (NAS) to be able to handle increases in traffic
volume predicted in 2025 and improve the efficiency of the air transportation system, Congress
enacted the Vision 100 – Century of Aviation Reauthorization Act in 2003, and created the Joint
Planning and Development Office (JPDO). The JPDO—composed of individuals from the
Federal Aviation Administration (FAA), NASA, the aviation industry, the Departments of
Transportation, Defense, Homeland Security, and Commerce, and the White House Office of
Science and Technology Policy—was tasked to develop a vision of the NAS in the year 2025
that promotes scalability of air traffic operations. The JPDO published an updated Concept of
Operations for NextGen that describes a high-level vision for the air transportation system for the
year 2025, including a description of the roles for the various operating elements within the air
transportation system [ref 7]. The ATD-1 ConOps is fully consistent with the Joint Planning and
Development Office (JPDO) NextGen ConOps.
1
Increasing the capacity and efficiency of the NAS is a primary goal of NextGen. Achieving
this goal requires that the capacity of the high-capacity airports and the efficiency of arriving
aircraft be simultaneously optimized.
NextGen Operational Improvements (grouped according to Solution Set) associated with IMTAPSS are:
 Initiate Trajectory Based Operations (TBO)
 102137 Automation Support for Separation Management (2014-2015)
 104120 Point-in-Space Metering (2012-2016)
 108209 Increase Capacity and Efficiency Using Area Navigation (RNAV) and
Required Navigation Performance (RNP) (2010-2014)
 Increase Arrival/Departure at High Density Airports (HD)
 104123 Time-Based Metering Using RNAV/RNP Route Assignments (2012-2016)
 104128 Time-Based Metering in the Terminal Environment (2015-2018)
 Increase Flexibility in the Terminal Environment (FLEX)
 104124 Use of Optimized Profile Descents (2010-2018)
 Increase Safety, Security, and Environmental Performance (SSE)
 109319 Environmentally and Energy Favorable ATM Concepts, Phase I (2011-2015)
1.2
Problem Statement
The FAA forecasts commercial aviation will grow on average 3.7% over the next twenty
years, with the number of revenue passenger miles to double by 2031 [ref 8]. Arrivals into highdensity airports, especially during peak periods and inclement weather, experience significant
inefficiencies resulting from use of miles-in-trail procedures and step-down descents. Use of
these current procedures contribute to reduced airport capacity, increased controller workload,
increased arrival delay, and increased aircraft fuel burn, emissions and noise. While advanced
continual descents arrival procedures exist at a limited number of sites, they are not well utilized.
1.3
Identification
Figure 1 shows ATD-1 within the FAA Concept Levels.
NextGen Mid-Term Concept of Operations for
the National Airspace System
(Concept Level 1)
Arrival/Departure High Density Airports
Concept for the Mid-Term
(Concept Level 2)
Mid-Term Concept of Operations for Arrival
Departure, and Surface Management (IADS)
(Concept Level 3)
Integrated Concept of Operations for ATD-1
(Concept Level 4)
Figure 1. ATD-1 Position within Operational Concept Hierarchy
2
1.4
Operational Need
The operational need for the operational capabilities represented the ATD-1 Concept of
Operations is driven by present day shortfalls in the areas of capacity, flexibility, efficiency,
safety and environment [ref 2].
1.4.1 Capacity
In 2008, there was a total of approximately 3.2 million hours of gate (departure), taxi-out,
airborne, and taxi-in delay for domestic flights, according to the FAA’s Aviation System
Performance Metrics (ASPM) system [ref 2]. This number is expected to more than double in the
next ten years without NextGen improvements. Today’s capacity in high-density airspace,
particularly around major metropolitan airports, is reaching its limit while ground automation
lacks the means to identify areas of unused capacity in busy overhead and arrival/departure
streams.
1.4.2 Flexibility
Today’s NAS is constrained by its infrastructure both in terms of service delivery and
management of the Air Navigation Service Provider (ANSP) workforce. The system offers
limited flexibility to respond to changes in traffic demand, weather, Special Activity Airspace,
and other events [ref 2]. From the perspective of the ANSP, facilities offer limited flexibility in
their management of ATM operations. They are not scalable to match service delivery, nor do
they effectively provide for business continuity.
1.4.3 Efficiency
The high cost of flight operations and increasing disruptions to the flying public require more
efficient and predictable operations. The cost to operators is exacerbated by limitations on
operating practices and routing options, while the flying public contends with an increase in
flight delays and cancellations. Rather than allow more direct routing to destination airports,
flight plans are constrained by airspace design limitations, fixed airways, and inefficient arrival
and departure procedures. Surface and flight operations, particularly those in high traffic density
areas, are not integrated to maximize operational efficiency and capacity during peak demand.
Aircraft navigation performance capabilities are not fully considered when providing separation
management services or solving traffic flow management problems, and open-ended clearance
amendments reduce the accuracy of conflict predictions generated by automation, as well as
reduce the efficiency of the aircraft fuel consumption.
1.4.4 Safety
As the primary mission of the FAA, safety must continue to improve and accommodate
increased traffic growth and new types of aircraft in the years to come. This will require focusing
on those flight operations in which accidents and incidents have historically been more likely to
occur, such as the runway environment, during convective weather events or periods of low
visibility, and operations in areas without surveillance services. The approach to aviation safety
must evolve into one in which safety information and lessons learned are shared more freely,
combined with a cultural transformation for users and service providers from a reactive to a
predictive approach to safety improvements.
3
1.4.5 Environment
Environmental concerns have become a global issue to which the air transportation system
must respond. The current airspace design and route structure typically requires aircraft to plan
and to fly to waypoints that consume additional fuel and time while contributing to greenhouse
gas emissions. Fortunately, reducing emissions, noise, and fuel consumption are a natural
outcome of initiatives to improve cost and efficiency. Current arrival and departure procedures
often include incremental climbs and descents that are undesirable both from a fuel consumption
and flight time perspective, and generate an undesirable noise footprint around airports.
1.5
Concept Overview
ATD-1 Concept of Operations combines advanced aircraft scheduling, controller decision
support tools, and aircraft avionics to enable efficient high-density terminal airspace arrival
operations. To achieve increased fuel efficiency during periods of high runway demand, aircraft
will use Area Navigation (RNAV) Optimized Profile Descents (OPDs) that include transitions to
a specific runway by connecting to Standard Instrument Approach Procedures (SIAP). These
advanced arrival procedures allow flight crews to use their onboard FMS capabilities to fly from
cruise to landing employing a continuous descent approach without controllers providing radar
vectors to the final approach course. Figure 2 below graphically presents the three technology
elements integrated in ATD-1.
Figure 2. Integrated Technologies in ATD-1 Concept of Operations
1.6
Integration with ANSP Ground Systems & Aircraft Systems
The ATD-1 ConOps and operations require integration on the ground side with the air traffic
management systems (i.e., TBFM), the en route automation system (i.e., ERAM), and the
terminal automation system (i.e., STARS). On the aircraft side, either full integration (in
particular the Flight Management System) or partial integration (such as an Electronic Flight
Bag) into aircraft systems is required.
4
2.0 Current Operations and Capabilities
This section provides a description of the present-day operational elements supporting
arrivals into high-density airports with emphasis on those aspects that ATD-1 proposes to
change.
2.1
Description of Current Operation
The stakeholders supporting arrival operations into high-density airports include:
2.1.1 Center Traffic Flow Management (TFM) Traffic Manager Coordinators (TMCs)
For airports with sufficient levels of traffic to necessitate arrival-metering operations,
Center TFM TMCs use TMA to perform metering by assigning arrival metering point time
(MPT) constraints for aircraft to cross into TRACON airspace at the arrival meter point (as well
as en route MPT constraints for aircraft upstream from the arrival sector). By assigning arrival
MPT constraints, TFM plans aircraft sequence and spacing (in time) across each arrival meter
point (and ultimately to the runway threshold) to help ensure that the TRACON will receive a
demand that matches the defined arrival capacity.
2.1.2 En Route ATC (ARTCC) Sector Controllers
En route controllers monitor flight progress and maintain separation in en route airspace,
issue descent clearances, and ensure that TFM specifications for sequencing and spacing are
maintained. When an aircraft has been assigned an MPT constraint, the en route controller
maneuvers the aircraft as necessary to ensure that the aircraft meets its assigned MPT constraint
and maintains separation with other aircraft. The en route controller uses the TMA schedules and
delay information displayed on their radar screens to meet the MPT constraints. This type of
maneuver could include a lateral maneuver (vectoring) such as turning out on a heading and then
later turning back direct to a fix on the route, an altitude maneuver, such as a step descent, or a
speed adjustment. Vectoring adjustments are the most commonly applied method, followed by
early descents and speed adjustments. Controllers also have the option of altering the sequence
of arriving aircraft (swapping) as long as the net separation distance does not impact the trailing
aircraft.
2.1.3 Terminal ATC (TRACON) Controllers
TRACON controllers monitor flight progress, separate departure and arrival flows using
altitude limits for departure and arrival aircraft, maintain separation among aircraft within each
specific flow, and merge arrival streams in TRACON airspace. After aircraft enter TRACON
airspace, arrival controllers monitor their descent, maneuvering them as necessary to maintain
required separation. TRACON controllers assign a number of altitude and heading changes to
establish the aircraft onto the landing runway’s final approach course. The TRACON controllers
have no information from the TMA to aid in these tasks. The controllers use their experience
and standard operating procedures to guide the aircraft from the entrance of the TRACON to the
runway threshold.
5
2.1.4 Flight Crews
The flight crew relies on ATC to maintain separation from other aircraft in their vicinity.
Once the aircraft begins the arrival phase of the flight, crews adhere to ATC instructions such as
altitude changes, radar vectors, and speed adjustments to achieve the appropriate sequence and
interval required.
An aircraft landing at a high-density airport generally executes a series of step-down descents
starting at its cruise altitude along a published airway, transitions to a Standard Terminal Arrival
Route (STAR), and enters terminal airspace at a metering fix or corner-post. The aircraft is then
handed off from the Air Route Traffic Control Center (ARTCC) to the Terminal Radar Approach
Control (TRACON). The aircraft will continue to fly the STAR; however since most of them do
not connect to the runway, the aircraft is given radar vectors to the final approach course from
terminal controllers.
During periods of light to moderate traffic, aircraft may be able to conduct a fuel-efficient
profile descent from cruise to the runway called an Optimized Profile Descent (OPD). Typically
these operations are only feasible during periods of very light traffic (for example, late at night)
due to the variability and unpredictability of the aircraft trajectories. The variability and
unpredictability makes it very difficult for the ANSP to maintain aircraft separation, and
therefore OPDs are not normally conducted.
An aircraft is able to plan and execute a vertical profile (altitude and speed) along a lateral
path that is optimized for its specific airframe using its Flight Management System (FMS). The
FMS has data on the detailed performance specifications of the aircraft, including engine model,
fuel onboard, and cargo weight, and it uses this and other information, e.g. present location,
altitude, forecast winds, etc., to optimize the vertical profile. The FMS will constrain the vertical
profile to match the speed and altitude constraints of the aircraft’s assigned arrival procedure.
Since the vertical profile is based on airframe-specific data and the aircraft’s current energy state,
each aircraft will have a different vertical profile. The differences between aircraft, particularly
between different airframe types, are significant. The FMS calculates the vertical profile prior to
the aircraft reaching its top-of-descent point, and it does not update the vertical profile after the
aircraft has started its descent. If the planned vertical profile is interrupted (i.e., the aircraft is
held at an intermediate altitude or vectored off the expected lateral path for spacing), the vertical
profile is not recalculated. Therefore, any interruption to the descent after it has begun will
decrease the realized fuel efficiency. During periods of high traffic congestion, nearly all aircraft
are interrupted to maintain separation between aircraft.
2.2
Current Supporting Infrastructure
During periods of congestion the operating mode is characterized by significant interactions
between the controller and pilots for the issuance of vectoring, descent clearances, and speed
clearances to moderate the congestion during the arrival process. The identification of congested
periods is often accomplished by ad hoc experience of traffic management coordinators or
through the automation provided by the Traffic Management Advisor (TMA). Whether it is the
ad hoc experience or the TMA automation, decisions are made on when and where to apply
delay such that the congestion can be safely moderated to the arrival runway capacity. Using ad
hoc experience, the identification of congestion is often done reactively by observing how the
approaches to the runways are being extended from the nominal (i.e., uncongested) procedures.
Upon observation that controllers need to continuously extend the final approach segment to
maintain aircraft separation minima (frequently referred to as “tromboning”), the TRACON
6
issues miles-in-trail (MIT) restrictions to the ARTCC to moderate the workload and flow. The
MIT restrictions are again ad hoc and experience-based, and they often cause excessive delay in
the ARTCC.
Using the TMA automation allows a proactive identification of congested periods to
distribute delay between the TRACON and ARTCC using meter fix crossing times, known as a
scheduled time of arrival (STA). Though the TMA predicts congestion at the runway and
moderates the flow at the meter-fixes at the ARTCC/TRACON boundary, the TRACON does
not have the ability to follow the TMA runway schedules due to a lack of controller interfaces
and limited TMA modeling of merging procedures within the TRACON. Even with this
limitation, the TMA’s proactive congestion identification and the arrival metering at the meterfixes has been shown to efficiently distribute delay and workload between the ARTCC and
TRACON while maintaining the throughput at the desired airport arrival rate. To account for the
lack of TRACON-TMA interfaces and limited TRACON procedure modeling, the TMA requires
scheduling pads to allow the TRACON to safely moderate the congestion, thus not using the full
runway capacity based only on separation requirements. During these periods of congestion, the
aircraft are descended early and vectored off their routes in the ARTCC. Within the TRACON,
the aircraft are also delayed by vectoring and speed reductions to maintain the required
separations for the flow of landing aircraft.
For the flight crew, the aircraft’s avionics systems have limited information on surrounding
traffic. The use of the Traffic Alert and Collision Avoidance System (TCAS) gives the flight
crew an approximate picture of the surrounding traffic, but it does not provide enough
information to allow relative maneuvering except during emergency situations. The flight crew
may also develop a mental model of the approximate location and intent of the other aircraft, but
again, there is insufficient detail to allow relative maneuvering. This lack of knowledge of
surrounding traffic makes the aircraft a passive participant in arrival management and dependent
on controllers for merging and spacing with other aircraft from takeoff to landing.
7
3.0 Justification and Description of Changes
ATD-1 ConOps addresses an essential element of NextGen. It integrates several important
flight deck and ground-based technologies to achieve trajectory-based operations into a highdensity airport during high-traffic periods. ATD-1 implementation will:
 Maximize the capacity of high-density airports, especially during high traffic periods, by
implementing:
- Comprehensive, more accurate scheduling of arriving aircraft to the runway
threshold.
- Flight deck and ground-based interval management systems that improve the
aircraft’s ability to adhere to the precise schedule and desired in trail spacing.
 Minimize en route delays by reducing the need for MIT restrictions.
 Reduce controller workload:
- FIM equipped aircraft should rarely require vectors or speed adjustments from the air
traffic controller to maintain separation or schedule as they execute a continuous
descent approach from top-of-descent to the runway threshold, passing through
several meter fixes and merge points along the descent.
- For aircraft not equipped with FIM avionics, the controller should rarely have to
vector the aircraft to maintain separation or schedule. The controller should only
have to issue speed adjustments to the pilot as determined by the Controller Managed
Spacing (CMS) automation.
 Significantly increase the efficiency of arrival operation into high-density airports by
permitting continuous descent arrivals even during peak traffic periods:
- Reduce fuel burn
- Reduce arrival delays
 Support OPDs for aircraft with and without FIM avionics to reduce environmental
impacts at high-density airports:
- Reduce noise
- Reduce emissions
 Permit the realization of trajectory management from before top-of-descent to the
runway:
- Increase the reliability of the schedule
 Promote accelerated ADS-B equipage and enable other advanced capabilities
ATD-1 ConOps implementation requires several changes to the current NAS system and
aircraft avionics, in particular:
 OPD from en route structure to an instrument approach procedure without requiring
vectors
 Changes to TMA to support terminal metering and integrated scheduling/spacing
 Changes to STARS to support ground-based spacing aids (CMS)
 Integration of TMA-TM, CMS, and IM tools into air traffic automation systems
 Development of avionics standards for ADS-B ‘In’ applications
 Development and installation of flight-test ready FIM avionics (Electronic Flight Bag,
etc.)
 Availability of FIM equipped aircraft for ATD-1 demonstration
8
4.0 ATD-1 Concept of Operations
4.1
Introduction
The operational goal of the ATD-1 Concept of Operations is to enable aircraft, using their
onboard FMS capabilities, to fly Optimized Profile Descents (OPDs) from en route altitude to
the runway, of an airport operating at a high throughput rate, using primarily speed control to
maintain separation and schedule. The three technologies in the ATD-1 ConOps achieve this by
calculating a precise arrival schedule that removes some of the excess spacing between aircraft,
the use of controller decision support tools to provide controllers a speed for an aircraft to fly to
meet a time at a particular point, and onboard software for flight crew that calculates a speed for
the aircraft to achieve a particular spacing behind the preceding aircraft.
The concept provides de-conflicted and efficient operations of multiple arrival streams of
aircraft, passing through multiple merge points, from top-of-descent to touchdown. IM-TAPSS
combines advanced arrival scheduling (TMA-TM) with advanced arrival procedures (CMS and
FIM) in the terminal environment of a high-density airport. Aircraft navigate along RNAV
routes using OPDs. These RNAV OPDs provide a lateral path from en route altitude to the
runway threshold, including transitions that connect the arrival route to approach procedure, and
specify vertical constraints if required and a speed for every segment of the OPD procedure. This
should allow flight crews to use their onboard FMS capabilities to fly from en route cruise
altitude to landing at the destination airport with fewer radar vectors and speed adjustments
required from controllers to the final approach course.
By integrating time-deconflicted arrival scheduling with Controller Managed Spacing tools
and flight deck Interval Management capabilities in the terminal environment of high-density
airports, the ATD-1 ConOps enables four important NextGen capabilities:
 Mixed Equipage Operations – A combination of ground-based and flight deck-based
Interval Management tools can help achieve sustained fuel-efficient operations during
periods of high throughput until operators upgrade or replace older, less-equipped
aircraft.
 Terminal Metering – Advanced arrival scheduling enables flow conditioning throughout
the entire arrival phase of flight to ensure efficiency gains achieved by advanced
automation in the en route airspace are not lost in terminal airspace.
 Trajectory-Based Operations – Integration of the scheduling with Interval Management
capabilities enables trajectory-based operations to be continued in terminal airspace
during periods of high throughput when fuel-efficient operations would otherwise be
interrupted to maintain aircraft separation.
 Performance-Based Navigation – Consideration of aircraft Interval Management
capabilities will allow a “best-equipped, best-served” priority to be given to early
adopters of advanced avionics.
4.2
Assumptions and Constraints
Detailed assumptions and constraints anticipated during the operational demonstration at the
procedural level are listed in Appendix D. Highlights include:
 ANSP develops and implements TMA with Terminal Metering.
9



ANSP develops and implements Decision Support Tools for the terminal controller to
effectively manage aircraft spacing for those aircraft not equipped for Flight-Deck
Interval Management (FIM).
Aircraft scheduled to land at the high-density airport during high traffic periods are
equipped for RNAV operations.
Some aircraft scheduled to land at the high-density airport during high traffic periods are
equipped for FIM operations. This includes: ADS-B “In”, Electronic Flight Bag and FIM
avionics.
Constraints to the expected ATD-1 operational environment include:
 ANSP retains responsibility for the schedule and aircraft separation.
 Flight crews retain responsibility for operating the aircraft in accordance with procedures
and instructions (both ATC and from FIM software).
 The Scheduled Time of Arrival (STA) does not normally change once established when
the aircraft crosses the “Freeze Horizon”. The Traffic Manager will retain authority to
change the STA (reschedule) based on current criteria, and controllers may swap the
sequence of aircraft after the “Freeze Horizon” and prior to TRACON airspace.
 The schedule information (STAs at the runway, meter fix, and merge points), in a format
that supports current day and ATD-1 ConOps procedures, will be available to Center and
TRACON controllers.
 The Center controller will be able to issue an FIM clearance to an aircraft, whether or not
the Target (lead) aircraft is within the same sector.
 Controller-to-pilot communications will remain “voice”.
4.3
Operational Environment
The operational environment for the ATD-1 ConOps is the latter part of NextGen Mid-Term.
The ConOps optimizes the efficiency of arrival operations into high-density airports as well as
the throughput of the airport. The ConOps will also work with current and future Air Traffic
Control (ATC) programs, and subscribe to FAA, Aeronautical Information Conceptual Model
(AICM), Aeronautical Information Exchange Model (AXIM) 5.0, and International Civil
Aviation Organization (ICAO) data standards. Key related programs include En Route
Automation Modernization (ERAM), Time Based Flow Management System (TBFM),
Automated Radar Terminal System (ARTS), and Standard Terminal Automation Replacement
System (STARS).
The primary capabilities required to implement this ATD-1 ConOps are:
 An advanced version of TMA that incorporates Terminal Metering (TMA-TM) [ref 9-12]
 Controller Managed Spacing (CMS) decision support software and displays [ref 13-14]
 Flight deck Interval Management (FIM) spacing software and displays [ref 15-18]
The TMA-TM scheduling tool is used to optimize the flow of aircraft into capacityconstrained areas and calculates Estimated Times of Arrival (ETA) at the runway for all aircraft.
At the ‘Freeze Horizon’, the ETAs are used to establish the arrival sequence, and adjusted so the
time between ETAs meets separation criteria between each aircraft pair. This time becomes the
10
STA for that aircraft, and remains fixed unless ATC directs the schedule to be recalculated. The
runway STA is used in the IM clearance and by the FIM spacing tool. The runway STA is also
used to determine the corresponding Scheduled Times of Arrival (STA) at various meter and
merge points along the aircraft’s flight path to the airport. The STAs at the runway and upstream
waypoints are used by CMS displays for controllers. TMA-TM also provides the STA and delay
times to the respective En Route controllers to maintain the optimum flow rates to runways from
the ARTCC to the TRACON. When flights approach a congested airport, TMA-TM is used to
determine how the multiple streams of incoming flights can be sequenced and scheduled to fully
utilize the runway(s) and other airport resources avoiding unnecessary delay while meeting all
operational constraints. TMA-TM extends the capabilities of TMA to handle multiple merges of
aircraft streams en route to the runway threshold. During this Mid-Term time period, voice
continues to be the primary form of controller-to-pilot communications.
A system block diagram showing the relationship of users in the ATD-1 Concept of
Operations is provided in Figure 3.
Figure 3. Block Diagram of Users in ATD-1 ConOps
4.4
Operations
Figure 4 below is a diagram illustrating the operational context for the increasing precision
enabled by the technologies and procedures of ATD-1.
11
Figure 4. Operational Context for ATD-1 Precision
4.4.1 TMA with Terminal Metering (TMA-TM)
A key element of the TMA-TM scheduling tool is determining an appropriate arrival
schedule and landing time interval between aircraft, then computing the appropriate speed
required to space aircraft close to the minimum time or distance allowed for the runway
conditions. The Traffic Management Advisor (TMA), as presently deployed by the FAA, assists
ARTCC controllers and traffic managers in meeting scheduled times of arrival (STAs) to closely
match the desired separations and Airport Arrival Rate, among other constraints. The FAA also
has systems and procedures being developed and deployed for Extended Metering and Coupled
Scheduling. While TMA and other decision support tools provided ancillary environmental
benefits, the primary objective of each was to reduce delay or to increase throughput.
The TMA-TM system is a trajectory-based strategic and tactical planning and control tool
that consists of trajectory prediction, constraint scheduling and runway balancing, controller
advisories and flow visualization (trajectory prediction, constraint scheduling, and runway
balancing exist in the current TMA). TMA-TM includes modifications to the terminal delay
model to accurately reflect the reduced TRACON flight times for OPDs, and enhancements to
benefit the conduct of OPD arrivals such as increased metering precision or tie-point timelines.
Enhancements have also been made to enable Controller Managed Spacing (CMS) displays.
Future scheduling enhancements of opportunistic time-advance and time recovery are being
developed.
12
4.4.2 Controller-Managed Spacing (CMS)
The CMS tools assist terminal controllers in achieving their goal of maximizing throughput
on capacity-constrained runways. They ensure that the terminal controllers have knowledge of
and follow the same schedule that en route controllers used to manage the flows of traffic into
the terminal airspace. The CMS tools display the TMA-TM derived information that is necessary
to more accurately achieve arrival schedule conformance using speed commands. This
information is intended to allow controllers to reduce the use of tactical vectoring, thereby
enabling aircraft to fly the arrival procedure as efficiently as possible [ref 13-14].
Figure 5 illustrates three levels of controller decision support tools proposed for ATD-1:
 Timelines and Early/Late Indicators (left-most of three boxes in top row)
 Timelines to assess an aircraft’s schedule conformance by comparing its estimated
time-of-arrival (ETA) with its STA at the runway and at various merge points.
Early/late indicators in an aircraft’s Full Data Block (FDB) enable controllers to
quickly assess the schedule-conformance information for that aircraft.
 Slot marker circles (middle box in top row)
 Slot marker circles translate the temporal schedule information to a spatial target on
the controller’s planview display. The slot marker circles indicate where an aircraft
should be now if it were to fly the RNAV OPD at speeds to meet all the TMA-TM
calculated STAs for meter points, merge points, and runway.
 Speed advisories (right box in top row)
 Speed advisories show an airspeed and fix name in the aircraft’s FDB to help
controllers formulate speed clearances. Flying the advised speed until rejoining the
nominal OPD speed profile at the named fix is predicted to place the aircraft back on
schedule by the fix. Speed advisories can be configured to replace the early/late
indicator in an aircraft’s FDB when spacing errors exceed a prescribed minimum
threshold and an appropriate advisory can be computed.
13
Figure 5. Clockwise from the left: (a) timeline including spacing bracket, (b) FDB in
timeline condition, with early/late indicator, (c) dwelled FDB and slot marker in slot
marker condition, (d) FDB and slot marker in advisory condition, (e) spacing cones and
route display.
4.4.3 Flight Deck Interval Management (FIM)
FIM enables the flight crew to actively assist both en route and terminal controllers in
achieving their goal of maximizing throughput on capacity-constrained runways. It enables the
controller to issue a single strategic clearance to flight crews of spacing-capable aircraft to
achieve the Assigned Spacing Interval (ASG) behind a Target (lead) aircraft at the Achieve-By
Point (the runway threshold in ATD-1). The flight crew then manages their speed along their
lateral and vertical path to achieve precise inter-arrival spacing by the achieve-by point.
The spacing operation is initiated near top of descent when the flight crew receives an IM
clearance from the controller to begin spacing. The IM clearance must include the Target aircraft
identifier spacing goal. Other information elements may be included in the clearance if available
to the controller and necessary to achieve the desired objective. In cases where the Target
aircraft is not yet within ADS-B range, a Scheduled Time of Arrival (STA) at the achieve-by
point may be included as part of the IM clearance from ATC. In addition, the spacing tool needs
the arrival procedure of the Target aircraft (if not on the same route as the IM aircraft) and the
Target aircraft’s planned final approach speed (improves arrival precision at the runway).
During the ATD-1 demonstration, controllers will issue the IM clearance using voice
communication. The flight crew selects the target aircraft from a list of ADS-B targets and enters
the ASG, the Target aircraft’s arrival procedure and final approach speed (if provided) into the
FIM spacing tool. The tool calculates the airspeed required to arrive at the runway at the STA
(only if the Target aircraft is not within ADS-B range), or the airspeed required to achieve the
14
relative spacing interval by the runway. After determining the FIM speed is feasible, the flight
crew flies that speed and notifies ATC that IM spacing has begun. FIM aircraft are expected to
transition to relative spacing well before reaching the achieve-by point and the upstream merge
point. Flight operations continue as normal except the airspeed flown is determined by the FIM
equipment instead of the FMS or ATC. If the flight crew is no longer able to follow the speed
command, or experiences a system error, they
contact the controller to terminate spacing
operations and revert to traditional control
mechanisms. At any time, the controller can
intervene with additional speed or vector clearances.
Cockpit displays for the flight crew to conduct
FIM operations will be based on the airline and
avionic partners participating in the ATD-1
demonstration. Options include displaying the FIM
speed on an Electronic Flight Bag (EFB) or on the
Primary Flight Display (PFD). Figure 7 is an
example of a PFD with the FIM speed calculated by
the onboard spacing software shown in the upper
left corner in green numbers, and shown as a green
speed bug on the right side of the speed tape.
Figure 6. Option of IM Speed Display
4.5
Benefits to be Realized
4.5.1 Overall Benefits
Advanced arrival procedures generally provide less flexibility for the controller to maintain
aircraft separation using traditional tactical control techniques, but they provide increased
flexibility for the airspace user to select fuel-efficient descent profiles. The integration of
scheduling and spacing is needed to achieve increased arrival time accuracy and its associated
inter-arrival separation prediction. While advanced scheduling, controller-managed spacing and
flight deck interval management each exhibit benefits individually, their integration is needed to
achieve their full benefits at high-density airports. Advanced scheduling allows better planning
of arrival operations by considering separation at key terminal merge points. Controller-managed
spacing increases the arrival time accuracy of non-FIM aircraft, and flight deck interval
management further increases the inter-arrival separation precision of those aircraft so equipped
and should reduce controller workload as well.
An overview of intended benefits from ATD-1 technologies and procedures include:
 Higher throughput and more efficient flight paths
 Key metric is increased inter-arrival precision
 Less path stretching used to maintain separation (fuel savings)
 Fewer level segments used to absorb delay (fuel savings)
 Increased throughput during high-density operations
 Less tactical intervention to maintain separation (workload reduction)
15


Promote accelerated ADS-B equipage and encourage development other advanced
capabilities, such as In-Trail Follow (ITF), Runway Incursion Warning (SURF-IA), and
Cockpit Display of Traffic Information Assisted Visual Separation (CAVS)
Provide a technology demonstration of a major integrated NextGen capability for
terminal area operations
4.5.2 Benefits to ANSP
Increased arrival time accuracy allows arrival schedules to be planned earlier and to a higher
degree of certainty. These schedules allow the use of strategic speed control to achieve the
desired aircraft separation, or less delay taken in the form of path stretching in terminal airspace.
Operationally, this means shorter and fewer fuel-inefficient level segments at lower altitudes. As
a result, aircraft can absorb delay more fuel-efficiently, and fuel consumption is reduced.
Increased inter-arrival precision reduces the spacing buffers and reduces the frequency of
controller intervention to maintain separation. Smaller spacing buffers also increase the
achievable runway throughput at high-density airports. As a result, the delay that needs to be
absorbed during periods of arrival congestion decreases, and fuel consumption is reduced.
Use of advanced arrival procedures minimizes the need for radar vectoring of each and every
flight by controllers. Instead, flight crews are able to use their onboard Flight Management
System (FMS) capabilities to efficiently navigate from cruise to landing. Radar vectoring is used
less frequently and only when speed control is insufficient to maintain aircraft separation.
4.5.3 Benefits to NAS User
Use of FIM reduces the required spacing buffers compared to current and CMS operations
due to precision of the onboard spacing tool. In-trail aircraft will have some trajectory prediction
errors that are correlated, and FIM allows these errors to be eliminated from the spacing buffer.
Continued conformance to the arrival schedule in terminal airspace ensures that aircraft do
not get re-sequenced or rescheduled unnecessarily.
Use of FIM capabilities allows the delegation of routine spacing to the flight deck. Spacing
will be achieved and maintained using small speed corrections to the arrival procedure’s nominal
speed profile. These speed adjustments will be provided by onboard automation instead of by
voice clearances from the controller.
Use of ADS-B In and the corresponding FIM capabilities allow flight crews to take a more
active role in arrival spacing than is currently possible under current procedures and technology.
4.5.4 Benefits to Airport
The precision of the schedule and the ability of controllers and flight crew to execute that
schedule using ATD-1 procedures should produce longer periods of sustained high-throughput at
the airport runways.
Use of environmentally efficient arrival routes (OPDs) during high-density periods reduces
noise and greenhouse gas emissions from aircraft.
16
5.0 Operational Scenarios
The procedures for a “Nominal” (expected or typical) scenario are described first, followed
by several variations of that scenario. In both the nominal ATD-1 scenario and variations of the
nominal scenario, metering and speed control alone are generally sufficient to achieve the
schedule. The “Off-Nominal” scenarios are driven by events that require TMA-TM to generate a
schedule change, (such as changing an aircraft’s assigned route of flight or landing runway), and
may not be part of the ATD-1 demonstration.
Most controller-pilot phraseology used today remains unchanged (such as sector check-in
and check-out, initiation of descent, etc.), however some new phraseology is needed for ATD-1
operations (details in Appendix B). When possible, the phraseology aligns with the existing
Interval Management documentation [ref 18], proposed IM Data Link messages [ref 19], and
proposed Tailored Arrival procedures [ref 20], with modifications made for a voice environment.
Arrival and approach procedure examples are shown in Appendix F. Existing routes into the
Dallas – Ft Worth airport have level segments removed to simulate an OPD, and added
procedures to connect the arrival procedure to the instrument approach. Finally, speeds were
defined for every segment of the arrival and approach except to enable the TMA-TM and FIM
software to calculate the same STAs and speeds required to achieve it.
5.1
ATD-1 Nominal Scenario
An overview of the ATD-1 Nominal scenario is shown Figure 7, with a flow chart of the
controller and flight crew procedures in Figure 8. Figures 9 through Figure 12 present more
details of the ATD-1 scenario by phase of the Nominal scenario, and link to the appropriate
procedures shown in Figure 8.
Prior to reaching the “Freeze Horizon”, the TMA-TM scheduling software continuously
calculates the Estimated Time of Arrival (ETA) for that aircraft to all eligible runways based on
route of flight, intended speed, and forecast wind. When the aircraft crosses the “Freeze
Horizon”, the TMA-TM tool selects the most suitable runway, establishes a Scheduled Time of
Arrival (STA) to that runway that optimizes that aircraft’s trajectory, and ensures no time
conflicts at the runway threshold and TRACON meter fixes with the preceding aircraft. The
STA is presented to ARTCC and TRACON controllers (all information may not be available
during the ATD-1 timeframe). The ARTCC controllers use the TMA-TM information enhanced
with the optimum runway assignment (timeline table shown on left side of Figure 5). TRACON
controllers use either the CMS information or issue an IM clearance so that the aircraft avionics
and flight crew correct the time error.
CMS and IM operations are initiated by ATC as soon as feasible to achieve the schedule.
The ATD-1 goal is for the ARTCC controller to initiate both CMS and IM operations prior to
TOD to take advantage of what is normally a lower workload environment for controllers and
flight crew. Although the long-term ATD-1 operations allow TRACON controllers to issue IM
clearances, the communication infrastructure needed to provide that information is not expected
to be in place by the demonstration, therefore TRACON controllers will not issue IM clearances
during ATD-1. When the infrastructure is in place to enable TRACON controllers to issue or
amend IM clearances, the controller and flight crew procedures have been designed to not
require the flight crew to go ‘Head Down’ to interact with the IM spacing software (see
‘Suspend’ and ‘Resume’ operations and phraseology sections).
17
Figure 7. ATD-1 Operational Scenario
18
S
c
h
e
d
u
l
e
T
M
A
T
M
Aircraft
state
data
0.1 TMA-TM
Calculate schedule
0.2 TMA-TM
Schedule to
Center
1.1.1 ATC-C
Issue speed (FC-NI) or
IM clearance (FC-IM)
1.3.1 FC-FIM
Acknowledge IM clearance
1.2.1 FC-CMS
Acknowledge
and fly airspeed
I
n
i
t
i
a
t
i
o
n
1.3.2 FCFIM
Enter data in
avionics
C
E
N
T
E
R
1.3.3 AV
Calculate airspeed
No
1.3.5 FC-FIM
Notify ATC
unable IM ops
TMA-TM
19
ATC
non-IM aircraft
1.3.4 FCFIM
Speed
Yes
FIM aircraft
2.1.1 ATC-C
Monitor separation
of all aircraft
O
p
e
r
a
ti
o
n
2.1.2 ATC-C
Correct spacing error
C
E
N
T
E
R
2.2.1 FC-CMS
Acknowledge &
fly speed
2.1.3 ATC-C
Amend or terminate IM
clearance if required
2.3.1 FC-FIM
Fly IM speed;
monitor changes
2.1.4 ATC-C
Transfer aircraft to
TRACON controller
T
R
A
C
O
N
0.3 TMA-TM
Schedule to
TRACON
2.1.5 ATC-T
Monitor separation
of all aircraft
2.1.6 ATC-T
Correct spacing error
2.2.2 FC-CMS
Acknowledge
& fly speed
2.3.2 FC-FIM
Fly IM speed;
monitor changes
2.1.7 ATC-T
Update or terminate IM
clearance if required
T
e
r
m
2.1.8 ATC-T
Transfer aircraft to
Tower controller
T
W
R
TMA-TM
ATC
3.2.1 FC-CMS
CMS complete
at FAF
non-IM aircraft
Figure 8. Operational Procedure Flowchart
20
3.3.1 FC-FIM
IM complete at Final
Approach Fix
FIM aircraft
Figure 9. Schedule Phase of ATD-1 Scenario
Figure 9 shows the subset of aircraft and activities that occur during the “Schedule” phase of
the ATD-1 operation, with the number in the text box corresponding to the same number in
Figure 8. The numbers in the left column of the table below also correspond to Figure 8.
0.1
0.2
21
Aircraft crosses the “Freeze Horizon”. The TMA-TM software calculates a schedule, to
include time error per sector for CMS operations by ATC, and the IM clearance to be
issued to flight crew of aircraft equipped for that operation.
Schedule and CMS/IM information is sent to Center and TRACON controllers.
Figure 10. Initiation Phase of ATD-1 Scenario
Figure 10 shows the subset of aircraft and activities that occur during the “Initiation” phase,
with numbers in the text box corresponding to the numbers in the left column of the table below.
1.1.1
1.2.1
1.1.1
1.3.1
1.3.2
1.3.3
1.3.4
1.3.5
22
Center controller issues “expected” runway assignment and speed commands to crew of nonIM equipped aircraft.
Non-FIM Flight crew acknowledges runway and speed instruction from controller.
Center controller issues an IM clearance to flight crew of IM equipped aircraft.
FIM flight crew accepts the IM clearance via read back. The flight crew now fly the spacing
software IM speed, unless the crew notifies ATC they are unable the IM operation.
FIM Flight crew enters the runway assignment and IM clearance data into the aircraft avionic
spacing software, verifies the data is correct, then activates the spacing software.
The FIM aircraft software calculates the Mach number or Indicated Air Speed needed to
achieve the assigned spacing interval behind the Target aircraft by the runway threshold.
The FIM flight crew determines if the speed is operationally feasible. (Previous research
indicates the time from ATC issuing the IM clearance until the flight crew determining the
feasibility is approximately 30 to 45 seconds.)
If the calculated IM speed is not operationally feasible, the FIM flight crew will notify ATC
that they are unable to conduct the IM operation.
Figure 11. Operation Phase of ATD-1 Scenario
Figure 11 shows the subset of aircraft and activities that occur during the “Operation” phase,
with numbers in the text box corresponding to the numbers in the left column of the table.
2.1.1
2.1.2
2.1.3
2.3.1
2.1.4
23
The controller has separation responsibility for all aircraft.
The controller uses CMS information to assign speeds to crews of non-IM equipped aircraft.
The controller may amend, suspend, or terminate an IM clearance as operationally required.
The flight crew will fly the IM speed unless the speed is operationally infeasible.
Transfer of aircraft control to the next controller is unchanged from today’s procedures, with
the addition of the FIM flight crew including ‘INTERVAL SPACING’ as part of the first
transmission with the new controller.
Figure 12. Termination Phase of ATD-1 Scenario
Figure 12 shows the subset of aircraft and activities that occur during the “Termination”
phase, with numbers in the text box corresponding to the numbers in the left column of the table.
If the CMS or IM operation terminates as intended at the Final Approach Fix, there is no
controller – flight crew communication required.
3.2.1
3.3.1
24
CMS operations by controllers are terminated no later than the Final Approach Fix.
IM operations by flight crew are terminated no later than the Final Approach Fix.
NOTE: if the STA was included in the IM clearance, the IM operation continues if the Target
aircraft’s ADS-B data is lost by transitioning to the assigned STA. If the STA was not
included in the IM clearance, the flight crew notifies ATC that they are “unable” the IM
operation if ADS-B data is lost. (See Section B.7.2.)
5.2
ATD-1 Nominal Scenario Variations
This section addresses typical events that occur during everyday normal operations, and are
expected to occur naturally during the ATD-1 operations. These events do not create significant
disturbances that require the schedule to be changed.
5.2.1 ATC assigns a temporary speed change to an aircraft conducting IM
The ATD-1 ConOps allows for controllers to suspend IM operations to issue speeds for a
short period of time, then instruct the flight crew to resume IM operations. This will be
particularly useful when the aircraft is below 10,000 feet and the flight crew’s ability to interact
with avionics is typically restricted.
(Note: if any aircraft is vectored off the route, both the TMA-TM schedule and the CMS
tools become inaccurate. If that aircraft is either a Target or FIM aircraft, the spacing tool
onboard the FIM aircraft becomes inaccurate. Any affected ATD-1 operation should be
terminated if an aircraft must be vectored off course.)
5.2.2 ATC amends an IM clearance
A controller may amend the Assigned Spacing Goal or the Target aircraft’s Final Approach
Speed of an IM clearance. The STA, Target aircraft, the route of the Target aircraft, and the
route of the ownship cannot be amended in an IM clearance, rather the current clearance must be
terminated and a new one issued if desired.
5.2.3 ATC issues an IM clearance to the FAF
An option exists to issue the IM clearance with the Final Approach Fix (FAF) as the
“Achieve-By Point” instead of the runway threshold. This provides an option if the Final
Approach Speed information is not available to the TMA-TM scheduling tool. The TMA-TM
tool will have to increase the size of the spacing buffer between aircraft to compensate for the
variability caused by different Final Approach Speeds of sequential aircraft.
5.3
ATD-1 Off-Nominal Scenarios
The following scenarios are significant events that typically require a change to the schedule,
and invalidates TMA-TM, CMS, and FIM software calculations (the planned trajectory is not
what is occurring). Future discussions will determine if ATD-1 operations will continue if these
events occur, or terminate the demonstration and use current day procedures.
5.3.1 ATC assigns a vector to either CMS or IM aircraft
The ATD-1 ConOps allows for controllers to issue vectors to achieve changes to the goal of
the operation. These events can occur at any time during an arrival, however for brevity they are
described only occurring with the Center controller.
5.3.2 ATC terminates an IM clearance
Operational needs may require ATC to change an aircraft’s assigned route or landing runway
(either the aircraft conducting the IM operation or the Target aircraft for the one conducting IM).
Furthermore, a change to the schedule may require a different arrival sequence, which may cause
a new Target aircraft for another aircraft conducting an IM operation. This event also requires
25
the IM clearance be terminated by ATC. In all cases, after termination, ATC has the option to
issue a new IM clearance to that aircraft, use CMS for that aircraft, or use current day procedures
for that aircraft.
5.3.3 Flight crew terminates an IM clearance
When flight crew of IM equipped aircraft are issued an IM clearance via voice from ATC,
the clearance read back is acceptance of the operation. If Target aircraft surveillance data is
received and the speed calculated by the spacing software is operationally feasible, no further
communication from the flight crew to ATC is required and the crew will fly the IM speed. If
the crew is not able to fly the calculated IM speed or the software cannot calculate a speed, the
flight crew must notify ATC it is terminating IM operations. The flight crew should state the
reason for terminating the IM operation to assist ATC in determining future action.
NOTE: the phraseology in Appendix B specifies that the flight crew state “unable” and ATC
state “cancel” when terminating an IM clearance.
5.3.4 ATC issues a new IM clearance
The existing IM clearance must be cancelled and a new IM clearance given if ATC intends to
change any of the following IM clearance data elements: the STA (if previously given), the
Target aircraft, the route of the Target aircraft, or the route of the IM aircraft. See Appendix B
for the associated phraseology.
26
6.0 Summary of Impacts
The anticipated impacts of the proposed concept on current operations are summarized in the
table below:
Current Operational Use
Enhanced Use with Integrated ConOps
Traffic
Management
Coordinators at
ARTCC
Use the Traffic Flow Management
System automation and TMA to
establish the sequence and schedule
for aircraft arriving at the highdensity airport.
Use the Traffic Flow Management System
automation and TMA-TM to establish a
higher fidelity sequence and more precise
schedule for aircraft arriving at the highdensity airport.
ARTCC Air
Traffic
Controller
Comply with facility procedures for
delivering aircraft to meet TMA
scheduled metering plans.
Comply with facility procedures for
delivering aircraft to meet TMA-TM
scheduled metering plans. This included
issuing IM clearances and the expected
runway.
TRACON Air
Traffic
Controller
Comply with facility procedures for
delivering aircraft to meet TMA
scheduled metering plans. Maintain
aircraft separation and deliver them to
the runway. There is no access to the
TMA schedule.
Comply with facility procedures for
delivering aircraft to meet TMA-TM
scheduled metering plans. For aircraft not
equipped for FIM operations, this includes
using CMS automation for determining the
aircraft’s speed required to meet the TMATM schedule.
Flight crew
Comply with all established
procedures and controller
instructions.
Comply with all established procedures,
controller instructions and speed adjustments
from the FIM automation.
User
27
7.0 References
The References section credits both published and unpublished works that are used
throughout the document to either support or refute statements or offer alternatives. Unpublished
references should be limited to those that are complete, but in the peer review process prior to
publication, and annotated as such. The references section should also include any higher level
or adjacent concepts on which this concept depends.
1. Robinson III, J. E., “ADS-B Enabled Green Operations Using Integrated Scheduling and Spacing
(AEGIS),” Demonstration Description and Plan, Version 2.3, Aug. 5, 2011
2. Federal Aviation Administration, “NextGen Mid-Term Concept of Operations for the National
Airspace System”, FAA ATO, Version 2.0, April 30, 2010
3. Federal Aviation Administration, “Concept of Operations (Draft) for Time-Based Flow Management
(TBFM)”, FAA ATO, Dec 3, 2009
4. Federal Aviation Administration, “Arrival Interval Management – Spacing (IM-S) Concept of
Operations for the Mid-Term Timeframe”, FAA ATO-E, Version 1.5.3, Coordination Draft, Oct 2011
5. Federal Aviation Administration, “Integrated Arrival, Departure, and Surface (IADS) Concept for the
Mid-Term”, working draft, Aug 23, 2010
6. Federal Aviation Administration, “Concept of Operations Guidance and Template”, FAA ATO,
Version 1.0, May 2011
7. Joint Planning and Development Office, “Concept of Operations for the NextGeneration Air
Transportation System, Version 3.2”, Sept., 2010
8. Federal Aviation Administration, “FAA Aerospace Forecast, Fiscal Years 2011-2031”
9. Isaacson, D.R., Swenson, H. N., Robinson III, J. E., “A Concept for Robust, High Density Terminal
Air Traffic Operations,” 10th AIAA Aviation Technology, Integration, and Operations Conference
(ATIO), Fort Worth, TX, Sept. 13-15, 2010
10. Robinson III, J. E., Kamgarpour, M., “Benefits of Continuous Descent Operations in High-Density
Terminal Airspace Under Scheduling Constraints,” 10th AIAA Aviation Technology, Integration, and
Operations Conference (ATIO), Fort Worth, TX, Sept. 13-15, 2010
11. Thipphavong, J., Mulfinger, D., “Design Considerations for a New Terminal Area Arrival
Scheduler,” 10th AIAA Aviation Technology, Integration, and Operations Conference (ATIO), Fort
Worth, TX, Sept. 13-15, 2010
12. Swenson, H.N., Thipphavong, J., Sadovsky, A., Chen, L., Sullivan, C., Martin, L., “Design and
Evaluation of the Terminal Area Precision Scheduling and Spacing System,” 9th USA/Europe Air
Traffic Management Research and Development Seminar (ATM2011), Berlin, Germany, June 13-16,
2011
28
13. Callantine, T., Palmer, E., Kupfer, M., “Human-In-The-Loop Simulation Of Trajectory-Based
Terminal-Area Operations,” ICAS2010, 27th International Congress of the Aeronautical Sciences,
Nice, France, Sept. 19-24, 2010
14. Kupfer, M., Callantine, T., Martin, L., Mercer, J., and Palmer, E., “Controller Support Tools for
Schedule-Based Terminal Operations,” 9th USA/Europe Air Traffic Management Research and
Development Seminar (ATM2011), Berlin, Germany, June 13-16, 2011
15. Barmore, B. E., Abbott, T. S., Capron, W. R., Baxley, B. T., “Simulation Results for Airborne
Precision Spacing along Continuous Descent Arrivals,” 8th AIAA Aviation Technology, Integration,
and Operations Conference (ATIO), Anchorage, AK, Sept. 14-19, 2008
16. Murdoch, J. L., Barmore, B. E., Baxley, B. T., Abbott, T. S., Capron, W. R., “Evaluation of an
Airborne Spacing Concept to Support Continuous Descent Arrival Operations,” 8th USA/Europe Air
Traffic Management Research and Development Seminar (ATM2009), Napa, CA, June 29 – July 2,
2009
17. “Advanced Merging and Spacing Concept of Operations for the NextGen Mid-Term,” Version 1.4,
FAA Surveillance and Broadcast Services Program Office, Washington, DC, Sept. 18, 2009
18. “Safety, Performance and Interoperability Requirements Document for Airborne Spacing-Flight Deck
Interval Management (ASPA-FIM),” RTCA DO-328, RTCA, Washington, DC, June 22, 2011
19. “Airborne Spacing – Flight Deck Interval Management (ASPA-FIM / FIM-S) Controller Pilot Data
Link Communications (CPDLC) Messages”, RTCA SC-214/EUROCAE WG-78 and RTCA SC186/EUROCAE WG-51 Tiger Team, Draft 2.0, 7 Nov 2011
20. “Document Change Proposal to 7110.65U, Para 4-2-8 (Tailored Arrival Clearance) and Para 4-5-7
(Altitude Information)”, FAA AJE-32, March 10,2011 and Feb 9, 2012
21. Abbott, T. S., “A Revised Trajectory Algorithm to Support En Route and Terminal Area Self-Spacing
Concepts,” NASA/CR-2010-216204, NASA Langley, Hampton, VA, Feb. 2010
22. Abbott, T.S., “Airborne Spacing for Terminal Arrival Routes (ASTAR), Version 11, Software
Interface Document”, NASA Langley, Hampton, VA, Sept 27, 2011
29
Appendix A: Acronyms and Definitions
This Appendix contains acronyms and definitions that are used repeatedly throughout the
document, and are central to the ATD-1 Concept of Operations. Acronyms that are well known
(FAA, NASA, etc.) or used only once as a reference (AICM, AXIM, etc.) are not included.
Acronym
--
Term
Airborne Metering
4DT
Four-dimensional trajectory
Achieve-By Point
ADRS
Air Data Radar Simulation
ADS-B
Automatic Dependent Surveillance
– Broadcast
ANSP
Air Navigation Service Provider
ARTCC
Air Route Traffic Control Center
ASG
Assigned Spacing Goal
ASTAR
Airborne Spacing for Terminal
Arrival Routes
Definition
A form of time-based metering in which air traffic controllers
issue clearances to active flights in their sectors that cause the
flights to absorb metering delays.
The centerline of a path formed by segments that link
consecutive trajectory change points; each point defined by a
longitude, latitude, altitude, and some waypoints with a time or
speed restriction.
The point on the IM aircraft’s flight path where the ATC
assigned Spacing Interval behind the Target aircraft is expected
to be achieved. For ATD-1, this point is the runway threshold
(alternative is the Final Approach Fix). [ref 18]
Application that simulates the radar workstations of air traffic
controllers by viewing a radar display of, and data pertaining to
virtual aircraft.
ADS-B is a technology where aircraft avionics (or ground
equipment) autonomously broadcasts the aircraft’s (or ground
vehicle’s) position, altitude, velocity, and other parameters.
“ADS-B out” refers to the broadcast of ADS-B transmissions
from an aircraft or vehicle, and “ADS-B in” refers to receiving
and displaying traffic to the flight crew or vehicle operator.
The aircraft’s position, altitude, and velocity is typically
determined using the aircraft’s GPS navigation system (other
sources such as inertial navigation systems may be used), and
the ADS-B system broadcasts that information with other data.
The organization that directs and provides separation of aircraft
on the air and ground.
Facility responsible for controlling aircraft en route in a
particular volume of airspace (a Flight Information Region)
between airport approaches and departures.
The time between the target (lead) and IM aircraft assigned by
the controller as part of the IM clearance. The time is selected
to achieve the controller’s goal of establishing an efficient flow
while maintaining separation from the target aircraft. [ref 18]
Advanced flight deck-based automation that optimizes
throughput by bringing aircraft to the runway threshold at a
specific time in trail with the preceding aircraft (see SI).
Constantly commands speed adjustments in order to position
an aircraft to 1) arrive at the final-approach-fix at an assigned
time in trail and 2) to fly the profile speeds in between these
adjustments.
A-1
Acronym
ATC
Term
Air Traffic Control
ATD-1
Air Traffic Management
Technology Demonstration
ATM
Air Traffic Management
CDA
Continuous Descent Arrival
CDTI
Cockpit Display of Traffic
Information
CMS
Controller-Managed Spacing
CNS
ConOps
Communication, Navigation, and
Surveillance
Concept of Operations
EFB
Electronic Flight Bag
ETA
Estimated Time-of-Arrival
FAS
Final Approach Speed
Definition
ATC is a service provided by ground-based controllers to
direct and safely separate aircraft on the ground and in the air.
It is commonly used to describe the responsibility and actions
specifically provided by controllers, whereas when ANSP is
used, it generally refers to the entire organization.
The first of a planned series of NASA NextGen Airspace
Program technology demonstrations. This demonstration
integrates three research efforts to achieve high throughput
fuel-efficient arrival operations using precision time-based
schedules, speed control, and CNS technologies.
ATM is the management of air traffic and airspace through the
use of defined strategic planning and programs designed to
efficiently provide for the movement of air traffic. It
encompasses the organization and tactical execution of the
programs through the ANSP by regulating aspects of airspace,
traffic flow, and the safety of NAS operations through national
and local partnerships, and collaboration with end users.
A CDA is a flight procedure where the vertical profile of an
arrival procedure (STAR is an example) has been optimized so
that it can be flown as a continuous descent with the aircraft’s
engines at “idle” or “near-idle” from a high altitude until touch
down on the runway. In the ATD-1 ConOps, it is further
defined as the trajectory of a specific aircraft type at a specific
weight, flown through a specific wind field. Consequently
there are no vertical boundaries in a CDA. [Note: ATD-1 is
based on the use of OPDs]
CDTI is a flight deck based avionics component that allows the
in-flight display of surveillance information concerning
surrounding air traffic.
Controller support tools and displays to assess an aircraft’s
conformance to the arrival schedule, and provide speeds to
resolve any error.
Communications, navigation, and surveillance systems used
together in support of air traffic management.
Document describing a proposed operation that utilizes new
technologies or procedures.
An electronic information management device that helps flight
crews perform flight management tasks more easily and
efficiently with less paper. A general-purpose computing
platform intended to reduce, or replace, paper-based reference
material often found in the Pilot's carry-on Flight Bag,
including the Aircraft Operating Manual, Flight Crew
Operating Manual, and Navigational Charts (including moving
map for air and ground operations).
The current estimate of the aircraft’s arrival at a point based on
forecast winds, but not adjusted to compensate for other
airborne traffic. The ETA is recalculated when an event
occurs, such as a change in speed or trajectory.
The speed flown by the aircraft from the FAF to touchdown on
the runway. There are flight crew and airline variances on
when this speed is achieved.
A-2
Acronym
FDB
Term
Full Data Block
FIM
Flight deck Interval Management
FMS
Flight Management System
--
Freeze Horizon
FRUIT
False Replies Unsynchronized In
Time (or False Replies Uncorrelated
In Time)
GIM
Ground-based Interval Management
IM
Interval Management
IM Speed
MCDU
Interval Management – Terminal
Area Precision Scheduling and
Spacing
Multifunction Control Display Unit
MF (MP)
Meter Fix (Meter Point)
MIT
Miles-in-Trail
MP
Merge Point
MPT
NAS
Metering Point Time
National Airspace System
IMTAPSS
Definition
Lines of information next to aircraft icon containing pertinent
data for the air traffic controller
Flight crew makes use of specialized avionics that provides
speed commands for interval management. Exclusively the
airborne component of entire IM system.
An FMS is a computerized avionics component found on most
commercial and business aircraft to assist pilots in navigation,
flight planning, and aircraft control functions. It is composed of
four major components: FMC (Flight Management Computer),
AFS (Auto Flight System), Navigation System including IRS
(Inertial Reference System) and GPS, and EFIS (Electronic
Flight Instrument System).
After an aircraft crosses the freeze horizon for an En Route
Flow Management Point (ERFMP) or Arrival Flow
Management Point (AFMP) the scheduled crossing time for
that aircraft is no longer updated; it is frozen.
Unwanted transponder replies triggered by other interrogators,
causing reception interference. As air traffic density (and
therefore the number of transponders) increases, the level of
FRUIT is expected to increase as well.
Ground-based functions intended to support interval
management by providing accurate & consistent arrival
spacing to precondition arrival streams for Optimized Profile
Descents (OPDs) and fully utilize the runways.
Systems to achieve and maintain spacing between aircraft.
Includes flight deck (FIM) and ground-based (GIM) elements.
The speed calculated and provided by the aircraft FIM
equipment during an IM operation to achieve the Spacing
Interval behind the Target aircraft by the Achieve-By Point.
The integration of the three (TMA-TM, CMS, and FIM)
technologies and procedures demonstrated in ATD-1.
The flight crew interface to the FMS. MCDU is located next to
throttles to enter info into FMS and CPDLC.
A fix along an established route at which aircraft will meet a
temporal (time) constraint by adjusting its speed. Meter Fixes
(also referrerd to as Meter Points in other concepts) occur in en
route airspace and at the TRACON arrival entry points, and
within TRACON airspace in ATD-1. The speed adjustments
can be assigned by ATC (for example, CMS operations) or
managed by the flight crew (for example, FIM operations).
A specified distance between aircraft, normally, in the same
stream associated with the same destination or route of flight.
Points within TRACON airspace where two arrival routes from
different directions to the same runway converge. Merge
Points may have time constraints applied to them.
Time calculated for an aircraft’s arrival at a given meter point.
The system of airspace, routes, navigation aids, controllers,
airports, facilities, and procedures.
A-3
Acronym
OPD
Term
Optimized Profile Descent
RNAV
Area Navigation
RNP
Required Navigation Performance
RTA
Required Time of Arrival
--
Resume
--
Spacing Interval
STA
Scheduled Time of Arrival
STAR
Standard Terminal Arrival Route
--
Suspend
-TCP
Target Aircraft
Trajectory Change Point
Definition
Similar to CDAs, OPDs are designed to reduce fuel
consumption, emissions, and noise during descent by allowing
aircraft to be flown in a constant descent during arrival with
engines near idle throttle from en route altitude to the runway
threshold. However the OPD procedure specifies not only the
lateral path, but vertical boundaries and a speed for every
segment of the procedure as well. The vertical boundaries of
the OPD are established to accomodate the range descent
trajectories of expected aircraft types and weights, as well as
expected wind fields. Speeds are defined to capitilize on the
use of speed control by controllers and flight crew to achieve
spacing and maintain separation.
Aircraft navigation along flight path using ground-based or
space-based navigation aids, or a combination of the two.
RNP is the navigation performance required for operation
within defined airspace, and corresponds to nautical miles from
route centerline to boundary. RNP may be used but is not a
requirement for ATD-1.
RTA is the time entered by the flight crew into the FMS to
arrive at a particular waypoint. This time is assigned by ATC,
and is typically the STA. In the ATD-1 ConOps, the term STA
is used exclusively.
ATC may instruct the flight crew to resume the previously
issued IM clearance.
The true horizontal along-path spacing (expressed in time)
between the IM and Target aircraft. The SI should equal the
ASG by the Achieve By Point (runway threshold). [ref 18]
STAs are calculated by the TMA-TM software to meet all of
the scheduling and sequence constraints, and are displayed at
the controller workstations. Set at ‘Freeze Horizon’, and
normally not changed. Changing the STA is a ‘reschedule’,
and is manually triggered by the Traffic Manager in response
to a significant event (change in weather, change of runway
configuration, etc). During IM operations, controllers issue the
STA to the crew if desired.
A route established for the purpose of reducing pilot and
controller workload and reducing communications congestion
during arrival operations. Defines the lateral path and vertical
restrictions, however usually does not define a speed nor
connect to the instrument approach procedure (IAP).
ATC may momentarily suspend the IM operation and use CMS
or current day procedures, with the goal of resuming IM at a
later time.
The aircraft specified by ATC for the FIM aircraft to follow.
A full 4D trajectory is defined by a series of trajectory change
points (TCPs). Every point along the path where an altitude or
speed transition occurs. TCPs also define the beginning and
ending segments of turns, with the midpoint defined as a fly-by
waypoint.
A-4
Acronym
TMA
Term
Traffic Management Advisor
TMA-TM
Traffic Management Advisor with
Terminal Metering
TMU
Traffic Management Unit
TOD
Top Of Descent
TRACON
Terminal Radar Approach Control
Definition
The ARTCC based decision support tool TMA is used to
optimize the flow of aircraft into capacity-constrained areas
and calculates Estimated Times of Arrival (ETA) and
corresponding Scheduled Times of Arrival (STA) at various
points along the aircraft flight path to an airport. TMA also
provides the STA and delay times to the respective En Route
controller to maintain the optimum flow rates to runways from
the ARTCC to the TRACON. When flights approach a
congested airport, TMA is used to determine how the multiple
streams of incoming flights can be sequenced and scheduled to
fully utilize the runway and other airport resources avoiding
unnecessary delay while meeting all operational constraints.
An enhancement to TMA that calculates precise time-based,
conflict free schedules to the runway and all meter/merge
points en route to the runway.
A non-control, coordination position at the Air Route Traffic
Control Center (ARTCC) connected to the central flow control
function at the ATCCC and responsible for dissemination of
flow control information at the local level.
The computed transition from the cruise phase of a flight to the
descent phase, the point at which the planned descent to final
approach altitude is initiated. The top of descent is usually
calculated by an on-board flight management system, and is
designed to provide the most economical descent to approach
altitude, or to meet some other objective (fastest descent,
greatest range, etc.).
The ANSP facility responsible for providing ATC services in
the airspace surrounding high-capacity airports.
A-5
Appendix B: Phraseology
Phraseology currently used by controllers and pilots (sector check-in and check-out, initiation
of descent, change of route or speed, etc.) remains unchanged to the maximum extent possible.
For example, “120 knots” may be spoken as “ONE TWO ZERO KNOTS” or as “ONE
TWENTY KNOTS”. Flight crew may use their callsign at the beginning or end of read-back
transmissions.
No new phraseology has been identified yet for CMS operations. IM operations will benefit
from a modification of how aircraft callsign are spoken. The basis for the proposal is to ensure
quick and accurate communication of aircraft callsigns that are spoken differently than the data
tag used on controller and flight crew displays, and to differentiate between the aircraft that ATC
is addressing, versus the aircraft ATC is referring to in a spacing clearance. It is not envisioned
that the phonetic alphabet will be used in these procedures, for example ROMEO PAPA ALPA
ONE NINER TWO.
 When addressing the crew of CMS or IM aircraft: no change to current procedures
o Example: DELTA THREE FOUR FIVE
 When referring to the Target callsign during an IM clearance: use alpha-numeric
o Example: AMERICAN ONE EIGHT SIX, FOR INTERVAL SPACING, AT
THRESHOLD SPACE NINER FIVE SECONDS BEHIND (R A P ONE SIX)
The proposed phraseology in this Appendix required for IM operations are derived from
FAA documents and the IM Working Group [ref 18, 19], and incorporates proposed changes to
controller and pilot phraseology for Tailored Arrival procedures [ref 20]. The IM clearance will
be given by the ARTCC controller, and both ARTCC and TRACON controllers may amend,
suspend, or terminate the IM clearance. The phraseology in this paper and Appendix is written
to allow controllers to issue the IM clearance information separately and after the clearance for
the arrival and approach procedures (onboard spacing algorithm requires the complete trajectory
to calculate speeds needed to achieve a spacing interval at the runway).
One difference when using voice communication compared to Data Comm is the flight crew
immediately acknowledge receipt by reading back the clearance, and only at a later time notify
ATC by exception that they are unable to comply with the clearance. The phraseology in this
Section is further simplified from the IM clearance information and proposed Data Link
messages in the previous paragraph because during ATD-1 operations the spacing interval type
is always a “precise” value and the terminate point is always the runway threshold. The “IM
Tolerance” specified in Reference 18 will also not be issued when using voice communication.
Finally, as an optional element, the FAS of the Target aircraft may be added to the clearance
given by ATC to the flight crew performing the IM operation if that information is available.
The data elements of an IM clearance are listed below, with the two required elements in
bold:
 Scheduled Time of Arrival (STA) [optional; time at Achieve-By Point]
 Achieve-By Point [optional; normally runway threshold, may be the FAF or other fix]
 Assigned Spacing Goal [required; in seconds, to occur by the Achieve-By Point]
 Target (lead) aircraft identification [required; TGT-CALLSIGN]
 Target aircraft route [optional; not required if Target and IM aircraft on same route]
 Target aircraft’s Final Approach Speed (FAS) [optional; if available]
B-1
The phraseology is based on the following guidance:
 “FOR INTERVAL SPACING” is used at the beginning of an IM clearance to alert the
crew that IM procedures and equipment is to be used (not the FMS)
 “CROSS RUNWAY (number)” is used to define the STA if included
 “WHEN ABLE, SPACE” is used to convey the transition from the STA to the relative
spacing portion of the IM clearance
 “THRESHOLD” is used in lieu of “RUNWAY” when an STA is not included or an IM
clearance is amended
 “TARGET” is used in lieu of “(Target-Callsign)” when an IM clearance is amended
B.1
ATC issues and Flight Crew acknowledges an IM clearance
A preparatory call may be made by ATC based on their workload and the flight crew’s
familiarity with the IM operation. Any combination of the three optional IM clearance data
elements (STA, Target route, Target FAS) may be used or not used with each other.
NOTE: as described in the previous section, CMS and IM communication are instructions
from the controller about how to fly the route, and the route clearance is issued separately (based
on current guidance from subject matter experts). Therefore to reduce voice communication and
potential for error, the specific runway is included when a STA is assigned in a clearance (B.1.2),
but not required when a clearance is issued without a STA (B.1.3). If the guidance is to merge
the route clearance and IM clearance, examples of that phraseology based on Tailored Arrival
procedures are listed in Section B.8.
B.1.1 Preparatory (optional)
ATC: (Callsign), INTERVAL SPACING CLEARANCE AVAILABLE, ADVISE WHEN
READY TO COPY.
Crew: (Callsign) IS READY TO COPY.
B.1.2 Issue and acknowledge complete IM clearance
ATC: (Callsign), FOR INTERVAL SPACING, CROSS RUNWAY (one-seven Center) AT
(one-four-three-two plus one-five) ZULU. WHEN ABLE, SPACE (niner-zero)
SECONDS BEHIND (Target-Callsign) ON (Bonham Five OPD), PLANNED FINAL
APPROACH SPEED (one-four-five) KNOTS.
Crew: (Callsign) CROSS RUNWAY (one-seven Center) AT (one-four-three-two plus one-five)
ZULU. WHEN ABLE, SPACE (ninety) SECONDS BEHIND (Target-Callsign) ON
(Bonham Five OPD), FINAL APPROACH SPEED OF (one-four-five) KNOTS.
B.1.3 Issue and acknowledge IM clearance without STA (variation)
NOTE: the STA may be omitted if the Target and IM aircraft are within ADS-B
reception range when the IM clearance is given by ATC.
B-2
ATC: (Callsign), FOR INTERVAL SPACING, AT THRESHOLD SPACE (niner-zero)
SECONDS BEHIND (Target-Callsign) ON (Bonham Five OPD), PLANNED FINAL
APPROACH SPEED (one-four-five) KNOTS.
Crew: FOR INTERVAL SPACING, AT THRESHOLD SPACE (niner-zero) SECONDS
BEHIND (Target-Callsign) ON (Bonham Five OPD), FINAL APPROACH SPEED (onefour-five) KNOTS, (Callsign).
B.1.4 Issue and acknowledge IM clearance without STA or Target route (variation)
NOTE: Target aircraft’s route may be omitted from the clearance when the Target and
IM aircraft are on the same route. Based on avionics, the flight crew will either enter the route
information, or the onboard spacing algorithm will assume ownship route.
ATC: (Callsign), FOR INTERVAL SPACING, AT THRESHOLD SPACE (eight-five)
SECONDS BEHIND (Target-Callsign), FINAL APPROACH SPEED (one-two-six)
KNOTS.
Crew: FOR INTERVAL SPACING, AT THRESHOLD SPACE (eight-five) SECONDS
BEHIND (Target-Callsign), FINAL APPROACH SPEED (one-two-six) KNOTS,
(Callsign).
B.1.5 Issue and acknowledge IM clearance without STA, Route, or FAS (variation)
NOTE: the Target aircraft’s Final Approach Speed may not be known by the controller
issuing the IM clearance. The Target aircraft’s FAS may be given later in the operation (for
example, the TRACON controller), or never given to the IM flight crew (causing reduced
precision at runway threshold).
ATC: (Callsign), FOR INTERVAL SPACING, AT THRESHOLD SPACE (niner-five)
SECONDS BEHIND (Target-Callsign).
Crew: FOR INTERVAL SPACING, SPACE AT THRESHOLD (nine-five) SECONDS
BEHIND (Target-Callsign), (Callsign).
B.1.6 Issue and acknowledge IM clearance without FAS (variation)
NOTE: may occur if limited data is available to the ARTCC controller. Expect good
precision by the IM aircraft to the Final Approach Fix, less precision to the runway threshold.
ATC: (Callsign), FOR INTERVAL SPACING, CROSS RUNWAY (one-seven Center) AT
(one-seven-two-six plus one-five) ZULU. WHEN ABLE, SPACE (nine-five)
SECONDS BEHIND (Target-Callsign) ON (Bonham Five OPD).
Crew: FOR INTERVAL SPACING, CROSS RUNWAY (one-seven Center) AT (one-seventwo-six plus one-five) ZULU. WHEN ABLE, SPACE (nine-five) SECONDS BEHIND
(Target-Callsign) ON (Bonham Five OPD), (Callsign).
B-3
B.2
ATC issues an expected IM clearance or expected runway assignment
ATC may convey information to the flight crew to anticipate an IM clearance to take
advantage of lower workload conditions (for example, while the aircraft is at cruise altitude).
The crew is not required to enter the information into the spacing software, but may do so to
reduce workload later when the IM clearance is issued.
B.2.1 Issue and acknowledge an expected IM clearance
NOTE: An expected IM clearance may or may not include all of the data elements of a
complete IM clearance.
ATC: (Callsign), EXPECT INTERVAL SPACING TO RUNWAY (three-one) BEHIND
(Target-Callsign).
Crew: EXPECT INTERVAL SPACING TO RUNWAY (three-one) BEHIND (TargetCallsign), (Callsign).
B.2.2 Issue and acknowledge an expected landing runway assignment
After the schedule has been established, the Center controller will provide to all flight crew
the expected landing runway for their aircraft. For FIM equipped aircraft receiving an IM
clearance, the runway assignment is contained within the IM clearance (see Section B.1.2). For
FIM aircraft not receiving an IM clearance (for example, all IM information not available to
Center controller) and for all CMS aircraft, the Center controller should issue this information
prior to Top Of Descent (TOD).
ATC: (Callsign), EXPECT RUNWAY (two-four Right) AT LAX.
Crew: (Callsign), EXPECT RUNWAY (two-four Right) AT LAX.
NOTE: The ATD-1 ConOps requires the flight crew understand the entire aircraft trajectory,
from current location to runway threshold. The phraseology above is used when the aircraft is
on an OPD that connects to Instrument Approach Procedure at only one point. If several
waypoints may be used to connect the arrival to the approach, then the expected points must also
be specified.
ATC: (Callsign), AFTER (Sadde Six Arrival), EXPECT (Sappi), (Merce), RUNWAY (twofour Right) AT LAX.
Crew: AFTER (Sadde Six Arrival), EXPECT (Sappi), (Merce), RUNWAY (two-four Right) AT
LAX, (Callsign).
B.3
ATC amends and Flight Crew acknowledges an IM clearance
The values in an IM clearance for the spacing interval and Target aircraft’s Planned Final
Approach Speed may be modified by ATC as new information becomes available or operational
goals change. The cause of these types of events does not require a “re-schedule” or different
B-4
controller action of CMS operations. (If ATC must change the STA, Target aircraft, or the route
of either the Target or IM aircraft, the current IM clearance must be terminated and a new IM
clearance issued. These events typically do create a “re-schedule” or “ripple of the list”, and
trigger different CMS values. See Section B.7 for terminating a clearance.)
B.3.1 Amend IM clearance with new information (example, Target aircraft’s FAS)
ATC: (Callsign), AMEND INTERVAL SPACING CLEARANCE. TARGET FINAL
APPROACH SPEED IS (one-two-six) KNOTS.
Crew: AMEND INTERVAL SPACING CLEARANCE. TARGET FINAL APPROACH
SPEED (one-two-six) KNOTS, (Callsign).
B.3.2 Amend IM clearance with change to information (example, spacing interval)
ATC: (Callsign), AMEND INTERVAL SPACING CLEARANCE. SPACE (eight-zero)
SECONDS BEHIND TARGET.
Crew: AMEND INTERVAL SPACING CLEARANCE. SPACE (eight-zero) SECONDS
BEHIND TARGET, (Callsign).
B.4
Flight Crew notifies ATC that the IM operation has begun
It is desirable to have the flight crew notify ATC when the IM spacing has begun. Data from
simulator experiments indicate approximately 45 to 60 seconds are needed after ATC issues an
IM clearance for the crew to manually enter the data and the spacing software to calculate the
required speed.
Crew: (Regional Approach), (Callsign) INTERVAL SPACING BEHIND (Target-Callsign).
ATC: (Callsign), ROGER.
B.5
Flight Crew notifies ATC that an IM operation is being conducted
The current controller will make the receiving controller aware of aircraft conducting IM
operations through the data tag display or other coordination procedure. In addition, the flight
crew will include the information during check-in with the receiving controller.
Crew: (Regional Approach), (Callsign) PASSING (one-two thousand), INTERVAL SPACING.
ATC: (Callsign), ROGER.
B.6
Suspending and Resuming IM operations
The IM operation may be suspended and later resumed by ATC when needed by the
controller to achieve other objectives over a short time period. This may be used if both the
Target aircraft and the FIM aircraft remain on the assigned route.
B-5
ATC: (Callsign), SUSPEND INTERVAL SPACING, SLOW TO (two-three-zero) KNOTS.
Crew: (Callsign), SUSPEND INTERVAL SPACING, SLOW TO (two-three-zero) KNOTS.
ATC: (Callsign), RESUME INTERVAL SPACING.
Crew: RESUME INTERVAL SPACING, (Callsign).
B.7
Terminating an IM clearance prior to the Final Approach Fix
The IM operation is designed for the flight crew to correct spacing errors until the FAF, at
which point the crew uses the aircraft’s FAS and spacing error corrections are no longer made.
When the IM operation terminates at the FAF, no specific phraseology is required.
When the IM operation is terminated prior to the FAF, the person making that decision will
communicate it to the other party. Examples include the flight crew unable to continue spacing
because the speed calculated by the onboard spacing software is outside of an acceptable range
or the surveillance data from the Target aircraft has been lost, or ATC must vector the Target or
FIM aircraft off the assigned route.
B.7.1 Flight crew determines calculated IM speed is not feasible (too fast or too slow)
Crew: (Regional Approach), (Callsign) UNABLE INTERVAL SPACING DUE TO (speed).
ATC: (Callsign), ROGER. CONTINUE ON THE (Sadde Six OPD), FLY (published speed).
B.7.2 Target aircraft surveillance data lost (no ADS-B signal)
NOTE: this call is only required if ATC did not include the STA in the IM clearance. If
the STA was included in the clearance, the IM operation continues, the spacing algorithm uses
the STA for speed calculations, and no voice communication is required from the flight crew.
Crew: (Regional Approach), (Callsign) UNABLE INTERVAL SPACING DUE TO (no Target
ADS-B).
ATC: (Callsign), ROGER. CONTINUE ON THE (Sadde Six OPD), FLY (published speed).
B.7.3 Controller has other operational considerations
ATC: (Callsign), CANCEL INTERVAL SPACING, FLY (one-seven-five) KNOTS.
Crew: (Callsign), CANCEL INTERVAL SPACING, FLY (one-seven-five) KNOTS.
B.8
ATC issues and Flight Crew acknowledges OPD / IM clearance
The OPD is a published approach procedure that contains waypoints from the high-altitude
airway route structure to an Instrument Approach Procedure, without requiring the use of vectors
B-6
to create a single continuous trajectory. The phraseology in this sub-section is based on Tailored
Arrival procedures and phraseology. Similar to Tailored Arrivals, the OPD clearance consists of
the lateral path, vertical constraints, speed constraints, and connects to the Initial Fix of an
approach procedure to one runway. This contrasts with procedures used today that have multiple
waypoints that may be used to connect the arrival to the approach, and arrivals the may be
connected to several runways.
ATC: (Callsign), DESCEND VIA THE (Cedar Creek OPD). FOR INTERVAL SPACING, AT
RUNWAY THRESHOLD SPACE (one-zero-five) SECONDS BEHIND (TargetCallsign) ON THE (Bonham Five OPD), PLANNED FINAL APPROACH SPEED (onefour-five) KNOTS.
Crew: DESCEND VIA THE (Cedar Creek OPD). FOR INTERVAL SPACING, AT
RUNWAY THRESHOLD SPACE (one-zero-five) SECONDS BEHIND (TargetCallsign) ON THE (Bonham Five OPD), PLANNED FINAL APPROACH SPEED (onefour-five) KNOTS, (Callsign).
B-7
Appendix C: Scheduling and IM Algorithms
This Appendix is to ensure the algorithms used by the ground scheduling tool and airborne
spacing tool produce values expected by the other component of the ATD-1 ConOps.





C.1
Ground-based Scheduling Algorithm
The TMA-TM scheduling algorithm will use the published OPD to calculate the aircraft’s
ETA to the runway threshold.
As an aircraft crosses the ‘Freeze Horizon’, it’s ETA is added to the conflict free schedule of
STAs for all aircraft proceeding to that runway, and that time may be adjusted if needed.
The adjusted STA time at the runway threshold will be used to calculate times at all meter
points based on the speeds defined in the published OPD.
The upstream STAs at merge points or meter fix may deviate slightly from speeds shown on
the published approach to achieve deconfliction due to merge/diverge routes, etc.
If the times at meter fixes for a particular aircraft must be adjusted to ensure a conflict free
trajectory, that is the aircraft must fly a speed different than published to achieve consecutive
meter point times, then CMS procedures should be used for that aircraft.
C.2
Controller Managed Spacing Algorithm
Information for timelines early/late indicators comes directly from arrival schedules; thus, it
is to be communicated to TRACON controller workstations from TMA-TM.
Slot markers are computed via the following process:
 Retrieve and store the merge point and runway schedules. The merge point and runway STAs
are generated by and transmitted from TMA-TM. For each such scheduling point a schedule
is maintained to keep STAs and ETAs for all scheduled aircraft. The schedules are updated
every-time new scheduling information is received.

Compute the nominal trajectory. The nominal trajectory is the trajectory that the aircraft
would fly if it did not receive any control instructions from the controller and met all speed
and altitude restrictions that are specified in the nominal arrival procedure.

Time-shift the nominal trajectory to meet the merge-point STAs. After this computation each
trajectory point will have a nominal time-of-arrival that represents the time at which an
aircraft would arrive at this waypoint if it flew the nominal trajectory and arrived at the STA
at the next merge point.

Compute the nominal flight state. Given the nominal trajectory and the nominal times-ofarrival, use a trajectory-based interpolation algorithm to compute the aircraft’s state at the
point along the trajectory where the aircraft would be at the current time.

Store the nominal flight state with the aircraft record. This enables the values required to
display the slot marker to be retrieved.
Speed advisories are computed via the following process:
 Determine if a speed advisory is feasible. The speed-advisory algorithm first traverses
scheduling points between the current aircraft position and the runway and computes whether
C-1
the desired STA at each point lies within the window spanned by the earliest and latest time
of arrival. The algorithm uses information about the fastest and slowest speeds along the
relevant trajectory segments to make this determination.

Construct the advisory. For each scheduling point where an advisory is possible, iterate over
the possible speed range, changing the speed restrictions between the current aircraft location
and the point to test speed values that lie between the fastest and slowest allowable speeds.
For each test speed, compute the corresponding trajectory and evaluate the ETA at the
scheduling point. If the absolute difference between the STA and the ETA for the test speed
is less than a preset threshold (e.g., 2 s), indicate success, and quantize the result for display
(per adaptable parameters).
C.3
Flight-deck Interval Management Algorithm
More detailed information about the ASTAR algorithm used for IM operations is in Ref 20
and 21. The following are design goals of the airborne spacing algorithm assuming that the IM
clearance given to the flight crew is feasible:







The time error of the aircraft decreases as the operation progresses
 Error may increase if forecast wind incorrect
 More of the error is corrected within the TRACON to avoid over-controlling
IM aircraft should arrive within 5 seconds of the Spacing Interval at the Achieve By
Point (assumes flight crew monitor and fly the IM speed, the Target FAS is correct, etc.)
If safe separation exists behind ‘Target aircraft’ at beginning of IM operation, safe
separation will be maintained from beginning to end of IM operation
Additional speed changes for IM operation above those on published approach will be
minimized (no changes within 30 seconds of the previous change, no speed change
within 30 seconds of the next published speed change, etc.)
No speed increases once below 210 KIAS
No command speeds greater than 250 KIAS when the aircraft is below 10,000 MSL
Commanded speed will not exceed 10% greater than, or 10% less than, the speed for that
segment of the published route
C-2
Appendix D: Operational Assumptions and Requirements
This section outlines assumptions and requirements for ATD-1 procedures.
Schedule
 The scheduling software will have accurate aircraft data available, to include callsign,
route, and Final Approach Speed.
 Routes used by the ground schedule and airborne spacing software are from current
aircraft position to landing runway.
 The routes contain a speed for each segment of the arrival and approach.
 The scheduler has the information necessary to determine which aircraft are IM capable.
 The Target aircraft of an IM clearance must be transmitting ADS-B data (it does not
matter if the Target aircraft itself is conducting CMS or IM operations).
 CMS and IM operations can be performed in any traffic density, and in either visual or
instrument meteorological conditions.
 The ground tool will establish a STA at the runway for each aircraft. This time creates
the intended aircraft arrival sequence, and the spacing interval between aircraft meets or
exceeds wake vortex spacing, separation requirements , runway occupancy, etc.
 IM equipped aircraft will use the ATC-assigned runway time and route to calculate times
at the TRACON boundary and any other meter fix. The times calculated by the onboard
spacing software for the TRACON boundary and Final Approach Fix should be very
similar to times generated by the ground scheduler for that IM aircraft.
 The Target aircraft and IM aircraft will land on the same runway.
 The schedule will provide the controller information required to issue an IM clearance,
and that clearance will be feasible (speed close to procedure or current operations). It is
highly desired that ARTCC controllers issue the IM clearance, however may occur with
the TRACON controller during initial check-in.
 The range of current day RNAV performance is acceptable, and RNP is not required.
Initiation
 The controller will have positive control over all aircraft in that sector.
 Separation of aircraft exists and is expected to continue to exist for ATC to issue an IM
clearance to that flight crew.
 If the runway STA and upstream waypoint STAs are not based on the speeds of the
published procedure, an IM clearance may be issued to that aircraft however that aircraft
may not precisely achieve the upstream STAs.
 All IM clearances (STA, STA with IM, IM only, and amendments) will be issued via
voice from ATC to the flight crew.
 It is desirable that the IM clearance be issued prior to TOD, however may be issued by
the TRACON controller.
 The IM aircraft must receive ADS-B data from the Target aircraft, but is not required to
receive ADS-B data from any other aircraft.
 The approximate time expected from ATC issuing an IM clearance until the flight crew
accepts it is 10 seconds, and 60 seconds until the aircraft is at the appropriate speed.
D-1

The flight crew will notify ATC within 60 seconds of the initial clearance if the IM
operation is not feasible due to an operationally unacceptable IM speed.
Operation
 The instructions of a controller take precedence over the IM speed.
 The IM speed calculated by the spacing software is equivalent to a controller’s speed
instruction, that is, the IM speed supersedes the published speed on an arrival or approach
and must be flown unless the crew notifies ATC otherwise.
 The IM speed does not allow the crew to exceed regulatory (e.g., 250 KIAS below
10,000’ MSL, etc.) or airframe limits (flap-limit speed, etc.).
 The flight crew is expected to respond to an IM speed change within 30 seconds during
cruise, within 20 seconds during descent, and within 10 seconds inside the TRACON.
 The flight crew is expected to remain within 0.01 Mach or 10 KIAS of the IM speed once
it has been achieved.
 An aircraft flying an IM operation will achieve the assigned spacing interval behind the
Target Aircraft by the Achieve-by Point (the runway threshold).
 The controllers will have displays on the scope that indicate which aircraft are conducting
IM operations, and how that operation is progressing.
 Controllers will attempt to not issue vectors to aircraft unless safety concerns or other
operational considerations require they do.
 Controllers minimize assigning speed changes to IM aircraft unless safety concerns or
other operational considerations require they do. ATC assigned speeds take priority over
FIM calculated speeds; therefore the IM operation should be ‘suspended’ or ‘terminated’.
 Aircraft conducting IM operations are expected to arrive at the runway within 10 seconds
of the time estimated by the ground scheduling software.
 IM amendments should be given no later than during initial voice check-in with the
TRACON controller.
Termination
 After the Final Approach Fix, the onboard algorithm provides no speed commands to
correct spacing errors, and the flight crew have no FIM related tasks or displays.
 The flight crew will notify ATC if they terminate the IM operation prior to the Final
Approach Fix.
D-2
Appendix E: Information Flow
This section is an overview of data element used by each technology, the source and format of the data, and finally the users of the
data required to conduct ATD-1 Operations. The categories of need for the users are:
 R (required): data necessary for the operation to occur as described here, including safely reacting to non-normal events.
 E (expected): data required to achieve the expected outcome; however, if unavailable a small percentage of the time, the
operation can continue with less than optimal results.
 D (desired): data not required to achieve results, but useful to maintain operational efficiency during non-normal events.
  (not required or not relevant)
Data Element
Source
Format
TMA-TM
software
CMS
software
FIM
software
Non-FIM
crew
FIM flight
crew
Aircraft’s route
Host data, AOC
R
R
R
R
R
Aircraft capabilities
(RNP, FIM, etc)
Host data, AOC
R
R
-
R
R
Aircraft position
Radar, ADS-B
R
R
R
R
R
Forecast winds
various
E
-
E
E
E
Airport configuration
Airport
R
R
-
-
-
Runway allocation
Airport
R
-
-
-
-
Spacing requirement
7110.65
R
R
D
-
D
Planned arrival sequence
TMA-TM
R
R
-
-
-
STA to the runway
TMA-TM
R
R
R
-
D
R
R
-
-
-
STA to Meter Fixes
E-1
Data Element
Source
Format
TMA-TM
software
CMS
software
FIM
software
Non-FIM
crew
FIM flight
crew
FIM specific data
Aircraft’s STA at runway
[optional]
TMA-TM via
ATC
See Section B.1.2
R
-
D
-
D
Target aircraft
TMA-TM
See Section B.1.2
R
-
R
-
R
Spacing Interval
TMA-TM
See Section B.1.2
R
-
R
-
R
Target aircraft’s route
[optional]
TMA-TM
See Section B.1.2
R
-
R
-
E
Target aircraft’s position
ADS-B
See Section B.1.2
-
-
R
-
E
Target aircraft’s FAS
[optional]
ATC
See Section B.1.2
E
-
E
-
E
Actual winds
Ownship
Standard
-
-
E
-
E
FIM speed
FIM software
x.xx Mach or
xxx KIAS
-
-
R
-
R
FIM status
FIM software
-
-
R
-
R
E-2
Appendix F: Sample ATD-1 Arrival and Approach Procedures
Shown are sample arrival and
instrument approaches used during
previous NASA research that exhibit
the characteristics required for ATD1 (north-east arrival into Dallas – Ft
Worth airport and the Instrument
Landing System (ILS) to Runway 17
Center). These characteristics allow
the TMA-TM software to calculate
arrival times for all aircraft, and the
FIM spacing software to calculate the
speed required to achieve assigned
STA at the runway. In particular:

The arrival procedure
(BONHAM FIVE) connects
to a fix on the approach
procedure to Runway 17C
(PENNY located at bottom
left of procedure)

A speed is defined for each
segment of the arrival and
instrument approach
procedures (e.g., COVIE at
240 knots) until the Final
Approach Fix (JIFFY)
Figure 13. Sample Arrival Procedure (connects to instrument approach at PENNY)
F-1
Figure 14. Sample Approach Procedure (connects to Arrival via PENNY)
F-2