NAS2-98005 RTO-41

Technical Research in Advanced Air Transportation Technologies

Detailed Description for CE-7

En route: Collaboration for Mitigating Local TFM Constraints due to
Weather, SUA, and Complexity Constraints

#### Robert A. Vivona

#### November 2000

#### Prepared For: NASA Ames Research Center

#### Moffett Field, CA 94035-1000

![](media/image1.png)

[]{#__RefHeading___Toc500209454 .anchor}Preface

This report is the first version of a detailed description for the
Distributed Air/Ground Traffic Management (DAG-TM) Concept Element (CE)
7, En Route: Collaboration for Mitigating Local TFM Constraints due to
Weather, SUA, and Complexity Constraints. The ideas presented here are
preliminary and require additional work.

NASA is soliciting review of this report and welcomes comments. Comments
should be sent to:

-   Del Weathers, Manager, AATT ATM Concept Definition Sub-element, NASA
    Ames Research Center -- dweathers@mail.arc.nasa.gov

```{=html}
<!-- -->
```
-   Steve Green, Manager, AATT En Route Systems and Operations
    Sub-element, NASA Ames Research Center -- sgreen@mail.arc.nasa.gov

[]{#__RefHeading___Toc500209455 .anchor}Table of Contents

Preface [ii](#__RefHeading___Toc500209454)

Table of Contents [iii](#__RefHeading___Toc500209455)

Table of Figures [iv](#__RefHeading___Toc500209456)

1.0 Introduction [1](#__RefHeading___Toc500209457)

1.1 Background [1](#__RefHeading___Toc500209458)

1.2 Objectives [1](#__RefHeading___Toc500209459)

1.3 Scope [2](#__RefHeading___Toc500209460)

2.0 Problem Definition [2](#__RefHeading___Toc500209461)

2.1 Constrained Airspace Problem Definition
[2](#__RefHeading___Toc500209462)

2.2 Constrained Airspace Problem Types [3](#__RefHeading___Toc500209463)

2.3 Efficiency and Capacity Limitations to Traffic Flow Management in
Constrained Airspace [4](#__RefHeading___Toc500209464)

3.0 Approach [6](#__RefHeading___Toc500209465)

3.1 High Level Benefit Mechanisms [6](#__RefHeading___Toc500209466)

4.0 Operational Requirements [7](#__RefHeading___Toc500209467)

5.0 Operational Environment [7](#__RefHeading___Toc500209468)

5.1 Airspace Structure and Constraints [8](#__RefHeading___Toc500209469)

5.2 Traffic Mix and Equipage [9](#__RefHeading___Toc500209470)

5.3 CNS Infrastructure [9](#__RefHeading___Toc500209471)

5.4 ATM Environment [9](#__RefHeading___Toc500209472)

6.0 Operational Characteristics [10](#__RefHeading___Toc500209473)

6.1 ATSP View [12](#__RefHeading___Toc500209474)

6.2 Pilot View [15](#__RefHeading___Toc500209475)

6.3 AOC View [17](#__RefHeading___Toc500209476)

7.0 NAS Functional Impacts [18](#__RefHeading___Toc500209477)

7.1 Functional Requirements [18](#__RefHeading___Toc500209478)

7.2 Functional Design [23](#__RefHeading___Toc500209479)

8.0 User/Operator Roles and Responsibilities
[24](#__RefHeading___Toc500209480)

8.1 ATSP [24](#__RefHeading___Toc500209481)

8.2 Pilot [25](#__RefHeading___Toc500209482)

8.3 AOC [25](#__RefHeading___Toc500209483)

9.0 Operational Modes and Scenarios [25](#__RefHeading___Toc500209484)

9.1 Normal or Nominal Mode Scenarios [25](#__RefHeading___Toc500209485)

9.2 Off-Nominal Mode Scenarios [29](#__RefHeading___Toc500209486)

9.3 Failure Mode Scenarios [29](#__RefHeading___Toc500209487)

10.0 Operational Process/Sequence Diagrams
[29](#__RefHeading___Toc500209488)

11.0 Benefits [31](#__RefHeading___Toc500209489)

12.0 Issues and Key Decisions [33](#__RefHeading___Toc500209490)

References [35](#__RefHeading___Toc500209491)

Appendix A: Operational Requirements Table
[36](#__RefHeading___Toc500209492)

Appendix B: Operational Requirements References
[43](#__RefHeading___Toc500209493)

[]{#__RefHeading___Toc500209456 .anchor}Table of Figures

Figure 1: Problems in Constrained En Route Airspace
[5](#__RefHeading___Toc500209495)

Figure 2: Relationship of CE-7 Operational Environment to other NASA and
FAA Efforts [7](#__RefHeading___Toc500209496)

Figure 3: Stages of User-ATSP Collaboration as Function of Time to
Constrained Airspace [10](#__RefHeading___Toc500209497)

Figure 4. Dynamic Re-Sectorization [13](#__RefHeading___Toc500209498)

Figure 5. Dynamic SUA Access and Negotiation
[14](#__RefHeading___Toc500209499)

Figure 6: Functional Flow of Data between CE-7 DSTs
[24](#__RefHeading___Toc500209500)

Figure 7: Example Scenario [26](#__RefHeading___Toc500209501)

Figure 8: Constrained Airspace Resolution Sequence Diagram
[30](#__RefHeading___Toc500209502)

1.  []{#__RefHeading___Toc500209457 .anchor}Introduction

    1.  []{#__RefHeading___Toc500209458 .anchor}Background

The Distributed Air/Ground Traffic Management (DAG-TM) concept describes
potential modes of operation within the Free Flight concept defined by
the RTCA Task Force 3. The goal of DAG-TM is to enhance user flexibility
and efficiency and increase system capacity, without adversely affecting
system safety or restricting user accessibility to the National Airspace
System (NAS).

To explore the DAG-TM concept, the AATT Project formed a DAG-TM Team
that met during 1999 and developed a Concept Definition \[1\]. This
document defined 15 DAG-TM "concept elements", covering ATM operations
in all phases of flight. The defined phases were:

-   Gate-to-Gate (information access and exchange)

-   Pre-Flight Planning

-   Surface Departure

-   Terminal Departure

-   En Route

-   Terminal Arrival

-   Terminal Approach

-   Surface Arrival

In 2000, the AATT Project selected an initial set of four concept
elements (CEs) to pursue further concept exploration (research)
activities.

-   CE-5: En Route Free Maneuvering

-   CE-6: En Route Trajectory Negotiation

-   CE-7: En Route: Collaboration for Mitigating Local TFM Constraints
    due to Weather, SUA, and Complexity

-   CE-11: Terminal Arrival: Self-Spacing for Merging and In-Trail
    Separation

In May 2000, a DAG-TM Workshop \[2\] was held at the NASA Ames Research
Center to explain to industry the AATT Project's activities and plans
for the concept. The workshop focus was on the four initial CEs being
developed. Under Task Order 41, a contractor team consisting of System
Resources Corporation and Seagull Technology is preparing detailed
descriptions of each of the four selected CEs. This document is a
detailed description of CE-7, En Route: Collaboration for Mitigating
Local TFM Constraints due to Weather, SUA, and Complexity.

1.  []{#__RefHeading___Toc500209459 .anchor}Objectives

The objectives of Task Order 41 include:

-   Evaluate the concept through existing documents that define the
    current level of understanding.

-   Identify ambiguities within the concept and resolve issues through
    interviews with NASA experts.

-   Identify and resolve inconsistencies between AATT objectives and the
    concept.

-   Develop a detailed concept description to provide guidance for the
    continued research in this concept through 2004.

-   Provide updates/enhancements to the AATT Air Traffic Management
    Operations Concept (ATM/OPSCON) to incorporate the relevant aspects
    of the DAG CE.

    1.  []{#__RefHeading___Toc500209460 .anchor}Scope

The description of CE-7 is intended to add further detail to facilitate
further research into the concept. It is not, however, a research plan.
The research plan is a separate document being developed by NASA that
describes how the concepts presented here will be investigated.

The detailed description has a focus of operational and system
requirements, and deliberately avoids design information to the extent
possible. The detailed description will provide concept definition and
clarification to assist in defining the design of decision-support
automation, roles and procedures, and experimental assessments to test
the CE-7 concept.

Finally, specifications are beyond the scope of this document, since
capabilities to support the CE-7 concept should evolve as a result of
the research to be conducted. To avoid confusion with widely discussed
tools such as Controller Pilot Data Link Communications (CPDLC) whose
specifications are being developed or discussed external to AATT, this
description uses general terms to describe the capabilities necessary to
support this concept.

2.  []{#__RefHeading___Toc500209461 .anchor}Problem Definition

    1.  []{#__RefHeading___Toc500209462 .anchor}Constrained Airspace
        Problem Definition

CE-7 is focused on efficient traffic flow management (TFM) solutions to
"constrained airspace" problems. For this discussion, constrained
airspace is defined as impacted en route airspace that contains flights
that transit a common region but do not share a common destination. For
each flight, a constrained airspace problem causes flight deviations due
to en route impediments independent of the flight's destination. This
definition distinguishes constrained airspace from transition airspace,
where the impacted en route airspace contains flights that transit a
common region to a common terminal area. Transition airspace problems
(the classical focus of the Center TRACON Automation System (CTAS))
cause flight deviations (delay) due to impediments related to the
flight's common destination (e.g., arrival metering and spacing in
response to terminal congestion).

Though constrained airspace and transition airspace have been defined
independently, the reality is that an en route facility may have to
handle both constrained airspace problems and transition airspace
problems simultaneously. For example, Denver Center may have to handle
metering to Denver Terminal Radar Approach Control (TRACON) at the same
time as handling weather that is causing deviations to over-flight[^1]
traffic into adjacent centers. The aircraft that are being metered are
being impacted by a transition airspace problem (predicted traffic
demand exceeding the Denver TRACON acceptance rate). The over-flight
traffic is being impacted by a constrained airspace problem (predicted
traffic demand exceeding acceptable sector loading in weather impacted
sectors). The metered traffic are all transitioning to Denver TRACON
(the common destination) whereas the over-flight traffic do not all have
the same destination airport.

2.  []{#__RefHeading___Toc500209463 .anchor}Constrained Airspace Problem
    Types

There are three basic types of constrained airspace problems: negative
impacts caused by losing a section of airspace ("Lost Airspace"
problem), controllers/users not taking advantage of newly available
airspace ("Gained Airspace" problem), and unexpected negative impacts
caused by acceptance of user requests or preference changes ("User
Request" problem).

1.  *Lost Airspace Problem*

Airspace is "lost"[^2] when traffic demand exceeds the airspace's
allowable capacity level. There are two ways that a section of airspace
can be lost: either traffic demand increases above the allowable
capacity level or the allowable capacity level drops below traffic
demand. When traffic demand exceeds the allowable capacity level, the
flow through the impacted airspace must be reduced by rerouting traffic
away from the airspace and/or adding flow-rate restrictions into the
airspace. The size of lost airspace can be smaller than a sector or as
large as many sectors. Since CE-7 is focused on solutions to TFM
problems, the impact of the lost airspace is assumed to affect the
traffic flow of more than one sector controller.

A sector's capacity may be monitored in terms of its "dynamic
density."[^3] The dynamic density concept postulates that the air
traffic control (ATC) workload of a sector (or more generally, a region
of airspace) can be measured based on the density and complexity of its
predicted traffic \[3, 4, 5\]. The maximum operationally allowable value
of dynamic density (i.e., a maximum allowable controller workload) can
then be established by traffic managers, as a function of
traffic/airspace situation, based on empirical data and experience. When
dynamic density is predicted to exceed this acceptable value, the sector
is considered "lost."

There are three main causes of lost airspace problems. The first cause
is due to excessive traffic demand. When the predicted number of
aircraft in a sector causes that sector's dynamic density to increase
above its allowable level, some of the traffic demand must be alleviated
(either through rerouting aircraft or flow rate reduction) to bring the
dynamic density below accepted levels. The second cause is the
activation of Special Use Airspace (SUA). When an SUA becomes active, it
has to be avoided and any aircraft predicted to enter the SUA while
active must be re-routed.[^4] The third cause is the formation of
weather that is unsuitable or undesirable for flight operations (e.g.,
turbulence, convective activity). Weather can impact airspace by forcing
deviations around hazardous airspace as well as decreasing the
acceptable dynamic density in those sectors that are impacted (e.g.,
increased workload per flight due to re-routing around weather within a
sector). Weather also is dynamic and can move from one sector to
another, causing the acceptable dynamic density for sectors to be a
function of time. Like all lost airspace problems, when the weather
causes allowable sector dynamic densities to decrease below the
predicted dynamic density for the existing traffic demand, there must be
a decrease in flow rate (either through rerouting or flow rate
reductions) to achieve the acceptable levels.

2.  *Gained Airspace Problem*

Airspace is "gained" when traffic demand drops below the airspace's
allowable capacity level or the capacity level is increased above
current traffic demand. This is not a problem as much as it is
potentially a missed opportunity to achieve user and/or service provider
benefits. The newly available airspace presents options to decrease
congestion in other airspace or to enable user flexibility to increase
flight efficiency or make up time.

The causes of airspace to be gained are the exact opposites of those for
lost airspace. A decrease in traffic demand allows more aircraft to be
sent through impacted sectors. De-activation of SUA airspace opens that
airspace for flights that are currently routed around the airspace.
Weather dissipation returns acceptable levels of dynamic densities to
their previous maximum values, allowing more traffic to be accepted.

It should be noted that lost and gained airspace problems often
interact. The most obvious example is when weather is moving through a
facility. As the weather leaves one sector and enters another, the first
sector's allowable capacity increases (gained airspace) while the second
sector's capacity decreases (lost airspace).

3.  *User Request Problem*

Controller acceptance of user-preferred requests for flight path changes
may have a negative downstream impact on air traffic operations that
neither the controller nor user can predict. This impact may be in the
form of increased congestion/workload for a downstream sector, and/or
unanticipated delays for the user (which may outweigh the potential
benefit originally sought by the user). This situation may occur today
because of two factors. First, users do not have access to an accurate
prediction of the future state of the NAS to form "intelligent" requests
that account for probable downstream impacts. Secondly, controllers that
receive a user's request do not have the predictive ability (beyond a
tactical conflict probe[^5]) to anticipate downstream congestion and TFM
restrictions. It should be noted that the negative impacts observed in
User Request Problems are usually Lost Airspace Problems.

Emphasis on the use of preferential routing in future free flight
concepts makes this a problem of continuing interest. [^6]

3.  []{#__RefHeading___Toc500209464 .anchor}Efficiency and Capacity
    Limitations to Traffic Flow Management in Constrained Airspace

All three constrained airspace problems effectively relate to
limitations in the capacity of en route airspace. Lost airspace causes a
direct decrease in available airspace capacity. Under-utilized gained
airspace is effectively a wasteful "loss" of airspace. User requests
that cause downstream complexity problems also result in lost airspace.
In the presence of capacity decreases, NAS operations become restricted.

Currently, the air traffic service provider (ATSP) imposes constraints
on users when NAS operations are predicted to be restricted in certain
regions of en route airspace due to bad weather, SUA and airspace
congestion/complexity (see Figure 1). These constraints may take the
form of speed changes, altitude changes, or path changes, all of which
represent a deviation from the preferred trajectory planned by the user.
In some instances, these NAS operational constraints may affect aircraft
long before they are near the affected region of airspace.

In many cases, the deviations issued by the ATSP are different from what
would be preferred by the user (both flight deck (FD) and airline
operations center (AOC)). There may be multiple ways in which the
constraint can be satisfied, and the deviations imposed by the ATSP may
not be the most efficient (or desired) in terms of meeting the users'
business objectives. Examples may include: the choice of flights to be
deviated, the direction of the deviation, the type of deviation (route,
altitude, speed), route deviations around airspace/weather through which
the user might be willing to fly, or route deviations that involve
flying through airspace/weather that the user would prefer not to
penetrate.

![](media/image2.wmf)

[]{#__RefHeading___Toc500209495 .anchor}Figure 1: Problems in
Constrained En Route Airspace

Inefficiencies occur in the resolution of constrained airspace problems
due to current-day limitations (including the lack of decision support)
in the ability of controllers and traffic managers to select the most
advantageous combination of aircraft, route of flight and operational
constraints for the airspace. TFM initiatives tend to focus on "easy to
control" streams of traffic (e.g., easiest solution, not most
efficient), which causes in-equitable distribution of deviations among
aircraft. The lack of an ability to reliably identify and diagnose
constrained airspace problems well before they occur creates reactive,
non-collaborative solutions.

Inefficiencies arise during selection of the most advantageous solution
when confronted with a mandatory change (lost airspace), through the
inability to identify whether non-mandatory opportunities exist to gain
operational benefits (gained airspace) and through the inability to
identify and avoid negative impacts of proposed user requests.

3.  []{#__RefHeading___Toc500209465 .anchor}Approach

An approach to solving local TFM inefficiencies associated with
Constrained Airspace Problems is to create system-wide collaboration
between the ATSP at the impacted Air Route traffic Control Center
(ARTCC) and the users (represented by FD crews and/or AOC) with the
objective of eliminating or mitigating the impact of predicted NAS
operational constraints. This approach is consistent with the
collaborative decision-making approach used at the national level
between users and the Air Traffic Control System Command Center
(ATCSCC).

For lost airspace problems, the objective is to mitigate the airspace
capacity impact by involving users in the flow-restriction decision.
Solutions are characterized by user-ATSP collaboration that may vary in
form as a function of time horizon (i.e., time to go until a particular
flight, or group of flights, are predicted to reach the "constrained
airspace"). Prior to the formulation of a TFM initiative by the local
Traffic Management Unit (TMU), users have the ability to identify
potential airspace constraints and request deviations to avoid them.
When a TFM initiative is required, users have the opportunity to
collaborate on the flights selected and the methods of deviation to
maximize user preference. When a TFM initiative needs to be implemented,
user preference information is known by the local TMU and deviations are
as consistent with the preferences as is allowable.

For gained airspace problems, both ATSP and users have the ability to
identify aircraft deviations that gain operational benefit (to users
and/or ATSP) by utilization of the additional airspace. Gained airspace
presents an opportunity to the ATSP to reduce the complexity of
neighboring sectors that are congested (i.e., lost airspace). For users,
gained airspace presents an opportunity to improve flight
characteristics, such as reductions in time to fly and fuel consumption.

For user request problems, the negative downstream TFM impacts of user's
request are avoided by ATSP evaluation of requests for constrained
airspace impacts prior to acceptance. Similarly, users can avoid
requesting changes that cause (or are impacted by) downstream congestion
by evaluating the request against predictions of future NAS state.

To enable such a collaborative approach, decision support tools (DSTs)
are required for the ATSP and the users. These DSTs provide the
stakeholders with the ability to predict constrained airspace problems
and support collaborative resolutions.

1.  []{#__RefHeading___Toc500209466 .anchor}High Level Benefit
    Mechanisms

The benefits for this approach are created through:

-   Enabling of collaborative solutions

-   Early notification of advantageous/disadvantageous events

-   Support in developing minimum impact resolutions

The use of collaborative solutions provides user input into the solution
of constrained airspace problems, creating solutions consistent with
user business models and enabling user benefits. Users even have the
ability to identify and resolve potential constrained airspace problems
before a TFM initiative is initiated, allowing for a completely user
defined solution.

Early notification of constrained airspace problems enables solutions
that require less impact on user-preferred trajectories for resolution.
Early notification also enables the identification and utilization of
gained airspace, providing direct capacity and efficiency benefits.

DST support in developing minimum impact resolutions ensures that the
selection and implementation of a TFM initiative is not excessive,
increasing efficiency over today's operations. By developing solutions
that minimize deviations from existing user preferences, user benefit is
maximized.

The expected benefits of this concept are described in detail in Section
11.0.

4.  []{#__RefHeading___Toc500209467 .anchor}Operational Requirements

Appendix A contains a table of Operational Needs Statements (ONS)
extracted from the *ATS Concept of Operations for the NAS in 2005*
\[6\], and 26 other NASA, FAA, RTCA and Eurocontrol documents (see
Appendix B for a complete listing of document titles). These ONS
represent requirements for the future NAS, as identified by the ATC
community. The selected ONS are consistent with the approach and
concepts presented in this document and provide implicit traceability
between CE-7 and the ideas expressed within these ATC community
documents.

5.  []{#__RefHeading___Toc500209468 .anchor}Operational Environment

The operational environment of CE-7 is within en route airspace,
specifically dealing with operational problems that are not concerned
with the transition of aircraft to a terminal airspace. This concept is
concerned with TFM at the local (ARTCC) level as opposed to the national
(ATCSCC) level. Figure 2 illustrates the relationship of CE-7's
operational environment relative to the environment for DAG CE-8 ("En
Route/Terminal Arrival: Collaboration for User-Preferred Arrival
Metering") and the role of the FAA's ATCSCC.

+-----------------+------------------------+--------------------------+
|                 | **Local TFM**          | **National TFM**         |
+-----------------+------------------------+--------------------------+
| Constrained     | CE-7                   | ATCSCC                   |
| Airspace        |                        |                          |
|                 | (e.g., Weather, SUA,   | (e.g., Collaborative     |
|                 | and Sector Complexity  | Re-Routing)              |
|                 | Problems)              |                          |
+-----------------+------------------------+--------------------------+
| Transition      | CE-8                   | ATCSCC                   |
| Airspace        |                        |                          |
|                 | (e.g., Metering/       | (e.g., CDM for Ground    |
|                 | Miles-in-Trail)        | Delay Program)           |
+-----------------+------------------------+--------------------------+

[]{#__RefHeading___Toc500209496 .anchor}Figure 2: Relationship of CE-7
Operational Environment to other NASA and FAA Efforts

At the local TFM level, the CE-7 concept supports collaboration during
the application of TFM initiatives within constrained airspace while the
CE-8 concept supports collaboration during the application of TFM
initiatives within the transition environment. Though both concept
elements may use similar TFM methods and would both be implemented
primarily within the local TMU, the transition airspace solution for
CE-8 is characterized by a different TFM environment than that for CE-7.
For example, predicting the cause, start and size of a TFM initiative
within transition airspace can often be estimated well in advance of the
initiative, since transition problems are usually caused by the arrival
of scheduled flights to the terminal airspace (e.g., the "noon balloon"
rush at ZFW). CE-8 TFM initiatives are also impacted by the presence of
existing TFM tools (e.g., TMA) and restricted in the choice and extent
of certain control strategies (e.g., re-routing has limited
applicability since all aircraft must eventually penetrate the terminal
airspace). Both the CE-7 and CE-8 solutions will ultimately need to be
combined or at a minimum, coordinated since a single TMU may have to
deal with constrained and transition problems simultaneously.

At the National TFM level, only the ATCSCC would be responsible for user
collaboration in dealing with problems in both constrained and
transition airspace. In constrained airspace, the ATCSCC will develop
and implement the appropriate TFM initiative when there are multiple
facilities involved (i.e., three or more) or when the TFM constraint is
beyond the time horizon of CE-7 (i.e., 2 hours or more) and involves two
facilities. An example of collaboration at the National Level in
constrained airspace is the Collaborative Re-routing program under
development by the FAA. If a TFM initiative is developed at the local
level (i.e., within CE-7) but involves more than one facility, then the
ATCSCC will facilitate the coordination between the two facilities, but
will not be involved in the development of the initiative. In transition
airspace, the ATCSCC will develop and implement the TFM initiatives when
transition problems are extreme enough to require pre-emptive action
several facilities in advance of the terminal airspace (e.g., a weather
cell causing extreme delays at JFK would effect all inbound flights,
including those as far away as LAX). An example of such a collaborative
National TFM initiative is the use of Collaborative Decision Making
(CDM) during ground-delay programs. The coordination of transitioning
TFM initiatives from the local (CE-7 and CE-8) to the National (ATCSCC)
levels, when necessary, is an area requiring further definition.

A detailed description of the CE-7 operational environment is broken up
into four sections: airspace structure and constraints; traffic mix and
equipage; CNS infrastructure; and ATM environment.

1.  []{#__RefHeading___Toc500209469 .anchor}Airspace Structure and
    Constraints

The CE-7 concept applies to all airspace structures envisioned from
today's domestic airspace through those planned for future free flight
concepts. The concept is not impeded by the lack of a fixed route
structure or by variable sector and/or facility boundaries.

The concept assumes dynamic re-sectorization is an available TFM control
strategy for the ATSP, but does not require its availability. In this
strategy, the sector geometry of the airspace is dynamically changed to
distribute the traffic load among sector controllers to better match
airspace structure (dynamically) to actual traffic demand/routing. \[7\]
This has the potential to better balance situations where one sector is
overloaded while another is not. Dynamic density measures are used to
identify optimal sectorization. This concept is described in more detail
in Section 6.1. The CE-7 concept takes advantage of whatever level of
dynamic sectorization is available. Initial implementations are expected
to be limited to a selection of fixed geometry shapes due to limitations
in Host computer (fix posting area) processing. The final implementation
should provide complete flexibility in selection of sector geometry to
dynamically match traffic demand.

The use of SUA is assumed to exist and possibly be expanded to include
commercial access to space and other future applications. The ability to
dynamically negotiate SUA availability is a concept control strategy
that will be discussed in more detail in Section 6.1.

Constraints are caused when traffic demand exceeds local-airspace
capacity. They either occur to aircraft after entering en route airspace
or after the aircrafts' predicted arrival time into en route airspace
(e.g., as in the case of satellite departures). Constraints include all
en route constraints except those caused by transition to a terminal
airspace (see Section 2.1). The main constraints are caused by weather
(turbulence, convective activity), SUA activation, and excessive traffic
complexity within a sector(s). No additional constraints above those
experienced today are expected.

2.  []{#__RefHeading___Toc500209470 .anchor}Traffic Mix and Equipage

The CE-7 concept applies to all traffic mixes and aircraft equipage
levels, from today through mature free flight concepts. The concept does
not require advanced cockpit equipage, but additional benefits are
achievable by some users if available.

Advanced cockpit systems are required to support collaboration between
the FD and the ATSP, though collaboration from the FD is not mandatory.
For users without AOC (e.g., in-flight re-planning support), FD to ATSP
collaboration is the only available form of user collaboration. Aircraft
are assumed to equip to various levels of collaboration capability,
based on individual user business models. Not all aircraft are assumed
to have FD collaboration capability. Minimally equipped users may gain
some benefits (compared to the current system) due to the improved
overall efficiency of NAS operations and greater accommodation of
user-preferences by the ATSP.

The traffic mix for this concept assumes a mixture of aircraft with
various levels of advanced cockpit automation. It is assumed that there
is a mixture of aircraft with/without AOCs and with/without airborne
(FD) collaboration capability. The minimum equipage required to operate
will be the same as that required for the current ATC system, in order
to facilitate NAS access by all users.

3.  []{#__RefHeading___Toc500209471 .anchor}CNS Infrastructure

The Communications, Navigation, and Surveillance (CNS) infrastructure of
the NAS must support advanced data sharing between users and ATSP to
facilitate a common awareness of NAS state and support effective
collaboration. This infrastructure must include a suitable air-to-ground
data transfer mechanism between the FD and ATSP and the FD and AOC in
the form of a datalink system. A ground-to-ground data transfer system
between the AOC and ATSP must also be available. No other significant
changes from today's CNS capabilities are anticipated.

4.  []{#__RefHeading___Toc500209472 .anchor}ATM Environment

The CE-7 concept applies to all Air Traffic Management (ATM)
environments from today through mature free flight concepts. The need
for traffic flow management is required in free flight environments
because localized areas of congestion will still form and ground-based
TFM remains the main resolution method.

CE-7 assumes that user flexibility is the rule, not the exception. All
aircraft are on either an approved flight plan that represents the
flight's user-preferred trajectory[^7] or that the aircraft is free
maneuvering and broadcasting a representation of the flights intent. It
is assumed that some aircraft do require ground-based positive control,
but that these aircraft exist within the same environment as the
free-maneuvering aircraft. Deviations from user-preferred trajectories
are due to ATM actions for congestion relief and separation assurance or
due to changes in user preferences. All aircraft (including
free-maneuvering aircraft) are subject to TFM initiatives developed by
the local TMU.

CE-7 TFM provides system-wide collaboration and distributed
decision-making between the ATSP at the local (ARTCC) level and multiple
users (FD and/or AOC). TFM constraints, when necessary, are goal
oriented (e.g., RTA) as opposed to solution oriented (e.g., reduce to
250 kt). Solutions are implemented at the lowest level in ATM to
facilitate quick response and maximum TFM attention to individual
flights. Local TFM procedures are consistent with, but independent of
collaboration between users and National TFM (ATCSCC).

6.  []{#__RefHeading___Toc500209473 .anchor}Operational Characteristics

![](media/image3.wmf){width="2.972916666666667in"
height="3.75in"}User-ATSP collaboration to resolve constrained airspace
problems varies as a function of time horizon (i.e., time to go until a
particular flight, or group of flights, are predicted to reach the
"constrained airspace"). The amount of distributed decision-making
varies widely with time horizon, focusing on user solutions for longer
time horizons and ATSP solutions for shorter time horizons. In all three
stages, the goal is to identify lost airspace, gained airspace, and user
request problems and facilitate efficient resolutions. A general
description of the collaboration and decision-making in each stage of
the resolution process is described below. Details of the ATSP, pilot,
and AOC views during each stage follows in the subsequent subsections.
An example scenario illustrating ATSP and user participation is provided
in Section 9. An operational sequence diagram showing the functional
flow between the ATSP (sector and TMU), FD, and AOC is presented in
Section 10.

[]{#__RefHeading___Toc500209497 .anchor}Figure 3: Stages of User-ATSP
Collaboration as Function of Time to Constrained Airspace

The three stages of user-ATSP collaboration as a function of time
horizon are illustrated in Figure 3. The first stage, Preemptive User
Action, involves traffic upstream of potentially impacted airspace
(e.g., lost airspace due to congestion), but at a time horizon larger
than when the local TMU would begin to formulate a traffic management
initiative to resolve the constraint. During this stage, the user can
decide to avoid (in the case of lost airspace) or utilize (in the case
of gained airspace) the potentially impacted airspace by making user
preference change(s) through user request(s) to the ATSP. [^8] The user
can also decide to make no action, preferring to wait and see if the
airspace change (lost or available airspace) actually materializes.
Because this is the longest time horizon stage, users make trade-offs
between the likelihood (probability) of the airspace change occurring
and the impact to flights if the change does occur. In this preemptive
stage, the user is initiating solutions through user requests without
explicit collaboration with the ATSP. Therefore, the ATSP handles these
requests in the same manner as other, non-flow conformance-induced
requests. If the preference change requests are accepted by the ATSP,
the need for a TFM initiative may be avoided using user-preferred
deviations without involving explicit collaboration between user and
ATSP.

The second stage, Collaborative TFM, occurs as traffic approaches the
impacted airspace, and is characterized by a collaborative (user-ATSP)
process for mitigating the impact of user deviations arising from en
route TFM initiatives. The process starts by the TMU selecting a control
strategy for the TFM initiative (e.g., rerouting and/or spacing) and
notifying the affected users of this strategy and any collaboration
constraints.[^9] This allows the users to define preference changes
based on the impending initiative (i.e., user preferred modifications or
alternatives to the proposed initiative) and to submit them to the TMU
as user requests. The TMU can accept and implement the request if it is
an acceptable modification to the TFM solution, or reject the request.
After acceptance of user requests, the TMU re-evaluates the TFM
initiative to determine if further deviations are necessary[^10]. If the
user preference changes resolve the impact on the airspace, then no
further TFM action needs to be taken.

If the problem is not resolved within the Collaborative TFM time horizon
window, then the process enters the third stage: TFM Action. During this
stage, the ATSP decides upon and implements a TFM initiative to off-load
the impacted airspace. Assuming completion of the Collaborative TFM
stage prior to initiation of TFM Action (i.e., the problem did not
"pop-up" within the TFM Action time horizon), the ATSP has user
preferences to resolve the problem, but these preferences are not enough
for a complete resolution. The ATSP identifies any additional changes to
the traffic flow, possibly considering one-way (non-collaborative)
inputs from the users (workload permitting), to complete the problem
resolution.

To support user-ATSP collaboration, "intelligent" generation of user
preferences, and effective TFM control strategies and initiatives, a
shared model (between users and ATSP) of the predicted state of the NAS
is essential. Users need accurate predictions of future NAS states,
including the impact of any planned/proposed/potential TFM actions, to
generate user preferences during the Preemptive User Action and
Collaborative TFM stages that support the resolution of constrained
airspace problems. The ATSP needs accurate NAS predictions, including
user preferences and actions, to support effective TFM problem
identification and resolution in all three stages. The ATSP must also be
able to identify the effect of planned/proposed TFM initiatives to
successfully "close the loop" and ensure minimum impact initiatives.

### 

1.  []{#__RefHeading___Toc500209474 .anchor}ATSP View

Supporting the ATSP in each stage of user-ATSP collaboration is a
TMU-based DST. The purpose of this DST is to support the ATSP in early
identification and resolution of constrained airspace problems. The DST
resides in the TMU and supports Traffic Management Coordinators (TMCs)
in identifying the need for and developing efficient, user-preferred TFM
initiatives. Each ARTCC TMU has its own TMU DST. Inter-facility (TMU
--to-TMU) procedures support the integration of TFM initiatives across
ARTCC facilities.[^11]

The TMU DST provides the TMC with identification of constrained airspace
problems and the impact on the predicted traffic flow. This includes
identification of flights impacted by scheduled and unscheduled SUA
activation, weather cell formation, and sector overloading caused by
congestion (i.e., traffic predicted to exceed allowable sector
capacity). The tool also supports the identification of flights that can
take advantage of scheduled and unscheduled SUA de-activation and
weather cell dissipation. When a user request for a preference change is
received, the TMU DST evaluates this request and identifies any
predicted sector congestion problems that will arise if accepted.

To support user requests received by the sector controller from the FD,
the TMU DST is integrated with the sector DSTs (e.g., En Route Descent
Advisor (EDA) or User Request Evaluation Tool (URET)). The TMU DST
automatically evaluates requests received by the sector controller DST
for congestion problems. Sector controllers are alerted to traffic flow
management problems outside of their sectors before accepting the
request. The sector controller DST has complimentary functionality to
the TMU DST to resolve unavoidable, very short time horizon
(intra-sector) problems (e.g., Conflict Probe for Weather Avoidance).

The TMU DST also provides the TMC with automatic and manual resolution
support for constrained airspace problems. Automatic resolutions provide
advisories to the TMC on which TFM control strategy should be
implemented, which aircraft should be deviated, and the magnitude of the
deviation. Manual (or "what-if") resolutions allow the TMC to evaluate
different TFM control strategies, aircraft selections and deviation
magnitudes, for their impact on the NAS, and select the appropriate
strategy. The TMU DST supports automatic transfer of TFM initiative
information to the AOC(s) (e.g., affected aircraft, proposed route
changes and flow constraints, etc.), FD (e.g., proposed constraints) and
sector controllers (e.g., clearances) for collaboration and
implementation.

A key function of the TMU DST is to support the TMC in selecting an
appropriate TFM control strategy for resolving the constrained airspace
problem. The TMC can choose from four options:

1.  Re-routing

2.  Spacing

3.  Dynamic re-sectorization

4.  Dynamic access to SUA

Route changes simply deviate the impacted flights away from/to the
lost/newly available airspace. Route changes are available for all lost
and gained airspace problems. Care must be taken to not exceed
acceptable levels of dynamic density of sectors along the new routing.
If re-routing is selected as the TFM control strategy, the TMU DST
supports the TMC in selecting which flights to re-route and their new
route to minimize deviations from the user preferred routes and avoid
new congestion problems.

Spacing involves throttling down the flow rate to reduce the
amount/complexity of traffic into congested airspace. The same flights
penetrate the impacted airspace, albeit at a lower rate. Spacing is
available for lost airspace problems except when the available airspace
capacity is zero (e.g., for SUA activation). Spacing may be achieved by
spacing en route flights and/or the timed-control of near-by departures
that contribute to the congestion. This form of departure control is
characterized by the coordination/control of a few flights, at the local
facility level, as opposed to the larger-scale national ground delay
program coordinated through the ATCSCC. During spacing operations, the
TMU DST supports the controller in the selection of appropriate spacing
parameters (e.g., miles-in-trail) for the aircraft entering the impacted
airspace.

Dynamic re-sectorization, illustrated in Figure 4, involves the
modification of the NAS configuration to balance resources (sector
boundaries) with traffic demand. In the case of Figure 4, sector A was
re-configured to a smaller region (reducing the flow of traffic within
it) while sector B becomes larger to accommodate the flow. Dynamic
re-sectorization is used to distribute traffic load from one sector to
another. During re-sectorization, the TMU DST supports the TMU in
identifying the new sector boundaries to most effectively distribute the
traffic load.

![](media/image4.wmf)

[]{#__RefHeading___Toc500209498 .anchor}Figure 4. Dynamic
Re-Sectorization

The fourth control strategy is a novel one that involves the negotiation
of dynamic access to SUA. The concept is to enable the ATSP to negotiate
with the authority controlling the SUA (e.g., Department of Defense,
space-launch management) to gain access to the SUA when additional
airspace is required (e.g., during lost airspace problems due to weather
or congestion) when the SUA is scheduled to be active. Dynamic access to
SUA has the potential to dramatically increase airspace/capacity
resources for the ATSP during constrained operations.

Under certain conditions, the value of the SUA to its authority may
decline while its potential value to the user community rises (see
Figure 5).

![](media/image5.wmf){width="3.2381944444444444in"
height="2.4763888888888888in"}

[]{#__RefHeading___Toc500209499 .anchor}Figure 5. Dynamic SUA Access and
Negotiation

For example, under poor weather conditions, certain military training
operations (or launch activities) may become less desirable. The
controlling authority may consider a postponement of operations
depending on their constraints in budget and schedule. At the same time,
the same weather may be the cause (or related to) a near-by area of
congestion that is resulting in significant user deviations. The dynamic
value of the user's access to that SUA may rise dramatically. If a
negotiation process could be developed along with a supporting mechanism
for "trading" airspace resources, dynamic SUA access may prove to be an
economically critical element in the TFM control-strategy "toolbox."
During constrained operations, the TMU DST evaluates the dynamic value
of the SUA to the ATSP and suggests a negotiable "window of
availability" for when the ATSP could most take advantage of the
airspace. This enables the ATSP to negotiate for the least amount of SUA
de-activation time required to relieve the congestion in other airspace.
If negotiation is successful, then the re-routing procedures for newly
available airspace are used to relieve the congestion.

1.  *Preemptive User Action Stage*

During this stage, the ATSP is receiving user preference change requests
and using the sector and TMU DSTs to evaluate the impact of the requests
on the airspace. The sector controller DST receives the user preference
changes, checks them for local (sector oriented) acceptability and if
acceptable, transmits them to the TMU DST for evaluation. If the sector
DST finds a local problem with the request (e.g., a conflict within the
sector), the sector controller rejects the request. If the TMU DST
identifies a flow conformance issue with the preference change, the
sector controller is alerted and the change is rejected. Preference
changes are received by the sector controller from the FD, instead of by
the TMU from the FD or AOC, because user-ATSP collaboration has not yet
begun. At this stage, these preference change requests are handled by
the ATSP just like any other non-TFM user request changes.

Because the TMU has access to the same predictions of future NAS state
as the user, the TMC is aware that the increase in user preference
change requests to the sectors are attempts by the users to avoid a
potential TFM initiative (the potential problem is identified by the TMU
DST). If the user requests do not cause additional congestion problems
and support the resolution of the potential constrained airspace
problem, the change request is approved and notification sent to the
sector controller. If any of the requests are predicted to cause
additional constrained airspace problems, they are denied. If the user
request is acceptable for both control and TFM, the sector controller
alerts the FD that the user request is accepted.

It should be noted that this process does not occur for free-maneuvering
aircraft. Because a TFM initiative is not currently being collaborated
on or implemented by the TMU, TFM constraints have not been issued to
free-maneuvering aircraft. Until they have been constrained by the TMU,
free-maneuvering aircraft can freely change their intent with
interaction with the ATSP.

2.  *Collaborative TFM Stage*

During this stage, the TMC identifies the constrained airspace problem
using the TMU DST and selects a control strategy (supported by the TMU
DST) that most efficiently resolves the problem. The TMC notifies the
affected users of the predicted operational constraint and transfers the
data necessary to support user analysis of preferred options for
potentially impacted flights. A key aspect of this supporting data is
the identification of the TFM initiative that would be implemented, if
necessary, including the intended control strategies and projected
extent of deviations. Any restrictions to degrees of freedom allowed for
collaboration (e.g., no southerly route changes accepted due to other
issues in that area) are also sent to the users. As user preference
change requests are received, the TMC re-evaluates the need for the
initiative (using the TMU DST), accepts appropriate user requests and
makes any necessary modifications to the planned initiative. Accepted
user requests are implemented by the TMU by either: (1) sending the
preference change to the sector controller as a clearance or (2)
directly approving a request made by a free-maneuvering aircraft.

If the problem is resolved by the user requests, the initiative is
cancelled. If the end of the Collaborative TFM time horizon is reached,
the TMC begins the implementation of the initiative in the TFM Action
stage.

3.  *TFM Action Stage*

During this stage, the TMC implements the TFM initiative begun in the
Collaborative TFM stage. Any preference change requests received during
the Collaborative TFM stage are used to identify potential preferred
solutions to the constrained problem. The TMU receives one-way (no
collaboration) preferences from users (e.g., would rather move aircraft
A than aircraft B), which they will attempt to accommodate. The final
TFM initiative is implemented similar to today (through sector
controller clearance changes) for all aircraft other than
free-maneuvering aircraft. For free-maneuvering aircraft, restrictions
are sent directly to the FD for implementation.

1.  []{#__RefHeading___Toc500209475 .anchor}Pilot View

For all non-free-maneuvering aircraft, the FD receives clearances from
the ATSP (to implement initiatives) and provides local user preference
change requests to the sector controllers. If the user has an AOC, the
aircraft compliments AOC information by identifying safety concerns to
proposed trajectory modifications. For aircraft without AOCs, if
collaboration is desired, the FD fully represents the user in
collaboration with the TMU. In this case, the FD is supported by
advanced cockpit automation enabling the crew to perform long term
flight plan optimization, determine desired user preferences and
negotiate with the ATSP. Collaboration from the flight deck is not
mandatory.

1.  *Preemptive User Action Stage*

For FD-based collaboration with the ATSP, the FD monitors the predicted
status of the NAS for sector complexity, weather, and available
airspace. The pilot must consider both the probability of an event
occurring (e.g., a TFM initiative with corresponding trajectory
deviations, or newly available airspace), and the cost/benefit of taking
preemptive action. If the user desires a preemptive action, the FD
either (1) develops and requests from the sector controller a trajectory
modification or (2) directly implements the deviation if the aircraft is
free maneuvering. If a requested trajectory modification is accepted by
the ATSP, the FD initiates the new trajectory.

If the aircraft has an AOC, then the FD still monitors the predicted
status of the NAS, if so equipped.[^12] In this case, the FD performs
the same function as in FD-based collaboration, but with the added
responsibility to coordinate flight changes with the AOC. Either the FD
or the AOC could develop the desired trajectory modification, but in
both cases, the FD makes the request to the sector controller or
implements the desired change (if free maneuvering).

If the aircraft is not equipped for collaboration (assumed also not
equipped for free maneuvering) but has an AOC, the AOC coordinates any
desired pre-emptive trajectory modifications with the FD. After
resolving any safety or comfort issues, the FD makes the request to the
sector controller. If accepted by the ATSP, the FD initiates the new
trajectory. If the aircraft can free maneuver, the FD would implement
this change after receipt from the AOC.

2.  *Collaborative TFM Stage*

For FD-based collaboration with the ATSP, the FD receives the predicted
operational constraint (control strategy) and the degrees of freedom
available for collaboration. Using advanced cockpit automation, the FD
determines whether to modify their trajectory and if so, what new
trajectory path is desired. The FD communicates any preferred trajectory
modifications to the TMU. If accepted by the ATSP, the FD initiates the
new trajectory either (1) through receipt of a new clearance from the
sector controller or (2) by directly changing their path if free
maneuvering.[^13]

If the aircraft has an AOC, then the FD may still perform collaboration
with the TMU. In this case, the FD performs the same function as in
FD-based collaboration above, but with the added responsibility to
coordinate flight changes with the AOC. It is more likely that the AOC
would chose to perform the collaboration, especially if the AOC were
planning to collaborate on a number of aircraft. In either case, the FD
would implement the desired modification after either receiving an
updated restriction from the TMU (for free-maneuvering aircraft) or a
new clearance from the sector controller.

If the aircraft is not equipped for collaboration (assumed also not
equipped for free maneuvering) but has an AOC, the AOC coordinates any
desired user preference modifications with the FD. After resolving any
safety or comfort issues, the AOC collaborates with the TMU. If accepted
by the ATSP, the FD initiates the new trajectory when received as a new
clearance. If the aircraft can free maneuver, the FD would implement
this change after receipt of the new restriction from the TMU.

3.  *TFM Action Stage*

During this stage, the FD implements the TFM initiative by accepting
sector controller clearances that were developed by the sector
controllers to safely conform with the constraints/restrictions of the
TFM initiative or adapting to TMU restrictions (free-maneuvering
aircraft).

2.  []{#__RefHeading___Toc500209476 .anchor}AOC View

It is assumed that each AOC has automation and procedures developed to
provide individual user business case decision-making support for that
user. The details of these procedures and automation are beyond the
scope of this document. It is assumed that a reasonable prediction of
the NAS state from the ATSP is required to support the intelligent
selection of user preference changes by the AOC.

1.  *Preemptive User Action Stage*

During this stage, the AOC monitors the predicted status of the NAS for
sector complexity, weather, and available airspace. The AOC then
evaluates, for each flight, the probability of a TFM initiative (and
corresponding trajectory deviations) or newly available airspace, and
the cost/benefit of taking preemptive action to request a flight-plan
change to avoid potential problem areas or utilize the new airspace. If
the benefit of preemptive preference changes is determined to be
significant, the AOC selects the flights to deviate and develops new
preferred trajectories for each flight. If the impact of the constrained
airspace is high cost or if the cost of the preference change is low,
the AOC may select to make a change even if the probability of the
problem actually occurring is low. Proposed user requests are
coordinated with the FD to remove any aircraft safety concerns in
implementing the change. To avoid both the FD and the AOC trying to
submit preferences at the same time (e.g., FD making non-TFM related
preference changes), the AOC will alert the FD when they are involved in
a possible TFM preference request change situation. If a user request
change is determined to be favorable by the AOC and FD, the AOC submits
the change request to the FD to (1) submit to the sector controller or
(2) implement if free-maneuvering. If submitted to the sector
controller, the FD implements the preference change when accepted by the
sector controller.

2.  *Collaborative TFM Stage*

During this stage, the AOC receives from the TMU the predicted
operational constraint and data necessary to support user analysis of
preferred options for potentially impacted flights. This includes the
proposed TFM initiative, control strategy, affected flights, and any
restrictions to degrees of freedom allowed for collaboration (e.g., no
southerly route changes accepted due to other issues in that area). The
AOC then develops (using AOC automation) preferred selection of flights
and trajectory modifications to avoid the impacted airspace. Proposed
user requests are coordinated with the FD to remove any aircraft safety
concerns in implementing the change. To avoid both the FD and the AOC
trying to submit preferences at the same time (e.g., FD making non-TFM
related preference changes), the AOC will alert the FD when they are
involved in a possible TFM preference request change situation. The
desired user preference changes are submitted to the ATSP by the AOC. If
the request is accepted, the FD implements the preference change when
received as a new clearance by the sector controller or when received
from the AOC if free-maneuvering. If any requests are rejected and time
permits, the AOC initiates a second round of collaboration with the TMU
to identify acceptable preference changes.

3.  *TFM Action Stage*

During this stage, the AOC provides one-way input preferences to the TMU
(e.g., would rather move aircraft A than aircraft B), but does not
collaborate on these preferences. The AOC re-evaluates their current
plan for the airline fleet based on the implemented TFM initiative and
develops any new user requests.

7.  []{#__RefHeading___Toc500209477 .anchor}NAS Functional Impacts

    1.  []{#__RefHeading___Toc500209478 .anchor}Functional Requirements

        1.  *Communications*

The CE-7 concept impacts the current NAS communications architecture by
requiring a datalink between the FD and both the ATSP (TMU and sector
controllers) and AOC, and improved ground communication between the ATSP
and the AOCs.

Datalink must support the transfer of information for a range of FD
capabilities. This includes, at a minimum, the transfer of preferences
to the ATSP and the transfer of data between the FD and the AOC to
support collaboration on desired preference changes. For aircraft
without an AOC, the datalink must also support the distribution of data
required for FD collaboration with the ATSP, if so equipped. This data
includes predictions of the future NAS state, schedule and status of
SUA, weather models and identified constrained airspace problems and
their proposed TFM initiatives

Ground communications between the ATSPs, AOCs and other agencies must be
able to support the transfer of data required for collaboration. Data
going to the user includes predictions of the future NAS state, schedule
and status of SUA, weather models and identified constrained airspace
problems and their proposed TFM initiatives. Data going to the ATSP
includes user preferences and schedule and status of SUA. Internal ATSP
data includes weather models and wheels-up times for en route departure
aircraft.

2.  *Navigation*

The CE-7 concept does not directly impact the current NAS navigation
architecture. Advanced airborne system functions, such as conflict
detection and resolution and required time of arrival, can be leveraged
to enable additional benefits, but are not a requirement for the
concept. Other advanced navigation functions such as area navigation
(RNAV) may provide the ATSP more flexibility in implementing TFM
initiatives (e.g., more accurate re-routing of aircraft).

3.  *Surveillance*

The CE-7 concept impacts the current NAS surveillance architecture by
requiring improved calculation of wheels-up times for en route departure
aircraft. More accurate wheels-up times improves the predictability of
en route departure aircraft entrance into potentially constrained
airspace which leads to better departure time control (one of the
available TFM control strategies).

The use of current Enhanced Traffic Management System (ETMS) and Host
surveillance data, or their equivalent, is assumed.

4.  *Automation*

CE-7 requires the addition of four new DSTs to the current NAS
automation architecture. They are the ARTCC TMU DST, the ARTCC sector
DST, the FD DST and the AOC DST.

1.  *[ARTCC TMU DST]{.underline}*

The TMU DST supports the ATSP in accepting user preferences while
avoiding future congestion problems, identifying constrained airspace
problems, collaborating with users, and developing efficient and
user-preferred TFM initiatives.

The identified inputs for this DST include:

-   Track and flight plan data

-   User preference change requests

-   Schedule and status of SUA

-   Weather models (size, severity and probability to penetrate)

-   Wheels-up times for local en route departures

The identified functionality for this DST includes:

-   Trajectory generation

```{=html}
<!-- -->
```
-   4D prediction of flights

-   30-90+ minute time-horizon (30+ minutes) predictions

-   Route transitions predictions (e.g., departure) to en route airspace

```{=html}
<!-- -->
```
-   Area Hazard detection

```{=html}
<!-- -->
```
-   Detect intersection of flight trajectories with dynamic areas of
    airspace

-   Calculate time duration of penetration

```{=html}
<!-- -->
```
-   Identification of constrained airspace problems

```{=html}
<!-- -->
```
-   Identify projected lost airspace, affected flights, and time
    duration

    -   Dynamic density measure used to identify congested airspace

    -   SUA schedule and status used to identify
        activation/de-activation

    -   Weather models used to identify impacted airspace (display of
        weather cell intensity)

-   Identify projected gained airspace and flights that could utilize
    this airspace to:

    -   Reduce other airspace sector complexity

    -   Achieve user benefit

-   Identify user requests that cause longer term negative impacts

```{=html}
<!-- -->
```
-   Develop TFM Initiative

```{=html}
<!-- -->
```
-   Select "best" control strategy for problem

    -   Develop efficient route modifications for affected aircraft

    -   Develop spacing restriction values for affected en route
        aircraft and time control values for local en route departure
        aircraft

    -   Develop new sectorization to distribute traffic load

    -   Identify negotiable SUA, window of de-activation, and affected
        flights to offload congested airspace

    -   Select optimum combination of above choices

-   Provide "what if" capability to try out different control strategies

-   Identify user benefit of newly available airspace and make available
    to user

```{=html}
<!-- -->
```
-   Support Collaboration

```{=html}
<!-- -->
```
-   Send NAS info to support "pre-emptive" and collaborative user
    decisions

    -   Predicted dynamic density

    -   Acceptable levels of dynamic density

    -   Weather

    -   SUA

-   Send proposed TFM initiative and collaboration constraints to AOC or
    FD

-   Send projected user benefit of newly available airspace to user

-   Accept user preferences (original and revised) and update proposed
    TFM initiative

-   Send proposed TFM initiatives to adjacent ARTCC TMU for
    inter-facility coordination

    -   Manually update the TFM initiative based on other TMU
        requirements

-   Manually input SUA revised de-activation window and update TFM
    initiative analysis during SUA negotiation

```{=html}
<!-- -->
```
-   Implement TFM Initiative

```{=html}
<!-- -->
```
-   Send re-route directions to appropriate sector controllers for
    clearance change

-   Send spacing restrictions to sector controllers

-   Send time control values to the appropriate departure control
    facilities/positions (may be an en route controller, terminal, or
    tower controller)

-   Send new airspace sectorization to ARTCC staff for implementation

The identified outputs of this DST include:

-   Future NAS state predictions

-   Identified constrained airspace problems

-   Proposed TFM initiatives, including collaboration constraints

-   Potential benefits for newly available airspace

-   Route modifications

-   Spacing restrictions

-   Departure time control values

-   New airspace sectorization

    1.  *[ARTCC sector DST]{.underline}*

For CE-7, the sector DST supports the ATSP in accepting user preferences
and delivering clearances to aircraft. It is assumed that this DST has
other functionality related to non-CE-7 requirements (e.g., resolve
tactical situations). The functionality described below should be
considered in addition to any other requirements for this DST imposed by
other concepts.

The identified inputs for this DST include:

-   Track and flight plan data

-   User preference change requests

-   Schedule and status of SUA

-   Weather models (size, severity and probability to penetrate)

-   Route modifications

-   Spacing restrictions

-   New airspace sectorization

-   Acceptance/rejection of user requests

The identified functionality for this DST includes:

-   Evaluate user requests

```{=html}
<!-- -->
```
-   Send request to TMU DST for evaluation

-   Alert the sector controller to negative impacts of request beyond
    that controller's awareness

-   Enable automated acceptance/rejection of request

```{=html}
<!-- -->
```
-   Implement TFM control strategies

```{=html}
<!-- -->
```
-   Implement spacing (flow-rate) restrictions (e.g., EDA functionality)

-   Implement route modifications

-   Adapt to new sectorization

The identified outputs of this DST include:

-   ATSP clearances

-   Accept/reject preferences from the FD

-   Accept/reject flow conformance modifications from TMU

    1.  *[AOC DST]{.underline}*

The AOC DST is required to support the user's development of user
preferences in consideration of the current and probable future state of
the NAS.

The identified inputs for this DST include:

-   Future NAS state predictions

```{=html}
<!-- -->
```
-   Schedule and status of SUA

-   Weather models (size, severity and probability to penetrate)

-   Identified constrained airspace problems

```{=html}
<!-- -->
```
-   Predicted TFM initiatives, including collaboration constraints

-   Potential benefits for newly available airspace

-   FD preferences and constraints for collaboration with AOC

The identified functionality for this DST includes:

-   The development of this automation is based on the specific business
    model of each user and a list of their specific functionality is
    beyond the scope of this document.

The identified outputs of this DST include:

-   User preference change requests

-   AOC preference information for collaboration with FD

    1.  *[FD DST]{.underline}*

The FD DST is required to support the user's development of user
preferences. It is assumed that this DST has other functionality related
to non-CE-7 requirements (e.g., free-maneuvering). The functionality
described below should be considered in addition to any other
requirements for this DST imposed by other concepts.

The identified inputs for this DST include:

-   Schedule and status of SUA

-   Weather models (size, severity and probability to penetrate)

-   Future NAS state predictions

-   Identified constrained airspace problems

-   Proposed TFM initiatives, including collaboration constraints

-   Potential benefits for newly available airspace

-   AOC preferences

-   ATSP clearances

The identified functionality for this DST includes:

-   The development of this automation is based on the specific business
    case of each user and a list of their specific functionality is
    beyond the scope of this document.

The identified outputs of this DST include:

-   User preference change requests

-   FD preference information for collaboration with AOC

    1.  *Weather*

The CE-7 concept impacts the current NAS weather architecture by
requiring improved weather modeling designed for TFM applications. The
definition of these weather products is still a subject of research, but
aspects of the weather model must include:

-   Size and severity of weather cells

-   Impact of weather on traffic flow

```{=html}
<!-- -->
```
-   All weather types (icing, fog, status, etc.)

-   Definition of whether aircraft preferences will allow penetration of
    weather

-   Effect of weather could be a function of aircraft type (e.g., jets
    will penetrate but turboprops won't) or aircraft position (e.g., the
    closer a flight is to its destination, the more likely it will be to
    penetrate)

    1.  *Traffic Management*

The CE-7 concept impacts the current NAS traffic management architecture
by assuming the availability of two new traffic flow management control
strategies: dynamic re-sectorization and dynamic access to SUA. Dynamic
re-sectorization is an existing concept that is being leveraged by CE-7.
Each proposed implementation stage is incorporated into the CE-7 concept
when available. Dynamic access to SUA is a new control strategy concept
that requires future study.

The relationship between CE-7 activities at the local TFM level and
ATCSCC TFM activities at the national level (see Section 5.0) is
consistent with the current traffic management architecture. CE-7
focuses mainly on intra-facility problems with the ability to handle
adjacent ARTCC issues through coordination with the other ARTCC TMU.
Large, multi-ARTCC problems (e.g., ground delay programs) are still
handled by the ATCSCC.

When lost airspace problems impact an ARTCC's available airspace to the
extent that a largely coordinated effort between ARTCCs is required,
usually caused by large weather systems, the ATCSCC becomes involved in
the solution. DST functionality residing in the ATCSCC with a dynamic
density metric (same as in local TMUs) to evaluate the impact of weather
on lost airspace can provide the cues necessary to identify when the
ATCSCC becomes involved. CE-7 complements the national strategic ATCSCC
TFM service by supporting more localized TFM activities at the
operational level closest to an actual "problem" in the en route
airspace.

1.  []{#__RefHeading___Toc500209479 .anchor}Functional Design

Figure 6 shows the functional flow between the DSTs described in section
7.1.4.

The TMU DST receives track, flightplan, SUA schedules and status,
weather information, and local en route departure wheels-up times from
external, ground-based sources (1). The TMU DST also receives user
preference change requests from the AOC DST (3a), the Sector DST (4a),
and the FD DST (5A).

The Sector DST receives track, flight plan, SUA schedules and status,
and weather information from external, ground-based sources (2). The
Sector DST also receives user preference change requests from the FD DST
(6a). Route modifications, spacing restrictions, new airspace
sectorization, and user request acceptance/rejection notifications are
received by the Sector DST from the TMU DST (4b).

The AOC DST receives SUA schedules and status, weather information,
future NAS state predictions, identified constrained airspace problems,
proposed TFM initiatives, and potential benefits for newly available
airspace from the TMU DST (3b). The AOC DST also receives FD preferences
and constraints from the FD DST (7a).

The FD DST receives SUA schedules and status, weather information,
future NAS state predictions, identified constrained airspace problems,
proposed TFM initiatives, and potential benefits for newly available
airspace from the TMU DST (5b). The FD DST also receives ATSP clearances
from the Sector DST (6b). The FD DST receives AOC preferences for
collaboration from the AOC DST (7b).

![](media/image6.wmf){width="5.997916666666667in"
height="6.101388888888889in"}

[]{#__RefHeading___Toc500209500 .anchor}Figure 6: Functional Flow of
Data between CE-7 DSTs

8.  []{#__RefHeading___Toc500209480 .anchor}User/Operator Roles and
    Responsibilities

Based on the operational characteristics described in Section 6.0, the
roles and responsibilities of the ATSP, Pilot, and AOC are summarized
below.

1.  []{#__RefHeading___Toc500209481 .anchor}ATSP

-   Collaborate with users (AOC and/or FD as appropriate) to
    avoid/resolve TFM initiatives

```{=html}
<!-- -->
```
-   Identify and alert users to constrained airspace problems

```{=html}
<!-- -->
```
-   Facilitate acceptance of user requests without undue negative impact
    on air traffic operations and unexpected delays

```{=html}
<!-- -->
```
-   Select operationally viable control strategy to maximize NAS
    performance (throughput) while accommodating user preferences to the
    extent possible.

-   Implement TFM initiatives

```{=html}
<!-- -->
```
-   Minimize deviations to preferences to maximum extent possible.

-   Maximize user flexibility to identify impacted flights and deviation
    degrees of freedom

```{=html}
<!-- -->
```
-   Minimize impact of losing airspace

```{=html}
<!-- -->
```
-   Gain benefits by allowing aircraft to take advantage of newly
    available airspace

```{=html}
<!-- -->
```
-   All other ATSP roles and responsibilities remain the same

    1.  []{#__RefHeading___Toc500209482 .anchor}Pilot

```{=html}
<!-- -->
```
-   Monitor for constrained airspace problems and proactively update
    their fight plan preferences to reduce the problem with
    consideration for their individual missions, if so equipped.

-   Develop and provide user preferences to ATSP, if so equipped

```{=html}
<!-- -->
```
-   Collaborate with ATSP to avoid/resolve TFM initiatives, if so
    equipped

```{=html}
<!-- -->
```
-   Ensure preference changes are safe for aircraft

```{=html}
<!-- -->
```
-   Coordinate preferences with AOC to effectively result in one common
    user representation

-   Adhere to restrictions applied by ATSP for TFM constraints, if
    equipped for free-maneuvering

```{=html}
<!-- -->
```
-   All other pilot roles and responsibilities remain the same

    1.  []{#__RefHeading___Toc500209483 .anchor}AOC

```{=html}
<!-- -->
```
-   Monitor for constrained airspace problems and proactively update
    fleet preferences to reduce the problem with consideration for their
    individual business models.

-   Develop and provide user preferences to ATSP

```{=html}
<!-- -->
```
-   Collaborate with ATSP to avoid/resolve TFM initiatives

```{=html}
<!-- -->
```
-   Coordinate preferences with pilot to effectively result in one
    common user representation

```{=html}
<!-- -->
```
-   All other AOC roles and responsibilities remain the same

9.  []{#__RefHeading___Toc500209484 .anchor}Operational Modes and
    Scenarios

    1.  []{#__RefHeading___Toc500209485 .anchor}Normal or Nominal Mode
        Scenarios

The following scenarios illustrate the CE-7 concept's nominal
interactions between participants and DSTs. The time windows for the
different stages of user collaboration are illustrative and not to be
taken as literal values. The exact values to support the CE-7 concept
will depend on the operational nature of specific scenarios and are a
subject for future research.

Figure 7 illustrates a group of en route, high altitude sectors. The six
aircraft displayed are all predicted to enter sector 29 during the same
time period. The two Federal Airlines (FAL) flights and the two National
Airlines (NAL) flights are all commercial jet transport aircraft (e.g.,
Boeing 737, Boeing 747, and Airbus 300). Both Federal and National have
AOCs and neither of these aircraft is assumed equipped to perform their
own TFM collaboration with the ATSP. N1729 is a business jet (e.g.,
Gulfstream IV). This aircraft is equipped for free maneuvering and to
perform its own TFM collaboration with the ATSP. N203R is a private
business jet not equipped for TFM collaboration with the ATSP and
without an AOC. The Economy Airlines (ECA) aircraft is a Boeing 737
commercial jet transport that is scheduled to depart from a satellite
airport within sector 15. Other aircraft are assumed impacting sector
29, but these seven are the only ones presented for discussion.

[]{#__RefHeading___Toc500209501 .anchor}Figure 7: Example Scenario

The scenario begins with user identification of predicted weather
impacts on sector 29. Both Federal's and National's AOC have received
current weather predictions for the airspace, a prediction of the future
NAS State and acceptable dynamic density levels from the TMU. Using
their AOC DSTs, they identify that the allowable dynamic density for
sector 29 is predicted to decrease (due to the weather) below the
currently predicted traffic load for that sector. The crew of N1729 has
also received the weather, NAS state, and dynamic density predictions
and using their FD DST have also identified that sector 29 is predicted
to have congestion problems based on the current traffic predictions.
Since the sector is not predicted to experience congestion for another
60 minutes, the ATSP has not yet developed a TFM initiative to relieve
the problem and the users have a chance to request preference changes to
avoid the airspace (Preemptive User Action stage).

In the National Airlines' AOC, the AOC DST identifies NAL 239 and NAL
888 as the two aircraft impacted by the predicted congestion. Using the
AOC DST, it is decided that NAL239's flight path should be changed to
avoid the congested area since the modification would have negligible
impact on the aircraft's flight time and fuel burn. If the aircraft were
to continue on its original flight path and be deviated, the impact
could be significantly larger. On the other hand, moving NAL888 would
have a much larger impact. National's AOC is hoping that by removing one
aircraft from the congested sector, combined with other airlines
removing aircraft from the sector, that the congestion problem will be
resolved and NAL888's flight path will not need to be modified. The
Federal Airlines' AOC determined that there is a chance that the weather
may dissipate prior to their aircraft entering sector 29. The flight
deck of N1729 determined the weather was not hazardous and decided to
penetrate the weather, risking possible restrictions by the ATSP.
Neither user decides to modify any flights at this time.

To implement the change for NAL239, National's AOC contacts the flight
and alerts them of the AOC desire to request a route change to avoid the
potentially impacted sector. The flight crew evaluates the proposed
change and works with the AOC to develop a new flight path that avoids
the congested airspace and is desirable by the crew (e.g., avoiding any
nearby areas of reported turbulence). When complete, the flight crew
then submits (via datalink) a user request to the sector controllers in
sector 17 for the new flight path. The sector DST in sector 17 receives
the route modification request and checks the new flight path within the
sector and into sector 15 to confirm that the flight path is conflict
free and acceptable to the controller (i.e., conforms to any other known
constraints). The sector DST also automatically sends the request to the
TMU DST to be checked for TFM acceptability. The TMU DST confirms that
the new path improves the overall TFM situation (in this case, by
reducing the predicted dynamic density of a potentially congested sector
downstream) and sends back an approval to the sector DST. The sector
controllers, evaluating the change is locally acceptable and approved
for TFM, accept the route modification and send the approval clearance
to the flight crew (either verbal or via datalink).

After the modification of NAL239's route, the dynamic density in sector
29 has been reduced, but not enough to bring it under the allowable
limits due to the impact of the weather cell. When the TMU identifies
(using the TMU DST) that the dynamic density of sector 29 is predicted
to exceed allowable limits in less than 30 minutes, the TMU initiates
development of a TFM initiative (Collaborative TFM Stage). Using the TMU
DST, the TMC evaluates the different control strategies. In this case,
there is no SUA local to the area, so dynamic access to SUA is not an
option. Because the congestion is due to weather, it is determined that
dynamic re-sectorization and spacing are not as desirable as rerouting
around the weather, though a ground hold on ECA782 is a viable option.
The decision is made to reroute N1729 and FAL320 to relieve the
congestion. This information, along with the restriction that deviations
east of sector 33 are not acceptable (due to other TFM issues in that
area), is sent to the impacted users (Federal's AOC and the N1729 flight
deck).

In Federal's AOC, it is preferred to modify FAL100's flight path over
FAL320, since FAL320 is currently behind schedule and needs to make a
tight connection at its arrival airport. Using the AOC DST, the Federal
AOC develops (in coordination with FAL100's FD) a preference change for
FAL100 instead of FAL320 that sufficiently reduces the predicted dynamic
density of sector 29 below allowable levels. This new preference must
combine with the rest of the proposed initiative to resolve the
congestion problem or the TMU will not accept the change to the
initiative. If the change from FAL320 to FAL100 is not "equivalent"
(i.e., interacts with the rest of the initiative to completely resolve
the problem), the TMU may accept the change to FAL100, but still
implement the change to FAL320 to complete the problem resolution. Once
an equivalent preference change is developed, the Federal AOC sends the
request to the TMU. The TMU DST receives the request, evaluates its
impact on the proposed TFM initiative, and either accepts or rejects the
request. If rejected, the AOC has another opportunity to make
adjustments and resubmit a request. In this case, the FAL100 preference
change is accepted. The TMU DST sends this request as a clearance change
to the sector 15 DST and the sector controller implements the requested
change (after sector DST evaluation) as a clearance.

In the case of N1729, the aircraft receives the proposed restriction
from the TMU as part of the TFM initiative. The free-maneuvering
aircraft then plans a new trajectory that will avoid the restricted
airspace (sector 29). When the new trajectory is completed, N1729
implements the trajectory change independent of the ATSP. N1729 could
have waited until the TFM initiative was implemented (at this stage, the
restriction is just the TMU's proposed initiative), but decided that an
earlier deviation would be more beneficial and the likelihood that the
restriction would be removed was small.

Because the collaboration successfully resolved the congested airspace
problem, no TFM Action stage is required. If collaboration with Federal
Airlines or N1729 were not completed in time, the proposed TFM
initiative would be implemented by the TMU by sending the route
modifications to the sector DSTs as clearance modifications or by
issuing the restriction to the free-maneuvering aircraft.

An alternative solution to the above scenario can be illustrated by
having the TMU select a different control strategy for the TFM
initiative in the Collaborative TFM stage. Again, the scenario begins
with user identification of predicted weather impacts on sector 29 and
the pre-emptive action by the National Airlines AOC to modify NAL 239.
When the TMU identifies (using TMU DST) that the dynamic density of
sector 29 is predicted to exceed allowable limits in less than 30
minutes, the TMU initiates development of a TFM initiative
(Collaborative TFM Stage). Using the TMU DST, the TMC evaluates the
different control strategies. This time, the TMU decides to use spacing
instead of re-routing.

The TMU sends the spacing initiative, along with the restriction that
deviations east of sector 33 are not acceptable, to the impacted users
(National's AOC, Federal's AOC, and the N1729 flight deck). In
National's AOC, it is determined that even though there will be delay to
NAL888, a re-route would be less beneficial and the airline does not
collaborate to modify the TFM initiative.

The flight deck of N1729 receives from the TMU that they will be subject
to spacing if they enter sector 29. The free-maneuvering aircraft
determines that it would prefer to re-route around the sector than to
incur the spacing delay. N1729 then develops and implements a new
trajectory that avoids the restricted airspace (sector 29). Because
N1729's path no longer enters sector 29, it will not be impacted by the
spacing restriction.[^14] After N1729 updates its broadcasted intent,
the TMU and AOC DSTs identify a reduction in the spacing delay for the
other aircraft entering sector 29, due to a reduction in sector
complexity caused by N1729 no longer entering the sector.

In the Federal Airlines' AOC, the AOC DST identifies FAL100 and FAL320
as the two aircraft impacted by the TFM initiate. Using the AOC DST, it
is decided that re-routing FAL100's flight path to avoid the congested
area is desired to reduce the potential spacing delay on FAL320. With
N1729 no longer entering the sector, Federal Airlines is predicting that
re-routing FAL100 should remove all spacing delay within the sector. The
Federal Airlines AOC follows the same procedure as in the previous
scenario to change FAL100's trajectory.

After the modification of N1729 and FAL100's route, the dynamic density
in sector 29 was reduced enough to bring it under the allowable limits
due to the impact of the weather cell. When the TMU identifies (using
the TMU DST) that the dynamic density of sector 29 is not predicted to
exceed allowable limits, the TMU lifts the TFM initiate (spacing)
developed earlier and the potentially impacted flights continue with
their original flight paths. Because the collaboration successfully
resolved the congested airspace problem, no TFM Action stage is
required.

2.  []{#__RefHeading___Toc500209486 .anchor}Off-Nominal Mode Scenarios

There are no currently identified off-nominal mode scenarios that drive
concept development.

3.  []{#__RefHeading___Toc500209487 .anchor}Failure Mode Scenarios

There are no currently identified failure mode scenarios that drive
concept development. If the TMU DST fails, then operations occur as
today. If an AOC or FD DST fails, then that airline or aircraft does not
collaborate on a solution and the TMU DST develops the most acceptable
resolution given the available information. If the sector DST fails,
then operations at the sector work as today.

10. []{#__RefHeading___Toc500209488 .anchor}Operational Process/Sequence
    Diagrams

Figure 8 illustrates the interaction among the users and ATSP for the
CE-7 concept. The lines in black show the interactions when an AOC,
non-collaborating FD, TMU and sector controller are involved. The red
information represents additional interactions that occur when the FD is
performing collaboration. The light green information shows the
additional interactions when the aircraft is free maneuvering. If no AOC
is present, then the FD follows the red (if collaborating), light green
(if free maneuvering) and black line interactions and the AOC column is
ignored.

![](media/image8.wmf){width="5.991666666666666in"
height="7.895833333333333in"}

[]{#__RefHeading___Toc500209502 .anchor}Figure 8: Constrained Airspace
Resolution Sequence Diagram

Constrained airspace problem identification starts with a continual
process of dynamically updating the state of the NAS for accurate
predictions of future states. As aircraft fly through the system, the
ATSP (TMU and sector) continually monitor the state of operations and
evaluate whether there are problems that need resolution. The sector
controller focuses on control issues (e.g., conflicts between aircraft)
while the TMU focuses on TFM issues (e.g., constrained airspace
problems). Users also evaluate the state of the NAS, as well as the
state of their fleet (AOC only), and change their preferences based on
their own business models. Preference changes are negotiated between AOC
and FD and (1) submitted by the flight deck to the sector controllers
and implemented as updated clearances or (2) implemented by the FD
directly if free maneuvering. Aircraft state and other data are also
sent to ground-based DSTs to calibrate their performance data, enabling
more accurate NAS state predictions.

When a constrained airspace problem is identified, both the user (AOC
and/or FD depending on which has collaboration responsibility) and TMU
are alerted of the problem (through their shared model of predicted NAS
state). In this stage, the user (AOC and/or FD) develops preference
changes, coordinates them between the FD and AOC, and has the flight
deck (1) submit them to the sector controller or (2) implement them if
free maneuvering. If submitted to the sector, the sector controller's
DST, integrated with the TMU DST, evaluates the acceptability of the
request and either accepts or rejects the request. Accepted requests are
implemented by the flight deck and added to NAS state predictions,
allowing the user to identify if more preference changes are desired. If
the potential problem is resolved, then the AOC and TMU resume their
normal operations.

If the problem is not resolved, the TMC selects a control strategy and
sends this and other collaboration data to the users. The users evaluate
the proposed TFM initiative and develop preference changes (in either
the AOC or FD) to modify its implementation towards a more
user-preferred solution. These preference changes, coordinated between
the FD and AOC, are sent by the user (AOC and/or FD) to the TMU for
acceptance. If accepted, the TMU alerts the user and, if the aircraft is
not free maneuvering, sends the preference to the sector controller as a
clearance. The trajectory change is added to the state of the NAS
prediction. The TMU evaluates the current proposed initiative and makes
modifications as necessary. If the potential problem is resolved, then
the user and ATSP resume their normal operations.

If the problem is not resolved, then the TMC selects the final control
strategy, using user preferences as input, and begins implementing the
TFM initiative through clearances to the sector controller or
restrictions to free-maneuvering aircraft. The TMU evaluates the state
of the NAS and refines the initiative as necessary until the problem is
completely resolved. Once the problem is resolved, the user and ATSP
resume their normal operations.

11. []{#__RefHeading___Toc500209489 .anchor}Benefits

The goal of the CE-7 concept is two-fold:

1.  Increase the accommodation of user-preferred deviations in
    constrained en route airspace

2.  Increase user efficiency, ATSP productivity and system capacity

The concept mechanisms to provide capacity, flexibility, user and ATSP
efficiency, predictability, access and environment benefits are
described below. Safety impacts are also discussed.

# Capacity

Capacity benefits are achieved through maximum utilization of en route
airspace. Improved (DST supported) early and collaborative planning by
the TMU and AOC avoids the creation of capacity limited airspace and
mitigates its impact when unavoidable. Dynamic access to SUA increases
the TMUs airspace capacity resources by providing airspace that is not
currently available today. The use of existing airspace capacity
resources is increased through DST support in the identification of
newly available (gained) airspace. Through improved utilization of
airspace at the local (ARTCC) level, the negative impacts of imposing
broader initiatives at the national (ATCSCC) level are avoided.

# Flexibility

Flexibility benefits are achieved through increased accommodation of
user preferences enabling user optimization of individual flights and
fleet/banks of flights. By enabling collaborative TFM, including a
pre-emptive user action stage, user preferences are incorporated into
all resolutions of constrained airspace problems. Early detection of
newly available airspace provides user opportunity to request preference
changes to take advantage of this airspace. Use of DSTs by user and ATSP
avoids the request/acceptance of preference changes that do not provide
the expected flexibility benefits.

# Efficiency: Users & Service Provider

User efficiency benefits are achieved through improved, collaborative
TFM and acceptance of user preferences. Early identification of
congested airspace and DST support in accepting user preference changes
in resolving congestion decreases user costs by minimizing deviations
from preferred routes. User collaboration in TFM solutions and ATSP DST
support enables selection of the most advantageous (benefits driven)
combination of route of flight and operational constraints for each
flight to reduce flight arrival and departure delays, flight time,
distance, and/or fuel consumption. Collaboration enables the user to
optimize selection of flights deviated, and the direction, type (route,
altitude, or speed), and magnitude of deviations. Early detection of
newly available airspace provides user opportunity to request preference
changes to reduce operating costs for each flight. Use of DSTs by users
and ATSP avoids the request/acceptance of preference changes that do not
provide the expected efficiency benefits.

Service provider efficiency benefits are achieved through improved,
collaborative TFM. Early decisions and distributed decision-making
increase ATSP productivity through decreased workload. Early detection
of newly available airspace and dynamic use of SUA provide efficient
mechanisms for reducing TFM constraints while decreasing congestion
during constrained operations.

# Predictability

Predictability benefits are achieved through early collaborative
planning providing increased NAS state predictability.

# Access

Access benefits are achieved through dynamic SUA access maximizing the
availability of airspace resources for user planning and ATSP
utilization.

# Environment

Environment benefits are not specifically addressed in this concept.

# Safety Impacts

Safety improvements may be achieved through improved TFM decision-making
decreasing the chance of flow rates exceeding the capacity limits of NAS
resources.

12. []{#__RefHeading___Toc500209490 .anchor}Issues and Key Decisions

The CE-7 concept is still in an early stage of development. The main
issues concerning the concept revolve around validation/refinement of
the basic concept and development of the details. Validation of the
concept should be done with operations staff at an early stage to
confirm the concept is going down the right path. Functionality and
actor relationships can be refined through discussions with TMC and AOC
staff. Lessons learned from Mitre's CRCT tool development can be used to
directly refine the basic CE-7 concept.

One large issue still remaining to be resolved is the transition from
local TFM solutions (i.e., CE-7) to National TFM solutions (i.e.,
ARTCSCC). Today, the ARTCSCC can dictate TFM solutions whenever more
than one facility's operations are impacted. Since increased user
benefits can be achieved using local (as opposed to national) TFM
solutions, it is desired to allow CE-7 solutions to extend beyond one
Center's boundaries into adjacent en route airspace, when appropriate.
At some point, the additional workload due to increased coordination
between the facilities will negate the benefit of developing
multi-facility TFM solutions at the local level. CE-7 needs to: (1)
determine when the transition from a local to a National solution is
most beneficial; (2) develop a concept for coordinating efforts between
the TMUs to support local multi-facility solutions; and (3) develop a
concept for coordinating efforts between the local TMUs and the ATCSCC
to support the transition.

Another large issue still remaining to be resolved is how to effectively
create a common prediction of the NAS state. CE-7 relies on the users
and ATSP having a common prediction of the NAS state to enable effective
collaboration and intelligent preferences. However, the process for
developing this prediction, including what information is shared between
users and the ATSP, is still undefined. Some of the questions to be
answered include:

-   How is congestion and its related impacts predicted

-   Is the data shared identical or do the users and ATSP have data
    tailored specifically for their use

-   Are there other key states for TFM and user decisions, other than
    ones already mentioned (e.g., weather, SUA status, acceptable levels
    of dynamic density)

-   What other TFM initiatives may be implemented and how is initiative
    data presented to the users

Concurrent with resolving the remaining concept issues, development of
key technologies for the concept can progress in preparation for the
development of a CE-7 prototype TMU DST. A list of development efforts
includes:

-   Development and validation of using dynamic density, including

```{=html}
<!-- -->
```
-   Validation of the basic metric

-   Impact of spacing

-   Subjective selection of acceptable dynamic density levels

```{=html}
<!-- -->
```
-   Development and selection of TFM control strategies

```{=html}
<!-- -->
```
-   How to best apply combinations of spacing/metering and re-routing?

-   Development of dynamic SUA negotiation

    -   Economic (business case) analysis of the value of SUA
        negotiation

```{=html}
<!-- -->
```
-   Development of time horizon windows for each collaboration stage

-   Required DST capability to support collaboration

-   Required accuracy of NAS state predictions

```{=html}
<!-- -->
```
-   Definition of ATM-focused meteorological research and development,
    including:

```{=html}
<!-- -->
```
-   Prediction accuracy and metrics defined for TFM applications

-   Distribution for shared situation awareness (ATSP-FD-AOC)

-   Weather prediction probability

-   Models of severity used in conflict probing

[]{#__RefHeading___Toc500209491 .anchor}References

1\. AATT Project, "Concept Definition for Distributed Air/Ground Traffic
Management (DAG-TM)" Version 1.0, September 30, 1999.

2\. Free Flight DAG-TM Workshop, NASA Ames, May 23-24, 2000.

3\. Sridhar, Banavar, Kapil S. Sheth and Shon Grabbe, "Airspace
Complexity and its Application in Air Traffic Management,\" MS 210-10,
NASA Ames Research Center, Moffett Field, CA, December 1998.

4\. Brinton, Chris, Bill Pawlak, Ken Lancaster, Kim Crouch and David
Rothenberg, "Air Traffic Control Complexity Research and Application"
(Presentation), Wyndemere Incorporated, William J. Hughts Technical
Center, August 29, 1997.

5\. Heimerman, Kathryn, \"Proceedings of the First FAA Dynamic Density /
Air Traffic Control Complexity Technology Exchange Meeting,\"
MT98W0000015, MITRE Corporation, McLean, VA, November 1997.

6\. Federal Aviation Administration, "ATS Concept of Operations for the
National Airspace System in 2005-Narrative (Narrative)", Washington DC,
September 30, 1997.

7\. Pawlak, William S., Anita Bowles, Vikas Goel, and Christopher
Brinton, "Initial Evaluation of Dynamic Resectorization and Route
Coordination (DIRECT) System Concept,\" Wyndemere Incorporated, August
27, 1997.

8\. System Resources Corporation, "TO-42 AATT Operational Concept for
ATM Year 2001 Update (AATT01)," for NASA Ames Research Center, Moffett
Field CA, November 2000.

[]{#__RefHeading___Toc500209492 .anchor}Appendix A: Operational
Requirements Table

This table contains the Operational Needs Statements (ONS) extracted
from the *ATS Concept of Operations for the NAS in 2005*, and 26 other
NASA, FAA, RTCA and Eurocontrol documents. The following ONS represent
requirements for the future NAS, as identified by the ATC community. The
selected ONS are consistent with the approach and concepts presented in
this document and provide implicit traceability to the concepts
established within existing community concepts. Appendix B contains a
complete list of documents from which the ONS were extracted.

The following ONS were extracted from the Traffic Management--
Synchronization Enhancement Area of the AATT Operational Concept for ATM
Year 2001 Update document \[8\].

+----------+-----------------------------------------------------------+
| OPSCON   | # OPSCON Description                                      |
| Number   |                                                           |
+----------+-----------------------------------------------------------+
| 1_220,   | These tools (automated coordination) reduce the burden of |
| 5_270    | routine tasks while increasing the provider's ability to  |
|          | evaluate traffic situations and plan the appropriate      |
|          | response. This increases productivity and provides        |
|          | greater flexibility to user operations, which is          |
|          | especially important given the potential for reduced      |
|          | vertical separation minima and increased traffic density. |
+----------+-----------------------------------------------------------+
| 1_375,   | Through a data link to the properly equipped cockpit,     |
| 4_370    | provide users- routine communications- updated charts,    |
|          | current weather, SUA status, and other data- basic flight |
|          | information services, including forecast weather, NOTAMs, |
|          | and hazardous weather warnings- airport information,      |
|          | including Runway Visual Range (RVR), braking action and   |
|          | surface condition reports, runway availability, and wake  |
|          | turbulence and wind shear advisories                      |
|          |                                                           |
|          | \- clearances and frequency changes in the form of        |
|          | pre-defined messages.                                     |
+----------+-----------------------------------------------------------+
| 1_422    | The most obvious user benefit is a reduction in the       |
|          | per-flight direct operating cost that every user          |
|          | operating under IFR can obtain through real-time          |
|          | optimization of their flight trajectory.                  |
+----------+-----------------------------------------------------------+
| 1_435    | Controller workload under peak traffic remains equivalent |
|          | to the workload controllers absorbed in the 1990s under   |
|          | lighter traffic demand. This increased ATC efficiency has |
|          | been achieved through the implementation of decision      |
|          | support systems for traffic management and control,       |
|          | dynamic alteration of airspace boundaries, reduced        |
|          | vertical separation minima, improved air/ground           |
|          | communications and coordination, and enhanced             |
|          | ground/ground coordination aids.                          |
+----------+-----------------------------------------------------------+
| 1_438    | Before changing a flight's trajectory, the controller     |
|          | must ensure not only that the revised trajectory is free  |
|          | of conflicts, but that the transition to that trajectory  |
|          | is also conflict free. The system therefore provides a    |
|          | 'trial plan' conflict probe for testing alternative       |
|          | trajectories.                                             |
+----------+-----------------------------------------------------------+
| 2_195    | Real-time trajectory updates reflect more realistic       |
|          | departure times, resulting in more accurate traffic load  |
|          | predictions, and increased flexibility due to the         |
|          | imposition of fewer restrictions.                         |
+----------+-----------------------------------------------------------+
| 3_185    | continuous updating of the flight object improves         |
|          | real-time planning for both the user and the service      |
|          | provider. \... improves the effectiveness of ongoing      |
|          | traffic management initiatives and the collaborative      |
|          | decision making                                           |
+----------+-----------------------------------------------------------+
| 3_220,   | Through the system, provide access to -Automated Terminal |
| 3_635    | Information System (ATIS) and other airport environmental |
|          | information, including RVR, braking action and surface    |
|          | condition reports, and current precipitation, runway      |
|          | availability, and wake turbulence and wind shear          |
|          | advisories- arrival, departure, taxi schedules, and taxi  |
|          | routes- airborne and surface surveillance information-    |
|          | flight information and pilot reports- weather             |
|          | information, including current weather maps- clearance    |
|          | delivery and taxi instructions- traffic management        |
|          | initiatives.                                              |
+----------+-----------------------------------------------------------+
| 4_450    | more effective collaborative decision making, with the    |
|          | AOCs collaborating with ATM in deciding TFM initiatives   |
|          | which are then data linked to the pilots and service      |
|          | providers.                                                |
+----------+-----------------------------------------------------------+
| 4_541    | Information outputs make all relevant flight object data  |
|          | available to the operational position (ATC, TM, and FAS)  |
+----------+-----------------------------------------------------------+
| 4_600    | service providers utilize the decision support systems to |
|          | monitor traffic flows, NAS performance, and weather.      |
+----------+-----------------------------------------------------------+
| 4_755    | the pilot will be able to select which route he wishes to |
|          | follow.                                                   |
+----------+-----------------------------------------------------------+
| 4_765    | Pilots \... fly to meet required times of arrivals        |
+----------+-----------------------------------------------------------+
| 4_770    | Free maneuvering operations in low density areas is being |
|          | performed.                                                |
| 5_355    |                                                           |
+----------+-----------------------------------------------------------+
| 4_775    | High density areas still require the oversight from ATC   |
|          | for sequencing and primary separation assurance.          |
+----------+-----------------------------------------------------------+
| 5_125    | By the year 2000, ATC considers AOC and flight deck       |
|          | preferences while assigning routes and controlling        |
|          | aircraft.                                                 |
+----------+-----------------------------------------------------------+
| 5_145    | These metering and merging separation procedures could    |
|          | provide the crew the flexibility to more efficiently      |
|          | manage their flight with respect to aircraft performance, |
|          | crew preferences, and ATC considerations by allowing      |
|          | aircraft to stay on the cleared route in cases were ATC   |
|          | would otherwise have to vector the aircraft to achieve    |
|          | the desired spacing.                                      |
+----------+-----------------------------------------------------------+
| 5_210    | Decision support systems such as the conflict probe       |
|          | assist the provider in developing safe and effective      |
|          | traffic solutions.                                        |
+----------+-----------------------------------------------------------+
| 5_235,   | Additional intent and aircraft performance data is        |
| 5_440    | provided to decision support systems, thus improving the  |
|          | accuracy of trajectory predictions. This information is   |
|          | combined and presented on the service provider's display. |
+----------+-----------------------------------------------------------+
| 5_295    | Improved decision support tools for conflict detection,   |
|          | resolution, and flow management allow increased           |
|          | accommodation of user-preferred trajectories, schedules,  |
|          | and flight sequences.                                     |
+----------+-----------------------------------------------------------+
| 5_330    | The NAS-wide information system is continually updated    |
|          | with changes in airspace and route structures, and with   |
|          | the positions and predicted time-based trajectories of    |
|          | the traffic.                                              |
+----------+-----------------------------------------------------------+
| 5_420    | user intent and aircraft performance data to decision     |
|          | support systems, thus improving the accuracy of           |
|          | ground-based trajectory predictions.                      |
+----------+-----------------------------------------------------------+
| 5_510    | Cockpit technology improvements will allow more           |
|          | user-preferred routings, SID to STAR or from              |
|          | airport-to-airport.                                       |
+----------+-----------------------------------------------------------+
| 5_530    | This will facilitate more effective collaborative         |
|          | decision making, allowing users to collaborate with ATM   |
|          | in deciding TFM initiatives.                              |
+----------+-----------------------------------------------------------+
| 5_545b   | traffic management services are provided in the en route  |
|          | area                                                      |
+----------+-----------------------------------------------------------+
| 5_575    | Decision support systems will assist in conflict          |
|          | detection and the development of conflict resolutions.    |
+----------+-----------------------------------------------------------+
| 5_620    | Decision support tools will also help service providers   |
|          | to collaborate with users when SUA restrictions are later |
|          | removed or changed.                                       |
+----------+-----------------------------------------------------------+
| 5_640    | The profile is produced through improved information      |
|          | sharing, collaborative decision making, and the           |
|          | projection of flows based on weather and wind patterns.   |
+----------+-----------------------------------------------------------+
| 5_670    | The traffic flow service provider will have the same      |
|          | automation tools as those providing separation assurance. |
+----------+-----------------------------------------------------------+
| 5_685    | The service provider will also be involved in the         |
|          | coordination of modified flight trajectories for active   |
|          | flights.                                                  |
+----------+-----------------------------------------------------------+
| 5_695    | This will allow earlier and immediate coordination with   |
|          | either the pilot or the airline operations center to      |
|          | provide adjustments with minimal intervention and         |
|          | movement.                                                 |
+----------+-----------------------------------------------------------+
| 5_700    | Traffic flow service providers will work with the service |
|          | provider in active communication with the pilot to        |
|          | re-plan the flight trajectory.                            |
+----------+-----------------------------------------------------------+
| 5_740    | Modified routes can be developed collaboratively between  |
|          | the AOC and the service provider and then data linked to  |
|          | the cockpit and downstream ATC facilities.                |
+----------+-----------------------------------------------------------+
| 5_790    | high density areas still require the oversight from ATC   |
|          | for sequencing and primary separation assurance.          |
+----------+-----------------------------------------------------------+
| 6_205    | Rapid delivery of clearances by the service providers,    |
|          | and responses by the flight deck, are achieved through    |
|          | increasingly common use of data link.                     |
+----------+-----------------------------------------------------------+
| 6_300    | Provide additional user intent and aircraft performance   |
|          | data to decision support systems, thus improving the      |
|          | accuracy of ground-based trajectory predictions.          |
+----------+-----------------------------------------------------------+
| 6_415b,  | Service providers, aided by supporting automation and     |
| 6_455b   | electronic visual displays, are able to acquire and view  |
|          | timely and reliable flight information to dynamically     |
|          | address necessary changes to the trajectories.            |
+----------+-----------------------------------------------------------+
| 6_430    | The service provider has access to the NAS-wide           |
|          | information system as well as projected demand for the    |
|          | day.                                                      |
+----------+-----------------------------------------------------------+
| 6_525b   | ATC oversight is still required for sequencing, but       |
|          | collaborative decision making has greatly increased among |
|          | the service provider, AOC, and the aircraft.              |
+----------+-----------------------------------------------------------+
| 7_160    | Through collaborative decision making, future service     |
|          | providers will focus on providing the best, seamless      |
|          | service to all users.                                     |
+----------+-----------------------------------------------------------+
| 7_300    | Using increased knowledge of the intent of traffic flow   |
|          | initiatives, arrange user resources to help solve traffic |
|          | flow problems.                                            |
+----------+-----------------------------------------------------------+
| 7_650    | Increasingly, national and local TFM service providers    |
|          | adapt to an environment of increased user flexibility,    |
|          | collaborative partnership, and information sharing among  |
|          | themselves and with the airspace users                    |
+----------+-----------------------------------------------------------+
| 7_655    | in a severe weather situation, increased collaboration    |
|          | among users and service providers enables shared          |
|          | decisions on how to avoid the severe weather and deal     |
|          | with the resultant short-term capacity shortage           |
+----------+-----------------------------------------------------------+

The following ONS draw a parallel between the CE-7 approach at the Local
TFM (ARTCC TMU) level and the current concepts for TFM at the National
(ATCSCC) level. The selected ONS are consistent with the approach and
concepts presented in this document and illustrate how the CE-7
approaches to TFM collaboration at the local level is consistent with
FAA approaches to TFM collaboration at the National level. These ONS
were extracted from the Traffic Management -- Strategic Flow Enhancement
Area of the AATT Operational Concept for ATM Year 2001 Update document
\[8\].

+----------+-----------------------------------------------------------+
| OPSCON   | # OPSCON Description                                      |
| Number   |                                                           |
+----------+-----------------------------------------------------------+
| 1_374    | To support current flow management capabilities and       |
|          | planned enhancements, the TFM infrastructure will be      |
|          | upgraded to an open client-server infrastructure.         |
+----------+-----------------------------------------------------------+
| 1_421    | the flying public and private sector will directly        |
|          | benefit from reduced transportation costs and increased   |
|          | schedule/connectivity. The general public will indirectly |
|          | benefit from the resulting economic growth (national      |
|          | productivity and gross national product) enabled by a     |
|          | more productive and efficient transportation system.      |
+----------+-----------------------------------------------------------+
| 2_195    | Real-time trajectory updates reflect more realistic       |
|          | departure times, resulting in more accurate traffic load  |
|          | predictions, and increased flexibility due to the         |
|          | imposition of fewer restrictions.                         |
+----------+-----------------------------------------------------------+
| 2_225    | When a flight plan is filed, update projections of NAS    |
|          | demand in the NAS information system.                     |
+----------+-----------------------------------------------------------+
| 2_275    | Service providers will move to a collaborative            |
|          | interaction with the user, where both reveal strategies   |
|          | and constraints and mutually develop solutions to         |
|          | problems.                                                 |
+----------+-----------------------------------------------------------+
| 2_350    | Air traffic service providers maintain a continuously     |
|          | updated data base of airspace and flow restrictions.      |
+----------+-----------------------------------------------------------+
| 4_290,   | Consider user preferences when it is necessary to assign  |
| 5_340,   | routes and control aircraft. User preferences may be      |
| 6_225,   | received from the AOC or the flight deck                  |
| 3_240    |                                                           |
+----------+-----------------------------------------------------------+
| 4_430    | Service providers also remain informed on distant weather |
|          | conditions in order to anticipate changes to the daily    |
|          | traffic flow, and requests from other facilities. This is |
|          | especially important when working with tower service      |
|          | providers to manage runway configuration changes.         |
+----------+-----------------------------------------------------------+
| 4_440,   | When traffic management initiatives are required, service |
| 4_640    | providers collaborate with users to resolve congestion    |
|          | problems through adjustment of user schedules.            |
+----------+-----------------------------------------------------------+
| 4_450    | more effective collaborative decision making, with the    |
|          | AOCs collaborating with ATM in deciding TFM initiatives   |
|          | which are then data linked to the pilots and service      |
|          | providers.                                                |
+----------+-----------------------------------------------------------+
| 4_500    | Data acquisition from the flight deck, airline operations |
|          | center, service provider, and interfacing NAS systems     |
|          | \... These inputs provide more information concerning     |
|          | traffic status and predictions, status of individual      |
|          | flights, pilot intent, user preferences, and traffic      |
|          | plans generated by upstream and downstream automation     |
|          | systems                                                   |
+----------+-----------------------------------------------------------+
| 4_541    | Information outputs make all relevant flight object data  |
|          | available to the operational position (ATC, TM, and FAS)  |
+----------+-----------------------------------------------------------+
| 4_600    | service providers utilize the decision support systems to |
|          | monitor traffic flows, NAS performance, and weather.      |
+----------+-----------------------------------------------------------+
| 4_605    | They will also use these tools to report on               |
|          | departure/arrival resources, and to identify airspace and |
|          | airport congestion problems.                              |
+----------+-----------------------------------------------------------+
| 4_620    | Through the NAS-wide information system, service          |
|          | providers also remain informed on distant weather         |
|          | conditions in order to anticipate changes to the daily    |
|          | traffic flow, and requests from other facilities.         |
+----------+-----------------------------------------------------------+
| 4_641    | incorporation of user preferences such as desired arrival |
|          | or departure sequences.                                   |
+----------+-----------------------------------------------------------+
| 4_645,   | the service providers work with the national traffic      |
| 4_445    | management function to solicit user input concerning flow |
|          | constraints, and these constraints are entered into the   |
|          | NAS-wide information system as planned or current         |
|          | operational requirements.                                 |
+----------+-----------------------------------------------------------+
| 4_730    | secure data link capabilities are introduced for tactical |
|          | control.                                                  |
+----------+-----------------------------------------------------------+
| 5_125    | By the year 2000, ATC considers AOC and flight deck       |
|          | preferences while assigning routes and controlling        |
|          | aircraft.                                                 |
+----------+-----------------------------------------------------------+
| 5_245    | flights will be routinely operated on user-preferred en   |
|          | route trajectories, with fewer aircraft constrained to a  |
|          | fixed route structure. These trajectories are             |
|          | accommodated earlier in the flight and continue closer to |
|          | the destination than is currently allowed.                |
+----------+-----------------------------------------------------------+
| 5_280,   | More aircraft provide real-time winds and temperatures    |
| 5_500    | aloft, resulting in better weather information for        |
|          | forecasting and traffic planning.                         |
+----------+-----------------------------------------------------------+
| 5_295    | Improved decision support tools for conflict detection,   |
|          | resolution, and flow management allow increased           |
|          | accommodation of user-preferred trajectories, schedules,  |
|          | and flight sequences.                                     |
+----------+-----------------------------------------------------------+
| 5_320    | Demand and capacity imbalances are resolved, in           |
|          | collaboration with the users, via voluntary changes in    |
|          | trajectories or through the establishment of temporary    |
|          | routes and transition points in the affected area.        |
+----------+-----------------------------------------------------------+
| 5_330    | The NAS-wide information system is continually updated    |
|          | with changes in airspace and route structures, and with   |
|          | the positions and predicted time-based trajectories of    |
|          | the traffic.                                              |
+----------+-----------------------------------------------------------+
| 5_525    | The status of active and proposed flights and NAS         |
|          | infrastructure will be available to NAS users and service |
|          | providers.                                                |
+----------+-----------------------------------------------------------+
| 5_625    | the traffic flow service provider's role will have        |
|          | changed to include coordination of dynamic airspace       |
|          | structuring, more strategic management of traffic,        |
|          | coordination of new trajectories, and the management of   |
|          | major flows.                                              |
+----------+-----------------------------------------------------------+
| 5_650    | Any capacity problems due to SUA schedules, staffing, or  |
|          | weather are identified.                                   |
+----------+-----------------------------------------------------------+
| 5_660    | The service provider will be given demand forecasts       |
|          | throughout the day via the continually updated NAS-wide   |
|          | information system.                                       |
+----------+-----------------------------------------------------------+
| 5_665    | As conditions change, initiatives will be reviewed and    |
|          | adjustments made, through coordination with all affected  |
|          | facilities and users.                                     |
+----------+-----------------------------------------------------------+
| 5_675    | By resetting control parameters \... the probe becomes a  |
|          | density tool which the service provider uses to identify  |
|          | areas and times of higher density.                        |
+----------+-----------------------------------------------------------+
| 5_680    | By working strategically with upstream separation         |
|          | assurance providers and the users, some density problems  |
|          | will be mitigated                                         |
+----------+-----------------------------------------------------------+
| 5_700    | Traffic flow service providers will work with the service |
|          | provider in active communication with the pilot to        |
|          | re-plan the flight trajectory.                            |
+----------+-----------------------------------------------------------+
| 5_705    | Modified trajectories will also be developed              |
|          | collaboratively with the airline operations center and    |
|          | distributed to the flight deck via data link, and to      |
|          | downstream facilities via the NAS-wide information        |
|          | system.                                                   |
+----------+-----------------------------------------------------------+
| 5_735    | Increased collaboration between the airline AOC and the   |
|          | ATM system occurs as the AOC interactively probes         |
|          | proposed route changes.                                   |
+----------+-----------------------------------------------------------+
| 5_745    | working with TFM specialists, the AOC helps define and    |
|          | implement TFM initiatives to relieve airspace congestion. |
|          | Collaboration is extended as AOCs have an expanded role   |
|          | in determining the landing sequence of company flights.   |
+----------+-----------------------------------------------------------+
| 5_795    | With the reduction in analog voice communications as the  |
|          | result of full use of data link capabilities and the      |
|          | implementation of new traffic management procedures and   |
|          | technology, dynamic resectorization allows fewer          |
|          | communication frequency changes for en route aircraft.    |
+----------+-----------------------------------------------------------+
| 6_185    | Automation and procedural changes will help service       |
|          | providers to be more strategic in solving potential       |
|          | conflicts, traffic congestion, and demand for user        |
|          | preferred trajectories.                                   |
+----------+-----------------------------------------------------------+
| 6_250,   | Adjust the airspace structure and/or trajectories when    |
| 6_420,   | demand exceeds capacity.                                  |
| 6_485    |                                                           |
+----------+-----------------------------------------------------------+
| 7_100    | Information exchange and collaboration continue to be     |
|          | critical components of traffic management through the     |
|          | year 2000.                                                |
+----------+-----------------------------------------------------------+
| 7_105    | Improved information exchange among users and service     |
|          | providers enables shared insight about weather, demand,   |
|          | and capacity conditions and allows for improved           |
|          | understanding of NAS status and TFM initiatives.          |
+----------+-----------------------------------------------------------+
| 7_110    | Users are key participants in the planning process of     |
|          | traffic flow initiatives. As users receive improved       |
|          | knowledge of the intent of traffic flow initiatives, they |
|          | may arrange their own resources to help solve the flow    |
|          | problems.                                                 |
+----------+-----------------------------------------------------------+
| 7_130    | Improved information about capacity constraints allows    |
|          | these users to adjust their operations accordingly,       |
|          | helping to resolve problems without TFM intervention.     |
+----------+-----------------------------------------------------------+
| 7_145    | An increase in collaboration among users and service      |
|          | providers for both planning and strategic problem         |
|          | resolution emerges as a result of increased information   |
|          | exchange.                                                 |
+----------+-----------------------------------------------------------+
| 7_150    | Databases and decision support systems that use these     |
|          | databases enable a shared view of traffic and weather     |
|          | among all parties so that proposed strategies can be      |
|          | evaluated.                                                |
+----------+-----------------------------------------------------------+
| 7_160    | Through collaborative decision making, future service     |
|          | providers will focus on providing the best, seamless      |
|          | service to all users.                                     |
+----------+-----------------------------------------------------------+
| 7_165    | Traffic Flow Management (TFM) initiatives affect all      |
|          | users similarly                                           |
+----------+-----------------------------------------------------------+
| 7_170    | users with an AOC or AOC-like capability have an          |
|          | opportunity to collaborate more efficiently and           |
|          | effectively with TFM service providers to address         |
|          | specific flow restrictions.                               |
+----------+-----------------------------------------------------------+
| 7_175    | users will be better able to plan their flight \... and   |
|          | to minimize congestion or possible delays due to the \... |
|          | information made available by the NAS-wide information    |
|          | system.                                                   |
+----------+-----------------------------------------------------------+
| 7_180    | This system (NAS-WIS)will include up-to-date information  |
|          | such as capacity and aggregate demand at airports and     |
|          | other NAS resources, airport field conditions, traffic    |
|          | management initiatives in effect, and Special Use         |
|          | Airspace status                                           |
+----------+-----------------------------------------------------------+
| 7_182    | Users equipped with advanced FMS and datalink continually |
|          | provide updates to ETAs at ATM-designated waypoints. This |
|          | enables an accurate depiction of current and forecast     |
|          | traffic loads in critical airspace                        |
+----------+-----------------------------------------------------------+
| 7_190,   | Traffic Flow Management (TFM) employs the philosophy of   |
| 7_285,   | problem resolution at the lowest level possible.          |
| 7_315    |                                                           |
+----------+-----------------------------------------------------------+
| 7_210    | 'what-if' tools for both the service provider and the NAS |
|          | user allow proposed strategies to be evaluated.           |
+----------+-----------------------------------------------------------+
| 7_215    | Because NAS users will have increased flexibility in      |
|          | planning routes and schedules, and because the NAS relies |
|          | less on routine restrictions and fixed routes to          |
|          | structure traffic, managing NAS resources becomes more    |
|          | dynamic and adaptive.                                     |
+----------+-----------------------------------------------------------+
| 7_220    | Better decision support systems will help service         |
|          | providers visualize demand and manage the more complex    |
|          | traffic flows.                                            |
+----------+-----------------------------------------------------------+
| 7_225    | decision support systems that evaluate NAS performance in |
|          | real-time will enable the service provider to be more     |
|          | responsive and develop more effective traffic management  |
|          | strategies.                                               |
+----------+-----------------------------------------------------------+
| 7_251    | a system-wide perspective is presented in the form of     |
|          | 'national profiles' that describe national operational    |
|          | conditions, including the overall NAS environment, and    |
|          | national capacity and demand.                             |
+----------+-----------------------------------------------------------+
| 7_252    | The national operational environment information just     |
|          | discussed provides all traffic managers with an overall   |
|          | view of conditions at cardinal points within the NAS that |
|          | will affect operations from the current time through      |
|          | several hours into the future.                            |
+----------+-----------------------------------------------------------+
| 7_255    | Manage programs and flow initiatives to mitigate          |
|          | instances where demand exceeds capacity.                  |
+----------+-----------------------------------------------------------+
| 7_270    | Monitor user compliance with traffic flow management      |
|          | initiatives and apply punitive controls as necessary.     |
+----------+-----------------------------------------------------------+
| 7_305    | Resolve traffic flow management issues collaboratively.   |
+----------+-----------------------------------------------------------+
| 7_395    | Increased collaboration between service providers and     |
|          | users in problem resolution improves overall system       |
|          | effectiveness.                                            |
+----------+-----------------------------------------------------------+
| 7_400,   | Enhanced decision support systems improve NAS monitoring, |
| 7_340    | performance measurement, and strategy development.        |
+----------+-----------------------------------------------------------+
| 7_441    | In appropriate situations, automation enables TM          |
|          | Initiative developer, TM personnel, ATC personnel, and    |
|          | user personnel to negotiate revisions to the planned      |
|          | Initiative, using the system's fast-time                  |
|          | simulation/analysis and information-sharing functions     |
+----------+-----------------------------------------------------------+
| 7_475    | They use the NAS-wide information system to manage        |
|          | information about current and predicted NAS conditions as |
|          | well as past performance.                                 |
+----------+-----------------------------------------------------------+
| 7_485,   | Because local service providers have access to the        |
| 7_320,   | NAS-wide information system, projected demand for the     |
| 6_495    | day, and tools to strategically identify areas and times  |
|          | of higher density, traffic flow management issues can be  |
|          | efficiently resolved at the local level.                  |
+----------+-----------------------------------------------------------+
| 7_490,   | In coordination with the national flow management, and in |
| 5_655    | collaboration with the user, local traffic flow           |
|          | management explores alternatives for managing the         |
|          | potential problems.                                       |
+----------+-----------------------------------------------------------+
| 7_495    | The ATCSCC stays informed about traffic flow restrictions |
|          | initiated locally.                                        |
+----------+-----------------------------------------------------------+
| 7_500    | Working with service providers at terminal and en route   |
|          | facilities, the ATCSCC also initiates and coordinates     |
|          | traffic flow restrictions of a broad scope,               |
|          | strategic/tactical nature when required.                  |
+----------+-----------------------------------------------------------+
| 7_505    | ATCSCC service providers also play a lead role in         |
|          | improving overall NAS service by managing national        |
|          | programs that modify national procedures and techniques   |
|          | governing daily operations.                               |
+----------+-----------------------------------------------------------+
| 7_510    | Keeping abreast of NAS status and local traffic           |
|          | management initiatives is efficiently done with the       |
|          | NAS-wide information system.                              |
+----------+-----------------------------------------------------------+
| 7_515    | Less time is spent on status checking, allowing service   |
|          | providers and users to focus on analyzing situations and  |
|          | on coordinating traffic management strategies.            |
+----------+-----------------------------------------------------------+
| 7_555    | To anticipate where and when demand might exceed          |
|          | capacity, both local and national traffic flow managers   |
|          | rely on decision support systems.                         |
+----------+-----------------------------------------------------------+
| 7_565    | A decision support system helps the service provider      |
|          | evaluate the impact of proposed strategies on the NAS by  |
|          | identifying options for avoiding problematic traffic      |
|          | situations.                                               |
+----------+-----------------------------------------------------------+
| 7_570    | The NAS-wide information system makes information         |
|          | available to all service providers for a common           |
|          | understanding of situations \... they can collaboratively |
|          | plan strategies that are not only more responsive to the  |
|          | situation, but also consider the needs of the entire NAS. |
+----------+-----------------------------------------------------------+
| 7_650    | Increasingly, national and local TFM service providers    |
|          | adapt to an environment of increased user flexibility,    |
|          | collaborative partnership, and information sharing among  |
|          | themselves and with the airspace users                    |
+----------+-----------------------------------------------------------+

[]{#__RefHeading___Toc500209493 .anchor}Appendix B: Operational
Requirements References

The following is a complete list of documents from which the ONS were
extracted.

EUROCONTROL, "Air Traffic Management Strategy for 2000+ Volume 2",
November 1998.

Federal Aviation Administration, "Addendum 1: Operational Tasks &
Scenarios (Addendum)", US Department of Transportation, Washington DC,
July 23, 1998.

Federal Aviation Administration, "Air Traffic Services Performance Plan
for Fiscal Years 1998-2000, Air Traffic Services", Washington DC, August
13, 1999.

Federal Aviation Administration, "ATS Concept of Operations for the
National Airspace System in 2005-Narrative (Narrative)", Washington DC,
September 30, 1997.

Federal Aviation Administration, "ATS Concept of Operations for the
National Airspace System for the Mature State of Free Flight", US
Department of Transportation, Washington DC, 1998.

Federal Aviation Administration, "National Airspace System Architecture
Version 4.0", US Department of Transportation, Washington DC, January
1999.

Federal Aviation Administration, "Safe Flight 21: Functional
Specification", US Department of Transportation, Washington DC, May 15,
1999.

National Aeronautics and Space Administration, "Concept Definition for
Distributed Air/Ground Traffic Management (DAG-TM) Version 1.0",
Advanced Air Transportation Technologies (AATT) Project, Aviation System
Capacity (ASC) Program, September 30, 1999.

RTCA, Inc., "A Joint Government/Industry Operational Concept for the
Evolution of Free Flight", Prepared by the RTCA Select Committee on Free
Flight Implementation, Washington DC, August 1997.

System Resources Corporation, "TO-7 En-Route Constrained Airspace
Concept Definition", For NASA Ames Research Center, Moffett Field CA,
September 1999.

System Resources Corporation, "TO-16 Multi-Facility TMA Requirements for
Philadelphia Installation", For NASA Ames Research Center, Moffett Field
CA, January 15, 1999.

System Resources Corporation, "TO-23 Assessment of Research and
Development Efforts Supporting Future Operational Concepts for the
National Airspace", For NASA Ames Research Center, Moffett Field CA,
August 1999.

[^1]: Over-flight traffic is defined as traffic within an en route
    center that enters from an adjacent center and exits to another
    adjacent center. This definition separates this traffic from arrival
    traffic (traffic that transitions to its destination terminal area
    within the center) and departure traffic (traffic that transitions
    from its origin terminal area within the center).

[^2]: The term "lost" is used to refer to the need to reduce the
    predicted traffic load below the accepted capacity level of the
    airspace. It is not intended to mean that a section of airspace is
    unusable, though the activation of an SUA could definitely create
    such a situation. The term "lost" will be used throughout this
    document to describe all situations where a region of airspace is
    predicted to exceed its traffic capacity.

[^3]: Dynamic density is also sometimes referred to as sector or
    airspace complexity, but dynamic density is the more widely
    published term and will be used synonymously with sector and
    airspace complexity throughout this document.

[^4]: There are cases where aircraft can enter SUA airspace when active
    (e.g., within a Military Operations Area if separation assurance can
    be maintained), but the concept is unaffected by this distinction
    since the number of allowable aircraft would be very small,
    requiring the majority of flights to be rerouted.

[^5]: Current conflict probes, including URET, do have the capability to
    probe for conflicts into downstream sectors (approximately a 20
    minute time horizon) and to identify SUA penetration, but they are
    not capable of supporting the identification of TFM problems and
    restrictions.

[^6]: Prior to "free routing," ATC preferred routes procedurally
    restricted flights through congested areas along predictable routes.
    With the advent of free routing, the connection between routes and
    congested airspace isn't nearly as clear since many areas of
    congestion are managed through control of fixed-route traffic
    streams.

[^7]: The extent to which the flight plan reflects the actual flight's
    user-preferred trajectory is based on the equipage level of the
    flight. The flight plan could be anything from today's flight plan
    to a user-negotiated flight plan that does not follow a fixed route
    structure (e.g., CE-6).

[^8]: A similar situation occurs for traffic when they are outside of
    the time horizon for an existing traffic flow initiative. Though
    traffic close to the constrained airspace may currently be affected
    by the initiative, users could continue to make preemptive
    preference changes to avoid their aircraft from being added to the
    initiative (e.g., maneuver early to avoid a congestion area, before
    the TMU constrains them).

[^9]: During the end stages of the preemptive user action stage, the
    ATSP may alert the users as to when the Collaborative TFM stage will
    begin. Alternately, the stage would begin when the control strategy
    and collaboration constraints are initially sent to the users.

[^10]: Theoretically, multiple rounds of collaboration could occur until
    the time horizon enters the next stage (TFM Action).

[^11]: The issues surrounding multi-facility coordination between TMUs
    are covered in Section 12.

[^12]: The decision of whether the FD will equip to enable FD
    collaboration when AOC collaboration is available is a decision that
    will be made based on each user's business model. CE-7 assumes that
    a user may have both FD and AOC collaboration capability available
    and dictates the requirements for collaboration in this case.

[^13]: Free-maneuvering aircraft have the opportunity to collaborate on
    the type of restriction imposed during this stage. For example, an
    aircraft that is being spaced may request the option to avoid the
    airspace instead. This is a different interaction than if the
    aircraft is not free-maneuvering and wants to collaborate a
    different path to avoid a piece of airspace.

[^14]: The spacing restriction is not removed, but since the aircraft
    does not enter the sector, the restriction will not have an impact
    on the aircraft's trajectory.