00188.41-01

NAS2-98005 RTO-41

Technical Research in Advanced Air Transportation Technologies

Detailed Description for CE6

En route Trajectory Negotiation

**G. J. Couluris**

**November 2000**

**Prepared For:**

**NASA Ames Research Center**

**Moffett Field, CA 94035-1000**

**Prepared By: Seagull Technology, Inc.**

**Los Gatos, CA 95032-2547**

![](media/image1.png)

**Preface**

This report is the first version of a detailed description for the
Distributed Air/Ground Traffic Management (DAG-TM) Concept Element (CE)
6, En Route Trajectory Negotiation. 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

Steve Green, Manager, AATT En Route Systems and Operations Sub-element,
NASA Ames Research Center -- sgreen@mail.arc.nasa.gov

**Contents**

1\. Introduction [7](#introduction)

1.1 Background [7](#background)

1.2 Objectives [8](#objectives)

1.3 Scope [8](#scope)

2\. Problem Description [9](#problem-description)

2.1 Problem [9](#problem)

2.2 Solution [9](#solution)

2.3 Potential Benefits [10](#potential-benefits)

3\. Approach [12](#approach)

3.1 Overview [12](#overview)

3.2 Operational Integration [13](#operational-integration)

3.3 Technical Integration [14](#technical-integration)

4\. Operational Requirements [16](#operational-requirements)

5\. Operational Environment [17](#operational-environment)

5.1 Airspace Structure And Constraints
[17](#airspace-structure-and-constraints)

5.2 Traffic Mix and Equipage [17](#traffic-mix-and-equipage)

5.3 CNS Infrastructure [17](#cns-infrastructure)

5.4 ATM Environment [17](#atm-environment)

6\. Operational Characteristics [19](#operational-characteristics)

6.1 ATSP Operations [19](#atsp-operations)

6.1.1 TFM Constraints [19](#tfm-constraints)

6.1.2 Potential Conflicts [20](#potential-conflicts)

6.1.3 User Request for Trajectory Change
[22](#user-request-for-trajectory-change)

6.1.4 Trajectory Prediction and Assessment
[22](#trajectory-prediction-and-assessment)

6.1.5 Trajectory Negotiation [25](#trajectory-negotiation)

6.2 FD Operations [29](#fd-operations)

6.3 AOC Operations [29](#aoc-operations)

7\. NAS Functional Impacts [30](#nas-functional-impacts)

7.1 Functional Requirements [30](#functional-requirements)

7.1.1 Communications [30](#communications)

7.1.2 Navigation [31](#navigation)

7.1.3 Surveillance [32](#surveillance)

7.1.4 Automation [32](#automation)

7.1.5 Weather [32](#weather)

7.1.6 Traffic Management [32](#traffic-management)

7.2 Functional Design [33](#functional-design)

8\. User/Operator Roles and Responsibilities
[35](#useroperator-roles-and-responsibilities)

8.1 ATSP Roles and Responsibilities
[35](#atsp-roles-and-responsibilities)

8.2 Pilot Roles and Responsibilities
[35](#pilot-roles-and-responsibilities)

8.3 Dispatcher Roles and Responsibilities
[35](#dispatcher-roles-and-responsibilities)

9\. Operator Modes and Scenarios [36](#operator-modes-and-scenarios)

9.1 Normal or Nominal Mode [36](#normal-or-nominal-mode)

9.2 Off-Nominal Mode Scenarios [37](#off-nominal-mode-scenarios)

9.3 Failure Mode Scenarios [38](#failure-mode-scenarios)

10\. Operational Processes/Operational Sequence Diagrams
[39](#operational-processesoperational-sequence-diagrams)

11\. Benefits [40](#benefits)

12\. Issues and Key Decisions [42](#issues-and-key-decisions)

Appendix A. Operational Requirements Table
[46](#appendix-a.-operational-requirements-table)

Appendix B. Automated Resolution Advisories
[50](#appendix-b.-automated-resolution-advisories)

References [54](#references)

**Figures**

Figure 6-1 En Route TFM Constraint Propagation
[20](#__RefHeading___Toc498242314)

Figure 6-2 Multi-Sector Potential Conflict Situations
[21](#__RefHeading___Toc498242315)

Figure 6-3. Avoidable Interruptions [24](#__RefHeading___Toc498242316)

Figure 6-4. Application of an Uplinked Waypoint Constraint
[25](#__RefHeading___Toc498242317)

Figure 6-5. User-preferred routes [26](#__RefHeading___Toc498242318)

Figure 6-6. Re-routes to form spacing trail. [26](#OLE_LINK1)

Figure 6-7. Spacing with minimum deviation.
[27](#__RefHeading___Toc498242320)

Figure 6-8. Path-independent spacing. [27](#__RefHeading___Toc498242321)

Figure 7-1. CE-6 Functional Design Diagram
[33](#__RefHeading___Toc498242322)

Figure 10-1 CE-6 Operational Sequence Overview
[39](#__RefHeading___Toc498242323)

**En route Trajectory Negotiation**

**For**

**User-preferred Separation Assurance and Local TFM Conformance**

# Introduction

## 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,
which met during 1999 and developed a Concept Definition.^ref.1^ This
document defined 15 DAG-TM "concept elements", covering air traffic
management (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 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 objectives and operational concepts for CE-6, En Route Trajectory
Negotiation.

## Objectives

This detailed description has the following objectives:

-   It provides technical transfer and sharing of information within the
    NASA research community. It is intended to capture the current
    thinking of NASA researchers concerning the future ATM environments
    and capabilities that may be created by this concept.

-   It is a guide for a planned program of research in this concept
    through 2004.

-   It is consistent with AATT objectives as described in the AATT Air
    Traffic Management Operations Concept (ATM/OPSCON).

## Scope

The description of CE-6 is intended to provide enough detail to form a
basis for further research into the concept. It is not, however, a
research plan. The research plan is a separate document being developed
by NASA which describes how the concepts presented here will be
investigated, and how statements presented here as hypotheses will be
tested.

The detailed description has a focus of operational and system
requirements, and deliberately avoids design information to the extent
possible. Specifications are omitted from this document, since
capabilities to support the CE-6 concept should evolve as a result of
the research to be conducted. To avoid confusion with widely discussed
tools such as automatic dependent surveillance (ADS), ADS-Broadcast
(ADS-B) or controller-pilot data link communication (CPDLC) whose
specifications are being developed or discussed, this description uses
general terms to describe the capabilities necessary to support this
concept.

# Problem Description

The following problem, solution and benefits descriptions for CE-6 are
extracted from the DAG-TM Concept Definition.^ref.1^ These descriptions
address air traffic service provider (ATSP) problems in fully
accommodating user preferences as determined by aircraft flight deck
(FD) and aeronautical operational control (AOC) trajectory assessments
and plans.

## Problem

> *(a) ATSP often responds to potential traffic separation conflicts by
> issuing trajectory deviations that are excessive or not preferred by
> users.*
>
> In the current air traffic control (ATC) system, trajectory prediction
> uncertainty leads to excessive ATC deviations for separation
> assurance. Due to workload limitations, controllers often compensate
> for this uncertainty (which may be equivalent to or greater than the
> minimum separation standard) by adding large separation buffers for
> conflict detection and resolution (CD&R). Although these buffers
> reduce the rate of missed alerts, some aircraft experience unnecessary
> deviations from their preferred trajectories due to the unnecessary
> "resolution" of false alarms (i.e., predicted "conflicts" that would
> not have materialized had the aircraft continued along their original
> trajectories). In those cases where a potential conflict really does
> exist, the buffers lead to conservative resolution maneuvers that
> result in excessive deviations from the original trajectory. Moreover,
> the nature of the resolution (change in route, altitude or speed) may
> not be user-preferred. Due to a lack of adequate traffic, weather, and
> airspace restriction information (and displays), and also to a lack of
> conflict resolution tools on the flight deck, current procedures
> generally do not permit the user to effectively influence controller
> decisions on conflict resolution.
>
> *(b) ATSP often cannot accommodate the user's (FD or AOC) trajectory
> preferences for conformance with local traffic flow management (TFM)
> constraints.*
>
> The dynamic nature of both aircraft operations and NAS operational
> constraints often result in a need to change a 4-D trajectory plan
> while the aircraft is en route. Currently, the user (FD or AOC) is
> required to submit their request for a trajectory change to the ATSP
> for approval. During flow-rate constrained operations, the ATSP is
> rarely able to consider user preferences for conformance.
> Additionally, a lack of accurate information on local traffic and/or
> active local TFM constraints (bad weather, SUA, airspace congestion,
> arrival metering/spacing) can result in the FD or AOC requesting an
> unacceptable trajectory. The ATSP is forced to plan and implement
> clearances that meet separation and local TFM constraints, but may not
> meet user preferences. Further negotiation between the ATSP and FD can
> adversely impact voice-communication channels and increase ATSP and FD
> workload.

## Solution

> *(a) Reduce unnecessary and/or excessive ATSP-issued route deviations
> for traffic separation by enhancing ATSP trajectory prediction
> capability through user-supplied data on key flight parameters.*
>
> The user (FD and/or AOC) will provide information via data link on key
> parameters such as aircraft weight, trajectory intent (route,
> altitude, speed profile), local winds/temperature aloft, and
> navigational performance. The provision of this information will not
> adversely affect FD and/or AOC workload, and will be automated. An
> ATSP-based decision support tool (DST) will use this data to improve
> its trajectory predictions, resulting in improved CD&R performance.
> This improvement will: (1) Reduce the number of unnecessary conflict
> resolution maneuvers by decreasing the conflict prediction false-alarm
> rate; and, (2) Reduce the extent of excessive trajectory deviations
> for conflict resolution by decreasing the uncertainty in future
> positions of the aircraft.
>
> Appropriately equipped users will be able to submit their preferences
> for resolving conflicts. These preferences may include (but are not
> limited to): a specified 4D trajectory; a specified route, and/or
> altitude and/or speed profile; or, preferred degree(s)-of-freedom
> (route, altitude, speed) for conflict resolution. The trajectory
> negotiation process may involve single-flight collaboration between
> the ATSP and an individual user, or multiple-flight collaborations
> between the ATSP and multiple users for determining a balanced set of
> deviations among a "gaggle" (group) of flights. Following the
> selection of a conflict-resolution plan, the ATSP then transmits (via
> data link) the conflict-free trajectory solutions to the
> appropriately-equipped aircraft for execution (thereby further
> reducing trajectory uncertainty and subsequent conflict false-alarm
> and missed-detection rates). It is emphasized that the ATSP retains
> full responsibility for separation assurance.
>
> *(b) Facilitate trajectory change requests for en route aircraft by
> providing the user (FD and/or AOC) the capability to formulate a
> conflict-free user-preferred trajectory that conforms to any active
> local-TFM constraints.*
>
> By making use of information on local traffic and TFM constraints, the
> user is able to formulate intelligent trajectory change requests that
> are likely to be acceptable to the ATSP and therefore less
> workload-intensive for the ATSP to evaluate and coordinate. Using data
> link, the AOC transmits relevant information on airline
> preferences/constraints to the FD. The flight crew use a FD-based
> trajectory planning decision support tool to compute a conflict-free
> user-preferred trajectory that conforms to any active local TFM
> constraints (bad weather, SUA, airspace congestion, arrival
> metering/spacing). The FD transmits the desired trajectory to the ATSP
> via data link. The ATSP uses their decision support tool to review the
> request, and in most cases, finds the request acceptable and issues a
> clearance for the new trajectory. If the request is not acceptable,
> the ATSP denies the request and may use their decision support tool to
> formulate an alternative clearance or provide additional information
> on ATSP requirements/constraints. It is emphasized that the ATSP
> retains full responsibility for separation assurance.

## Potential Benefits

-   Reduction in excessive deviations for separation assurance, due to
    improved CD&R capabilities of ATSP-based decision support tools,
    enabled by user-supplied data on key flight parameters.

-   Reduction in non-preferred deviations for separation assurance, due
    to user-ATSP collaboration for conflict resolution maneuvers.

-   Increased ATSP accommodation of user requests for trajectory
    changes, due to the user's ability to intelligently formulate
    trajectory change requests that conform to local traffic and TFM
    constraints.

-   Reduced ATSP workload, due to improved CD&R capabilities (enabled by
    user-supplied data) for separation assurance, and intelligent user
    requests for trajectory changes that conform to local traffic and
    TFM constraints

# Approach

CE-6 operates in en route airspace to increase system flexibility and
user preference accommodation through use of ATSP-user trajectory
negotiation, augmented by advanced airborne and ground-based decision
support automation. The two problems solved by CE-6 address
complementary situations that require:

(a) *resolution of potential conflicts due to violations of aircraft
    minimum separation rules*

(b) *conformance with local TFM constraints*

Situation "a" is the case in which trajectory negotiation is used to
resolve potential aircraft conflicts in the absence of local TFM
constraints. Situation "b" is the case in which trajectory negotiation
is used to provide conformance with TFM constraints, but this
conformance must also satisfy aircraft minimum separation requirements.
Both situations may occur simultaneously, or situation "a" may occur in
isolation from the other.

The approach taken by CE-6 is to implement the general capability to
resolve simultaneous potential violations of aircraft separation and
local TFM constraints. CE-6 is designed to provide all the functions,
processes, procedures and facilities to implement the general solution
to the union of both situations. CE-6 enables the resolution of isolated
potential aircraft conflicts as a sub-capability in which trajectory
negotiation is simplified by the exclusion of TFM constraint factors.

## Overview

CE-6 provides an ATSP focus for implementing en route trajectory
negotiation within the framework of distributed decision-making between
ATS users and providers. ATSP retains full responsibility for separation
assurance, but users are integrated into the solution processes. Users
are able to exercise initiatives and participate in the en route traffic
management decision-making processes pertaining to the prevention of
violations to aircraft separation and local TFM constraints. CE-6
provides the mechanisms for dynamically incorporating user-determined
trajectory data and preferences into the assessment and the resolution
or avoidance of potential violations. These mechanisms include processes
for exchanging information, identifying and evaluating complex traffic
situations, and determining and implementing solutions.

The trajectory negotiation process implemented in CE-6 identifies,
reviews and resolves traffic management situations requiring corrective
or approval action with respect to potential violations of aircraft
separation and local TFM constraints. This process emphasizes the use of
continual updates of flight and atmospheric information together with
advanced decision support tools to support high-fidelity trajectory
prediction and situation assessment and real-time collaboration between
users and ATSP. This approach: enables the ATSP, FD and AOC operations
to accurately assess situations and formulate resolution options;
affords ATSP the opportunity to present information to users describing
traffic situation and trajectory constraints; affords users the
opportunity to present self-optimization preferences for ATSP
consideration; and promotes the application of resolutions that are
sensitive to user preferences. The resulting ATSP flexibility in
determining airspace use allows aircraft to fly efficient trajectories
based on the changing traffic and atmospheric conditions.

For effective trajectory negotiation, CE-6 requires development of
advanced ATSP, FD and AOC automation, and their [operational and
technical integration]{.underline} based on advanced communications
capabilities and human-centered pilot and controller pilot procedures
and technologies. These functions must be properly structured and
integrated to enable users and ATSP to evaluate traffic situations
accurately and determine and implement optimal courses of action. The
operational integration focuses on the establishment of human-centered
processes and interfaces for using the computer-derived information
cooperatively among ATSP, FD and AOC to make the best use of trajectory
negotiation. The technical integration focuses on derivation,
transmission and compilation of valid flight data for use by
computerized systems to evaluate and predict actual trajectories,
identify and examine constraints and generate trajectory alternatives
with high accuracy.

## Operational Integration

CE-6 implements trajectory negotiation by providing ATSP and users with
the means for exchanging potential conflict, TFM constraint and
trajectory information to improve their situation assessment and
planning processes. User-provided data enable ATSP automation to predict
and evaluate trajectories accurately, and AOC-provided data enable users
to determine appropriate trajectory preferences:

-   AOC provides user flight operations and aircraft performance
    descriptors to ATSP, and FD provides updates of trajectory status,
    intent, preference and atmospheric measurements to ATSP. This
    information is integrated into the ATSP surveillance, flight data
    and associated computational processes to enhance decision support
    tool performance.

```{=html}
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-   ATSP provides the users with atmospheric forecasts and local TFM
    constraints such as required time of arrival (RTA), altitude, speed
    or spacing restrictions, route restrictions due to special use
    airspace, weather or sector traffic congestion, and airport
    acceptance rates and delays.

-   ATSP provides users with information describing potential violations
    of aircraft separation and TFM constraints, and may provide
    information describing ATSP-generated trajectory resolution
    alternatives or restrictions applicable to user-generated
    resolutions.

These data exchange and trajectory evaluation exercises enable ATSP and
users to determine and negotiate clearances that provide efficient
resolutions of potential violations of aircraft separation and TFM
constraints or permit efficient trajectory changes in response to user
requests.

The CE-6 operation employs a human-centered operational design that
leverages the advanced capabilities of the automation, pilot and
controller computer-human interface (CHI), and communication, navigation
and surveillance (CNS) functions available in the DAG environment. A key
component of these functions is improved trajectory prediction and
assessment, which enables extended probing along the projected
trajectory to perform aircraft CD&R and TFM constraint infraction
detection and resolution. A theoretically perfect CE-6 trajectory
prediction and assessment function would support resolution of all
potential violations along the entire trajectory prior to each
aircraft's entry into en route airspace. The theoretical limit of en
route probing would be the implementation of user and ATSP-negotiated,
violation-free 4-dimensional flight plans, which would eliminate
potential conflicts while satisfying any local TFM constraints. Delays
and diversions from the negotiated flight plan would be precluded in
this theoretically perfect operation.

In the realistic environment of CE-6, trajectory prediction and
assessment is not perfect and its accuracy diminishes with longer
look-ahead. However, trajectory analysis in the DAG environment would be
superior to that of current operations, and CE-6 trajectory accuracy
would support reliable aircraft CD&R and local TFM constraint probing
well beyond the scope defined by current sector sizing practices. Hence,
CE-6 implements trajectory negotiation for airspace that currently would
be a multi-sector environment such that ATSP evaluates aircraft
separation and local TFM requirements over an extended downstream
look-ahead span. Trajectory negotiation is used to establish a reliable
violation-free plan for the effective range of the aircraft CD&R and TFM
constraint probe. Notionally, ATSP monitors the flight along a
previously negotiated trajectory and would not intervene except when or
until a violation is projected.

This control-by-exception operation is based on a trajectory-centric,
rather than sector-centric, concept for distributing separation
assurance responsibility. Theoretically, a trajectory-orientated ATSP
operation might be established without sectorization in a futuristic
environment. However, for planning purposes based on practical
considerations, CE-6 is assumed to operate in a sector structure similar
to that currently employed. In this operation, the probe examines
aircraft separation and local TFM constraints in the multi-sector
airspace that includes the current and downstream sectors. Negotiation
is used to agree on a violation-free trajectory plan for this extended
range, alleviating requirements for subsequent downstream intervention.

The CE-6 controller and pilot operating procedures and associated CHI
are designed to support trajectory negotiation and dissemination of
constraint information for single and multi-sector coverage. ATSP data
entry and display, decision support tool and communication systems are
structured to facilitate detection and assessment of potential
violations and their resolution through ATSP-user negotiation and
inter-controller coordination. The CHI allows for the handling of a
range of complex potential violation or constraint conformance
situations. The aircraft involved in a potential violation may be in the
same sector as each other at the time of negotiation or in different
sectors, and the location of the potential violation may be the sector
containing one or more of the subject aircraft or a downstream sector.
Trajectory constraint specifications may pertain to a single reference
fix and control parameter, or a sequence of fixes and combinations of
parameters defining crossing time, spacing, speed, altitude or other
traffic management requirements.

Controllers are provided with capabilities to define a trajectory
solution or solution options, and to test, evaluate, bound, accept,
adjust or reject trajectory options generated by ATSP automation tools
and user-generated trajectory change requests. Pilots are provided with
capabilities to assess, bound, accept, or reject FD or AOC-generated
trajectory change requests and ATSP-generated trajectory resolutions.
Dispatchers have analogous capabilities. Controllers, pilots and
dispatchers are able to respond to each other's trajectory plans as part
of the process of achieving consensus.

## Technical Integration

The CE-6 operation is enabled by advanced ATSP, FD and AOC automation
coupled with advanced CNS technology. These technologies provide the
mechanisms for reliably determining and describing the attributes, state
and intent of aircraft and the air traffic system, accurately evaluating
aircraft separation and TFM constraint factors, correctly determining
trajectory options and preferences, and effectively performing
trajectory negotiation. A critical technical integration component is an
air-ground and ground-ground data link system which enables the
efficient exchange of data among ATSP, FD and AOC.

Automation tools are used in CE-6 to assist controllers, pilots and
dispatchers in conducting aircraft separation and local TFM constraint
conformance tasks. These automation tools perform trajectory prediction
and assessment calculations using highly-accurate information describing
aircraft operating characteristics, traffic, TFM constrains, and
atmospheric conditions. Data link enables the automatic exchange of
[calibration data]{.underline} describing aircraft and system
attributes, and facilitates exchange of trajectory [negotiation
data]{.underline} between ATSP and users.

Calibration information are transmitted between ATSP and user computer
operations using automated data link capabilities. These messages
contain information used by ATSP, FD and AOC automation to perform
high-fidelity modelings of trajectories, traffic situations and
atmospheric conditions. Calibration data describe flight operations and
aircraft performance factors, aircraft state and trajectory intent, and
atmospheric measurements and forecasts.

Negotiation transactions between controllers, pilots or dispatchers
include trajectory preference and preference interrogation, trajectory
change request, trajectory constraint, trajectory trial plan and
clearance, and acceptance and rejection messages.

ATSP decision support tools and surveillance functions are critical CE-6
components. Trajectory prediction and assessment automation functions
assimilate calibration and appropriate negotiation data, evaluate
aircraft separation and local TFM constraint conformance factors,
generate and assess trial plan options where necessary, and provide
controller interface capabilities for conducting trajectory negotiation
with users. ATSP automation also processes and transmits atmospheric
forecasts by data link. The ATSP surveillance system provides traffic
situation data. User-derived aircraft status and intent data is fused
with ATSP radar track data to provide the surveillance accuracy required
for reliable trajectory prediction and assessment computations.

Flight deck avionics systems are integrated into the CE-6 operation.
Aircraft flight management systems (FMSs) process calibration and
negotiation data. Advanced FMS units generate aircraft status,
trajectory intent and atmospheric measurement information for air-ground
down linking. FMSs also generate trajectory preference and restriction
data, and provide pilot interface capabilities for conducting trajectory
negotiation with ATSP. The accuracy of the status and intent data and
the capability to maintain trajectory clearance conformance depend on
the performance levels of the navigation and guidance systems onboard
aircraft.

AOCs generate flight plan and operations data that are used in ATSP and
FMS trajectory prediction and assessment computations. AOC decision
support tools provide dispatcher interface capabilities for conducting
trajectory negotiation with ATSP by ground-ground data link and with
pilots by air-ground data link.

# Operational Requirements

This section contains a description of the Operational Needs Statements
(ONS) which apply to CE-6. These ONS have been created to support the
development and ongoing revision of the AATT ATM/OPSCON.

See Appendix A for the operational requirements, presented as a table.
CE-6, Trajectory Negotiation, applies to two different service areas as
defined in the AATT ATM/OPSCON. The table lists the ONS addressed by
CE-6 first in the Separation Assurance service area and then in the
Traffic Management -- Synchronization service area.

# Operational Environment

This section describes the assumptions behind development of the concept
description for en route trajectory negotiation, conditions under which
this concept applies, and the applicable operational environments. The
section describes airspace structure and constraints, traffic mix and
equipage, CNS infrastructure, and ATM environment

## Airspace Structure And Constraints

CE-6 is applicable to departure, cruise and arrival phases of flight in
the domestic en route operational domain, and is extensible to oceanic
and terminal area domains. The airspace is sectorized within Center and
TRACON jurisdictions. A route structure with named waypoints exists, but
this system is not essential to the CE-6 concept. Hemispherical altitude
rules and step-climb procedures exist, but these are not essential to
CE-6.

## Traffic Mix and Equipage

CE-6 is applicable to commercial, general aviation and military aircraft
equipped to participate in trajectory negotiation. Essential avionics
include accurate navigation performance, advanced FMS, and data link
capabilities.

## CNS Infrastructure

Data link communication integrates ATSP, FD and AOC operations.
Air-ground data link provides two-way communication between FD and ATSP
and between FD and AOC. Addressable and broadcast air-ground
communications are employed. Ground-ground data link provides two-way
communication between ATSP and AOC. Air-ground voice communications
continue to be used, but are replaced to the extent appropriate by data
link.

The Global Positioning System (GPS) is certified for en route
navigation, but not necessarily as sole means. Advanced FMS units
support data link-based trajectory negotiation transactions between ATSP
and FD.

FMS-derived aircraft state and intent data is downlinked to ATSP and
fused with secondary surveillance radar (SSR) data to provide accurate
trajectory and situation assessment information.

## ATM Environment

An overview of CE-6 en route trajectory negotiation operational
environment is presented in the following paragraphs in comparison to
that of the current system baseline.

**Baseline ATM Environment** \-- The baseline represents current
operations in which air-ground voice communication is used for
trajectory negotiation between controllers and pilots. Information
required by ATM automation functions is obtained from static databases
(e.g., nominal aircraft performance parameters and procedures data),
flight plan (e.g., intent data), and radar surveillance (e.g., aircraft
state data) sources. Controllers manually perform trajectory prediction
and assessment based on radar and flight plan data to determine aircraft
separation and local TFM constraint conformance resolution actions.
Controllers use computer message entry and display devices to interface
with the radar and flight data processing systems and, where
implemented, Center-TRACON Automation System (CTAS) operations.

**CE-6 ATM Environment** \-- CE-6 introduces automated exchange of
trajectory-specific aircraft data in an integrated ATSP, FMS, AOC
operation. CE-6 capabilities transmit air-ground data link messages
between FMS and ATM computer systems and ground-ground data link
messages between ATM and AOC systems. FD provides ATSP systems with
selected aircraft state, intent, and atmospheric measurement data. AOC
provide ATSP systems with selected flight plan and preference, aircraft
performance, and operating procedure data. ATM provides FD and AOC
systems with atmospheric forecast data.

CE-6 calibration message transactions are automated data exchanges of
technical parameters specifying trajectory status and intent and
atmospheric characteristics. The calibration data link messages are
generated by FMS units and ATSP and AOC automation systems. CE-6
negotiation message transactions are controller and pilot data link
communications associated with trajectory clearances, maneuvers,
constraints and change requests.

The data link-based integration of ATSP, FD and AOC operations enable
improved performance of decisions support tools and other automation
functions associated with the CE-6. The ATM automation processes and
displays more accurate aircraft state data, such as heading and speed,
to improve controller situational awareness. However, a key function of
the CE-6 data exchange is the provision of aircraft-derived data to
improve trajectory modeling accuracy in advanced ATM decision support
tools. The data link-provided aircraft state data describing
FMS-determined current position and velocity vector and extensive
downstream intent data significantly improves trajectory determination
and prediction solutions and trial plan and clearance conformance
assessments relative to calculations based only on radar and flight plan
data. Trajectory calculation accuracy also is improved by incorporating
atmospheric model updates based on the downlinked wind and temperature
measurements, rather than more static atmospheric modeling. User-derived
aircraft weight, top of climb, top of descent, climb and descent
profile, and threshold crossing speed information provided and updated
for each flight enable more accurate determinations of transition
trajectories than those based on static tabular data describing nominal
profiles. ATSP is better able to predict trajectories and control
inter-aircraft positioning, enabling reductions in excess spacing
buffering. The overall result of improved trajectory modeling is more
effective potential conflict detection and resolution, sequencing and
scheduling, trajectory conformance assessment, and clearance advisory
generation by ATM decision support tools. These capabilities enable ATSP
to accurately manage trajectories, and facilitate trajectory negotiation
between ATSP and FD.

FD and AOC decision support systems and are able to take advantage of
the ATSP-generated wind and weather forecasts to update flight planning
and flight following factors, and make more-timely determinations of
trajectory change requirements. The ATSP-disseminated atmospheric
parameters enable calibration of a common ATSP, FD and AOC weather
database, reducing instances of inconsistent trajectory assessments
between ATSP, FD and AOC systems.

# Operational Characteristics

CE-6 En Route Trajectory Negotiation is an evolving operational concept
that has been the subject of various research and development
activities,^ref.1-55^ many of which are ongoing. The concept description
presented in this document is based on the research conducted to date,
and is developed through direct adoption, application or logical
extension of the previous findings. The CE-6 description draws heavily
from the previous research reports. This description is offered as a
basis for further development of the concept, providing topics for
future research to prove their operational, technical and economic
feasibility or to identify and develop design improvements and
alternatives. The CE-6 concept given herein is subject to further
examination, analysis and testing to fully mature the En Route
Trajectory Negotiation concept.

This CE-6 DAG-based concept assumes trajectory negotiation is conducted
primarily between ATSP and FD using air-ground data link, with AOC
participating by exchanging information with ATSP by ground-ground data
link and by providing FD with flight plan preference updates by
air-ground data link. ATSP and FD are the primary trajectory negotiation
agents for CE-6, and AOC provides critical support to these agents.

CE-6 implements ATSP, FD and AOC capabilities needed to conduct
effective trajectory negotiation. These trajectory negotiation-enabling
capabilities are those used to generate and assemble trajectory-relevant
data at ATSP, FD or AOC sources, to exchange and process these data, and
to provide automation support for controller and pilot decision-making
and dispatcher operations. Automation tools provide trajectory analysis
and planning and CHI functions used for controller and pilot negotiation
of conflict-free clearances in conformance with local TFM constraints.
The integration of these operational processes and interfaces are
described in the following paragraphs with respect to ATSP, FD and AOC
CE-6 functions. Technical integration is addressed in the next section
of this document.

## ATSP Operations

The CE-6 concept integrates controller, pilot and dispatcher roles and
responsibilities, operating procedures, supporting automation and CNS
technologies to enable trajectory negotiation while maintaining or
enhancing safety. This concept is based on the capability of performing
effective, accurate, extended-range trajectory planning unconstrained by
sector boundaries to identify and accommodate user preferences and
aircraft separation and local TFM constraints. For the ATSP operation,
CE-6 introduces multi-sector trajectory processing in which sector team
operations are coupled rather than being predominantly focused on
airspace internal to their individual sectors. Sector teams work
cooperatively to develop trajectories clearances that conform to
aircraft separation and TFM constraints in multi-sector airspace so that
downstream sector teams subsequently have less need to perform
trajectory intervention.

### TFM Constraints

Figure 6-1 provides a perspective on the CE-6's fit into broader TFM
operations. Figure 6-1 illustrates a case in which aircraft bound to
Chicago O'Hare International Airport (ORD) are subject to delay due to
airport capacity overload. The delay is systematically propagated
upstream through a series of organized flow constraints which result in
dynamic local TFM constraints on ORD-bound aircraft exiting Denver
Center (ZDV). The constraints may be miles-in-trail spacing-based or
time-based metering requirements. TFM constraints may include altitude,
speed and other procedural restrictions. The constraints are applicable
at specific reference fixes or jointly applicable at the Denver Center's
outbound boundary regardless of crossing point and altitude. These local
TFM constraints are further propagated within Denver Center as metering
and procedural restrictions applicable at individual sector boundaries
are or within sectors.

![](media/image2.wmf){width="5.704861111111111in"
height="3.576388888888889in"}

> Source: ref. 26,29

[]{#__RefHeading___Toc498242314 .anchor}Figure 6-1 En Route TFM
Constraint Propagation

The ORD-bound flights depicted in Figure 6-1 generally are in cruise or
climb mode in Denver or Minneapolis Center airspace, and negotiations
focus on completing climb profiles if appropriate and defining and
establishing downstream cruise trajectories. But, as these aircraft
approach ORD, such as when flying through Chicago Center airspace, the
CE-6 operation also considers descent requirements pertinent to terminal
area traffic operations in examining downstream aircraft separation and
TFM constraints. These trajectory negotiation processes require
integration with arrival and departure sequencing and spacing
automation.

Each sector team responsible for TFM constraint conformance conducts
trajectory negotiation with aircraft in its airspace. The constraints
are applicable at reference points within the sector or at downstream
points. Trajectory negotiation for downstream constraint conformance
takes into account traffic factors along the multi-sector trajectory.

### Potential Conflicts

Potential violations of aircraft separation requirements exist
concurrently with local TFM constraints or in isolation if flow
management is not in effect. In either case, the location of potential
conflicts in multi-sector airspace addressed by CE-6 are analogous to
those illustrated in Figure 6-2.^ref.35,44^ The CE-6 multi-sector scope
is not restricted to adjacent sectors as shown in Figure 6-2, but this
four-sector configuration illustrates potential conflict-airspace
combinations relevant to trajectory negotiation. These potential
conflicts in general include aircraft crossing, merging and overtaking
situations for climb, cruise and descent modes.

![](media/image3.png){width="4.6in" height="5.2in"}

> Source: ref.35,44

[]{#__RefHeading___Toc498242315 .anchor}Figure 6-2 Multi-Sector
Potential Conflict Situations

The intrasector and external potential conflicts (Cases A and B in
Figure 6-2) are situations in which each aircraft conduct trajectory
negotiation with the same sector team. The ATSP negotiation process in
the intrasector situation (Case A) is within the jurisdiction of that
sector team. But in the external situation (Case B) where the potential
conflict point is in a downstream sector, the negotiation process
accounts for the separation assurance responsibilities of both sector
teams.

The external intruder and intersector potential conflicts (Cases B and
C) are situations in which each aircraft conduct trajectory negotiation
with different sector teams. The negotiation process is conducted in
accordance with the jurisdictional responsibilities of both sector
teams.

### User Request for Trajectory Change 

Trajectory negotiation also is invoked in response to a user request to
change the trajectory, normally based on flight plan optimization. The
request generates an ATSP examination of the requested trajectory for
TFM constraints such as those depicted in Figure 6-1 and potential
conflicts such as those depicted in Figure 6-2. The negotiation is
conducted between the aircraft and its current controlling sector team,
and could involve consideration of downstream sector jurisdictional
responsibilities.

### Trajectory Prediction and Assessment

ATSP automation in conjunction with data link provides capabilities to
identify trajectory options that satisfy TFM constrains without
violating aircraft separation requirements, identify and resolve
potential conflicts with and without TFM constraints, and respond to
user-generated trajectory change requests. CE-6 incorporates user
preferences into the resolution process, advises users of TFM
constraints, and facilitates trajectory negotiation.

CE-6 automation implements computational processes to predict
trajectories and assess aircraft separation and TFM constraints.
Accurate trajectory analysis is essential to CE-6, and is supported by
comprehensive data exchange between ATSP and users and advanced aircraft
dynamics modeling.

**Data Exchange** -- CE-6 exchanges calibration data between ATSP and
users using data link. Calibration data provide a dynamically-updated,
common set of flight operations, aircraft state, intent and performance,
and atmospheric information for processing by FMS units and ATSP and AOC
automation. These capabilities are important to the accuracy and
compatibility of computational algorithms used for trajectory
prediction, enabling high-fidelity FMS and decision support tool
performance. The calibration data also are used to enhance the
information displayed to controllers, supporting situation awareness.

The calibration data enable improved trajectory prediction accuracy in
advanced ATSP decision support tools relative to pre-CE-6 operations.
Aircraft state data describing FMS-determined current position and
velocity vector and extensive downstream intent data significantly
improve trajectory determination and prediction solutions and flight
trajectory and clearance conformance assessments relative to
calculations based only on radar and flight plan data. Trajectory
calculation accuracy also is improved by incorporating atmospheric model
updates based on the downlinked wind and temperature measurements,
rather than more static atmospheric modeling. Aircraft weight data and
the top of climb, top of descent, climb and descent profile, and
threshold crossing speed information provided and updated for each
flight by AOC systems enable more accurate determinations of transition
trajectories than those based on static tabular data describing nominal
profiles. The overall result of improved trajectory modeling is more
effective potential conflict detection and resolution, sequencing and
scheduling, trajectory conformance assessment, and clearance advisory
generation by ATM decision support tools.

**Aircraft Trajectory Dynamics Modeling** -- Previous research^ref.30^
has identified aircraft dynamics modeling requirements for 4D-trajectory
predictions:

> The approach used is to integrate the point-mass model kinetic
> equations of motion based on first principles. This models the three
> translational dimensions and the primary rotational dimension
> ("roll"). Instead of simplifying the equations of motion to represent
> average dynamics, all the primary kinetic and kinematic terms are
> preserved (Thrust-minus-Drag, Weight, acceleration, and wind gradient)
> to ensure that the predicted dynamics are able to match reality under
> the wide variety of operational conditions. Extensive field testing
> has been conducted to validate the accuracy of this
> approach.^ref.31,32,54^
>
> For reasons of traffic growth (requiring less uncertainty to squeeze
> out extra capacity) and integration with FMS, this approach reduces
> errors related to second-order dynamics. This approach may be "tuned"
> for greater 4D accuracy by simply improving the input data. Lateral
> paths are modeled as a series of straight segments and curved-path
> turns. The turns are defined to be compatible with FMS
> lateral-navigation standards which defines waypoints as "fly-by" or
> "fly-over." The curved-path is predicted as a function of predicted
> ground speed in the turn (based on predicted airspeed and winds aloft)
> and bank angle/acceleration (defined in the performance model database
> as a function of altitude and phase of flight). The vertical profile
> models performance \[(T-D/)W\], speed schedule, altitude (non-standard
> atmosphere) and wind gradient. Corrections are provide for
> non-standard atmospheres (non-standard temperature), non-standard
> altimeter settings, and variations in weight if accurate weight data
> are available.
>
> This trajectory-integration process also accounts directly for the
> thrust and drag models of each aircraft type thus allowing the model
> to be tuned to each flight's performance envelope if the specific
> configuration is provided (via flight plan or data link
> communications). More importantly, the approach models the affect of
> speed profile and wind gradient on the vertical rate, both of which
> have a substantial impact relative to the other factors. The model
> predicts the speed profile based on its speed advisories for flow-rate
> conformance (just the situation when it is most important to model the
> vertical profile accurately). If flow rate constraints are not in
> effect, the model uses its estimate of the current speed profile
> and/or preferred-speed database for future flight segments.
>
> Note 4D trajectory-prediction accuracy has an impact on airspace
> capacity. In order to achieve an acceptable conflict-probe time
> horizon and missed-alert rate, "buffers" must be added to trajectory
> predictions to mitigate the impact of prediction uncertainties. One
> method is to add a "conformance bounds" around the baseline trajectory
> prediction. This approach is an effective means for reducing missed
> alerts, but the penalty involves a loss of airspace to support the
> buffer, and a greater rate of false alarms. This is particularly
> relevant for traffic situations (such as arrival metering) where many
> flights must be compressed to spacings that are on the order of the
> minimum requirements for separation. As 4D
> trajectory-prediction-accuracy performance improves, the need for
> conformance bounds (buffers) is reduced.

**Aircraft Separation and TFM Constraint Assessment Probe** -- ATSP
automation operates a potential conflict and TFM constraint probe along
a projected trajectory. This trajectory may be that corresponding to the
currently predicted flight path, a user requested change, or an
alternative flight path. The probe generates alerts of potential
violations. The probe's look-ahead range is based on concerns of
preventing missed alerts and limiting false alarms, and is determined by
the accuracy of the trajectory prediction model. The probes application
should avert the worst case scenario depicted in Figure 6-3 in which the
resolution of false alarm leads to a missed alert.

![](media/image4.wmf){width="3.248611111111111in"
height="2.036111111111111in"}

> Source: ref. 26,30

[]{#__RefHeading___Toc498242316 .anchor}Figure 6-3. Avoidable
Interruptions

CE-6 uses the probe in an algorithmic process that generates mutual
resolution of aircraft separation and TFM constraints. Based on previous
research,^ref.30^ the process is one that first resolves the TFM
constraints and then uses this solution as a boundary condition for the
potential conflict solutions. This inner-outer loop calculation approach
is effective when flow-rate conformance accuracy is small compared to
the separation requirement. Accuracy of this magnitude is required for
CE-6 trajectory prediction and the corollary capability to deliver
aircraft to a fix according to plan.

Trajectory projections beyond Center boundaries require special
consideration. Each Center's data processing system has limited
information for traffic in adjacent Centers' airspace, and automated
prediction and assessment of trajectories across Center boundaries are
subject to inaccuracy. Except where TFM constraint conformance at these
boundaries is sufficient to accommodate inter-Center traffic, special
information exchange and coordination of potential conflicts for
aircraft approaching Center boundaries is warranted.

**TFM Constraint and Related Data Dissemination** -- ATSP automation
compiles and distributes TFM constraints, meteorological and traffic
data to users by data link to enable users to generated acceptable
trajectory change requests in the CE-6 concept. Data describing airspace
and airport congestion, meteorological forecast, severe weather, SUA,
and flow rate constraints is voluminous, and would be used by AOC
automation to determine flight plan and schedule preferences and
constraints. These data are transmitted to the aircraft for use in
aligning specific trajectory change requests with dynamic local TFM
constraints, subject to potential conflict resolution.

Local TFM constraint and meteorological data transmitted to FD by ATSP
would need to be compatible with FMS processing capabilities. These data
are succinct specifications of metering and procedural restrictions and
wind and temperature forecasts along the predicted trajectory. Figure
6-4 illustrates an example of an FMS determining a preferred descent
profile in response to an altitude restriction, enabling negotiation of
the top of descent location.

![](media/image5.wmf){width="4.906944444444444in"
height="2.963888888888889in"}

> Source: NASA

[]{#__RefHeading___Toc498242317 .anchor}Figure 6-4. Application of an
Uplinked Waypoint Constraint

To further support FMS assessment of potential trajectory changes, ATSP
also may provide TFM constraints and meteorological data for reference
points along logical alternative trajectories. In all likelihood, RTAs
or RTA ranges would be required rather than miles-in-trial spacing
unless the FD is capable of processing and integrating trajectory data
for other traffic into the TFM constraint information to determine
spacing fit. These data requirements further accentuate the need for
accurate and efficient trajectory modeling by ATSP automation.

### Trajectory Negotiation

ATSP automation generates trajectory amendment advisories for
controllers responding to potential conflict and TMA constraint
violations and trajectory change requests, and provides the CHI
functions necessary for trajectory negotiation with FD.

**Aircraft Separation and TFM Constraint Conformance** \-- Advisories
generated by CE-6 decision support tools describe route speed, heading
or altitude change maneuvers and spacing, time, speed, altitude crossing
constraints at reference fixes along projected trajectories. The
advisories are based on analysis of extended trajectories, enabling
sector teams to perform conformance planning for multiple flights over
multi-sector airspace. Previous research^ref.26^ provides an
illustration of the capabilities of CE-6 relative to current operations
in resolving complex traffic situations:

> Three flights in Figure 6-5 are initially on user-preferred eastbound
> routes. The circles indicate the relative sequence of the un-delayed
> flights when the first flight crosses the boundary. The natural order
> of arrival at the boundary is B, C, and A. Consider the situation
> where the downstream center (ARTCC 2) imposes an miles-in-trial
> spacing restriction at the boundary. Without automation assistance, it
> would be difficult for sector controllers to visualize and space their
> flights relative to flights in other sectors that are orthogonal to
> the flow. Referring to Figure 6-5, the controller in Sector 2 would
> have difficulty in spacing aircraft B relative to A or C. To overcome
> this problem, traffic management coordinators re-route aircraft A and
> C (see Figure 6-6) to form a stream that can be visualized and
> controlled by Sectors 2 and 5 controllers. Depending on the natural
> distribution of flight paths, these re-route actions add a significant
> flight cost penalty. Once streams are formed, spacing adjustments
> typically involve vectors. Although speed control can help fine-tune
> spacing under current procedures, it is often too little to establish
> spacing because of performance mismatches and limited range within a
> sector (for speed changes to take effect). In-trail flows also reduce
> the opportunity for faster aircraft to pass slower ones when the
> faster aircraft would naturally arrive first at the spacing-reference
> fix. Once spacing is established within a stream, additional
> deviations may result from conflicts with crossing traffic.
>
> ![](media/image6.wmf){width="2.783333333333333in"
> height="2.3631944444444444in"}
>
> Source: ref.26

[]{#__RefHeading___Toc498242318 .anchor}Figure 6-5. User-preferred
routes

> ![](media/image7.wmf){width="2.763888888888889in"
> height="2.3631944444444444in"}
>
> []{#OLE_LINK1 .anchor}Source: ref.26

Figure 6-6. Re-routes to form spacing trail.

> Application of the CE-6 trajectory-prediction and probing capability
> associated provides solutions that are more sensitive
> user-preferences. Figure 6-7 illustrates the resulting situation,
> assuming that the downstream receiving facility will still require an
> in-trail stream at the hand off. As long as the tools and procedures
> result in conformance prior to the spacing-reference fix, each of the
> cross-stream sectors may work their flights independently and thus
> delay the merge until the spacing-reference fix.
>
> ![](media/image8.wmf){width="2.763888888888889in"
> height="2.342361111111111in"}
>
> Source: ref.26

[]{#__RefHeading___Toc498242320 .anchor}Figure 6-7. Spacing with minimum
deviation.

> Additional benefit could be achieved if the downstream receiving
> facility relaxed the requirement for an in-trail flow at the hand off.
> At the theoretical extreme, the automation could help controllers
> deliver an equivalent spacing across a wide stream of flights (Figure
> 6-8) with the absolute minimum deviation from each user\'s preferred
> route. Of course, depending on the amount of delay required (i.e.,
> relative to the aircraft\'s performance and speed envelope), a certain
> vectoring may be necessary to space each flight. Figure 6-8 approaches
> the user-desired concept of free routing where flow-restrictions are
> implemented, as needed, with RTA assignments. In fact, spacing
> solutions could be used to determine RTA assignments for equipped
> aircraft.
>
> ![](media/image9.wmf)
>
> Source: ref.26

[]{#__RefHeading___Toc498242321 .anchor}Figure 6-8. Path-independent
spacing.

> Figures 3-7 and 3-8 illustrate several of the advantages to the
> spacing tool approach. First, the degree of route deviations required
> for spacing conformance is minimized. Second, the traffic density and
> spacing workload is distributed across more sectors. This distribution
> of flights reduces the impact of dissimilar speeds among sequential
> flights, in a stream, thus allowing more opportunity for natural
> overtakes. It also provides for a more equitable distribution of
> delays based on the nominal performance of the aircraft. In addition,
> the integration of aircraft separation and TFM constraint conformance
> tools result in more efficient trajectories with fewer false alarms
> and missed alerts. By allowing flights to remain on independent paths
> (delaying any merge until the spacing-reference fix), speed control
> may be exercised more effectively.

The solutions generated by CE-6 automation are based on accurate
aircraft performance models, which provide practical trajectories that
can be flown by the aircraft. The capability of ATSP to define realistic
trajectory solutions is vital to the negotiation process in that
iterative communications with FD regarding trajectory option are
averted. Accurate performance modeling also enables negotiation
procedures in which realistic bounds on potential conflict or TFM
constraint conformance options are determined by ATSP and presented to
users to solicit solution preferences. The type of ATSP-FD negotiation
that is used would depend on traffic intensity and situation complexity.
In constrained airspace during intense traffic and workload conditions,
the transmittal to FD of trajectory solutions rather than trajectory
bounds data by ATSP would facilitate the negotiation process by limiting
the range of options under consideration. In less time-critical
situations, trajectory bounds data would enable FD to identify
trajectory optimization preferences beyond those proposed by ATSP.

**Controller Operations** \-- CE-6 ATSP automation provides controller
interfaces for managing the trajectory prediction, probing and
conformance resolution operations and conducting trajectory negotiation
with FD.

Data entry and display devices and attendant procedures provide
controllers with options to select aircraft stream and reference fix
subjects for traffic flow management. Aircraft streams are defined
according to flight origin or destination, routing, flight direction,
airspace region to be penetrated, aircraft type, or other logical
classification. A reference fix may by an individual published waypoint
or a temporary waypoint manually positioned by controllers, a set of
waypoints, and arbitrary arc, a formal boundary, or other meaningful
designator. Reference fixes may be in the controller\'s sector airspace
or downstream sectors.

Generally, a network of reference fixes would be established to manage
multi-sector traffic. Controllers in different sectors would use this
common set of reference fixes to coordinate operations. By this process,
sector teams would determine aircraft separation and TFM constraint
conformance resolutions based on common traffic planning goals (e. g.,
crossing time schedules or spacing restrictions at waypoints several
sectors downstream).

Controller\'s have options for managing the resolution tactics
applicable to aircraft separation and TFM constraint violations and
trajectory change requests. Controllers define the degree of freedom
permissible for use by decision support tools in constructing trajectory
options. These allow trajectory changes to be defined according to
speed, altitude, vectoring and routing parameters or to be
unconstrained. Controllers use automatic resolution advisory tools (see
Appendix B) to examine trajectory options for potential conformance
violations. These modes allow a range of controller interaction in
defining the trajectory options. Controller are provided with tools to
modify, exchange, store and recall and the trial plans.

ATSP trajectory negotiation with FD is conducted using an extensive set
of formalized data link messages supported by data display and entry
devices that facilitate message manipulation. The messages are
structured parametrically to enable efficient transmittal of trajectory
intent, preference, constraint and request data and approval, rejection
and acknowledgement information. The message data composition and format
are such that they are readily understood and processed by controllers,
pilots and automated functions.

## FD Operations

FD operations in CE-6 are complimentary to those described in the
preceding paragraphs for ATSP. FD exchanges trajectory data with ATSP,
determines trajectory preferences, and negotiates clearances. The FD
would not have computerized computational resources comparable in
processing capability to those of ATSP automation, and FD operations are
scaled accordingly. Flight-specific and time-responsive trajectory
analysis tools and concise negotiation procedures are essential to FD
participation in CE-6. Lengthy clearances would be problematic.^ref.53^

Pilots view and compose data link messages using selectable menus.
Trajectories transmitted to FD for negotiation define an extended 4D
flight path or near-term maneuver requirements. The extended 4D flight
path describes crossing time, speed and altitude for waypoints along the
projected trajectory. Near-term maneuver requirements describe speed,
heading or altitude assignments or bounds on these assignments. The FMS
automatically reviews the message to confirm consistency with aircraft
performance capabilities, and advises the pilot accordingly on the
message display. Inconsistencies between ATSP and FMS aircraft models,
databases and trajectory analysis algorithms, such as those involving
dissimilar speed, altitude or route change or heading/vectoring/path
stretching solution strategies, would disrupt the negotiation process
and are precluded in CE-6.

Pilots perform a logical validation and assessment of the ATSP
trajectory proposal. At minimum, pilots have the option to respond to an
uplinked message with and affirmative acknowledgement (i.e., ROGER),
affirmative acknowledgement with automated loading (autoload) of the
message into the FMS mode control selection panel (i.e., ROGER/ENTER),
or negative acknowledgement (i.e., UNABLE). Autoload is a simple,
single-stroke, selection entry by the pilot, which precludes manual
copying of the message contents.

Pilots may also choose to examine trajectory options to determine
preferences. Previous research^ref.53^ indicates that negotiation
procedures should be established that would enable the FMS to
automatically generate a trajectory preference or trajectory change
request based on pilot-set parameters. For example, the pilot would
specify the speed range usable by the FMS in determining a profile, or
accept or modify speed bounds suggested by ATSP. The pilot would review
the resulting profile generated by the FMS to assess acceptability, and
invoke the single-stroke automated transmit (autosend) function to
downlink the message.

## AOC Operations

AOC decision support systems would take advantage of the ATSP-generated
wind and weather forecasts to update flight planning and flight
following factors, and make timely determinations of requirements to
update the filed flight data. The ATSP-disseminated atmospheric
parameters would locally calibrate a common ATSP and AOC gridded weather
database, reducing instances of inconsistent trajectory assessments
between ATM and AOC systems. AOC transmits trajectory preference updates
to FD by data link as warranted by flight plan analysis.

# NAS Functional Impacts

This section discusses the NAS impacts, including planned NAS
architecture components, of the concept as described. Section 7.1
describes functional requirements, and section 7.2 shows the functional
design which derives from these requirements.

## Functional Requirements

The following functional changes from the current NAS, expressed in
terms of technology and infrastructure, are needed to support the
concept. These are described in the areas of communications, navigation,
surveillance, automation, weather and traffic management.

### Communications

Trajectory negotiation is facilitated through use of two-way air-ground
data link between ATSP computer systems and the FMSs on the flight decks
and two-way ground-ground data link between ATSP and AOC computer
systems. AOC also provides trajectory planning data to FD through
air-ground data link. Calibration data are exchanged to support
trajectory modeling and analysis, and negotiation data are exchanged to
support trajectory adjustment. Calibration data exchanged between ATSP
and FD systems include dynamic factors describing trajectory state and
intent and atmospheric conditions. Calibration data exchanged between
AOC and ATM systems generally include less-dynamic factors describing
aircraft performance and flight operating procedures. Negotiation data
exchanged between ATSP and FD systems describe trajectory preferences
and constraints. The following paragraphs summarize the data link
message categories pertaining to trajectory negotiation.

[Flight-Specific Operating Factors]{.underline} -- These data affect
flight performance and normally vary day-by-day from flight-to-flight.
These data would be transmitted to ATM from the AOC pre-departure by New
Age Flight Plan^ref.37^ by ground-ground data link, and subsequently
updated as appropriate. Flight-specific factors include usable takeoff
and landing runways, acceptable arrival and departure runway delay,
approach and landing qualifications of crew and aircraft, required time
of arrival (RTA) and FMS capabilities, and applicable cost index.

[Aircraft-Specific Performance and Procedures]{.underline}-- These data
refer to both engine/airframe performance characteristics and specific
airline/pilot standard operating policies or practices, specific to each
aircraft or aircraft type. These data are relatively static, and would
not change on a flight-by-flight, day-to-day basis. This data would be
transmitted to ATM from the AOC pre-departure via a New Age Flight Plan
by ground-ground data link. Relevant performance data include thrust and
drag calibration factors, actual thrust and drag models, and selected
performance parameters such as ascent and descent rates or envelopes as
a function of speed profile. Relevant procedural data include turn rates
or bank angles as a function of aircraft state and thrust management
procedures or target ascent and descent rates.

[Aircraft State]{.underline} \-- Aircraft state data include
time-critical flight status information. These data would be transmitted
from the aircraft periodically by air-ground data link. State data
include present aircraft position, altitude, velocity, heading, weight,
actual navigation performance, and other trajectory dynamics (i.e.,
track angle and altitude change rate).

[Trajectory Intent]{.underline} -- These data describe the
user-calculated active downstream trajectory corresponding to the
current flight plan and clearances. These data would initially be sent
from AOC in a New Age Flight Plan with additions/changes downlinked from
the aircraft to ATM by air-ground data link. Intent data would be
updated typically whenever: (1) a flight plan edit occurs, (2) a
waypoint is crossed, (3) a trajectory is changed due to tactical
maneuvering or environmental conditions, or (4) upon ATM interrogation.
Intent data for a string of downstream four-dimensional trajectory
control points (e.g., en route waypoints, TOD, arrival fix) could
include each control point's name, 2D location, altitude, and crossing
time and weight. Additionally the data may include the point type and
the turn radius associated with a flight path transition. Intent data
would describe preferred speed and altitude profiles for climb, cruise
and descent segments, and runway threshold crossing speed.

[Atmospheric Characteristics]{.underline} -- Meteorological data include
aircraft in-flight measurements of atmospheric state and ATSP
dissemination of atmospheric forecasts. The in-flight atmospheric
measurements would be transmitted from the aircraft to ATM periodically
by air-ground data link. Atmospheric predictions would be uplinked
according to scheduled event or upon request to aircraft. The request
would specify data content and scope (e.g., weather grid or points along
a trajectory for a specific time period). Atmospheric state data include
wind speed and direction, air temperature, air pressure, and turbulence
reports.

[Trajectory Preferences]{.underline} -- The air-ground data linked
preference information include FD or ATSP-generated trajectory trial
plan and change request messages, proposed near-term speed, altitude and
heading maneuver and fix crossing requirements messages, interrogation
message requesting preference data, and acceptance and rejection
messages. Trajectory trial plan, change request and near-term preference
data are analogous to intent data except the preference data apply to
provisional trajectories.

[Trajectory Constraints]{.underline} -- The air-ground data linked
constraint information include trajectory speed, altitude, route and
time bounds issued by ATSP or FD, local TFM procedural restrictions
issued by ATSP, and updates issued by FD concerning aircraft performance
envelopes, runway acceptability, crew and aircraft qualifications,
aircraft equipage, and other operational factors.

The data link communication message system is a critical element in
integrating ATSP, AOP and AOC operations and technologies in CE-6. The
data link message set used for trajectory negotiation is designed to be
in conformance with the data processing requirements of ATSP, AOP and
AOC automation. The data content and structure or these messages support
the trajectory determination, prediction and assessment functions of FMS
units and ATSP and AOC decision support tools.

### Navigation

There are no new functional navigation requirements imposed by the CE-6
concept beyond those that are subjects of current development efforts of
the aviation industry. GPS is certified as a means of navigation and
supports the determination of accurate trajectory state information and
accurate adherence to trajectory intent. The on-board navigation system
has a Required Navigation Performance (RNP) level with sufficient
accuracy to support trajectory negotiation applications.

Aircraft participating in CE-6 operations have [advanced FMS
units]{.underline} capable of accurately adhering to a planned position,
altitude, and time-defined trajectories, including RTA applications.
These advanced FMS units typically include a central flight management
computer, airplane systems inputs of air data, inertial reference and
engine sensor parameters, digital flight control computers, and a pilot
interface consisting of electronic flight displays, mode control
selection panel, and control display unit (CDU). The display system
includes a primary flight display, a navigation display, an engine
display, and the data link message display. FMS vertical profile
planning programs compute crossing speeds, altitudes and times at
downstream waypoints based on altitude and cost index selection
parameters. The navigation database contains pre-specified routes,
fixes, and arrival and departure procedures with altitude and speed
constraints by waypoint. The FMS retains the active and provisional
trajectories, which may be may be modified, exchanged, stored and
retrieved. The active route provides guidance and situation information,
and the provisional route enables review of proposed routing and
profiles or FD-initiated trajectory changes.^ref.53^

### Surveillance

Aircraft participating in CE-6 operations are equipped to transmit their
state and intent information computed in the FMS. The ATSP surveillance
function fuses the FMS-derived state information with that obtained from
area radar.

### Automation

CE-6 ATSP decision support tools support the following automation
functions:

-   develop knowledge of state and intent of traffic

-   develop knowledge of atmospheric conditions

-   perform trajectory modeling

-   perform aircraft separation and TFM constraint violation probing

-   accept user preferences

-   perform trajectory trial planning

-   provide interactive display interface for trajectory negotiation

These automation functions are supported by appropriate two-way data
link between ATSP, FD and AOC.

### Weather

ATSP provides accurate atmospheric modeling of winds aloft, temperature,
pressure and turbulence conditions, and provides gridded and along-track
atmospheric forecast information to aircraft. These data are updated
regularly by down linking of wind and temperature measurements from
participating aircraft.

### Traffic Management

There are no changes required for strategic traffic management at the
Command Center level. Local traffic management participates in setting
the TFM constraints at the ATSP sector and facility level. Local TFM
constraints include miles-in trail spacing, time-based metering, and
altitude, speed, route and related procedural restrictions.

## Functional Design

Figure 7-1 is a high level functional design diagram showing those NAS
systems and services that are essential for supporting CE-6. Current and
future air traffic systems and services which are general to ATM but not
specifically utilized in CE11 are not shown.

![](media/image10.wmf){width="5.677777777777778in"
height="6.2756944444444445in"}

[]{#__RefHeading___Toc498242322 .anchor}Figure 7-1. CE-6 Functional
Design Diagram

The aircraft maintains accurate state and intent information and
trajectory conformance using GPS as the primary navigation input to the
FMS. Each aircraft transmits state and intent information ground
receivers. The down linked state data are fused with secondary
surveillance radar data for improved total situation awareness by ATSP.
The aircraft downlinks atmospheric measurements and ATSP uplinks
atmospheric forecasts. AOC transmits aircraft performance and flight
operations information to ATSP and trajectory planning information to
the aircraft. ATSP conducts aircraft separation and TFM constraint
violation probing, and transmits provisional trial plan or trajectory
bounds data to the aircraft. ATSP also provides the aircraft with local
TFM constraints. Aircraft FMS assess the trial plan or trajectory bounds
data, generate trajectory preferences or trajectory change requests.
These are subsequently transmitted to ATSP after pilot review,
modification and approval. Controllers and pilots review and assess
trial plans, constraints, and request, and negotiate trajectory
adjustments using interactive display interfaces.

# User/Operator Roles and Responsibilities

This section addresses impacts on CE-6 on the roles and responsibilities
of the active participants, focusing on controller and pilots.

## ATSP Roles and Responsibilities

The air traffic controllers manage aircraft in a similar manner as
today, but employ advanced decision support tools and data link
communication. Controller operating functions associated with CE-6
include the use of automatic resolution advisories and interactive
display interfaces (see Appendix B).

## Pilot Roles and Responsibilities

In CE-6, pilots use the FMS interactive display function integrated with
data link communication to conduct trajectory negotiation with ATSP.
CE-6 provides pilots with concise trajectory negotiation procedures and
capabilities to modify trajectory planning parameters and modify,
exchange, store and retrieve active and provisional trajectories in the
FMS.

## Dispatcher Roles and Responsibilities

CE-6 does not have significant effects on AOC operator roles and
responsibilities.

# Operator Modes and Scenarios

This section illustrates the CE-6 concept using a hypothetical flight.

## Normal or Nominal Mode

Before the departure of BRC926, a LAX to ORD flight, the AOC submits
information to ATM describing trajectory intentions and preferences
specific to today's flight and the aircraft's standard performance
characteristics. These calibration data include take-off weight, runway
preferences, acceptable delay factors, climb, descent and cruise profile
characteristics, and the aircraft engine and aircraft operating
specifications. CTAS processes these data to define alternative surface
routings and departure trajectories to and from the user preferred and
other qualifying runways. CTAS uses this information to update the
airport taxi routing and runway utilization plan. CTAS also uses
aircraft position data sent by ADS data link during taxi-out to update
route and trajectory alternatives.

After takeoff from its preferred runway, BRC926 periodically downlinks
aircraft state information to ATSP by air-ground data link, including
current position, time, heading, altitude, and velocity vector, and
atmospheric state measurements describing current wind , temperature and
pressure. Upon receipt of the initial aircraft airborne state report,
ATM uplinks an atmospheric forecast to BRC926 describing the predicted
meteorological state at 3D points along the planned flight trajectory.
BRC926's FMS uses the atmospheric prediction data and its database of
local standard departure procedures to recalculate its projected
trajectory based on its current ATM clearance. BRC926 then downlinks a
trajectory intent report describing the FMS-projected Mach/CAS speed and
altitude climb profile and times and altitudes at downstream waypoints.

The FMS-derived and AOC-provided calibration data are used by the ATSP
automation to predict the departure trajectory as well as to construct
alternative trajectories. The high fidelity trajectory prediction and
assessment capability afforded by the calibration data, aircraft
dynamics modeling, and conflict probe and trial planning DSTs, enables a
controller to identify an efficient maneuver adjustment to BRC926 that
avoids a potential conflict with an arrival flight to the airport. This
maneuver permits removal a standard local procedural altitude
restriction that would require BRC926 to cross under the crossing and
descending arrival traffic pattern. This maneuver deviation is less
costly than would be the altitude restriction. This provisional
trajectory plan is uplinked to the aircraft. The FMS reviews the plan
and determines that the plan conforms with the aircraft's performance
capabilities and is more fuel-efficient than the current active
trajectory. The pilot cognitively accepts the plan and transmits a
ROGER/ENTER downlink message which autoloads the plan into the FMS as
the active trajectory. Similarly, the ATSP provisional plan is converted
to active status by the automation, and noted by the controller.

ATSP automation uses the aircraft state reports to display accurate
position, heading and speed data for BRC926, enhancing the controller's
ability to monitor the trajectory dynamics and verify compliance with
the clearance. BRC926 continues to downlink aircraft state and
atmospheric measurement periodically during climb, and will do so for
the remainder of the trip.

BRC926 downlinks a report of the FMS-determined aircraft weight at top
of climb. This information is used by ATSP to calibrate its flight state
data and modeling processes, enhancing trajectory prediction accuracy.
Also at top of climb, BRC926 downlinks a request for an atmospheric
prediction update. ATM responds by uplinking an atmospheric forecast
describing the predicted meteorological state at the downstream
waypoints along the current planned trajectory. The FMS-projected
trajectory is recalculated, and BRC926 downlinks a trajectory intent
report describing the FMS-preferred speed and altitude profile and times
and altitudes at downstream waypoints. The data linked information are
used by ATSP to enhance the ATM trajectory prediction models that are
supporting multi-sector probing for potential violations of aircraft
minimum separation and local TFM spacing constraints along BRC926's
intended trajectory. The automated probing identifies down-sector TFM
spacing violations that, according to the results of ATSP trial
planning, could be resolved by an altitude diversion to BRC926. Instead
of transmitting this resolution to the aircraft, the controller elects
to uplink the relevant TFM spacing constraint information using
automated procedures. The FMS determines that a speed reduction is a
preferred fuel-efficient solution, and the pilot downlinks the
corresponding trajectory change request. The controller probes this
alternative for potential conflicts and TFM constraint violations,
determines that it is acceptable, and approves the speed change by data
link acknowledgement. The FMS and ATSP active trajectories are updated.

These air-ground data link transactions by BRC926 during cruise are
repeated at trajectory change points, such as top of step climb and key
turn points, as well as at occurrences of deviations from the intended
trajectory. ATSP decision support tools continue to update trajectory
predictions, perform trajectory probing, and display advisories and data
to controllers.

At a scheduled time prior to top of descent, ATM uplinks an atmospheric
prediction update and a trajectory intent interrogation. The atmospheric
forecast describes the predicted meteorological state at 3D points along
the currently planned descent trajectory. In response to the
interrogation, the BRC926 FMS recalculates its forward trajectory and
downlinks a trajectory intent describing the FMS-projected Mach/CAS
speed and altitude descent profile, arrival runway threshold crossing
speed, and the arrival runway and runway exit identifiers. ATSP
automation processes the dynamically updated calibration information to
refine the arrival airspace and runway utilization plan.

This air-ground and ground-ground data linked information improves the
accuracy of the ATSP trajectory prediction models in comparison to the
current baseline ATM system. ATSP automation processes the assembled
calibration data (i.e., aircraft performance, pilot procedures, flight
operating factors, aircraft state, intent and atmospheric parameters) to
define alternative arrival trajectories to the user preferred and other
qualifying runways. As result of the ATSP assessment, BRC926 is issued a
provisional plan to reduce cruise speed before top of descent without
changing the top of descent location. The resulting trajectory is the
most cost-effective alternative for the prevailing traffic situation.
The FMS confirms the plan's acceptability, the pilot approves, and the
clearance change negotiation is completed through routine data link
transaction and data processing procedures.

## Off-Nominal Mode Scenarios

There are no currently identified off-nominal mode scenarios that drive
CE-6 concept development.

## Failure Mode Scenarios

There are no currently identified failure mode scenarios that drive CE-6
concept development. If ATSP CE-6 decision support tools fail, ATM
operations revert to those of the current system. If a FD or AOC
automation function fails, that operator or aircraft cannot participate
in CE-6 services and the ATSP develops the most acceptable resolution
given the available information.

# Operational Processes/Operational Sequence Diagrams

An overview of the CE-6 operation is depicted in Figure 10-1.

![](media/image11.wmf){width="6.025in" height="7.457638888888889in"}

[]{#__RefHeading___Toc498242323 .anchor}Figure 10-1 CE-6 Operational
Sequence Overview

# Benefits

En route trajectory negotiation improves the performance of FMS and ATM
automation and enhances situation awareness, resulting in improved
flight operating efficiency, reduced workload and associated safety
impacts. The primary potential benefits of the CE-6 are derived from
improvements in the trajectory assessment and prediction capabilities of
advanced ATSP automation and FMS units. The effective operation of many
advanced ATSP automation enhancements (e.g., potential conflict and
local TFM constraint violations probe and various sequencing, scheduling
and spacing algorithms) and FMS features depend primarily on the
capability to accurately determine current aircraft state and predict
future states. The accuracy of these underlying trajectory algorithms
are enhanced by the higher fidelity aircraft performance information,
aircraft state and intent data, and atmospheric measurement and forecast
data provided by the CE-6. Trajectory negotiation significantly enhances
these benefits by including user preferences as a major factor in the
trajectory decision-making processes. Additional benefits are provided
by displaying more accurate trajectory state information derived from
the calibration data to controllers to assist in evaluating the current
and evolving traffic situation and negotiating the appropriate response
for delivering aircraft to the desired end state.

Key CE-6 potential benefits impacts are summarized in the following
paragraphs.

**Capacity**

[More Efficient Use Airspace System Capacity]{.underline} -- Due to more
accurate current and predicted situation information (e.g., aircraft
position and velocity vector, winds aloft, runway exit), FMS-equipped
aircraft conform better to planned or assigned trajectories and ATSP is
more responsive to changing situations. These improvements enable
effective negotiation and implementation of sequence and schedule plans
designed to increase throughput and reduce delays .

[Enhanced ATM En Route Sequence and Schedule Planning]{.underline} --
Improved automated trajectory analysis and negotiation capabilities
enhance the ability of advanced ATM automation tools to develop aircraft
sequence and schedule plans to fully utilize available airspace
capacity, resulting in reduced delays due to better planning.

**Flexibility**

[Expanded Range of Resolution Options]{.underline} \-- Data exchange and
trajectory negotiation enable ATSP and users to be aware of, consider
and adapt to each others\' constraints and preferences.

**Efficiency**

[More Fuel and Time Efficient Traffic Avoidance Resolutions]{.underline}
-- With improved surveillance and ATM automation prediction capabilities
using ATSP-FMS-AOC data, the knowledge of the structure of potential
conflicts and intervention options is improved, leading to negotiation
of more efficient conflict resolution maneuvers.

[Reduced ATM Interruptions for False Potential Conflict
Determinations]{.underline} -- Improved trajectory data exchange
processes and automated trajectory analysis capabilities reduce the
likelihood of incorrect predictions of violations of minimum separation
requirements, reducing unnecessary trajectory delays and diversions.

**Access**

[Improved Access to High-Density Operations]{.underline} \-- Improved
sequence and schedule planning and situation assessment by ATM
facilitates access by non-scheduled users requesting entry into
high-density operations.

# Issues and Key Decisions

CE-6 is under initial development as a concept. The key issues concern
refinement and validation of the basic concept and development of the
details. Validation of the concept should involve operations staff at an
early stage to confirm the concept is proceeding in the proper
direction.

Specific issues are identified in Appendix B-2 of the DAG TM Research
Plan ^ref.2^ as excerpted below:

"Operations" categories

## Separation assurance while adhering to RTA {#separation-assurance-while-adhering-to-rta .Table-Entry-2}

-   Will the ATSP be able to maintain separation assurance for
    conflicting aircraft on high-energy idle-thrust descents?

## Mixed-equipage integration and segregation {#mixed-equipage-integration-and-segregation .Table-Entry-2}

-   How will the ATSP simultaneously handle aircraft equipped and not
    equipped with FMS?

-   Can the ATSP integrate aircraft on 4D (RTA) trajectories with
    aircraft on MIT trajectories?

## Time horizons {#time-horizons .Table-Entry-2}

-   What decision-freeze time horizons are needed in the trajectory
    request/evaluation/negotiation process?

-   How soon before entering the modified flight plan environment must
    the trajectory negotiation be complete?

-   How much time is required to complete trajectory negotiation?

-   At what point do negotiations need to be started to avoid excessive
    time pressure and workload?

-   When is the traffic and constraint information sufficiently reliable
    to submit a trajectory request and begin negotiation?

## Traffic situation complexity {#traffic-situation-complexity .Table-Entry-2}

-   What is the level of dynamic density that exceeds controller ability
    to perform safe separation with no route structure?

-   Assuming ATSP has ultimate responsibility for separation assurance,
    is there an upper feasibility limit of traffic situation complexity
    for which the trajectory request/evaluation/negotiation process can
    be applied?

## Environmental predictions {#environmental-predictions .Table-Entry-2}

-   How is the trajectory negotiation process affected by large changes
    in weather and winds?

## CNS infrastructure & aircraft capability limitations {#cns-infrastructure-aircraft-capability-limitations .Table-Entry-2}

-   What CNS architecture and capabilities (ground and airborne) are
    needed to support air-ground trajectory negotiation?

-   What level of certifications will be required for FD systems, and
    will this level be low enough to justify this concept element as a
    distinct transition step on path to free maneuvering?

## Negotiation {#negotiation .Table-Entry-2}

-   How far will the ATSP allow negotiation to continue before enforcing
    a final solution?

-   Under what conditions would the ATSP find the trajectory request
    unacceptable?

"Human Factors" categories

## Roles & responsibilities {#roles-responsibilities .Table-Entry-2}

-   What are sector controller, TMC, and TFM roles and authority for
    approval of proposed amendments? (e.g., does sector controller have
    authority to deny an amendment outside of his sector? If not, how
    are ground approvals coordinated?)

-   Will a D-side controller be required to prevent loss of R-side SA
    while accommodating user preferences.

-   If the ATSP is responsible for separation assurance, does the FD
    need to perform conflict detection before making a trajectory
    request?

-   What is appropriate balance between FD and AOC in developing user
    preferences for proposed Flight Plan amendment?

-   Does the ATSP have the authority to refuse a conflict-free /
    constraint-free trajectory request that was submitted to meet user
    preferences?

## Workload mgmt, task balancing {#workload-mgmt-task-balancing .Table-Entry-2}

-   How does the trajectory request/evaluation/negotiation process
    affect workload for flight crew and ATSP?

## Using automation {#using-automation .Table-Entry-2}

-   How much does the pilot need to know about the data and process used
    in trajectory calculations?

-   Can automation reduce ATSP workload in handling high frequency of
    flight plan amendments?

-   What automation capabilities would the ATSP find useful in conflict
    detection and provisional planning?

## Situation awareness and predictability {#situation-awareness-and-predictability .Table-Entry-2}

-   Will the ATSP be able to maintain adequate SA in the passive
    compliance-monitoring role?

## Coordination and negotiation {#coordination-and-negotiation .Table-Entry-2}

-   How is intra-and inter-facility coordination affected by the
    trajectory negotiation process, especially if trajectory is deemed
    unacceptable by only one ATSP?

-   How are pilot and ATSP \"cognitive models\" of \"simple\"
    trajectories balanced in the negotiation process?

"Data Exchange" categories

## Content, frequency, accuracy {#content-frequency-accuracy .Table-Entry-2}

-   What content and fidelity must be transferred in a trajectory
    request for a confident evaluation to be performed by the ATSP?

-   What fidelity of aircraft performance capability and user
    preferences does the ATSP need to know for trajectory request
    evaluation?

-   How much of the remaining flight plan must be included in the
    trajectory request?

-   Under what conditions or time horizons should trajectory requests
    specify 2D, 3D, or 4D trajectories?

-   What fidelity of traffic information and spatial and temporal
    constraints is required to form robust trajectory requests?

-   What information does the ATSP need to adequately monitor trajectory
    compliance?

## Data link mechanism {#data-link-mechanism .Table-Entry-2}

-   What data link bandwidth is required for trajectory negotiation?

-   What data exchange update rate is required to maintain data
    integrity?

-   What communication capabilities and characteristics (e.g., data
    integrity, addressing latency, data rate) are required to support FD
    trajectory requests to the ATSP?

-   How is the constraint information needed by the FD to develop robust
    trajectory requests maintained and transferred to the user?

"Decision Support" categories

## Overall functionality: FMS designed for trajectory-negotiation operations {#overall-functionality-fms-designed-for-trajectory-negotiation-operations .Table-Entry-2}

-   How does the FD DST integrate user preferences (FD/AOC), near term
    conflicts, and aircraft performance to arrive at optimal, conflict
    free 4D trajectory request?

## Overall functionality: ATSP DST designed for trajectory-oriented operations {#overall-functionality-atsp-dst-designed-for-trajectory-oriented-operations .Table-Entry-2}

-   What ATSP DST capabilities are required to facilitate \"trajectory
    orientation\"?

-   What ATSP automation capability is needed to ensure a solution
    trajectory exists which meets all constraints?

## Interface (display, input, alerting) {#interface-display-input-alerting .Table-Entry-2}

-   How will complex trajectories be displayed on a standard CDTI?

-   What display features are required to support the ATSP in monitoring
    trajectory compliance?

-   How is the new 4D-trajectory request presented (displayed) to the
    FD/ATSP for considerations?

## Constraint management {#constraint-management .Table-Entry-2}

-   Do constraints need to have relative priority assigned to ensure
    conflicts are resolved?

## RTA-capable CD&R algorithms {#rta-capable-cdr-algorithms .Table-Entry-2}

-   What assumptions and constraints are used in trajectory synthesis by
    the FD and ATSP?

-   Are identical algorithms required for FD and ATSP trajectory
    synthesis?

"Procedures" categories

## Negotiation {#negotiation-1 .Table-Entry-2}

-   If ATSP denies trajectory request, what additional information is
    transferred to the FD for possible negotiation?

-   How shall failsafe negotiation be insured in time for
    implementation?

-   What aspects of the negotiation process are automated and in what
    aspects does the human play a role?

## Trajectory-oriented ATSP {#trajectory-oriented-atsp .Table-Entry-2}

-   What ATSP procedures are required to facilitate \"trajectory
    orientation\"?

-   What procedure for information distribution should be followed by
    the ATSP after receipt of a trajectory request?

## Trajectory evaluation {#trajectory-evaluation .Table-Entry-2}

-   What procedures are followed when a trajectory request is
    unacceptable to the ATSP?

-   What procedures and tools are used by the ATSP to evaluate
    trajectory requests?

## Monitoring {#monitoring .Table-Entry-2}

-   What procedures are needed for the ATSP to monitor trajectory
    adherence?

## Degraded-mode operations {#degraded-mode-operations .Table-Entry-2}

-   What procedures are followed if the FD automation supporting
    trajectory request and negotiation fails?

-   What procedures are followed if the ATSP automation to support
    trajectory evaluation and negotiation fails?

-   How do interruptions in voice communications affect negotiation
    process?

-   Can procedures be developed to provide the level of robustness to
    communications failures provided by today\'s \"positive control\"
    procedures?

## Constraint management {#constraint-management-1 .Table-Entry-2}

-   After conflict free trajectory is negotiated that meet airspace and
    RTA constraints, is complete new negotiation needed for each new
    conflict?

"Safety" categories

## Automation failures {#automation-failures .Table-Entry-2}

-   Will conflict free FMS trajectories be robust to failures of
    individual aircraft to execute them accurately?

# Appendix A. Operational Requirements Table {#appendix-a.-operational-requirements-table .unnumbered}

#### A.1 Operational Requirements -- Separation Assurance Area {#a.1-operational-requirements-separation-assurance-area .unnumbered}

The following operational needs statements are addressed by CE-6,
Trajectory Negotiation for User-Preferred Separation Assurance. The
numbers provide a trace to the matrix of operational needs statements
supporting the AATT ATM/OPSCON.

+-----+----------------------------------------------------------------+
| **  | **ONS Text**                                                   |
| ONS |                                                                |
| \   |                                                                |
| #** |                                                                |
+=====+================================================================+
| 1_  | ADS-B enables positive control in non-radar environments.      |
| 235 |                                                                |
+-----+----------------------------------------------------------------+
| 1_  | Standards may vary depending on equipage and the quality of    |
| 365 | positional data for individual flights.                        |
+-----+----------------------------------------------------------------+
| 1_  | Through a data link to the properly equipped cockpit, provide  |
| 375 | users- routine communications- updated charts, current         |
|     | weather, SUA status, and other data- basic flight information  |
| 4_  | services, including forecast weather, NOTAMs, and hazardous    |
| 370 | 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_  | Controller workload under peak traffic remains equivalent to   |
| 435 | 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_  | User-Air Traffic Service Provider exchange of state and intent |
| 437 | data will improve the accuracy of, and consistency between,    |
|     | FMS and ground-based trajectory predictions.                   |
+-----+----------------------------------------------------------------+
| 1_  | Before changing a flight's trajectory, the controller must     |
| 438 | 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.           |
+-----+----------------------------------------------------------------+
| 1_  | Air safety has been increased through the implementation of    |
| 440 | conflict detection and resolution tools, the inclusion of the  |
|     | flight deck in some separation decision-making, and greatly    |
| 5_  | enhanced weather detection and reporting capabilities.         |
| 515 |                                                                |
+-----+----------------------------------------------------------------+
| 4_  | Improved navigation precision, coupled with changes in service |
| 110 | provider separation procedures allow an improved ability to    |
|     | accommodate user-preferred arrival/departure routes,           |
|     | climb/descent profiles, and runway assignment.                 |
+-----+----------------------------------------------------------------+
| 4_2 | This includes access to better information regarding the kind  |
| 51b | & amount of traffic coming into a terminal area. It also       |
|     | includes improved capability for conflict alert and for        |
|     | automated coordination between service providers within the    |
|     | terminal area and in neighboring facilities.                   |
+-----+----------------------------------------------------------------+
| 4_  | visual separation by pilots in terminal areas is expanded by   |
| 475 | 2005 to allow all-weather pilot separation when deemed         |
|     | appropriate by the service provider.                           |
+-----+----------------------------------------------------------------+
| 4_  | The increased use of this distributed responsibility is made   |
| 485 | feasible through improved traffic displays on the flight deck, |
|     | combined with appropriate rules, procedures, and training to   |
|     | support the new roles and responsibilities of the users and    |
|     | service providers.                                             |
+-----+----------------------------------------------------------------+
| 4_  | To assure aircraft separation, service providers use improved  |
| 490 | tools and displays.                                            |
+-----+----------------------------------------------------------------+
| 4_  | Aircraft-to-airspace and aircraft-to-terrain separation will   |
| 515 | remain the service provider's responsibility                   |
+-----+----------------------------------------------------------------+
| 4_  | the service provider maintains separation between controlled   |
| 520 | aircraft and active SUAs, and between controlled aircraft and  |
|     | terrain/obstructions.                                          |
+-----+----------------------------------------------------------------+
| 4_  | High density areas still require the oversight from ATC for    |
| 775 | sequencing and primary separation assurance                    |
+-----+----------------------------------------------------------------+
| 5_  | Decision support systems such as the conflict probe assist the |
| 210 | provider in developing safe and effective traffic solutions.   |
+-----+----------------------------------------------------------------+
| 5_  | Additional intent and aircraft performance data is provided to |
| 235 | decision support systems, thus improving the accuracy of       |
|     | trajectory predictions. This information is combined and       |
| 5_  | presented on the service provider's display.                   |
| 440 |                                                                |
+-----+----------------------------------------------------------------+
| 5_  | Since there are different separation standards depending on    |
| 240 | the flight's equipage and the quality of the positional data,  |
|     | service provider displays indicate the quality of the          |
| 5_  | resulting aircraft positions and the appropriate equipage      |
| 445 | information.                                                   |
+-----+----------------------------------------------------------------+
| 5_  | Improved decision support tools for conflict detection,        |
| 295 | resolution, and flow management allow increased accommodation  |
|     | of user-preferred trajectories, schedules, and flight          |
|     | sequences.                                                     |
+-----+----------------------------------------------------------------+
| 5_  | Structured routes are the exception rather than the rule, and  |
| 315 | exist only when required to meet continuous high density, to   |
|     | provide for the avoidance of terrain and active SUAs, and to   |
| 5_  | facilitate the transition between areas with differing         |
| 470 | separation standards.                                          |
+-----+----------------------------------------------------------------+
| 5_  | user intent and aircraft performance data to decision support  |
| 420 | systems, thus improving the accuracy of ground-based           |
|     | trajectory predictions.                                        |
+-----+----------------------------------------------------------------+
| 5_  | The use of satellite-based navigation and surveillance data    |
| 430 | will not only increase on-board capabilities ranging from      |
|     | cockpit traffic and enhanced collision avoidance logic, but    |
|     | will also be used by ground-system automation for enhanced     |
|     | conflict probe and alerting.                                   |
+-----+----------------------------------------------------------------+
| 5_  | Improving the provider's ability to identify conflicts will    |
| 520 | also reduce the number of occasions when there is              |
|     | intervention, allowing the user to fly the trajectory proposed |
| 5_  | with higher frequency.                                         |
| 580 |                                                                |
+-----+----------------------------------------------------------------+
| 5_  | As in the departure and arrival operations, increased decision |
| 550 | support allows significant improvement in en route separation  |
|     | assurance.                                                     |
+-----+----------------------------------------------------------------+
| 5_  | there will be improved coordination between the service        |
| 560 | provider and the flight deck to aid the flight in weather      |
|     | avoidance.                                                     |
+-----+----------------------------------------------------------------+
| 5_  | improved information available from common weather sources,    |
| 565 | service providers will be more effective in controlling        |
|     | aircraft in airspace that contains hazardous weather and in    |
|     | providing weather advisories to pilots.                        |
+-----+----------------------------------------------------------------+
| 5_  | Decision support systems will assist in conflict detection and |
| 575 | the development of conflict resolutions.                       |
+-----+----------------------------------------------------------------+
| 5_  | Service providers will continue to be responsible for          |
| 605 | maintaining separation between aircraft and certain types of   |
|     | airspace (specifically, active special use and adjacent        |
|     | controlled airspace), terrain, and obstructions                |
+-----+----------------------------------------------------------------+
| 5_  | When flights are in close proximity to the newly activated     |
| 615 | SUA, the provider will use aircraft-to-aircraft conflict       |
|     | detection tools as aids to prevent them from entering the      |
|     | restricted airspace. Both earlier intervention and the         |
|     | closer-proximity resolution activities result in more          |
|     | efficient routing of aircraft                                  |
+-----+----------------------------------------------------------------+
| 5_  | high density areas still require the oversight from ATC for    |
| 790 | sequencing and primary separation assurance.                   |
+-----+----------------------------------------------------------------+
| 5_  | Use of the ground based conflict probe has been modified to    |
| 805 | allow for airborne procedures to resolve most conflicts, thus  |
|     | allowing maximum routing flexibility with the least            |
|     | restrictions.                                                  |
+-----+----------------------------------------------------------------+
| 5_  | In en route airspace, the use of moving maps for CFIT          |
| 845 | avoidance, CDTI, and weather depiction has begun, albeit, the  |
|     | user application stressed may be different.                    |
+-----+----------------------------------------------------------------+
| 6_  | Most aircraft navigate using a global satellite navigation     |
| 155 | system whose improved accuracy will generate the required      |
|     | safety for reduced separation standards.                       |
+-----+----------------------------------------------------------------+
| 6_  | The pilot's ability to support climbs, descents, crossing and  |
| 380 | merging routes is supplemented by the service provider's       |
|     | conflict probe decision support system.                        |
+-----+----------------------------------------------------------------+
| 6_4 | Service providers, aided by supporting automation and          |
| 15b | electronic visual displays, are able to acquire and view       |
|     | timely and reliable flight information to dynamically address  |
| 6_4 | necessary changes to the trajectories.                         |
| 55b |                                                                |
+-----+----------------------------------------------------------------+
| 6_  | pilots may coordinate with service providers for clearance to  |
| 460 | conduct specified cockpit self-separation operations. \... the |
|     | pilot's view of nearby traffic supplements the service         |
| 6_  | provider's big picture of longer term traffic flow.            |
| 370 |                                                                |
+-----+----------------------------------------------------------------+

####   {#section .unnumbered}

#### A.2 Operational Requirements -- Traffic Management, Synchronization Area {#a.2-operational-requirements-traffic-management-synchronization-area .unnumbered}

The following operational needs statements are addressed by CE-6,
Trajectory Negotiation for User-Preferred Local TFM Conformance.

+-------+--------------------------------------------------------------+
| **ONS | **ONS Text**                                                 |
| \#**  |                                                              |
+=======+==============================================================+
| 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.                                           |
+-------+--------------------------------------------------------------+
| 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            |
+-------+--------------------------------------------------------------+
| 4_311 | Properly equipped aircraft are given authority to maneuver   |
|       | as necessary to avoid weather cells, or to follow such       |
|       | aircraft using self-spacing procedures.                      |
+-------+--------------------------------------------------------------+
| 4_315 | When appropriate, clear properly-equipped aircraft to        |
|       | self-separate and maintain sequence ("station-keeping").     |
| 3_225 |                                                              |
+-------+--------------------------------------------------------------+
| 4_316 | Appropriately equipped aircraft are given clearance to merge |
|       | with another arrival stream, and/or maintain in-trail        |
|       | separation relative to a leading aircraft.                   |
+-------+--------------------------------------------------------------+
| 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_585 | On final approach, the service provider may give the pilot   |
|       | responsibility for station keeping to maintain the required  |
|       | sequence and spacing to the runway.                          |
+-------+--------------------------------------------------------------+
| 4_646 | To enhance operations during peak capacity periods, arrival  |
|       | operations are enhanced by taking advantage of aircraft FMS  |
|       | to enable Required Time of Arrivals (RTAs) at designated     |
|       | approach points.                                             |
+-------+--------------------------------------------------------------+
| 4_755 | the pilot will be able to select which route he wishes to    |
|       | follow.                                                      |
+-------+--------------------------------------------------------------+
| 4_765 | pilots \... fly to meet required times of arrival            |
+-------+--------------------------------------------------------------+
| 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_115 | The use of en route airborne holding has been reduced with   |
|       | the implementation of other procedures that improve traffic  |
|       | flow patterns and make maximum use of available terminal     |
|       | capacity                                                     |
+-------+--------------------------------------------------------------+
| 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_200 | remain at that altitude until the point is reached from      |
|       | which an optimum descent profile should commence.            |
+-------+--------------------------------------------------------------+
| 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 provided  |
|       | to decision support systems, thus improving the accuracy of  |
| 5_440 | 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_345 | When appropriate, use a "metering spacing technique" to      |
|       | provide the user the flexibility to efficiently manage a     |
|       | flight.                                                      |
+-------+--------------------------------------------------------------+
| 5_400 | Perform some spacing activities that were previously         |
|       | performed by the service provider. These activities will be  |
|       | performed for metering or merging purposes. (Flight Deck)    |
+-------+--------------------------------------------------------------+
| 5_420 | user intent and aircraft performance data to decision        |
|       | support systems, thus improving the accuracy of ground-based |
|       | trajectory predictions.                                      |
+-------+--------------------------------------------------------------+
| 5_450 | Reduced or time-based separation standards will be developed |
|       | based on technology and aircraft capability, further         |
|       | increasing system capacity and safety.                       |
+-------+--------------------------------------------------------------+
| 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     | traffic management services are provided in the en route     |
| _545b | area                                                         |
+-------+--------------------------------------------------------------+
| 5_575 | Decision support systems will assist in conflict detection   |
|       | and the development of conflict resolutions.                 |
+-------+--------------------------------------------------------------+
| 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_710 | increased information exchange between the en route,         |
|       | arrival, departure and surface decision support tools will   |
|       | enable better coordination of cross-facility traffic flows   |
|       | with fewer constraints. These improved capabilities will     |
|       | also allow for greater accommodation of user requests,       |
|       | including carrier preferences on the sequencing of their     |
|       | arrival aircraft.                                            |
+-------+--------------------------------------------------------------+
| 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_285 | Perform some separation and merging activities that were     |
|       | previously performed by the service provider.                |
+-------+--------------------------------------------------------------+
| 6_300 | Provide additional user intent and aircraft performance data |
|       | to decision support systems, thus improving the accuracy of  |
|       | ground-based trajectory predictions.                         |
+-------+--------------------------------------------------------------+
| 6_380 | The pilot's ability to support climbs, descents, crossing    |
|       | and merging routes is supplemented by the service provider's |
|       | conflict probe decision support system.                      |
+-------+--------------------------------------------------------------+
| 6     | Service providers, aided by supporting automation and        |
| _415b | electronic visual displays, are able to acquire and view     |
|       | timely and reliable flight information to dynamically        |
| 6     | address necessary changes to the trajectories.               |
| _455b |                                                              |
+-------+--------------------------------------------------------------+
| 6_460 | pilots may coordinate with service providers for clearance   |
|       | to conduct specified cockpit self-separation operations.     |
| 6_370 | \... the pilot's view of nearby traffic supplements the      |
|       | service provider's big picture of longer term traffic flow.  |
+-------+--------------------------------------------------------------+
| 6_465 | Pilots may obtain approval for special maneuvers such as     |
|       | reduced separation in-trail climb, in-trail descent, lead    |
| 6_375 | climb, lead descent, limited duration, station keeping as    |
|       | well as lateral passing maneuvers                            |
| 6_240 |                                                              |
+-------+--------------------------------------------------------------+
| 6     | ATC oversight is still required for sequencing, but          |
| _525b | collaborative decision making has greatly increased among    |
|       | the service provider, AOC, and the aircraft.                 |
+-------+--------------------------------------------------------------+
| 7_125 | This approach is commonly referred to as "control by time of |
|       | arrival" \... Under this approach, both GA and DoD users     |
|       | would be able to make more effective use of NAS resources    |
|       | during reduced capacity conditions.                          |
+-------+--------------------------------------------------------------+
| 7_295 | Adhere to allocated arrival times assigned by the service    |
|       | provider. In some instances, international flights are       |
|       | excepted from this responsibility.                           |
+-------+--------------------------------------------------------------+
| 7_300 | Using increased knowledge of the intent of traffic flow      |
|       | initiatives, arrange user resources to help solve traffic    |
|       | flow problems.                                               |
+-------+--------------------------------------------------------------+
| 7_474 | Cumulative delay data \...enables \...controllers to         |
|       | allocate discretionary tasktime to coordinate expedited      |
|       | trajectories for flights that have absorbed delay, rather    |
|       | than for flights that have not been delayed.                 |
+-------+--------------------------------------------------------------+
| 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                       |
+-------+--------------------------------------------------------------+

# Appendix B. Automated Resolution Advisories {#appendix-b.-automated-resolution-advisories .unnumbered}

Previous reseach^ref.26^ provides the following description of a trial
planning concept which may be used as a basis for investigating an
automated resolution advisories interface for CE-6. Key features include
active and provisional trajectory planning and automatic, semi-automatic
and manual advisories:

> **Active and Provisional** **Planning** \-- Active and provisional
> trajectory planning supports trajectory negotiation by providing a
> configuration control mechanism for managing trajectory plans under
> dynamic ATC operations.
>
> [Definitions]{.underline}:
>
> Ownership: Only one sector owns a flight at a time. Ownership provides
> the controller "write" protection (for modifying the active trajectory
> plan) and the authority to issue clearances to an "owned" flight.
>
> Active: The active trajectory plan is the ATC plan that is "visible"
> to all sectors ("read-only" access), regardless of ownership. Only the
> sector with ownership can modify the active plan. The active plan
> reflects the best prediction that can be made by the DST given the
> current clearance and any expected transitions (e.g., delay strategy
> for flow-rate conformance, or a descent to cross a fix along a STAR).
> The active plan forms the basis for conflict probe and the monitoring
> of conformance to clearances and restrictions (in terms of altitude
> profile, speed profile, routing, and time). Active plans form the
> basis of flight information that is generally read-accessible by all
> "operators" (i.e., other controllers and users (pilot/AOC)). Active
> plans are particularly critical to the configuration management for
> distributed air-ground (user-ATM) trajectory planning such as
> trajectory negotiation or airborne free maneuvering.
>
> Provisional: The provisional-trajectory plan is a plan that may be
> created by any operator. By default, a provisional plan is only
> visible to the operator who created it. The creator of a provisional
> plan may modify it as desired (i.e., the creator is the only one who
> has default read and write access). The read-access rule may be
> modified by the creator (i.e., setting permission) to allow read
> access to any identified operator(s). No other operators have write
> permission. However, other operators who receive read permission
> (e.g., another sector, the R/D-side complement to the creator, or the
> user) may duplicate the plan and modify the copy as their own
> provisional (with its own read/write permission settings). The only
> operator who may upgrade a plan from provisional to active status is
> the controller with ownership (or in the case of free maneuvering, the
> pilot). Provisional trajectories are updated to reflect the latest
> state and planning data, but are not necessarily monitored to the
> extent accorded active plans.
>
> Modifications: Controllers may modify plans via manual and automatic
> functions. Depending on the controller's preferences, both active and
> provisional plans may be modified either automatically, by "active"
> advisories (e.g., an TMA constraint), or manually through discrete
> controller inputs. This mapping of "active advisories" to
> active/provisional plans allows the system to automatically update the
> plans based on the advisory functions invoked by the controller. This
> update is intended to reduce workload by minimizing controller
> interactions to cases that must be identified by exception (rather
> than rule). Within the ATM industry, manual updates of provisional
> plans are commonly referred to as "trial" plans.
>
> Locked: Active and provisional-trajectory plans may be "locked" by the
> owning controller (i.e., a lock freezes identifies aspects of the plan
> for the DST to freeze such as the current speed clearance in cruise).
> Any trajectory profile/segment that is locked is immediately monitored
> for conformance. The unlocked profile/segments are not monitored for
> conformance. For example, a controller may lock an active advisory for
> an arrival to descent 100 nmi from its destination, descend at Mach
> 0.82/330 knots, and cross the TRACON boundary at 14:41:52 GMT. Once
> locked, the DST will monitor that flight's conformance with its
> altitude, speed, lateral, and time predictions.
>
> Monitoring: Monitoring for conformance with altitude, speed, routing,
> and time profiles may be applied to both active and
> provisional-trajectory plans. Results regarding active plans are
> displayed on the primary displays for conflict probe,
> meet-time/spacing, and clearance conformance. Monitoring cues for
> analysis of active plan conformance (e.g., conflict probe) are
> prominently displayed automatically. Cues related to provisional plans
> will be displayed in the secondary display functions (e.g., a
> provisional/trial plan list), and displayed by exception according to
> human-factors standards and controller-defined preferences.
>
> The Active/Provisional-trajectory plan approach is based on the need
> to develop a system that maintains/supports the situational awareness
> of "owning" controllers and other operators. The potential for
> controller overload and confusion is great because of two factors: the
> complexity of provisional "hypothetical" plans, and the geometric
> growth of conflict trajectory analysis combinations that can exist
> when hypothetical plans are compared with all the possible
> combinations of other hypothetical plans across multiple sectors.
> These comparisons (specifically conflict probe and spacing) must be
> limited in a way that makes it easy for the controller to know and
> understand the basis of the advisories we are displaying.
>
> **Automatic, Semi-Automatic, and Manual Advisory Levels** \--
> Definitions:
>
> Automatic Advisories: Advisories that are generated without requiring
> dynamic controller input are "automatic." For example, a controller
> may configure CE-6 automation to automatically suggest cruise- and
> descent-speed advisories for any flights subject to arrival-metering
> delays. Automatic and semi-automatic advisory functions may be applied
> to flow-rate conformance (metering or spacing) and/or conflict
> resolution. A controller may configure their DST to automatically
> update the active plans of their "owned" flights based on the current
> advisory (as a form of controller intent). Alternatively, controllers
> may configure their DST to automatically create provisional plans
> based on the automatic advisories (leaving the active plans alone
> until the controller upgrades the provisional plan to active).
> Automatic advisories continuously update to reflect the latest state
> of the traffic and airspace.
>
> Semi-automatic Advisories: Semi-automatic advisories are a hybrid of
> automatic and manual functions. Controllers must activate the
> semi-automatic function by a dynamic input that indicates the
> flight(s) for which advisories are to be generated, and the type of
> advisory to be generated (i.e., the control "degree of freedom" such
> as speed for metering). For example, a controller may configure CE-6
> automation to generate path-stretch (delay) advisories only when the
> controller clicks on a flight and invokes the semi-automatic
> path-stretch mode. In response, CE-6 automation will determine the
> range (to vector) and the turn-back course that is necessary to absorb
> any remaining metering delay. Although this type of advisory requires
> explicit input from the controller, it minimizes controller workload
> by automatically determining the appropriate clearance advisory once
> it is invoked. Similar to automatic advisories, controller may
> configure their DST to automatically update the active plans of their
> "owned" flights based on the current advisory (as a form of controller
> intent). Alternatively, controllers may configure their DST to
> automatically create provisional plans based on the semi-automatic
> advisories (leaving the active plans alone until the controller
> upgrades the provisional plan to active). Controllers may configure
> their DST to either update semi-automatic advisories (to continuously
> reflect the latest state of the traffic and airspace), or provide a
> single advisory response that "times out" after a designated/default
> period of time.
>
> Manual Advisories: Manual advisory capability allows the controller to
> modify the state of DST predictions/analyses based on direct input.
> Manual input may be applied to either active plans (e.g., to update
> the intent model based on the latest clearance) or provisional plan
> (i.e., "trial" planning). In this case, the controller must not only
> decide on the control degree of freedom, but must also decide on the
> actual value (e.g., speed, altitude, routing) to use. DST advisories
> for items such as conflict probe and flow-rate conformance
> automatically provide the controller with feedback on the state of
> conformance based on the manual input. Manual inputs may be used by
> the controller to also override, correct, or guide the higher levels
> of advisory generation. For example, the controller may have selected
> an automatic cruise/descent-speed advisory for metering, but wishes to
> manually adjust the descent speed (e.g., trial plan) for conflict
> resolution. As the controller trial plans the descent speed to resolve
> a conflict, the automatic "meet-time" function responds by adjusting
> the cruise speed and top of descent to meet the time.
>
> **Mapping Of Automation/Advisory Level To Trajectory-Plan Type \-- The
> following table presents a mapping of the trajectory-plan types
> (active/provisional) against the level of automation/advisory that a
> controller may select. Depending on the situation, controllers may
> configure the DST functions to match one of the six combination
> cases.**

  ------------- --------------------- ------------------- ----------------------
  Trajectory    Level of                                  
  Plan Type     Automation/Advisory                       

                Automatic             Semi-Automatic      Manual

  Active        Controller choice for Controller choice   Controller choice (to
                applications with     (does the           update active plans &
                high probability of   controller want the intent based on actual
                acceptance            active plan to      clearance/decisions)
                                      reflect this        
                                      action?)            

  Provisional   Controller choice for Controller choice   Controller choice
                applications with     (accept trial plan  (trial planning)
                "lower" probability   or reset            
                of acceptance         parameters)         
  ------------- --------------------- ------------------- ----------------------

> The combination of automatic, semi-automatic, and manual advisory
> capabilities provides a powerful tool for minimizing controller
> workload. Depending on controller preferences, techniques, and the
> type of traffic problem, some cases are easier to generate
> "acceptable" advisories for than others. For example, past controller
> simulations indicate automatic "meet-time" advisories tend to have a
> better "batting average" of controller acceptance than conflict
> resolution. Contributing factors include the relative complexity of
> conflict problems compared to metering delays, and the fact that
> metering conformance tends to reduce conflicts (by meeting
> conflict-free metering times) as opposed to conflict resolutions
> (which may or may not lead to other conflicts or metering
> conformance). In any case, the combination of automation level allows
> controllers to customize their advisory support to the capabilities
> that best match their preferences and traffic problems. In addition,
> the combination allows the controller to use the manual tools as a way
> to correct advisories (by exception) rather than develop plans for all
> flights (as a rule). This combination overcomes the workload issue
> related to a system that depends entirely on trial planning without
> total automation that would take the controller out of the loop.

# References {#references .unnumbered}

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