# DAG Concept Element 6

**(Trajectory Negotiation for User-preferred Separation Assurance)**

# Overview Description

# January 31, 2002

# NAS2-98005

# Technical Research in Advanced Air Transportation Technologies

Final

Overview Description

# DAG Concept Element 6

# (Trajectory Negotiation for User-preferred Separation Assurance)

CDRL Item 5b

# Prepared under

# RTO -- 62

# AATT Operational Concept for ATM -- Year 2002 Update

#### January 31, 2002

#### Prepared For: NASA Ames Research Center

#### Moffett Field, CA 94035-1000

#### Prepared By: Titan Systems Corporation -- SRC Division

#### Billerica, MA 01821-4134

![](media/image1.jpeg){width="5.416666666666667in" height="0.75in"}

# DAG CE.6 - Trajectory Negotiation for User-preferred Separation Assurance

**Overview Description**

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.

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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 modeling 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.

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