Introduction > Context
> Issues for Analysis and Evaluation
The Flight Object Concept raises a number of issues. These issues are
listed here, along with recommendations for resolving them. All issues
should be addressed before the flight object can be implemented in an
operational environment.
Contents:
Collaboration Issues
1. Collaboration Among ATM Service Providers and
NAS Users
Issue: How can the Air Traffic Management (ATM) service providers
collaborate with the National Airspace System (NAS) users to share flight
object information?
Recommendation: Identify the types of flight information that
both the ATM service providers and the NAS users could benefit from sharing,
such as service provider and user intent (see also the issue
on use of intent, environmental, and weather information). Examine
how information sharing can affect the decision-making processes for both
the ATM service providers and the NAS users. Evaluate the usefulness of
different methods for sharing flight information.
2. Roles and Responsibilities for Collaboration Among
ATM Service Providers and NAS Users
Issue: What are the roles and responsibilities for the ATM services
providers and the NAS users in sharing flight object information?
Recommendation: Identify the source(s) of the different types
of information elements to be shared and determine the needs for those
types of information elements. Evaluate different possible assignments
of roles and responsibilities for creating, updating, and archiving the
shared information elements to determine the most efficient assignment
of roles and responsibilities for sharing the information among ATM service
providers and NAS users.
3. Types of Information to Support Collaboration
Among ATM Service Providers and NAS Users
Issue: What types of information elements are needed to support
collaboration among ATM service providers and NAS users?
Recommendation: Identify the different types of information elements
that may be useful in collaborating among ATM service providers and NAS
users. Examine the costs and benefits associated with sharing the different
types of information elements to determine which types of information
elements are most useful for collaboration.
4. Performance Metrics to Evaluate Collaboration
Among ATM Service Providers and NAS Users
Issue: What types of performance metrics are needed to evaluate
collaboration among ATM service providers and NAS users?
Recommendation: Identify the goals to be accomplished through
collaboration among the ATM service providers and NAS users. Explore various
available performance metrics to determine which metrics best support
the evaluation of collaboration and the determination of how well the
state goals are met. Top of Page
Planned Capability Issues
Issue: Some of the Free Flight Phase
2 (FFP2) capabilities identified in this paper have not yet been well
defined (such as High Altitude Services, or HAS). How will these capabilities
change as they become more defined, and how will the entire set of planned
capabilities evolve for the Free Flight Phase
1 (FFP1) and FFP2 time frames? Which capabilities are planned for
the beyond FFP2 time frame? How will
new capabilities, as well as capabilities that evolve over time, interact
with the flight object as it evolves to the concept described in this
website?
Recommendation: Periodically reassess the capabilities planned
for the FFP1, FFP2, and beyond FFP2 time frames to determine whether the
planned set of capabilities has changed
and how the definitions of the planned capabilities have evolved. Update
the Flight Object Concept in response to changes in the planned capabilities,
as well as changes in the concept itself. Top of Page
General Information Element Issues
1. Subset of Flight Information Elements
from the Host
Issue: For this website, a subset of the flight information elements
available in the Host Computer System
was chosen. The information elements in this subset are applicable to
the planned capabilities that have been identified for the FFP1 and FFP2
time frames. How will these Host information elements change as the planned
capabilities for the FFP1, FFP2, and beyond FFP2 time frames evolve?
Recommendation: Periodically reassess the capabilities planned
for the FFP1, FFP2, and beyond FFP2 time frames to determine whether the
subset of flight information elements available from the Host has changed
as the planned capabilities has evolved. Update the Flight Object Concept
accordingly.
2. Levels of Accuracy Required for
Information Elements
Issue: What level(s) of accuracy should be available through the
flight object for an information element that is used with different levels
of accuracy by different capabilities (such as current speed or heading)?
Should the flight object make that information element available with
the different levels of accuracy, or should the flight object make the
element available with the highest level of accuracy?
Recommendation: Determine the level of accuracy required by each
capability that uses each common information element. In cases where different
levels of accuracy are required for the same information element, evaluate
the costs and benefits of using that element with the highest level of
accuracy in each of the shared capabilities. Determine whether each information
element needs to be available with several levels of accuracy, evaluating
the associated costs for maintaining more than one representation of the
same information element within the flight object. Develop standards for
information elements as appropriate.
3. Incorporation of Advisories into the
Flight Object
Issue: How should an advisory [such as a Traffic
Management Advisor (TMA) metering assignment or a Passive
Final Approach Spacing Tool (pFAST) landing assignment] be incorporated
into the flight object? How do these advisories differ from constraints?
Recommendation: Evaluate the options for incorporating an advisory
into the flight object. Determine whether an advisory such as a TMA metering
assignment should be included in the flight as cleared:planned
portion of the flight object as a Traffic Flow Management (TFM)-requested
action, or as part of the “expected to be cleared” trajectory.
(See Representations of Future Flight Path.)
Also determine when the advisory would be available as part of the flight
as cleared:current portion of the flight object. For example, an advisory
can either be incorporated into the current flight plan after it has been
shown to the service provider, or after the service provider has amended
the flight plan to include the metering assignment.
4. Use of Intent, Environment, and Weather
Information in the Flight Object
Issue: This website includes descriptive and control-related
information elements for flights (see those for capabilities introduced
in the FFP1 and FFP2
time frames). What other types of information should be shared as part
of the flight object? Although it is generally agreed that intent (both
service provider and user intent) is likely to be quite useful, what types
of information describe intent and how could they be used by the ATM capabilities?
Would it also be useful to include environment and weather information
in the flight object?
Recommendation: Identify the types of intent information NAS users
provide for ATM service providers, the types of intent information that
the service providers need to resolve potential separation problems and
traffic flow situations, and then the useful types of intent information
that are not yet available to the service providers. Determine the steps
that are necessary to make the needed types of information available to
the service providers. In addition, examine the usefulness of including
service provider intent, environment, and weather information as part
of a shared flight object.
5. Shared Information Elements
Issue: How will the set of information elements that could be
shared for the FFP1
and FFP2 time frames
change as the planned capabilities for these time frames evolve and become
more defined? Which new information elements could be shared for the beyond
FFP2 time frame?
Recommendation: Periodically reassess the capabilities planned
for the FFP1, FFP2, and beyond FFP2 time frames to determine whether the
set of shared information elements has changed as the planned capabilities
evolve and become more defined. Update the Flight Object Concept accordingly. Top of Page
Trajectory Issues
1. Differences Between Today’s Flight Path
Representations
Issue: The flight path representations used today by the Host
Computer System and other ATM capabilities differ. The Host uses a flight's
converted route as cleared, along with the currently cleared altitude,
for posting flight progress strips, distributing flight information, and
checking track association. When a flight is not found to be where it
is expected, the Host's flight path representation is not updated. Other
ATM capabilities, such as User Request
Evaluation Tool (URET), use a four-dimensional trajectory as it is
expected to be cleared for problem prediction and trial planning. When
a flight is not found to be where it is expected, the other ATM capabilities
reconform the trajectory to incorporate the most recent position information.
(See Representations of Future Flight Path.)
Given the future plan for the Host Computer System to integrate its current
representation of past track with a four-dimensional trajectory for the
flight path projection, how will the ATM capabilities be affected? (See
also the issue on common trajectory representation.)
Recommendation: Identify the difficulties that occur as a result
of using different flight path representations in today's system. Identify
a type of flight path representation, such as a version of the four-dimensional
trajectory, that provides the information necessary to support Host processing
and the ATM capabilities. Determine how the Host and the ATM capabilities
could evolve to incorporate this type of flight path representation.
2. Trajectory Components
Issue: What types of information are considered part of a trajectory?
It is widely accepted that a trajectory should contain a string of four-dimensional
points that describe the future path for a flight. (See Representations
of Future Flight Path.) Should a trajectory also include service provider
or flight intent, such as avoiding a Special Use Airspace (SUA) or climbing
out of turbulent airspace? Should a trajectory include predicted separation
problems and resolutions associated with that flight?
Recommendation: Evaluate the cost and the benefits associated
with including additional types of information, such as intent or predicted
problems, in a trajectory. Determine which additional types of information
would be appropriate for including in a shared trajectory.
3. Flight Activation Event
Issue: Which flight activation event should initiate that flight's
representation in the flight as cleared:current portion of the
flight object? In the FFP1 and FFP2 time frames, a flight will be considered
activated when the Host receives the departure message for that flight.
In the beyond FFP2 time frame, should the flight be considered activated
when the pre-departure clearance is given?
Recommendation: Identify the system requirements for using the
pre-departure clearance for flight activation, as well as the potential
effects of the resulting changes for the capabilities sharing information
through the flight object. Evaluate the cost and benefits for activating
a flight (making the flight plan available in the flight as cleared:current
portion of the flight object) when the pre-departure clearance is given.
4. Common Trajectory Representation
Issue: A trajectory is the calculated prediction of an aircraft's
path based on a current or proposed flight plan, weather information,
aircraft and flight characteristics data, and other variables. Both URET
Core Capability Limited Deployment (CCLD) and TMA
from the Center-TRACON Automation System (CTAS) perform strategic operations
using trajectories for active flights in their airspace. The
table below describes a high-level comparison of the FFP1
trajectories that are used by URET CCLD and TMA from the Center-TRACON
Automation System (CTAS) (also see Representations
of Flight Path). Would the individual capabilities and the system
as a whole benefit from sharing a common trajectory? If so, which elements
of a trajectory should be shared among the capabilities accessing the
flight object? Should shared elements simply have a common representation
(and accuracy level), or should they be derived using a common algorithm
as well?
Recommendation: Evaluate the following options to determine which
option best serves the individual capabilities and the system as a whole.
- Provide a common trajectory to be used by all capabilities (a common
representation or also derived using a common algorithm).
- Retain capability-specific trajectories, making them available to
all other capabilities.
- Retain capability-specific trajectories, creating them from flight
information elements that are available to all of the capabilities.
- Retain capability-specific trajectories, sharing only the necessary
coordination information with other capabilities (for example, URET
could provide estimated fix arrival times to TMA and TMA could provide
assigned meter fix arrival times back to URET).
Comparison of FFP1 Application-Specific Trajectories
|
Trajectory Characteristics
|
URET CCLD-Specific
Trajectory
|
CTAS-Specific Trajectory (for TMA)
|
| Route processing |
Emulates Host (independent) for route
conversion |
Directly uses the Host's converted route
from the Aircraft Route Record Table (AK) |
| Climb and descent profiles |
Looks up rate as a function of aircraft
type and weight for a nominal speed |
Computes rate and acceleration as a function
of aircraft type, weight, and speed |
| Data source for internal flights |
Uses Host flight plan route, track position/velocity,
and mode-C altitude |
Uses Host flight plan route, track position/velocity,
and mode-C altitude |
| Data source for external flights |
Track data from Host computers at other
sites running URET CCLD |
Enhanced Traffic Management System (ETMS)
data |
| Trajectory provided |
Four-dimensional trajectory prediction
(piecewise continuous set of linearly-varying segments) |
Four-dimensional trajectory prediction
(piecewise continuous set of linearly-varying segments) |
Additional information on this issue is available from the following
source:
- MITRE/CAASD and NASA Ames Research Center, Trajectory Modeling
(TJM) Workshop Draft Summary Report, December 2-3, 1999.
- Available as a briefing
![[pdf]](/images/pdf.gif)
with notes to read description
Top of Page
Technical Issues
1. Availability of Host Flight Information through
the Flight Object
Issue: When can the Host's flight information become available
through an implementation of the flight object? In the FFP1 and FFP2 time
frames, it is expected that the Host's flight information will be available
outside of the flight object, through a direct connection with the ATM
capabilities (see Implementation Possibilities).
In the beyond FFP2 time frame, can the Host's flight information be available
through an implementation of the flight object?
Recommendation: Identify the requirements for making the Host's
flight information available through an implementation of the flight object,
as well as the potential effects of the resulting changes on the capabilities
sharing information through the flight object. Evaluate the cost and benefits
of making the Host's flight information available through an implementation
of the flight object.
2. Architecture for the Flight Object
Issue: What is the most efficient network, hardware, and software
architecture for sharing flight object information elements?
Recommendation: Examine various architectures (from centralized
to decentralized) to determine the most robust architecture for maintaining
and distributing flight object information elements.
3. Implementation of the Flight Object
Issue: What is the best alternative for providing flight object
information to multiple locations (hardware and software alternatives)?
Recommendation: Examine hardware and software alternatives for
implementing the chosen flight object architecture to determine how the
flight object can be most efficiently implemented with the required reliability,
availability, maintainability, and other important system characteristics.
4. Transition to the Flight Object
Issue: What is the best strategy for transitioning to the new Flight Object Concept, e.g., are there interim steps that make sense?
Recommendation: Identify possible strategies with interim steps
that transition from today's use of flight information to the new Flight Object Concept. Develop a plan to examine these strategies both analytically
and in laboratory exercises. Evaluate the strategies using pertinent performance
metrics to choose a feasible strategy that will enable early benefits
to users and service providers, as well as sensible interim steps towards
implementation of the complete Flight Object Concept. Top of Page
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