**Traffic Flow Automation System (TFAS)**

# Overview Description

# January 31, 2002

# NAS2-98005

# Technical Research in Advanced Air Transportation Technologies

Final

Overview Description

Traffic Flow Automation System (TFAS)

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"}

**ACKNOWLEDGEMENT**

The description presented in this document is based primarily on the
information in References 1 through 4 and discussions with Ron Reisman
of NASA Ames Research who helped review and improve this draft document.

**Table of Contents**

1.  **Description 1**

2.  **Operational Concept 1**

3.  **Functional Flow 6**

4.  **References and Bibliography 7**

# List of Figures

1.  **Typical Monitor-Alert TSD 2**

2.  **TFAS Monitor-Alert Graphs and Alert Timelines on TSD Display 2**

3.  **CTAS Elements of TFAS 4**

4.  **Moving TFAS M/A into ETMS Hub site and Field Sites 5**

5.  **Inter Center Trajectory Coordination 5**

6.  **TFAS Functional Flow 6**

# Traffic Flow Automation System (TFAS)

Overview Description

1.  **Description**

The purpose of the Traffic Flow Automation System (TFAS) is to help
Traffic Management Coordinators (TMCs) in the Air Route Traffic Control
Centers (ARTCC), the Systems Command Center (SCC), and Terminal Radar
Control facilities (TRACONs) to manage the flow in domestic U.S.
airspace and into 21 major pacing U.S. airports. TFAS will accomplish
this by applying Center/TRACON Automation System (CTAS) technology to
improve the short-term (up to 45 minutes into the future) reliability of
the SCC Enhanced Traffic Management System (ETMS) Monitor-Alert (M/A)
tool.

The M/A function is based upon the *traffic demand* at each monitored
airport, sector, and fix, and will generate an *alert* whenever traffic
demand is projected to exceed a pre-defined *alert threshold*. The ARTCC
TMCs, working with the impacted sector controllers, are then responsible
for taking any required actions to alleviate the overload and achieve an
orderly flow.

An example of the M/A sector display is shown in Figure 1. The Traffic
Situation Display (TSD) shows a Red Sector indicating an active alert
(sector overloaded), and Yellow Sectors that indicate sectors that might
soon be overloaded. TFAS creates additional graphics such as
monitor-alert graphs and alert timelines, as shown in Figure 2.

TFAS will run multiple instances of CTAS (one per ARTCC), on networked
workstations or on multi-processor application servers, to create a
national CTAS functionality. TFAS will function as a trajectory
prediction and scheduling 'engine' for ETMS. TFAS will deliver useful
information to the SCC and Traffic Management Units (TMUs) by improving
the accuracy of the current ETMS. No new GUIs nor procedures will need
to be developed nor added to the SCC/TMU toolset.

TFAS will be developed in two phases. Phase I will result in a
demonstration system for evaluation by FAA SCC personnel. It will be
capable of being used as a daily-use operational test bed. Phase II will
result in a robust operational augmentation to ETMS which can be turned
over to the FAA for use as an operational system.

**2. Operational Concept**

The FAA's SCC and ARTCC TMCs use the ETMS to manage national and Center
air traffic flows. By reducing ETMS trajectory-modeling errors, the
effectiveness of the ETMS Monitor-Alert tool might be improved, thereby
reducing delays due to en route congestion.

TFAS will simultaneously run 18 CTAS instances, one for each of the 18
CONUS ARTCCs, which include the airspace surrounding the 21 pacing U.S.
airports. TFAS will run in processors at ETMS Hub Site at the Volpe
Center.

Figure 1. Typical Monitor-Alert TSD

![](media/image4.jpeg){width="5.25in" height="4.2in"}

Figure 2. TFAS Monitor-Alert Graphs and Alert Timelines on TSD Display

The TFAS system will be comprised of separate CTAS systems adapted to
each of the TFAS Centers and airports, allowing for the most complete
system, with minimal changes to the current version of CTAS. During
Phase I, simplified adaptations of CTAS will be made. During Phase II,
these will be modified to incorporate more advanced scheduling, routing,
and procedural information as TFAS matures.

The underlying concept behind TFAS is to use the trajectory prediction
capabilities of CTAS with Traffic Management Advisor (TMA) to improve
upon the less accurate trajectory prediction capabilities of the current
ETMS, which in turn improves the accuracy of the Monitor-Alert (M/A)
function within ETMS. The improved accuracy will result in fewer false
alerts of upcoming capacity bottlenecks and fewer missed alerts, that
is, failure to get an alert when in fact an actual bottleneck occurs in
the future. TFAS will only be used to improve sector M/A and will not
affect fix or airport M/As.

TFAS will acquire flight plan, aircraft track, weather, and other
information from ETMS via the Input Source Manager (ISM). The typical
CTAS TMA system acquires aircraft data via an interface to the Center
Host computer. This provides CTAS with flight plans and radar track
data. The Host radar track data is updated every 12 seconds. The
logistics and code modifications necessary for utilizing Host data at
each facility preclude TFAS from using this Host data in Phase I. The
TFAS Phase I will connect to the ETMS system for track and flight plan
data.

As shown in Figure 3, each TFAS module (Center CTAS system) will keep
track of all sector Monitor-Alert conditions that will occur within the
next 45 minutes. The CTAS Route Analysis (RA) process has been modified
to produce a new aircraft trajectory event data-structure which contains
the times each aircraft enters and exits the sectors on its flight path.
Although the RA uses the Trajectory Synthesis (TS) process to generate
these Aircraft Sector Traversal Lists, the TS software itself did not
require modification for this purpose.

The Aircraft Sector Traversal Lists are passed to the Communications
Manager (CM), where sector occupancy counts are created from the
entry/exit time predictions . The CM software compares predicted
occupancy (i.e., number of aircraft traversing a sector within a
15-minute period) with the sector capacity limit. If a particular
sector's occupancy is greater than the capacity limit, a sector
Monitor-Alert condition is triggered.

The CM then sends the sector Monitor-Alert data to the TFAS Data Process
(TDP). The TDP is the repository for sector Monitor-Alert conditions
from all connected CMs. In this manner the TDP will assemble all CONUS
sector Monitor-Alerts.

The TDP will then scan the ETMS Traffic Monitor Database (TMD) file. If
TDP finds a sector Monitor-Alert in the TMD that is not in the TDP
database, that entry is deleted from the TMD file. If the TDP has a
Monitor-Alert condition that is not in the TMD file, then the TDP adds
this entry to the TMD. When this process is complete, the TMD file will
be identical to a normal ETMS file, except that the near- term (i.e.,
within 45 minutes of present-time) sector Monitor-Alerts will conform to
the TDP internal model.

As shown in Figure 4, TFAS sends this modified composite sector
Monitor-Alert database to the Hub Site ETMS processors and to the
Traffic Situation Displays at the SCC, Centers, and TRACONS. If TFAS has
not yet been implemented for a particular ARTCC, the Monitor-Alerts in
that Center are not modified by TFAS.

![](media/image5.wmf){width="5.238888888888889in"
height="6.061111111111111in"}

**Figure 3. CTAS Elements of TFAS**

A basic TFAS algorithmic rule is: one trajectory per aircraft-track per
ARTCC. Each TFAS module (i.e., CTAS system) will generate a 4-D
trajectory that nominally terminates at the Center boundary
coordination-fix. Each TFAS module's Communication Manager (CM) process
will transmit the time the aircraft is predicted to arrive at the
coordination-fix to the

destination Center's CM, along with other information required
generating a 4-D trajectory for

![](media/image6.wmf){width="7.0in" height="2.41875in"}**Figure 4.
Moving TFAS M/A into ETMS Hub Site and Field Sites**

the aircraft in that Center. Each TFAS module CM will transmit such data
to each adjoining Center's CM, and will receive such data from each
adjoining Center's CM. In this manner multi-Center trajectories can be
created for each aircraft, although these will actually be discreet
single-Center trajectories linked by exchanged coordination-fix data.
Figure 5 schematically represents this scheme for a single aircraft
originating in Center A and traversing Center B.

**Figure 5. Inter Center Trajectory Coordination**

**3. Functional Flow**

![](media/image7.wmf){width="5.80625in"
height="4.310416666666667in"}Figure 6 shows the functional flow of TFAS.
The functional flow diagram is neither a data flow nor a software
architecture diagram, and it does not represent how the TFAS function is
implemented in software. It is meant to illustrate what functions TFAS
performs and what are its primary inputs and outputs. The diagram was
derived by modifying the functional flow for ETMS as shown in Appendix
D. The grey boxes in the diagram are the primary functions that TFAS
replaces in ETMS. The CTAS Route Analyzer Function in TFAS replaces the
Flight Plan Processing function in ETMS and the CTAS Trajectory
Synthesizer replaces the Flight Modeling function in ETMS. All other
functions of ETMS are preserved, including the graphical user
interfaces.

##### **Figure 6. TFAS Functional Flow**

For each aircraft, the CTAS Route Analyzer takes flight plan information
to prepare a series of waypoints that the aircraft plans to traverse.
This information, along with aircraft flight data (position, speed,
profile), aircraft profile data (for the type of aircraft involved), and
geographic data such as sector and fix geometries, is used by the CTAS
Trajectory Synthesizer to calculate various flight times (e.g., ETAs)
and flight events (e.g., entry and leaving times of a sector) at various
points along the flight, and a speed/altitude profile for the aircraft.
This information for all aircraft forms part of the traffic demand
database (TDB). When the traffic demand is compared with the capacity of
the sectors, a Monitor-Alert is generated whenever the demand exceeds
the capacity. These Monitor-Alerts are sent to the various TSDs in the
SCC, Centers, and TRACONS for resolution by the TMCs.

**4. References and Bibliography**

1.  Advanced Air Transportation Technologies Sub-element 2: Benefits and
    Safety Assessments; Modeling and Simulation TFAS Task Area Plan,
    Version 1.5, January 30, 2001.

2.  TMS-TFAS Development Briefing, Volpe National Transportation Systems
    Center, November 2000.

3.  TFAS Volpe Program Review, Volpe National Transportation Systems
    Center, December 5, 2000.

4.  Enhanced Traffic Management System (ETMS) Functional Description
    (DRAFT), Version 6.0, Word Version 2, January, 2000, Volpe National
    Transportation System Center Report Number VNTSC-DTS56-TMS-002

5.  FAA Denver ARTCC Traffic Management System (TMS),
    <http://www.nw.faa.gov/ats/zdvartcc/tmu_tools.html>, September 24,
    2000

6.  FAA Order 7210.3, Facility Operations and Administration, August 10,
    2000; <http://www.faa.gov/ATPubs/FAC/>, Chapter 17, Section 6
    (Enhanced Traffic Management System (ETMS)), Section 7 (Monitor and
    Alert Parameters), Section 8 (Traffic Flow Management)

7.  FAA Order 7110.65M, Air Traffic control, August 10, 2000;
    <http://www.faa.gov/ATPubs/ATC/index.htm>. Chapter 11 Traffic
    Management Procedures.

8.  AFD Process Description for the Design, Development, Release, and
    Maintenance of Software, AFD.0001, NASA Ames Research Center,
    November 27, 1999, <http://iadt.arc.nasa.gov/ISO9000/index.html>

9.  AFD Software Project Plan for CTAS, AFD.0002, NASA Ames Research
    Center, January 5, 1999.
    <http://iadt.arc.nasa.gov/ISO9000/index.html>

> 10\. CSC/E2-97/7169, CTAS Route Analyzer FD/TLD -- Draft, November
> 1997
>
> 11\. CSC/E2-92/7170, CTAS Trajectory Synthesizer FD/TLD -- Final,
> October 1998