RTCA SC-214/EUROCAE WG-78
Air Traffic Services Safety and Interoperability Requirements
General Information
Paper Reference: Revision: Date: Status :
Surface Management – TAXI - 10-22-09 1st Discussion Paper
Messaging
Editor / Author: Review Meeting/Teleconference:
Chris Wargo, Mosaic ATM Inc. Prepared for the SubGroup Meeting Oct 25-30, 2009
443-994-6137 (ISPR SubGroup)
cwargo@mosaicatm.com
Steve Beamer FAA STBO Project
Position Paper Title:
Additional Messages Related to D-TAXI and Surface Management Automation Systems
Abstract and Proposed Action:
This position paper presents a recommendation for:
1. The use and definition of a new DM message, for “Pushback Time.”
2. The addition of an optional Required Time of Arrival data element to be added to the
Taxi Route Message for TEXT and graphics.
The recommendation is based upon the evaluations being performed within the ongoing FAA
Surface Trajectory Based Operations (STBO Proof of Concept Project
The paper also provides identification of other issues that are currently under analysis for
purpose of initial discussion and possible change recommendations.
later
Distribution
SC-214/WG- Additional Names Additional Names Additional Names
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Position Paper: Surface Management – TAXI Messaging Version 10-22-09
1. Surface System Management Background
The NextGen Concept of Operations, authored by the Joint Planning and Development Office
(JPDO), states that “4DTs [four-dimensional trajectories] may be used on the airport surface at
high-density airports to expedite traffic and schedule active runway crossings.” Achieving this
vision will require a series of advances in procedures, supporting automation systems, and
collaboration between air traffic control (ATC) and the flight operators. To conduct research on
trajectory-based operations (TBOs) applied to the airport surface, the FAA has established the
Surface Trajectory-Based Operations (STBO) project in the Advanced Technology Development
and Prototyping group of ATO-P. These capabilities, once confirmed, will deployed under the
NextGen Program know as the Tower Flight Data Management (TFDM) System. (Refer to
Appendix 1)
STBO is a set of capabilities and associated procedures that will deliver a specific aircraft to
specific place on the airport (e.g. runway) at a specific time to meet a specific event (e.g. takeoff)
in the most efficient manner possible. The aircraft’s engine and taxi operations will be optimized,
as well as stops on the airport surface minimized or eliminated, resulting in lower fuel burn,
lower carbon emissions, reduced noise, and enhanced surface safety.
The STBO project, which supports the FAA Flight Plan Goals of “Increased Efficiency,
Capacity and Safety,” will demonstrate and document requirements for a series of capabilities
leading to the NextGen vision for surface trajectory-based operations. Examples include local
data exchange which will lead to the sharing of flight readiness information and collaboration
that will enable pre-planned runway schedules integrated with airborne trajectory-based
operations. Surface flow management will reduce surface engine operating times, resulting in
fuel savings and reduced environmental impacts, and lead to collaborative resource allocation
and avoidance of surface gridlock. Digital taxi clearances will enable pre-planned and
coordinated airport surface trajectories and will lead to taxi conformance monitoring.
The objectives of surface flow management are to provide the taxi route planning integrated with
all other surface movements of departure and arrival aircraft and airports conditions such that
once the aircraft pushes back, there be no or least minimal stoppage of the aircraft along the
surface route. This is through both the non-movement and movement areas. Thus the aircraft
will be able to fit into an expected traffic flow profile that optimizes the departure to arrival
trajectory. It is understood to achieve this objective it will necessary to make use of time-based
operations. Accordingly, the pilot procedures aircraft avionics, and ground/tower controller
systems developed to support time-based surface movement objectives as well as those in the
airborne segments.
2. Time-based Taxi Operations
One method to move towards implementation of the end state result of TAXI 4D trajectories is
by the incremental implementation that starts with today’s voice- based messaging to the pilot
and then moves to a digital text-based message exchange. This could be followed by a graphic
map-based information exchange approach. The initial set of messaging definition for D-TAXI
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Position Paper: Surface Management – TAXI Messaging Version 10-22-09
and for graphical exchange is presented in the current draft and working papers of the SC-
214/WG-78 ISPR. A potential follow on step would integrate these into the development of a
surface trajectory approach that could follow a similar approach currently being drafted by the
4TRAD Working Group.
After initial functionality is established and demonstrated with operational evaluations, the focus
of the STBO project will turn to time-based taxi operations. The research and proof of concepts
development is directed at time-based taxi route generation. To assist the full transition the
researchers working on the FAA STBO project recommend two changes to the current Draft
ISPR. These changes will aid in supporting functionality expected to be deployed by the FAA in
the Tower Flight Data Management Program:
1. Additional of a Downlink Message (DM) to the D-TAXI services that would serve to
report and confirm the actual time of the aircraft pushback.
2. Additional of a Required Time of Arrival that can be optionally identified with the
location or position instructions associated with the taxi route instructions.
Additional recommendations impacting the use of the data link are expected to be better
understood during the validation time frame of the SC-214/WG-78 SPR development period.
These are:
A. Use coordinate systems (such as Lat/Long) for location and position identifications
B. Map exchange techniques other than fixed element style as defined the current documents
of SC-217.
C. Method of operating for surface trajectory operations.
3. Change Request Item 1. Downlink Message to Confirm Pushback Time
Analysis
Today the ATSU automation system knowledge that an aircraft has actually pushed back from
the gate/stand area can be obtained by two methods:
1. Use of surveillance systems installed to provide coverage of the “Non-movement or
ramp area”
2. The flight operator sharing of information received from the aircraft transmitted ACARS
Out message.
In method 1 the use of radar, ASDE-X (mulitlateration) or ADS-B position reports is being
trialed. The track data from the surveillance system’s ground processor is sent through
surveillance ground infrastructure to be processed by the ATSU’s surface management system
(SMS). The SMS system then processes the track data to detect aircraft movement and assign a
pushback status to the aircraft (this indicates that the aircraft is moving in the ramp area). This
detection processing is a statistical operation, and makes use of prior state information of
aircraft’s transponder code and flight ID. The latencies of the process are small in the order of 3-
15 seconds.
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Position Paper: Surface Management – TAXI Messaging Version 10-22-09
In method 2, the airport operator would remove any proprietary data from the received ACARS
OUT message, format a new message and then route it to the ATSU SMS. The latency these
actions would be expected to be in the 5-30 second range and in some cases may be in the
minutes.
A third method is proposed where the aircraft would send directly to the ATSU SMS a message
that provides the Pushback Actual Time. This would be the actual pushback time. The message
release triggers within the avionics would be the same for this new DM as that for the ACARS
related OUT message, but instead this DM would be addressed directly to the ATSU.
Confirmation of actual pushback time adds certainty to the taxi route planning operation,
provides a timely trigger to route update algorithms, and adds accuracy to taxi route
conformance automation. The ability to use this actual time data would be accomplished with
less latency than either the described method 1 or 2.
It is understood that the taxi route instruction still to be given from the “spot” of entry on the
active movement area.
Note the question of a message that reports aircraft “in” at the gate status is still under
consideration as this may be useful, but this message is not being requested at this time.
Recommendation
Add, as a last step to the D-TAXI Operating Methods for the following Section 5.1.5 D-TAXI
Services, a report stating the time that the pushback action took place.
Add a “New DM DTXX” to Table 5-32 CPDLC Downlink Message Elements
Msg ID: DT XX
Message Intent/Use: Report Time of Aircraft Pushback to ATSU
Message Element: [Time Out]
Add to a new message variable to Table 5-33: CPDLC Message Variables, Range, and
Resolution:
Variable: Time Out
Definition: Actual aircraft pushback time
Parameter: Time Hour (M)
Time Minute (M)
Time Second (M)
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Position Paper: Surface Management – TAXI Messaging Version 10-22-09
4. Change Request Item 2. Add Required Time of Arrival (RTA) Optional
Variable to Taxi Route.
Analysis
Future Surface traffic flow efficiency depends on being able to direct an aircraft to surface
positions at a specified time. The use if this Required Time of Arrival at surface
position/locations is fundamental to the intent achieving time-based aircraft traffic flow
management for the gate to runway. Within with the context of the D-TAXI text messages, the
additional of RTA will be a pre-cursor to the establishment of a surface 4D Trajectory capability.
The inclusion of the a surface RTA capability will allow for the future development of the
procedures and pilot/aircraft capabilities that can be managed based upon the time allow for the
transition as part of the pilot and avionics capabilities.
Current research is providing taxi route instructions that include RTA for each position/location
included in the taxi route. If the route is only a partial instruction then only that part of the route
would be given RTAs.
Integration studies of messaging these time-based routes to the aircraft are currently being
readied for analysis and would be expected to be operationally verified prior to the end of
Calendar Year 2011. Adding changes to the D-TAXI message elements now by adding the
optional RTA will ready the issued SC-214/WG SPR with the capability.
Recommendation
Add to the existing message variable “RTAsec Required Time Arrival” to the definition of the
variable “taxi route” as shown in Table 5-33: CPDLC Message Variables, Range, and
Resolution. This variable is used with new UM DT09(now UM319) and new UM DT10 (now
UM320) where the use of a sequence to define the taxi route may be used (i.e. there would be
multiple RTAs along the route). The “Position Information” variable used to define the “taxi
route” and how to add the RTAs with the correct relationship requires discussion.
It is requested that a companion change to include the display of RTA information also be
included in the Graphical Taxi Method.
5. Additional Changes Under Evaluation
STBO project researchers are currently evaluating two other potential change requests/comments
to the draft ISPR. These are:
A. Now that the 4D trajectory Operation method has been more clearly defined, assess if this
technique/approach can be used to support surface movement control. The approach
would follow the use of clearance to multiple waypoints, CPDLC (change instructions for
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Position Paper: Surface Management – TAXI Messaging Version 10-22-09
flight path), ADS-C (to gain aircraft flight path intent), and a trajectory report (self-
identified conformance).
B. Confirm acceptance of the use of the RTCA SC 217 defined approach for transmitting
pre-defined map elements as the means to transmit the graphical taxi instructions. Note
that this would include the assessment of the use other map transmission techniques
and/or position/location identification by other coordinate systems; such as,
Latitude/Longitude.
Although no specific recommendations are available at this time the STBO Project research team
will continue to assess the above two items.
Appendix 1. Terminal Flight Data Manager (TFDM) Program Background
TFDM is a new terminal LAN platform under development by Terminal Services intended
provide System-Wide Information Management (SWIM) capability. TFDM will also consolidate
the miscellaneous automation functions and displays within the air traffic control tower (ATCT),
including ASDE-X surface surveillance, ITWS/TDWR, Flight Data Input/Output (FDIO),
Advanced Electronic Flight Strip (AEFS), Electronic. Flight Strip Transfer System (EFSTS), and
Tower Data Link Services (TDLS).TFDM, as a new NextGen tower automation and display
system, is the platform to host future STBO capabilities.
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