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Controller-Pilot Datalink Communication (CPDLC)
A key component of the global CNS/ATM strategy.
By Anita Trotter-Cox, President, Assessment Compliance
Group, ATP/CFII. GIV, GI, 1124 WW.
Last
March, at an International Operators Conference, a briefing on "Aircraft/Operator
Requirements for CNS Programs" was provided by the FAA. Three slides in
particular caught my attention. The first read "CPDLC is an option in all
Pacific Oceanic Flight Information Regions (FIRs)" and also stated a concern
for "operator issues such as pilot knowledge, procedures and aircraft datalink
equipment configuration." The following slide read "CPDLC is scheduled
in the North Atlantic (NAT)--New York only--in November of this year,"
and the final slide read "State authorities need to provide timely information
to operators on CNS system requirements and options and operators need
to inform themselves of CNS developments."
A number of questions came to mind. As corporate
operators, will we have timely information on system requirements and options?
What is the status of the Controller-Pilot Datalink Communication software
development for business aircraft? Where can we find source documents for
policy and procedures? When the time comes, will our local FSDOs be up
to speed on the approval process? Will our training organizations have
the training programs in place before we are flying with the equipment
on board our aircraft? In other words, are we really as informed about
all this as we should be?
Airlines, large aircraft manufacturers and ATS
providers have all worked side-by-side with ICAO and State regulatory agencies
during the evolution of CNS/ATM. They are privileged to listen to industry
presentations on the status of the technology and participate in operational
trials where the procedural environment is experienced firsthand. This
statement by no means diminishes the years of hard work and effort needed
to bring about technological advances, improved safety and economic benefits
to all members of the global aviation community. But corporate operators
are generally not consistent members of these teams. They have to work
diligently through our business aviation associations, publications and
conferences to keep up with the results, decisions, pending airspace changes
and timelines established by these groups.
Fortunately, we now have the Internet -- no more
excuses for just not knowing. We can keep up with the progress of these
groups by accessing the relevant Web sites. Try doing a search on "CPDLC"
and you'll be pleasantly surprised. FAA (www.faa.gov/ats/ato/150.htm)
and Air Services Australia (usrwww.mpx.com.au/~cjr/introduct.htm)
have made great efforts to post as much relevant data as possible. Both
sites are educational and informative.
Pacific region
One of the main CNS/ATM system components is the
use of datalink for conducting routine aeronautical communications. CPDLC
service has not only been available but in use for communication between
aircraft and Air Traffic Control (ATC) in certain South Pacific FIRs since
1995. Now CPDLC is available in all Pacific Oceanic FIRs, including Tokyo,
Anchorage and Oakland. Because of the long routes and low traffic density,
this region is an excellent environment for operational trials. Most ATS
providers in this region are now preparing for the implementation of their
final, fully integrated system. As a result of this expanded ATC capability,
Pacific operators using CPDLC are expected to accelerate. Recent changes
to the US Government Flight Information Publication (FLIP) Alaska Supplement
now include datalink procedures.
Benefits
CPDLC will allow pilots and controllers to transmit
digital data messages directly between computers on the ground and computers
on board the aircraft. In the future, this will alleviate frequency congestion
problems and allow the controller to handle more traffic. Significant reduction
of response time and improvement in weather deviation request responses
have already been achieved in the South Pacific. One of the most important
aspects of this technology is its intended reduction of crew-input errors.
The crew can downlink a complex route clearance request, which the controller
can re-send when approved without typing all the coordinates. This technology
also reduces pilot/controller workload by allowing the FMS to automatically
downlink a report such as a waypoint crossing. This helps both the flightcrew
and the controller.
 |
As mentioned, CPDLC is intended
to increase safety by reducing communication errors and pilot workload,
improving the efficiency of airspace management and providing economic
benefits. Therefore, if more operators are equipped, the cost/benefit will
improve. Use of CPDLC in Pacific oceanic airspace is currently optional.
In the future, however, CPDLC could be considered a requirement for certain
designated routes. |
| ATC logon status: This page provides
the initial logon and display of the current Data Authority. |
|
Brief background
Conceptual design for the Future Air Navigation System
(FANS) is based on the use of satellite technology to manage air traffic.
Since the 1991 ICAO endorsement of CNS/ATM, the FANS committee has actively
worked with member States to explain and refine the economic necessity
and benefits of installing new CNS/ATM technology.
The FANS Interoperability Team (FIT) was formed
in 1997 as an international panel of operational and technical specialists.
The team is actually a sub-group of the Informal South Pacific ATS Coordinating
Group that brings together airline operators, ATS units, airframe and avionics
manufacturers and datalink service providers. FIT has resolved many technical
problems and has been instrumental in the standardization of international
datalink procedures.
South Pacific FANS operating experience shows
that considerable benefit derives from close monitoring of the end-to-end
system performance. This function is performed by the FIT Central Monitoring
Agency, which acts much like the Central Monitoring Agency in the UK for
the NAT RVSM airspace.
The general consensus is that without the work
of this group, the future of FANS and the whole concept of CNS/ATM would
not have progressed as it has. FIT is now being used as a model for the
creation of a similar group for the European Preliminary Eurocontrol Trials
in Air/Ground Datalink program.
Operational overview
ATS systems will use Field 10 (equipment) of the
ICAO flight plan to identify an aircraft's datalink capability. Pilots
will use the letter "J" in Field 10 and the characters "DAT/" should be
placed in Field 18, followed by one or more letters to indicate the type
of datalink equipment carried (e.g., "S" for satellite datalink, "H" for
HF datalink, etc.) once they receive operational approval. An initial ATS
Facilities Notification (AFN) logon must occur and can be initiated by
the pilot on the ground before departure. Initial AFN logon must also occur
when the aircraft arrives from an area where CPDLC is not provided.
|
| Verify report: This is the individual
ATC report status/control page. It provides the crew the capability to
arm or disable the report. In addition, up to four lines of free text can
be entered associated with each report. |
|
CPDLC uses the concept of Data Authority. There can
only be two Data Authorities (maximum of two ATS units) connected to the
aircraft for CPDLC at any one time, with only one of these connections
(Current Data Authority) being active. Unlike Automatic Dependent Surveillance
(ADS), CPDLC requires flightcrew interaction. The flightcrew is aware of
which ATS unit has the active connection and they actively use the functionality
to send response messages and reports. They are also aware of the hand-off
from one ATS unit to another. Workload and integration with other tasks
will be critical to situational awareness.
The next FIR on the cleared route is known as
the Next Data Authority (NDA). If an NDA message is not received by the
aircraft, the NDA does not exist and termination of the connection with
the current Data Authority will leave the aircraft without CPDLC connectivity.
If the next ATS unit is not datalink-equipped, an NDA message is not sent
to the aircraft. Prior to reaching the next FIR, the crew is instructed
to establish voice contact with the next ATS unit. The End Service message
sent by the Current Data Authority will terminate the active connection
and the aircraft will not be CPDLC connected with any ATS unit until the
pilot performs an initial logon to a datalink ATS unit.
An initial logon, which is the pilot's responsibility,
should occur somewhere between 15 and 45 minutes prior to the aircraft's
boundary estimate. When the pilot performs the initial logon to an ATS
unit, that unit becomes the Current Data Authority. A successful logon
is required for CPDLC.
Honeywell's
FMZ 2000 system
(CPU and CDU) displaying one
of the CPDLC pages currently
in development.
FMS display
Currently on the Boeing 747-400 FANS-1 FMS display,
the ATC LOGON/STATUS page is accessed by selecting the ATC button if no
connections currently exist. To perform an initial logon manually, the
pilot types the four-letter ICAO designator for the ATS unit. The pilot
then selects the LOGON TO button to move the designator to
where the four boxes are displayed. The pilot then enters the flight number
and selects the FLT NO button. This action moves the flight number
into the appropriate position and then activates a SEND button at the top
right of the display. On selection, the pilot will see LOGON SENDING then LOGON SENT and finally
LOGON ACCEPTED. Aircraft registration number and flight number must be
the same as those on the flightplan.
Examples of uplink messages that arm the avionics
to perform functions automatically are REPORT REACHING (level) and REPORT
PASSING (position). When one of these messages is received by the avionics,
the flightcrew is presented with the ARM prompt on the UPLINK and VERIFY
REPORT pages of the FMS. Selecting the ARM prompt on either page will arm
the report for transmission. The avionics will automatically send the downlink
report message when the event occurs.
Procedural issues
CPDLC involves new satellite communication systems,
new or modified flightdeck systems, new pilot, dispatcher and controller
procedures and knowledge, and new aircraft maintenance practices and procedures.
All of these will require standardized procedures and practices. Currency
requirements include a recommendation that pilots use CPDLC operationally
within 30 days of initial training. In addition, the pilot should use CPDLC
operationally or receive follow-on training at least every 60 days. Computer-based
training can be used as an option to meet this requirement.
Preflight procedures include NOTAM reviews for
planned and predicted outages. HF voice capability still remains a requirement
and must be monitored even when CPDLC is being used for position reports
and clearances. Operators must comply with the voice communications procedures
associated with CPDLC. Communications initiated with ATS by voice should
be completed by voice and communications initiated by CPDLC should be completed,
whenever possible, by CPDLC.
 |
| FAA slides shown during a briefing
on "Aircraft Operator Requirements for CNS Programs." |
A clear understanding of the CPDLC logon, connection,
failure and closure modes is required to develop acceptable flightcrew
procedures and training programs. It is essential that operators understand
the very significant differences in pilots' listening to, understanding
and reading back an ATC clearance issued by voice and pilots' receiving
a text message, reading it precisely and understanding and complying with
it. Transition to CPDLC challenges our current approach to understanding
situational awareness. Human factors activities are being included in the
CPDLC schedule.
Summary
In preparing this brief overview of CPDLC it was
a great challenge not to discuss ADS. Hopefully, operators will be curious
enough to research the available information on the Web. A detailed description
of this ATS application in the South Pacific can be found in the South
Pacific Operations Manual (SPOM), www.faa.gov/ats/ato/ 150.htm.
This document contains policies and procedures agreed upon by ATS providers,
operators and aircraft manufacturers. ICAO has used this document as a
basis for its Guidance Material on CNS/ATM Operations in the Asia/Pacific
Region, www.icao.org. This material will also be helpful when
revising your international operations manuals.
CNS/ATM is moving forward whether we are informed
or not. The burden and responsibility are truly ours. Our segment of the
industry is customer-driven. Therefore, we are the ones who have to be
asking questions of our aircraft and avionics manufacturers and training
organizations. It is essential that crews and technicians be properly trained
prior to using the CPDLC function. It is up to us to make strong recommendations
for ground school courses that provide an overview and background, operational
objectives and requirements and components (ground and air) of the CNS/ATM
system. Now is the time to starting making these requests.
Anita Trotter-Cox is an ATP/CFII pilot with GIV/GI/Westwind
1124 type ratings. She holds a Masters Degree from Washington University.
She is President of Assessment Compliance Group, located in Annapolis MD,
and provides flight departments (Part 91, 135 and 121) with International
operations procedures manuals and support for standardized procedures for
advanced technologies. info@aviationmanuals.com
(www.aviationmanuals.com). 
All pages copyright ©1999, Queensmith
Communications Corp. All right reserved.
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