1. Voice and Data Operations in the North Atlantic
Seminar on the Implementation of Data Link and Satcom Communications
Bangkok, Thailand, November 2003
Voice and Data Operations in the North Atlantic
Prepared by
Loftur Jónasson & Jennie Jónasson
Iceland Radio
This presentation is designed to give you a brief overview of data link implementation taking place today in the North Atlantic.
Iceland Telecom

2. World View Iceland & Thailand
The above slide is there to give you a perspective on the geographical relationship between Iceland and Thailand.

3. The Reykjavík Control Area
The above is an illustration of the Reykjavík Control area.
It is an exceptionally large oceanic area.
There is an agreement between the governments of Iceland and Denmark for the Iceland CAA to be responsible for all aircraft above F195 (Flight Level 19,500 feet) in the area covering Greenland.
The blue wavy lines show our VHF coverage areas. It is possible for an aircraft, depending on its track, to traverse through the entire Reykjavík Control Area and be in VHF coverage the entire time.

4. Some of our neighbouring areas
The above illustration is there to let you see the location of the areas that we will be talking about in this presentation.
The majority of traffic in the North Atlantic traverses through the Gander and Shanwick areas.
If the NAT (North Atlantic) Tracks are northerly on a particular day then the Reykjavík Control Area will have the majority of traffic.
A substantial part of the traffic going through the Reykjavík Control Area are on Random Routes or Polar Track Routes.
The Reykjavík Control area also has a large amount of general aviation traffic because we do not require that aircraft be HF radio equipped. We also have a large amount of military traffic because of the NATO base in Keflavík, Iceland and the US military base in Thule, Greeland.

5. The Desired End-State
The North Atlantic System Planning Group’s (NAT SPG’s) policy maintains that Standards and Recommended Practices (SARPs) compliant Aeronautical Telecommunication Network (ATN) data link technologies remain the desired end-state but greater flexbility has been agreed to for the use of other non-SARPs compliant technologies, in particular FANS-1/A.
ICAO established its North Atlantic Systems Planning Group (NAT SPG) in 1965 to study, monitor, evaluate the NAT air navigation system in the light of changing traffic characteristics, technological advances and traffic forecasts. See
The North Atlantic still has the goal of using ATN technologies.
In the meantime there are many FANS equipped aircraft flying and it seems logical to take advantage of this technology It must be remembered that the North Atlantic is a “Procedural” airspace as opposed to a “Tactical Airspace.”
Many stations in the North Atlantic are primarily HF and they have a limited number of HF frequencies available to them. HF frequency propagation varies by time of day, atmospheric conditions etc. This means that some of the limited number of HF frequencies available to stations can only be used at certain times of the day.
There are approximately 1,000 aircraft movements through the North Atlantic on a daily basis. The majority of westbound flights are during the day and the majority of east bound flights are during the night. Approximately 1/3 of these flights go through the Reykjavík Control Area.
If some of these aircraft can pass routine messages on using FANS data link technology, this frees up frequency space and allows aeronautical radio operators to spend more time with non-equipped aircraft. In addiiton, this gives the pilots and ATS providers practice using data link.

6. FANS FIRS
Iceland takes advantage of the ARINC Central ADS Server (CADS) system.
CADS allows areas to take advantage of FANS Systems without buying an expensive Front End Processor.
All messages are sent to ARINC Annapolis, Maryland, USA and then sent back.

7. Picture by ARINC of their CADS System
Gander ACC
Canada Met
Canada Met
SITA
ART/ADCC
ARINC
CADS Server
Annapolis, Maryland
Geographic Filer
Internetworking
Shanwick ACC
Met
AFTN
Reykjavík ACC
Met
Santa Maria ACC
ARINC
Network
Met
The above is ARINC’s illustration of how the Central ADS Server – “CADS” works.
New York ACC
Met
Other ACC
Other ACC
Met
Met
Picture by ARINC of their CADS System

8. Shanwick/Gander CPDLC System
CPDLC Host / FANS
Router
ARINC
/ SITA
NETWORKS
(ARINC, Annapolis)
CPDLC Uplinks / AFN
CPDLC
Requests /
AFN
VHF
SATCOM
Messages
X.25 NETWORKS
CAPSIN
(NATS)
APN
(ARINC)
HF Aeradio
CPDLC
Messages HF
X.25
X.25
The above illustration was created by the UK NATS and NavCanada. It describes their CPDLC (Controller Pilot Data Link Communications, or two-way data link) system.
Messages
To / From
HF Voice
Dispatch
CPDLC
Operator
Front End
ScOACC,
ATC / FDPS
(PRESTWICK)
GAATS (NAV CANADA)

9. Automatic Dependent Surveillance (ADS)
Prior to the implementation of ADS – all flights, FANS equipped or not, had to make position reports at approximately every 10 degrees
This took up a great deal of frequency time
Prior to 11 September 2001, traffic had been increasing in the North Atlantic at a rather dramtic rate. Many HF frequencies in the North Atlantic were at a point where they had more than they could handle. A great deal of frequency time was taken up with every one of the approximately 1,000 (Westbound and Eastbound) flights traversing through the North Atlantic being required make a Waypoint Position Report at approximately every ten degrees.
With the advent of ADS in the North Atlantic, FANS equipped aircraft (about 30% of today) no longer had to make Waypoint Position Reports. After the initial transition, this saved a great deal of frequency time and allowed radio operators to spend more time with non-FANS equipped flights. Since traffic levels are starting to get back to 10 September 2001 levels, ADS makes frequency congestion in the North Atlantic manageable.
On each HF Family in the North Atlantic, several radio stations are working each frequency, and certain frequencies are optimal at only certain times of the day. This limits the number of usable frequencies at high traffic times of the day. Although some radio stations (such as Iceland) have rather extensive VHF coverage, this is simply not possible for more than a fraction of the area covered.

10. FANS & North Atlantic Stations
Iceland
ADS
Shanwick
ADS & CPDLC
Gander
New York
ADS & CPDLC in some areas
Santa Maria
The group that is monitoring CPDLC (Controller Pilot Data Link Communications) indicated that CPDLC was performing satisfactorily for 96-97% of the flights using the system.
Iceland and Santa Maria plan to do CPDLC some time in Iceland and Santa Maria are considering integrating CPDLC into their FDPS (Flight Data Processing System) and thereby reaping full benefits of CPDLC.
Shanwick and Gander intend to to implement Phase 3 (see slide 12) of CPDLC by the end of this year (2003).
When Iceland and Santa Maria participate in CPDLC, they will enter at the same phase that Shanwick and Gander are currently at.

11. Cockpit Display With CPDLC Information
Uplink Message
CLIMB TO AND MAINTAIN FL300
CPDLC – Controller Pilot Data Link Communications
(this used to be called TWDL or Two Way Data Link)
CPDLC allows pilots and controllers to write directly to each other without using voice.
STATISTICS
According to the UK NATS and NAV Canada
an average of 170 aircraft a day log-on to CPDLC
this number has risen from approximately 100 aircraft a day at the beginning of Phase 2 (Autumn 2002) to up to 180 aircraft a day
1,109 our of 31,437 CPDLC downslinks were “Unsupported Messages” or 3.5%
- the number of CPDLC messages sent have been in excess of 70,000
Downlink Message
WILCO
<NEXT
SENDING...
CSR
CLR
DCT
FPL
MAP
MSG
EXE

12. CPDLC Phase 1, 2 & 3 Phase 1 Phase 2 Phase 3
Flight crews use data link to request speed and level changes and receive a response via voice
Phase 2
Flights receive VHF domestic frequency assignments via CPDLC
Phase 3
Flights receive clearances and response to clearance requests via CPDLC
Shanwick and Gander have been successfully utilising Phases 1 & 2.
They expect to implement Phase 3 by the end of the year.
Iceland intends on starting the implementation of CPDLC some time in Iceland will start at whatever phase Shanwick and Gander are already using.
This will of course save frequency time and avoid errors.
This allows radio operators to spend more time with non-FANS equipped aircraft.

13. Uplink & Downlink Downlink Air/Ground Data Network
Uplink is when the ground sends a message to the aircraft.
Downlink is when the aircraft sends a message to the ground.
For example –
Phase 1 - “Downlink messages only.”
Phase 2 – “Uplink messages added”
Phase 3 – “Uplink” in response to the “Downlink” from Phase 1
Uplink
ATC Controller
ATC Controller

14. HFDL (HF Data Link)
The HFDL issue is becoming more prominent as airlines are showing more and more interest in Polar flights and HFDL is the sole data link media that can provide continuous coverage over the Arctic region, therefore FANS operations there will have to rely on this media.
There has been a great deal of discussion about the inefficiency of HFDL as opposed to satellite and other forms of communication.
A limitation of HFDL is that it cannot be used at the same times as HF Voice because it shares a single antenna.
Statistics shows that 95% of HFDL messages are delivered in 3-4 minutes compared with seconds via satellite communications.
The reality is that Oceanic Polar flights can and sometimes do lose any and all communication with the ground when HF Voice conditions are poor. Receiving a position report 3-4 minutes late is better than not receiving any at all. HFDL may not be a true alternative to satellite for heavily congested areas – but it would be a great asset in the Polar region.
The availability numbers for HFDL are very similar to SATCOM. The propagation issues that affect HF Voice do not affect HFDL.

15. FMC WPR
FMC Waypoint Position Reports (WPR’s) are currently being looked at in the North Atlantic.
Alternative for non-FANS equipped aircraft.
FMC means Flight Management Computer.
FMC’s that are from certain manufacturers can send a type of Waypoint Posisition Report (WPR).
This provides an alternative for non-FANS equipped aircraft.
These Waypoint Position Reports (WPR’s) can be done manually or automatically.
It is ACARS based and goes through CADS. It cannot do CPDLC.
There have been some FMC trials using HFDL as a medium.
Some difficulties have arisen because the crews did not adhere to proper procedure.
Reults have been mixed – some initial results were encouraging and some regions have found that success criteria have not been met.
NAVCANADA will complete a thorough study in the Gander FIR using VHF Data Links and Satellites to determine whether the quality can be sufficient for operational service.

16. Human Factors & Transition Issues
Transition to data link is not initially a time-saver
Once pilots and operators get used to the system and procedures it does become a time-saver
It takes time to get used to any new technology and any new procedure that the new technology entails.
In a large FIR such as the Reykjavík Control Area, there can be many different VHF frequencies and HF frequencies assigned as the flight progresses. For pilots that were used to making position reports at approximately every 10 degress and getting the frequency for the next fix only, this can be overwhelming.
In the beginning of the ADS trials, some pilots did not make any radio contact at all, not realising that there was a need.
It will be interesting to see the transition issues that arise in the Reykjavík Control Area when CPDLC is implemented.
It is expected that after a brief transition period, that CPDLC will be a great success in the Reykjavík Control Area.

17. Oceanic Clearances and Data Link
Canada and The United Kingdom have indicated that they plan to implement “voiceless” Oceanic Clearance Deliveries by the end of 2004
Delivering Oceanic Clearances takes about 2 minutes per clearance and takes up a great deal of frequency time.
A “voiceless” Oceanic Clearance will save frequency time and greatly lessen the chance of errors which can easily be made with a voice delivery system.

18. ATN in the North Atlantic
Consideration of using ATN equipped B aircraft in CPDLC trials
There are several aircraft operators that are planning to equip their aircraft with ATN based SARPs compliant CPDLC. These are aircraft operators that intend to participate in the FAA Miami Build 1 or the Eurocontrol Maastricht Link trials.
The ADS functionality of these aircraft is not currently activitated.
If it is deemed possible to have these aircraft participate, it will be great step towards ATN in the North Atlantic.