1. Integrated information and telecommunications solutions AIRCOM Implementation VHF Digital Link Presented by Philip Clinch to ATN 2001 Conference 19 September 2001

2. Integrated information and telecommunications solutions SITA VHF Digital Link Objectives SITA has been working on VDL for 10 years to promote Air Traffic Service provider use of aircraft data links by defining a new VHF data link system whose design is approved by the ATS providers and which can at the same time replace the VHF ACARS system we use today to serve over 100 aircraft operators with 5000 aircraft.

3. Integrated information and telecommunications solutions VHF ACARS use for ATS applications VHF AIRCOM was used by Eurocontrol PETAL 1 which installed a very basic ATS application on pre-delivery AIRBUS aircraft flying between the Toulouse and Hamburg factories. When Eurocontrol launched PETAL phase 2 the CPDLC system was intended to communicate with aircraft having ATN avionics. SITA recommended mitigating the risk of ATN avionics delivery delays by opening up to aircraft with FANS-1/A CPDLC and Eurocontrol connected the CPDLC system to the VHF AIRCOM network.

4. Integrated information and telecommunications solutions PETAL Benefits from incorporating FANS The benefit to the PETAL project of opening up to FANS aircraft was to obtain a number of CPDLC equipped aircraft sufficient to maintain controller familiarity with data link. –Since January 2000 an average of 10 FANS flights per day have conducted CPDLC with controllers at Eurocontrol Maastricht. –FANS aircraft were the only PETAL participants in 2000 and they still represent 75% of the flights since the NEAN aircraft restarted participation. –PETAL CPDLC communications with FANS aircraft was critical to keeping up the project momentum.

5. Integrated information and telecommunications solutions VHF data link upgrade requirement While VHF ACARS is supporting CPDLC in the Petal 2 trial its performance is constrained because, when it was implemented in 1978 to minimize the avionics cost it used VHF analog voice radios. –The VHF analog ACARS data rate of 2.4 kbit/sec is not enough for the daily average of over 3000 aircraft that use the service in Europe and the eastern USA. –Aircraft data links with higher capacity would be easier to implement in other radio bands not managed by aviation authorities but this protection makes the VHF band attractive to ATS providers and their use of VHF data link triggered the definition of a new system.

6. Integrated information and telecommunications solutions VHF Digital Link Mode 2 SITA contributed to the ICAO decision in 1991 to task the Aeronautical Mobile Communications Panel with defining ATN subnetwork service provision by a VHF data link. –AMCP defined a common subnetwork protocol using a Mode 1 modulation scheme compatible with analog radios for validation purposes and a high speed Mode 2 modulation scheme requiring the use of digital radios. –AMCP decided VDL Mode 2 should use the modulation scheme selected by the the FAA for a system to support digitized voice which they called VDL Mode 3. –AMCP did not specify VDL Mode 2 provision of aircraft to aircraft links because they are not used in the ATN.

7. Integrated information and telecommunications solutions SITA Implementation of VDL Mode 2 SITA has started deploying a ground station that handles VDL Mode 2 and VHF analog ACARS. –SITA has since October 2000 installed our first VDL ground stations at Rockwell Collins, Honeywell, AIRBUS, Paris and Amsterdam. –Collins carried out VDL tests in October 2000 and AIRBUS in September 2001 carried out their first tests of VDL in the ATSU using the SITA VDL station at Toulouse. –The SITA VDL service supports an AEEC defined ACARS over AVLC (AOA) service which minimizes the cost of the airborne implementation while providing a platform for the subsequent addition of an ATN router and CPDLC.

8. Integrated information and telecommunications solutions VDL Mode 2 Benefits SITA input to VDL Mode 2 standardization ensured its implementation remained feasible by focusing on the objective or replacing VHF ACARS. –VDL Mode 2 is the only VDL mode that can credibly take over the ACARS support for ATS and AOC enabling the ATN CPDLC data link business case to profit from the value generated by increasing AOC data link capacity. –VDL Mode 3 support for data link is planned by the FAA for 2011, a generation after VDL Mode 2, and even then VDL Mode 3 would probably not support AOC data link. –VDL Mode 4 implementation would be driven by ADS-B but it could not provide the reliability needed for ADS-B if was also supporting engine reports and passenger lists.

9. Integrated information and telecommunications solutions VDL Mode 2 Institutional Issues The VDL Mode 2 technical issues have been resolved but debate continues over the service provider role. –The Eurocontrol Link 2000+ and FAA CPDLC programs assume that VDL Mode 2 service will be provided by the current ACARS service providers and ATS providers will pay for the traffic they exchange with aircraft. –Some ATS providers are deploying or housing the VDL Mode 2 stations in their territory and partnering with an airline service provider to deliver AOC traffic. –The dual role of ATS providers as VDL Mode 2 users and providers makes resolution complicated.

10. Integrated information and telecommunications solutions Conclusion VDL Mode 2 offers an aircraft to ground station data link with the highest data rate possible in a 25 kHz VHF channel and will be installed on most new jet aircraft delivered in the next decade. VDL Mode 2 competes with satellite data link and the other VDL modes have different competitors: –VDL Mode 3 competes with VHF analog voice using 8.33 kHz channels. –VDL Mode 4 competes with Mode S and UAT to support an ADS-B service.