In the cockpit, the Link 2000+ retrofit generally requires changes or additions in four areas. The aircraft must have a third radio that is VHF Digital Link Mode 2 (VDLM2)-capable; it must have a multi-function display that can show the text messages and allow for pilot responses; it must have an aural or visual alert that lets the pilots know a message has arrived, and it has to have a communications management unit (CMU) that acts as the CPDLC router and application. McDowall notes that the CMU “is the brains” of the operation.
The relatively high-rate (31.5 kbps) VDLM2-addressable messages are passed between air and ground using upgraded Arinc or SITA ground stations that typically carry Aircraft Communications Addressing and Reporting System (Acars) messages.
“For most airlines, it's a fairly significant upgrade for hardware and software for more than one [of the three] pieces of equipment,” says McDowall, noting that under a best-case scenario it will cost roughly $10,000 to meet the mandate. “Worst case is that there is not [a] third radio or CMU. Then it gets toward a significant cost.”
European airlines had the opportunity for help with those costs as part of a Eurocontrol subsidy program during the early “pioneer” phase of the Link 2000 program, which started in 2003. “Some did,” says McDowall of the aid. “The vast majority did not.”
The pioneer phase involved airlines and controllers using CPDLC in the Maastricht upper airspace sector, a practice that will continue in trial mode for equipped aircraft until more European air navigation service providers (ANSPs) phase in the new service.
A similar rollout in the U.S. will take a much more measured approach. As part of the Data Communications Integrated Services (DCIS) program, which the FAA awarded to Harris Corp. in September, CPDLC will be used by airlines to get updates to pre-departure clearances at five trial airports in 2015, followed by a broader implementation thereafter.
The contract includes $80 million to help airlines equip for CPDLC, which will initially work only with the aircraft using the Future Air Navigation System (FANS) 1/A architecture. This includes a different message set from the Aeronautical Telecommunications Network (ATN) protocol that Eurocontrol is implementing. FANS 1/A is typically used for air traffic services and Acars capability for oceanic routes. The contract calls for Harris to roll out the operational infrastructure for CPDLC in the airport environment by 2018 and in the en-route phase by 2023. While factory-built aircraft can already be equipped for the FANS 1/A CPDLC, retrofits for the U.S. operations could cost anywhere from $30,000 to $500,000 per aircraft for the legacy fleet, experts say.
A key difference between U.S. CPDLC and Link 2000+ is that the FAA is requiring that operators capture data link messages on the aircraft's cockpit voice recorder, while no such requirement exists in Europe. “Europe is looking to implement that, but there's nothing hard and fast on the recording,” says McDowall. “Some in Europe are upgrading recorders in advance but it depends on their ties to U.S. airlines. For the most part they're sitting tight. There are a lot of questions and a lot of uncertainty.”
The cost of the avionics upgrade could be highly dependent on whether the operator uses the original equipment manufacturer (OEM) or third-party provider.