Harris Corp. has agreements in place with five major carriers, including United Airlines, to equip more than 1,500 aircraft over the next six years with digital communications gear that will accelerate ground operations at 57 airports by mid-2019 and remove most voice communications with air traffic control in the en route environment beyond 2019.

The FAA estimates that the tally represents 80% of the “tipping point” number of aircraft needed to make controller-pilot data-link communications (datacomm) practical in terms of capacity increases that will provide a return on investment for airlines and the FAA.

John O'Sullivan, Harris's vice president of NextGen initiatives for civil programs, tells Aviation Week he is confident enough airlines will sign up by the end of October to reach the 1,900-aircraft goal and commit most of an $80 million “rebate” fund the FAA set aside to encourage operators to equip. Unlike Europe, which has a 2015 deadline for airlines to equip for datacomm to operate above 28,500 ft., the FAA has no mandates. The FAA plans to have the command-and-control infrastructure in place at 57 airports by 2019 and in the en route environment thereafter.

The project is part of the U.S. agency's broader data communications integrated services (DCIS) program, a key element in the transformation of the air traffic control system (ATC) from voice to automated air traffic management. Harris is the prime contractor.

Digital tower departure clearances (DCL) are the first step along the FAA's datacomm growth path, which ultimately will replace most voice messages with secure text messages and, in the 2025 time frame, extend to negotiations of 4-D trajectories between ATC and the flight deck. Europe's command set for 2015 is much broader than the FAA's initial application, with approximately 100 uplink and downlink messages available, most of which are predefined text messages for “noncritical” communications.

While it is not unusual for aircraft to receive an initial clearance digitally over a VHF Data Link (VDL) Mode 2 radio, changes to that initial clearance, often required by weather issues, must be made by voice and manually keyed into the aircraft's flight management system (FMS). With datacomm, ATC sends a digital message to the aircraft as well as the airline operations center. The pilots use bezel keys on the communications management unit in the cockpit to accept or deny the amended clearance, or ask for more time. Once the pilots accept the clearance, another key automatically transfers the route into the FMS.

To participate, an aircraft must be equipped with the Future Air Navigation System (FANS) 1/A architecture and a VDL Mode 2 radio. FANS 1/A has traditionally been used for air traffic services and Aircraft Communications Addressing and Reporting System (Acars) capability on oceanic routes. O'Sullivan says carriers must install the required equipment before receiving the rebate, which is computed based on the upgrades needed to participate. Airlines can use the rebates for new or existing aircraft. In many cases, the aircraft already have the needed systems but require a “service code” to enable the additional functionality. Upgrade costs can range from $30,000 to $500,000, and airlines choose the avionics vendors.

In its agreement with Harris, announced Oct. 21, United Airlines said it will equip 397 aircraft, mostly older Boeing 737s and 757s, with datacomm over the next six years. O'Sullivan was not able to identify the other carriers, but one is likely to be American Airlines, a partner with Harris on the DCIS contract, along with Thales, General Electric and Arinc.

United, which had earlier upgraded 35 aircraft, is taking part in DCL testing at Newark, N.J., where UPS, FedEx, British Airways, Lufthansa and Scandinavian Airlines are also participating. The FAA is operating a datacomm DCL testing site at Memphis, Tenn., with FedEx as well. The two airports are using a Thales automation platform for the trials, although all airports offering DCL will eventually use a new FAA-built tower data-link system under development.

O'Sullivan says lessons learned to date include some FMS interface issues and “loads and drops,” where the FMS rejects a routing. In some cases, the rejection was due to controllers using FAA-standard three-letter identifiers for airports rather than the international-standard four-letter identifiers.

By mid-2015, the so-called first-key sites— Salt Lake City, Houston Intercontinental and Houston Hobby airports—will begin offering datacomm DCL, and by 2019, the FAA plans for it to be in operation at 57 U.S. airports.

O'Sullivan says there will be “solid metrics” on the benefits of using datacomm for DCL in 2-3 years. In the meantime, the rebate fund helped the early adopters to “close the business case,” he says.