Product Focus: Data Comm

Data communications is a key transformational program within FAA’s NextGen effort. To meet future demands and avoid gridlock in the sky and at airports, the agency’s NextGen Data Communications Program is designed to advance today’s analog voice-only air-to-ground communications system to one in which digital communications become an alternate and eventual predominant mode of communication.

The goal of the Data Communications program is to improve air traffic control by delivering digital information between controllers and aircrews. By reducing voice communications congestion and related errors, FAA estimates that digital data communications will enable controllers to safely handle approximately 130 percent of current traffic.

In the evolution to NextGen, data communications will advance air traffic control from minute-by-minute instructions to collaborative management of flights from takeoff to landing. FAA considers the Data Communications Program as the critical next step in improving air safety, reducing delays, increasing fuel savings and reducing emissions.

ARINC 750 VHF data radio and ARINC data communications protocol standards already are in place, said Paul Prisaznuk, executive secretary of AEEC, the ARINC engineering standards organization. He added that airframe and avionics equipment manufacturers have what is needed on the airborne side.

“The user community is waiting for FAA and Eurocontrol action, harmonization, deployment of ground infrastructure, agreement on ATC procedures, training, etc.,” Prisaznuk said. “Most remaining issues are on the ground side. Any remaining airborne side impacts may be data message format changes through software and crew training issues. These pieces are not insignificant. However, our feeling within AEEC is that most standardization is completed. We are waiting for decisions from the ground side.”

Data Roadmap

FAA managers say they are progressing on the remaining challenges associated with NextGen data communications.

“Data communications is an extraordinarily complex integration challenge,” said Sandra Anderson, FAA’s Data Communications program manager. “On the FAA side, the implementation of data communications will touch all major FAA automation systems, involve integration of networks, and will require a robust VHF Data Link Mode 2 (VDL-2) air-to-ground communications link.

“On the aircraft side, data communications will affect the radio, communications management unit and, in most cases, the flight management system. But the fundamental integration challenge is integrating data communications into air-traffic management procedures … in effect, changing the way the controller and pilots perform their jobs, enabling considerable efficiency gains for airspace users.

“A capability as complex as data communications will always have technical issues to be solved, but there are no major technical barriers. The technology is here today. The real challenge is the horizontal and vertical integration of people, procedures and technology to enable data communications to perform in the National Airspace System.”

In those efforts, FAA’s Data Communications Program has been advised by the RTCA NextGen Implementation Task Force, or Task Force 5, which Anderson said helped the agency align with industry priorities. To provide even more coordination, the Data Communications Program began an initiative in January to collaborate with airspace users to ensure the program addresses both FAA and operator goals and constraints.

In April, the first data comm meeting took place through the ad hoc Data Link Users Forum to discuss technical considerations associated with the implementation of the initial Data Communications Tower Service.

The Data Communications Program was working through the final investment analysis phase of FAA’s acquisition management system.

Implementation dates are baselined at the end of this phase. The current implementation dates, which the Data Communications Program has been targeting for some time now, are 2014 for departure clearances and revisions, and 2016 for en-route services.

“We have developed a challenging schedule to move the departure clearance implementation one year earlier, and are in the process of internally vetting the schedule,” said Anderson. “The main challenge is getting the application software developed in the Enroute Automation Modernization System (ERAM) and Tower Data Link Services (TDLS) automation platforms and integrating the end-to-end system. The Data Communications Program is in the process of acquiring the services of an experienced integration contractor to accomplish this end-to-end service.”

The capability for airborne re-routes has been maturing in the lab environment for several years, according to Anderson. Basically, the re-route is shipped to the sector controlling the aircraft to be re-routed, conflict probe is automatically applied to detect potential conflicts, and the controller uses the standard display interface to uplink the re-route to the aircraft.

“The main issues are scheduling the enhancements and ERAM implementation capacity,” said Anderson. “In this time frame, there are multiple NextGen programs competing to include enhancements in ERAM software releases. We are coordinating with the ERAM Program Office to finalize the ERAM software release that will contain the data comm requirements.”

Equipage Issues

Up to this point, one of the biggest issues related to NextGen data communications has been getting operators to agree to equip their aircraft with the necessary systems. The concern is that implementation of a costly Automatic Dependent Surveillance-Broadcast (ADS-B) infrastructure, for example, doesn’t mean much if there are an insufficient number of aircraft properly equipped to communicate with the system. The Air Transport Association has said that FAA must demonstrate the benefits of ADS-B before it can support the equipage of airplanes operated by its member airlines.

“The challenge for the industry is to make the business case so that airlines and the other users of the system will buy the necessary avionics to make these applications work,” said David Ford, an independent consultant and former Lockheed Martin engineer who served as co-industry lead of Task Force 5. “The good news is that the FAA is putting the ADS-B and the data comm infrastructure in place. These are the enabling technologies that allow you to run applications that permit re-routes around weather, for example, and it is the benefits that come from the applications that let me save fuel or reduce flight times. That’s how I’m going to recoup my investment.”

That is itself a challenge because of the issue of a mixed fleet in which some aircraft are ADS-B and data comm equipped and others are not. Some are calling for a “best-equipped, best-served” policy where those airplanes equipped with the proper avionics get ATC priority. But there is presently no policy that addresses best equipped, best served.

“You have this transitional period while the fleet is building where you only have a handful of aircraft out there that can play” in the NextGen system. “How can you get them the benefits without hurting those who haven’t yet played?” asked Ford.

Then there are message assurance issues associated with Future Air Navigation System (FANS)-equipped aircraft and the standards being developed for satellite-based Air Traffic Management (ATM). The issue is one of safety. What sort of messages can be delivered over FANS versus those over ATM? Can control messages be sent over FANS without message assurance questions? FANS works for routine communications, but is it suitable for route changes?

“Not only do you have a mixed equipage situation, you also have a sub-layer there those I can deliver control messages to versus those I can’t,” said Ford.

“So how does the controller deal with that from a human factors perspective? How does a controller know on his or her display what are all of the different kinds of equipage that an airplane might have? This information will be embedded in a flight plan but an individual data block on a controllers display is only so big. It is something that will need to be addressed, but I think people are dealing with it.”

There’s also a question of prioritization of messages because ATC and airline operations center (AOC) messages will be transmitted and received over the same data link.

“From a priority perspective, ATC messages need to take priority because there’s a latency associated with them,” said Ford. “If you have 10 AOC messages that get out in front of one ATC message what’s your scheme for making the ATC message first? Right now I’m not sure that’s been solved.”

The RTCA task force recommended a number of steps that would address the low-hanging fruit of data comm implementation. The first is for revised pre-departure clearances (PDC). Flight crews get their departure clearance at the gate but often get a revised clearance such as a departure runway change while still taxiing. The crew must then hand enter that information into the flight management computer, which takes time and can result in error. Being able to handle revised PDCs digitally will expedite departure.

Second is routine communications such as switching frequencies between sectors. Then there’s the Go Button, which is basically a reroute around weather that also must be punched into the flight management computer at the same time the airplane is being flown. Doing that digitally is quicker, more accurate and safer.

Another recommendation would address issues like top of descent. “It is a big deal today to do optimal profile descents and idle descents,” said Ford. “Being able to communicate your top of descent, when you want to pull back on your throttle and do idle descents will be more efficient with data comm.”

The final investment decision and contract award for the ground infrastructure of data comm is scheduled for the third quarter of 2011. Capabilities like revised PDCs will be taken up in the Terminal Datalink System contract. Top of descent and the Go Button will be addressed in the ERAM contract, scheduled for the 2014-2015 timeframe.

Graphic courtesy FAA

FAA says data communications will be deployed in two segments: Segment 1, including ATC towers and enroute centers, in the 2014 timeframe, and Segment 2, including TRACONS and full aircraft FMS integration, in the 2017-2018 timeframe.