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NextGen Data Comm Facilitates Digital DCL

The FAA’s ambitious Data Comm DCL rollout is running ahead of schedule and already realizing operational benefits. Avionics Magazine examines how phase 2 will bring the text-based system to en route communication from 2019.

A critical part of the FAA’s Next Generation Airspace Modernization (NextGen) initiative, the Data Communications (Data Comm) program, is currently making inroads toward its five-year plan of enabling initial Controller Pilot Data Link Communications (CPDLC) services.

Data Comm technology enables text-format Departure Clearance (DCL) and other communications between controllers and the cockpit through technology already available on many aircraft through Future Air Navigation System (FANS) avionics. The concept of controller-crew digital communication is not new — it has been common practice in oceanic airspace for many years — but its application in the airport environment for critical DCL procedures takes the concept a step further.

Working with Harris as a ground equipment supplier, the FAA has moved quickly on Data Comm, having begun development in earnest during 2013 and made its final investment decision in October 2014. In August 2015, a first Air Traffic Control (ATC) tower began offering DCL, eight months ahead of schedule, while 56 airports should have the system available by late 2016; 32 towers, including Ontario, were operational with Data Comm in April.

Both Memphis and Newark airports trialed the prototype system in a campaign successfully concluded during January this year, working with airlines including FedEx. The benefits of Data Comm DCL are many, but Josh Kendrick, the company’s managing director of flight technical, identifies two prime benefits.

“First and foremost, it’s safer,” Kendrick says. “Human errors in voice controller-pilot communications are well documented. Data Comm clearances are fully loadable into the flight management system, therefore eliminating those errors. Second, the controller is able to amend the clearance as volume or weather conditions change, thereby eliminating the voice bottleneck during these high workload conditions.”

Kendrick is enthusiastic about Data Comm and notes that FedEx Express has been working alongside the FAA to introduce Data Comm to the National Airspace System (NAS). “The first trials occurred at our Memphis and Newark hubs, and a FedEx employee has chaired the NextGen Advisory Committee Integration Workgroup (NIWG) on Data Comm,” Kendrick says. “FAA and industry commitments made through this activity have enabled the FAA to deploy surface Data Comm a full 20 months ahead of schedule.”

Aircraft Compatibility

A large proportion of the air transport and business aviation fleet are technologically ready for Data Comm because the aircraft already use FANS avionics. By April 1, 2016, the FAA listed 820 such aircraft, while an incentive program had bolstered FANS equipage by a further 722 planes. According to the FAA, the program hopes to see 1,900 aircraft equipped by 2019.

For FedEx, achieving compatibility was no problem. “FedEx Express has almost two decades of experience with FANS. Most of our fleet is either equipped with or provisioned for it, so the upgrade path was relatively straightforward,” Kendrick says.

UniLink UL-800/801 communications management unit.Photo courtesy of Universal Avionics.

Jim Ward, program manager for the advanced flight deck at Gulfstream reports that FANS/CPDLC avionics were already available for the majority of its aircraft, but, “the rollout of datalink clearances has had some wrinkles, indicating that the CPDLC implementations are not the same and the interface definition may leave too much room for variability. The ARINC and SITA networks act a little differently and there are variations between avionics suppliers. Any changes needed on the airplane side require certification, and this can be a lengthy and expensive process.”

Ward notes that Gulfstream’s operators are giving the company good feedback, allowing the company to work through issues with their avionics suppliers and Harris. “After a rocky start, it appears to be working reasonably well, although not perfect,” Ward says.

For operators of aircraft without FANS provision, several upgrade options exist, including the FANS 1/A+ solution from Universal Avionics, which includes the UniLink UL-800/801 Communications Management Unit (CMU) with integral FANS functionality.

“From the Sabre 65 to the Falcon 900B, our solutions are capable of meeting future mandates and providing additional capabilities including [Wide Area Augmentation System (WAAS) Localizer Performance with Vertical guidance (LPV)], synthetic vision and CPDLC DCL,” says Carey Miller, director of corporate programs and business development at Universal Avionics.

The system already meets future FAA requirements, but if these should change, Miller says software alone can satisfy future requirements. Universal has seen an increase in demand for FANS 1/A+ and its customers have already noted Data Comm benefits. “[Operators have] seen advantages where changing weather has required all departing aircraft to receive a new clearance via voice communication. With DCL, our customers receive the new routing, enter it into the Flight Management System (FMS), and go, while others are still in line waiting to receive and read back their new voice clearance.”

Data Comm is therefore fast becoming the new DCL standard throughout the United States and into Canada, but similar developments under Single European Sky ATM Research (SESAR) initiative in Europe are working through Link 2000+, which is not directly compatible with Data Comm. Miller is quick to allay concerns that transatlantic operators might need to install discrete avionics to cope with the two systems. “We’ve recently added ATN-B1 Link 2000+ software functionality to our UniLink system and it will be certified soon,” Miller says.

Connectivity and Security

The key enabler throughout the NextGen program, connectivity through ground stations, is easily provisioned, but also potentially vulnerable to hostile interference. Jo Kremsreiter, president of AirSatOne, which primarily provides Satcom services to business aircraft operators through the Inmarsat and Iridium networks, says “VHF communications (air-to-ground) for Data Comm are a safety concern because they are more susceptible to jamming and spoofing by bad actors than satellite communications, which are much more difficult to intercept and by nature more secure.”

Kremsreiter notes that in January 2015, the Government Accountability Office advised the FAA that significant security control weaknesses remained in the system, threatening its ability to ensure safe and uninterrupted operations. At the same time the GAO also reported that the FAA had not developed a cyber-security threat model.

“The FAA reported that it has taken steps to ensure Data Comm processes and procedures are secure. Since the FAA is the regulatory authority and will maintain the Data Comm network, AirSatOne will follow its lead. We have our own security procedures in place for our network, process and procedures. Our first rule for security is to not talk publicly about the security we’ve implemented and we encourage others to do the same,” Kremsreiter adds.

He also notes important differences in the operation of satcom and VHF datalink services, including Data Comm. “A satcom datalink delivers FANS 1/A, [Airborne Flight Information System] AFIS, [Aircraft Communications, Addressing and Reporting System] ACARS and Data Comm through a separate pipe to the cockpit and ATC messages are given priority over non-safety communications. Because the pipe is separate, usage by the cabin will not affect the bandwidth (or capacity) of the pipe supplying critical communications to the flight deck,” Kremsreiter says.

“But a VHF datalink is only used for cockpit communications. As an example, SwiftBroadband is currently being used for commercial operations with FANS 1/A and has proven to be fast and effective. But when the SwiftBroadband channel is being used for FANS 1/A it is dedicated to the flight deck and can’t be used by the cabin. It’s important to note that datalink uses very little bandwidth compared to internet activity,” he adds.

Looking forward to the full Data Comm rollout, Kremsreiter says the company already delivers FANS 1/A and/or datalink, which includes some components of Data Comm, including CPDLC. Since FANS 1/A already consist of ADS-C and CPDLC, the company forsees very few challenges, if any, delivering CPDLC for domestic Data Comm.

He also notes that as existing datalink customers who travel across the North Atlantic Track in FANS airspace quite regularly start using CPDLC for Data Comm over domestic US airspace, the company will see an estimated usage increase of approximately 900 percent or more. “Aircraft equipped with FANS 1/A also have VHF datalink, so over domestic airspace their aircraft’s data management unit will automatically switch to the FAA’s VHF air-to-ground network, so its capacity will have to be able to handle the increase. As Data Comm is implemented, the industry will see and need to be prepared for a dramatic increase in data usage,” Kremsreiter says.

FAA NextGen Data Communications air traffic control En Route simulators.Photo courtesy of the FAA.

En Route Services

Implementing DCL through FANS avionics is the first phase in the Data Comm program, followed from 2019 by initial en route services. Software is under development for the 20 en route continental U.S. air traffic control centers to enable flight critical Data Comm connections between their controllers and aircraft cockpits.

Heading and altitude changes, routing around weather and hazards and other operational and safety data will be passed accurately and quickly with many of the benefits already being realized in phase 1. Operators are realizing efficiencies through crews receiving complete, accurate departure data in a single transmission, automatically received, checked and confirmed through aircraft and ground systems for entry into the aircraft FMS at the push of a button.

Gone are the potential confusions of poor voice reception, language barriers and other issues that frequently require pilots to read transmissions back several times until they are perfect. These same benefits will apply to en route communications, which will also include sign-off calls between pilots passing from a controller in one airspace sector to a controller in the next.

Looking at aircraft equipage, operators with FANS avionics installed are already capable of CPDLC and therefore ready for Data Comm phase 2, while AirSatOne’s Kremsreiter notes another benefit of its use for en route communication. “CPDLC requires less capacity than voice communications. As an example everyone should be familiar with, a cell phone voice call takes more bandwidth than a simple text message. When a cell phone has a weak signal, resulting in less bandwidth, a voice call can’t be made, whereas a text message can still be sent,” says Kremsreiter.

Text messaging is the essence of how Data Comm links controller and pilot. The controller enters the DCL or, from 2019, en route message, into a computer and chooses when to transmit it to the aircraft. The pilot confirms receipt digitally before entering the data into the FMS for action. Thus the message becomes flight critical, enhancing safety through its simplicity, but potentially open to scrutiny in the event of a mishap. For this reason, Kremsreiter cautions that operators will need to equip their aircraft with a Cockpit Voice Recorder (CVR) that stores not only voice, but also text messages between controller and pilot. AVS