Editor's Note

TCPDLC: Transitioning to Controller Pilot Data Link Communications

By by Woodrow Bellamy III | December 1, 2014
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The global air transportation industry is in the process of slowly transitioning to Controller to Pilot Data Link Communications (CPDLC) to help alleviate the increasingly congested voice communications between pilots and controllers that the industry has relied on over the last 40 years. That’s not to say text messages between controllers and pilot’s via Flight Management Systems (FMS) will completely replace voice communications, but the partial transition needs to occur in order to accommodate for the up-tick in air traffic, which is expected to increase by 5 percent annually over the next two decades.

CPDLC is happening everywhere. In Europe, the European Commission is mandating CPDLC avionics equipage for aircraft flying above 28,000 feet under its Single European Sky (SES) program. In the United States, FedEx and American Airlines, among other operators, are trialing the data link communication capability at Newark and Memphis International Airports under the NextGen program. In Canada, the country’s Air Navigation Service Provider (ANSP), Nav Canada, announced in the summer of 2014 that it had completed nationwide implementation of CPDLC technology at Area Control Centers (ACC). And on the North Atlantic Tracks, that busy stretch of airspace over the Atlantic Ocean between northeastern North America and western Europe, the North Atlantic Systems Planning Group also has a three-part plan to start requiring aircraft to equip with CPDLC avionics to fly the most optimal routes.

However, as with any new rollout of technology in any industry, there are challenges. These include technical difficulties for Air Traffic Management (ATM) to ensure proper functioning of the infrastructure that allows controllers to receive and exchange pre-defined CPDLC messages, and, of course, challenges on the user side with equipage costs and pilot training for the new technology.

Single European Sky Mandate

Data link communications between pilots and controllers in Europe are necessary, and considered by the European Commission to be a fundamental building block of the future implementation of SES functionalities. For example, it is considered a prerequisite for the deployment of i4D — the use of the fourth dimension of time in aircraft flight path trajectory management by controllers. That is why, in 2011, Europe mandated forward-fit CPDLC avionics equipage on all new production aircraft flying in European airspace above 28,500 feet. At that time, it was also originally decided that the second phase of that mandate would come into effect in February 2015, requiring legacy aircraft flying in European airspace to be retrofitted with CPDLC avionics. However, a number of unforeseen technical and economic challenges have forced the European Commission to discuss the now more likely possibility of delaying that mandate by five years. The delay is the result of an investigation into the use of CPDLC in European airspace by the European Aviation Safety Agency (EASA), which concluded that only 40 percent of operators would be ready to use the technology by February 2015, and that only about 70 percent of the necessary ground infrastructure to facilitate data link communications between controllers and pilots would be ready to use by then as well, according to the European Regions Airline Association (ERAA).

During an SES committee meeting in October 2014, the majority of aviation stakeholders present agreed that it would be in the best interest of the aviation community to delay the mandate by five years, according to Gzim Ocakoglu, a policy officer for the European Commission’s Single European Sky unit. “We have a draft of some text and we’re going through the usual legal procedures to have it adopted. We’re discussing the basically putting into this amending regulation, which would be to basically postpone or suspend the regulations for five years compared to the original adoption and date of February 2015. The motivation is that we’re now in a period of uncertainty with all of the identifications of those issues by the EASA investigation,” he says.

Regarding operator equipage, some of the challenges are both technical and monetary. To comply with the retrofit mandate, aircraft need to be equipped with either a Future Aircraft Navigation System (FANS) 1/A or a router, antenna, CPDLC messaging interface and device, alerting system, a recording system and a VHF Data Link (VDL) Mode 2 radio. Aircraft that are equipped with FANS systems are exempt from the mandate, says Craig Peterson, director of air transport avionics marketing at Rockwell Collins, who also discussed some of the challenges facing the European program.

“There was a pioneer phase of CPDLC where a certain number of pre-deployments and pre-equipages were undertaken and those there were discoveries made, and there were evolutions made, and they went pretty well. But when mass deployment became the phase of the program, there were some challenges that were encountered around frequency congestion. You might imagine as you change an infrastructure from [Very High Frequency] VHF voice to a VHF digital, and you get more and more equipped users in the airspace, there became a density and/or frequency congestion challenge that became somewhat of an unanticipated consequence, there were provider aborts, radios and equipment and routers and other things that did not behave in the environment as they were anticipated to behave,” Peterson says, noting that the economic climate in Europe presented some challenges as well. “There are still some regions in Europe where the ground infrastructure and the controller infrastructure are not yet deployed and are not yet in place and face significant fiscal and government policy issues because of the economic situation there in recent years.”

Despite the economic and technical challenges though, the aviation community in Europe definitely wants to see the ground infrastructure implemented, allowing airlines and operators to eventually take advantage of the benefits the CPDLC can bring to airspace efficiency in Europe.

“Voice communications channels are becoming progressively congested and should be supplemented by air-ground data link communications. Data link services can enable the provision of additional air traffic control capacity. These services should be introduced in a coordinated manner to optimize the potential benefits arising from them,” says Ocakoglu.

CPDLC Equipage and Benefits

Here’s what a pilot will see on the cockpit display when using Controller Pilot Data Link Communications (CPDLC) for a revised route clearance. Photo courtesy of NATCA.

Avionics manufacturers, system integrators and installers can expect to see a continued steady increase in demand for CPDLC technology over the next five to six years, especially as the ground infrastructure implementation continues in Europe and the United States. Under the FAA’s DataComm trials at Memphis and Newark airports, for example, operators that are trialing the technology report they are starting to see the benefits. American Airlines has partnered with Harris to equip 220 of its Boeing 737-800 aircraft in anticipation of future benefits from the NextGen DataComm program, according to Brian Will, director of airspace optimization and aircraft technologies at American Airlines.

“I think CPDLC has the potential to reduce delays. The FAA Data Comm program in the U.S. is moving forward to enable aircraft to receive amended ATC clearances — something we cannot do today except by voice radio. When multiple aircraft have to be re-cleared, for instance, for weather avoidance, the radio frequency becomes saturated and delays result. Revised departure clearance via DataComm will avoid these delays. This capability is being trialed in Memphis and Newark and appears to be successful,” says Will.

On the avionics side, companies such as Universal Avionics have introduced new products specifically designed to provide CPDLC functionality. At NBAA 2014, Universal unveiled its new Insight Integrated flight deck, which is expected to receive Supplemental Type Certification (STC) on the Cessna Citation VII by the second quarter of 2015.

“We are still seeing a demand in preparation for what is anticipated here in the U.S. for the future, which is FANS in domestic airspace. The demand is related to our UniLink UL-800/801 Communications Management Unit (CMU),” says Robert Clare, director of technical sales at Universal Avionics. He notes that the Insight flight deck supports integration with the company’s UL-800/801 CMU and FANS, and that “by 2015, aircraft that would normally fly a route across the Atlantic might not be allowed to transition through the North Atlantic Track System if they are not equipped for FANS.”

Clare says another benefit is reduced separation between aircraft. “In non-FANS procedural aircraft separation, errors in navigation and errors in voice communication are considered when determining the necessary airspace separation between aircraft,” he adds. Some companies are also specifically targeting legacy aircraft that will continue flying for airlines over the next 5 to 10 years, such as legacy Boeing 737s, which is the best selling commercial airliner in aviation history. Exton, Pa.-based avionics manufacturer Innovative Solutions & Support (IS&S), recently received a Supplemental Type Certificate for its NextGen flight deck upgrade for Boeing 737 classic series aircraft, which supports CPDLC functionality.

“This is one of the most successful aircraft series in commercial aviation history, both in terms of the number of aircraft delivered and the number remaining in service, many of which still carry the original flight deck equipment. These airframes have 15 to 20 years of useful life remaining, and with the increasing airline emphasis on adding aircraft with passenger capacity of around 100 seats servicing shorter routes, B737 Classics will in many cases replace smaller regional aircraft,” says Forrest Colliver, vice president of NextGen programs at Innovative Solutions & Support (IS&S). “The benefits we see in the integration of DataComm into the NextGen flight deck accrue primarily from two sources: the overall reduction in readback/hearback errors, which are difficult to eliminate in the current voice communication environment, and the transfer of DataComm and ADS-B message content directly to and from key flight deck avionics systems, such as the Flight Management System (FMS) and forward field of view primary display systems.”

The transition to CPDLC is happening, slowly but surely. Will data link communications ever fully replace voice communications between air traffic controllers and pilots? Probably not. But the implementation of ground infrastructure of CPDLC technology and airborne equipage with CPDLC avionics will allow the global aviation community to continue to obtain data about the most effective usage of the functionality and open up more possibilities to continue to accommodate for future increases in global air traffic.

“If you have 10 aircraft in a certain airspace and they all have to talk on the same frequency, the voice chatter can get pretty dense. If you can utilize this technology to lessen the amount of voice congestion and frequency congestion in an airspace, you can do a bunch of things,” says Peterson. “You can lessen pilot workload, you can lessen controller workload you can potentially increase that airspace throughput. You can also potentially create some cognitive understanding benefits. Not everyone has English as a first language and if you get into sets of communication platforms that have consistency that have commonality you can gain from comprehension benefits in the airspace from its deployment because the pilot will become familiar with that message, its intent, its requirement and instead of mishearing or misstating their intentions or commands, that can create some understanding and safety types of benefits for the airspace.”

Woodrow Bellamy IIIis the community editor for Avionics Magazine.

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