ATM Modernization

Miami ARTCC: Ground Zero for CPDLC

By David Jensen | July 1, 2003
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All eyes in the U.S. data link community are directed toward the Miami air route traffic control center (ARTCC), where Build 1 of the Federal Aviation Administration’s (FAA’s) controller pilot data link communications (CPDLC) program has been ongoing since October 2002. The center is fully equipped for CPDLC and its about 300 air traffic personnel, including 279 controllers, have been trained for data link communications.

And, it appears, all eyes will remain on Miami for some time to come, as the FAA’s Joint Resource Council (JRC) announced in late May it will defer plans for CPDLC Build 1A, which would have expanded the capability to seven additional ARTCCs, in Houston, Fort Worth, Memphis, Atlanta, Indianapolis, Cleveland and Jacksonville, Fla.

"FAA won’t abandon data link," Anthony Willet, chief of staff, Free Flight, insists. "We will continue the program in Miami. But our initial plan to deploy data link nationwide was interrupted by the economic turmoil facing the aviation industry since 9/11."

FAA officials have told Avionics Magazine that operating costs–for example the expense of training controllers–also was a factor in the JRC decision. And industry officials add that FAA has had to establish spending priorities and is shelving Build 1A to place full emphasis on the En Route Automation Modernization (ERAM) program. ERAM involves installing new National Airspace System (NAS) software in the ARTCCs’ host computers to support NAS Architecture 4.0, Free Flight, information security requirements, and other capabilities, including CPDLC.

The JRC decision was a disappointment to the airlines that participate, or plan to participate, in FAA’s CPDLC program. American Airlines, the CPDLC program’s launch carrier, and several other operators have invested in data link technology at a time when investment dollars are precious and few.

The decision was a blow to ARINC Inc., as well. It has been establishing a nationwide VHF data link Mode 2 (VDL-2) ground infrastructure to support CPDLC. "Our plans are changed as a result of the decision," says John Burks, ARINC’s program director for CPDLC. He explains that VDL-2 is a "shared network" for airline operations center (AOC) communications–replacing the analog aircraft communications addressing and reporting system (ACARS)–and for ATC communications. "We no longer will be able to sell the service for ATC [outside of the Miami region], and this will be a loss from a major investment."

Clearly disappointed in the JRC decision, some participants in CPDLC Build 1 "are talking in Washington to encourage a more robust program," says one airline official. "I’m not yet aware of active operators [in CPDLC] folding their tents." Burks adds that program participants hope Build 1A "can be redefined."

Positive results from Build 1 no doubt bolster the participants’ resolve. CPDLC is demonstrating it can do what it was meant to do: reduce air traffic controller workload and voice communication congestion. A study of Build 1 activity by the Mitre Center for Advanced Aviation System Development (CAASD) shows that an estimated 700 minutes of voice channel time was saved by 4,217 data link transactions performed from October 2002, when CPDLC entered initial daily use (IDU) as a fully certified system, to March 2003. (See Build 1 stats at

The time for data link message delivery averaged 1.5 seconds, according to Tim Hancock, FAA’s CPDLC operations and integration lead, with AUA-200. The reliability and quickness of the data transfer "amazed us in Miami," adds Mark Palazzo, the Miami center’s manager of operations. "When the controller hits the button to send the message to the cockpit, it’s almost instantaneous." Under the program pilots only give acknowledgments to uplinked messages from controllers, and the controllers send no aircraft movement directives via data link.

Growing Acceptance

So far, the benefits and controller acceptance of CPDLC at Miami have been largely anecdotal. "The equipage loads are not high enough to calculate controller workload reduction," says Hancock. Still, initial response has been quite positive. "We have seen increased usage of data link communications as the months have gone on and as controllers become more comfortable and proficient in its use," says Palazzo. "It is particularly embraced by the younger controllers, who know they’re going to be using CPDLC in the years ahead."

Comments regarding CPDLC from American pilots are largely positive, as well, although pilot viewpoints "run the gamut," admits Frank Cheshire, data link project coordinator for the airline. "You have pilots who are excited about this technology and those who thought it would reduce the workload more."

One pilot complaint "is a function of the boundary problem," says Cheshire, who also is a consultant and retired American Airline captain. "In certain regions, you now fly in and out of CPDLC coverage, and that can be a bit problematic," he explains. Even with the scaled-back version of Build 1A–it previously was to have all 20 ARTCCs participate–this problem would have been partially resolved.

Despite the program setback, American remains committed to CPDLC. It has decided to equip six more Boeing 767s–on top of the current 12 B757s and seven B767s–with the Rockwell Collins CMU-900 communications management unit and VHF-920 transceiver used for data link communications by August 2003.

The CIT Team

American, Collins, ARINC and the Miami ARTCC are principal members of the CPDLC integration team (CIT). Other key participants include the Air Line Pilots Association (ALPA), National Air Traffic Controllers Association (NATCA), Professional Airways Systems Specialists (PASS), and the U.S. Air Force (which flies a CPDLC-equipped Lear C-21A), as well as Delta Air Lines and Continental Airlines, which are preparing to participate in the program. CIT meetings are held monthly, normally at FAA’s Free Flight Office in Washington, D.C. "That’s the main forum to bring all the [CPDLC] stakeholders together," says Willett.

Willett believes the CIT team has been instrumental in CPDLC’s successful implementation in Miami and in tracking and resolving problems during the program’s ramp-up. "The FAA’s approach to deploying equipment over the years has been for us to watch the surprised look of controllers as the truck backs up to the loading dock with new equipment, which they see for the first time," he says. "But with the Free Flight approach, the users are involved from the get-go. There were no surprises."

"The unions nationally and at the Miami center were intimately involved in every aspect of our risk mitigation meetings in the CIT, as well as during the shaking out and design of the system at our Tech Center as far back as 2000," says Hancock. "That’s when we were sending union officials, as well as our operational controllers, up to Atlantic City [home of the FAA Technical Center] to work with the equipment and make suggestions on how to improve the hardware and software, especially with regard to human factors." In fact, representatives of NATCA and PASS have offices in the Free Flight Office.

"We also track action items as a team," he adds. The CIT team collaborates to resolve CPDLC problems, which Willett and Hancock agree have only been "nits" so far. "We’ve resolved every problem that has been laid on the table," says Willett.

The Free Flight chief of staff heaps praise on the Miami center staff. "They have an energetic, can-do workforce," says Willett. In addition to CPDLC, the Miami ARTCC has the traffic management advisor (TMA–a tool to assist controllers in developing arrival sequence plans for airports) and will have URET (user request evaluation tool) within the next few years. These other new technologies are part of the FAA’s modernization plan.


To prepare for CPDLC’s IDU, a national "training cadre" went to Miami to train the ARTCC instructors, who in turn trained the Miami controllers, according to Hancock. Each controller took a four-day air traffic (AT) training course, which included a "three-pronged approach," consisting of classroom lecture, computer-based instruction (CBI), and dynamic simulation in the Miami ARTCC’s training lab, where the hardware is identical to that used in the control room. Because of limitations in the size of the center’s classroom and simulation lab, only 12 to 15 controllers could be trained at once, so the Miami center held training sessions in two shifts, seven days a week.

Meanwhile, the facilities personnel who maintain the hardware and software took a six-day AT course in preparation for CPDLC operations. "Included in that course was human factors training at the Tech Center," says Palazzo. It also consists of software troubleshooting and hardware removal and replacement. The CPDLC program required no staff increase at the Miami center.

CPDLC training for the Miami ARTCC’s controllers and facilities personnel began in June 2001 but was interrupted during the winter months, when air traffic in Florida and the Caribbean increases significantly, and maximum manpower is required. The instruction continued in June 2002 and proceeded until the entire Miami staff was trained, in September 2002, a month prior to the IDU.

Pilot training at American was less time consuming, as the CPDLC operations in Miami entail no pilot-initiated, down-linked messaging–just acknowledgments. "Logging on to the system is the main challenge for the pilots," says Brent Blackwell, a B767 captain and American’s managing director-operations engineering.

Cheshire adds that much more pilot training was required for Europe’s PETAL (Preliminary Eurocontrol Test of Air/ ground data Link) trials, which American participated in two years ago. This was because pilots communicating via data link to the Maastricht upper area control center were to both downlink requests and receive uplinked directives involving aircraft movement, such as heading, altitude and minor route changes, he explains. Of course, while both projects were established to advance CPDLC, PETAL was a trials program, while FAA’s CPDLC is an operational program. The American pilots train for the U.S. program by using an interactive computer-based module and reading a reference training bulletin, to learn details on how the system works.

Message Sets

FAA’s Free Flight Office has taken a cautious approach toward CPDLC. Build 1 has controllers using just four message sets:

  • Initial contact, when a pilot checks in via CPDLC with a new controller and downlinks the aircraft’s assigned level–referred to as a "monitor/CAL" (confirmed assigned level);

  • Transfer of communications, when a controller instructs the pilot to change frequencies for communications with the next controller;

  • Altimeter service, in which the controller can manually or automatically uplink the current altimeter; and

  • Menu text, used to send advisory messages to pilots.

Most messages so far have involved initial contact, according to the Mitre CAASD study.

The control center supervisor holds the sole responsibility for the menu text function. "The lesson we learned from the FANS [future air navigation system] program is that we don’t want controllers sitting there and typing out messages," says Hancock. Without standardization in the use of words, phrases and abbreviations, communications could confuse pilots, he adds.

Menu text messages are advisory only, including phrases such as "check stuck mic" or "anticipate holding." Adding another example of a menu text message, Palazzo says, "In our Caribbean sectors–because we hand off to non-radar facilities–and in those sectors controlling aircraft over the Atlantic, we will build a message to [have pilots] contact aeronautical radio on a high frequency, and then we provide the frequency."

"We’re working with American pilots to see which menu text messages they find beneficial," says Hancock. "The goal is to expand the menu text function."

Where the Message Goes

Using standardized nomenclature, the supervisor composes free text messages–assignments to individual sector workstations–and sends them to the data link applications processor (DLAP), which interfaces with the Miami ARTCC’s host computer. Often called "the brains" for CPDLC, the DLAP provides database management, data recording, menu building and the user interface. It delivers the supervisor’s message via the NAS local area network to the host interface devices (HIDs), a digital two-way gateway to the host computer, which then feeds the message to the appropriate workstations. (The Miami ARTCC has 32 workstations.)

The system also includes a DLAP printer, which the supervisor can use to print the menu text messages for availability to a new shift of controllers, as part of a "prebriefing."

The message sent by a controller to the cockpit enters the national airspace data information network (NADIN), the pipeline to the NAS air-to-ground router, which directs the message to the VDL-2 ground station for transmission to the aircraft’s digital radio, then to the CMU–and all in about 1.5 seconds.

Pilots log into the CPDLC system via the context management application (CMA) processor, also located near the Miami center’s host computer. "It’s the processor that maintains the aircraft IDs that are logged in," Palazzo explains.

A synopsis of the uplinked menu text message, the pilot’s acknowledgment, the aircraft’s altitude, and the fact that the aircraft is logged into the CPDLC system appear in a window on the controller’s DSR (display system replacement) screen. "The system normally shows a very abbreviated version of the message," says Hancock. "We don’t want to make the controller’s scope too cluttered with text."

VDL-2 Ground Stations

VDL-2 coverage blankets the 500,000 square miles (1.3 million square kilometers) of airspace controlled by the Miami center, which is the seventh-busiest ARTCC (out of 20) in the United States. The center, located about a mile from Miami International Airport, logs an average of 2.3 million traffic operations annually; a peak day can see more than 8,000 operations. "We control the lower and upper airspace, as well as provide approach control services for Vero Beach and Fort Pearce [Florida]," says Palazzo.

For the data link operations, ARINC has installed 13 VDL-2 ground stations in Florida and on the Caribbean islands of Freeport, San Salvador and Grand Turk. "A couple of the installations represent upgrades," according to Burks. He adds that several ground stations are equipped with high-gain antennas, to boost the transmission range to 250 miles at 30,000 feet from the normal 200 miles.

ARINC began installing VDL-2 ground stations for CPDLC Build 1 in January 2002 and has been installing stations across the country. "We have 110 VDL ground stations in the U.S. now," Burks told Avionics Magazine in early May. "And we’re adding more ground stations each month. Our plan is to have 160 of them in operation by the end of this year."

ATN Compatibility

Currently, the 13 ground stations serving the Miami ARTCC are unique in that they alone are compatible with the Aeronautical Telecommunications Network (ATN) and are thus linked by the ICAO-specified protocol established for airspace system-wide communications. "We’re in the process of testing our final software load to install ATN in all [VDL-2] ground stations, and that will be done this year," Burks states.

"The reason all ground stations will be ATN-compatible is that we anticipated Build 1A would start this year," he adds, referring to the original plan of having nationwide CPDLC coverage. That goal now appears to be a long way away.

Aircraft Equipage for CPDLC

Despite FAA’s decision to defer CPDLC Build 1A, the number of aircraft being equipped for CPDLC is growing. American Airlines plans to have a total of 25 aircraft, B757s and B767s, equipped by August.

However, American has turned its sights on Eurocontrol’s operational CPDLC program, called Link 2000+. "Thirteen of our 767-300ERs will be equipped for data link and will be used on routes to Europe," says Frank Cheshire, American’s data link project coordinator. "We expect to resume data link services in Europe in the fall." (American participated in Eurocontrol’s PETAL [Preliminary Eurocontrol Test of Air/ground data Link] trials, which preceded Link 2000+.)

Other carriers are forging ahead with data link equipage for domestic routes. For example, Continental Airlines was to have had four of its B757-300s equipped for CPDLC in May. Boeing factory-installed the Rockwell Collins CMU-900 (pictured, right) in the Continental aircraft, and Timco was to have upgraded the communications management unit for ATN/CPDLC certification. Collins will hold the supplemental type certificate for the software upgrade, according to Frank Longo, a B777 captain, instructor pilot and Continental’s manager of advanced communications development. "Those four aircraft will be dedicated to Newark-to-Florida flights between November and April," says Longo. "We’re putting the finishing touches on our training package [for CPDLC]. We expect FAA approval of the package in 45 days," he told Avionics Magazine in mid-April.

Meanwhile, Delta Air Lines plans to equip four of its B767-400s for CPDLC, but not with Collins gear. Rather, the carrier has an arrangement with Teledyne Controls, which has developed an ATN router and CPDLC message set to upgrade its ARINC 758 CMU, already installed on Delta planes. Teledyne also provides the accompanying Thales VHF data link radio.

"We’re proceeding as planned," says Kent Horton, Delta’s general manager, avionics engineering. "We’ll begin flight testing in July, and by this fall, we will go operational with the system, assuming we pass all testing." Delta’s pilot training program for CPDLC is in the "final review process," says Horton, adding that, "more than training, it really is a familiarization process."

FedEx, too, is preparing to participate in the CPDLC program. The European Aeronautic Defense & Space Co. (EADS) is fitting the Collins package on Airbus 300s as part of a cargo conversion. FedEx plans to have the first A300 certified for CPDLC by this summer, according to Emil Hurtak, FedEx’s manager of avionics and electrical engineering. Seven more A300s are to be equipped by the end of 2003, as part of the overnight delivery service’s "initial" plan for CPDLC. "We probably will expand the program next year and proceed by equipping A310s for CPDLC," Hurtak says. FedEx is proceeding despite FAA’s recent suspension of the Build 1A because, he adds, "We feel this will give us experience with data link, and we’re still hopeful that pressure can be applied to the FAA to add message sets or somehow expand the program."

Upgrading CPDLC Software

The software for the airborne suite for CPDLC is certified to DO-178, Level D, which is quite adequate for operations in the FAA’s CPDLC program, based at the Miami ARTCC. Pilots in the program only acknowledge uplinked controller messages, and these involve no aircraft movement directives. Likewise Level D software was adequate for the Preliminary Eurocontrol Test of Air/ground data Link (PETAL) trials because all data link messages were verified by voice communications.

But to gain added efficiency from CPDLC–providing pilot-controller communications involving aircraft movement, with no need for an audio backup–the software must be upgraded to DO-178, Level C. Both Teledyne Controls and Rockwell Collins say they are prepared for such an upgrade to their communications management units.

"We have the traceability and documentation [for Level C approval]," says Jim Grace, Collins’ data link program manager for air transport. "What we need now is statement coverage analysis, which requires testing to ensure that all statements have been executed by a processor without adverse reaction."

Matthew Wing, Teledyne Controls’ marketing director-communications and cabin products, gives a similar report. "It will be certified to Level D, but the software for our CMU has been written to the Level C requirement," he says.

The date at which DO-178, Level C, software will be required for CPDLC seems to be a "moving target," says Wing. "It may be in 2005," adds Grace.

"Originally, Level C was to be introduced with [FAA’s] Build 1A program," says Wing. "Now it appears it may be with [Eurocontrol’s] Link 2000+ program."

Link 2000+ started in 2001, using Level D software. "We’d like Level C software as soon as possible," says program manager Alex Wandels, "but the avionics manufacturers seem to be cautious, and they are not convinced that the market is sufficient to invest in Level C–and I don’t blame them."

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