MITRE/CAASD staffers Alfreda Gipson (l) and Gary O'Malley view CPDLC displays at the William J. Hughes FAA Technical Center, Atlantic City, NJ.

Air traffic controllers and pilots will communicate less by two-way radio and more by digital messaging in the future. A new service, called Controller-Pilot Data Link Communications (CPDLC), uses new technologies and procedures to provide digital messaging for non-urgent communication. The Federal Aviation Administration (FAA) anticipates that CPDLC will improve air safety and controller productivity in busy sectors of the national airspace.

Currently, controller-pilot communication is by voice radio. In busy areas in which controllers handle many aircraft, the "party line" nature of voice radio can limit the ability to communicate. For example, pilots may key their microphones and accidentally "step on" the communications of other pilots or a controller. Or there may be "read-back" and "hear-back" errors, overlapping or simultaneous transmissions. With CPDLC, messages are digitally displayed on a computer screen in the cockpit instead of heard through headphones. Shifting routine transmissions from voice to data link eliminates many transmission problems and significantly improves the communication path between pilots and controllers.

An initial version of CPDLC, which automates the delivery of an initial set of routine messages, was put into daily use by controllers at the Miami Air Route Traffic Control Center on October 7, 2002. While its use has been limited by the number of equipped aircraft, the outcome thus far has been very favorable. American Airlines is the first airline to use this version of CPDLC, equipping 25 aircraft operating in the Miami Center airspace. The U.S. Air Force has added one aircraft to the operation. In addition, Delta, Continental, and Fed Ex have made commitments to join the operation in the near future. CPDLC builds upon a concept already used by airlines to communicate with their flight crews. The air-ground digital radio network and some of the avionics used by CPDLC today were originally developed to support the airlines' operational communications. And the communication mechanism and message formats have been standardized internationally for the air traffic control version of this service so that CPDLC can be used worldwide.

Cumulative minutes saved (right axis) is shown over 12 months using CPDLC. The amount of voice channel time saved represents additional time controllers can be focusing on other tasks that improve service to the air space user.

MITRE's Center for Advanced Aviation Systems Development (CAASD) worked with the FAA, American Airlines, Rockwell Collins Inc., ARINC Inc., and the Computer Sciences Corporation to develop and implement CPDLC. CAASD has a long history of work in data links, laying the groundwork for this initiative. Over the years, we've developed integrated, end-to-end data link solutions across government agencies, service providers, and the aviation community. We were integral in helping to define international standards, as well as domestic U.S. procedures and requirements for the ground systems and aircraft avionics to meet those standards. These efforts required a range of knowledge and experience, from systems engineering to operational expertise in Very High Frequency Digital Link Mode-2 technology, software certification expertise, and controller and pilot operations and procedures.

"While we are proud of what we've accomplished so far, Miami is just the first step," says Ed Hahn, a CAASD associate program manager responsible for our current work on CPDLC. "We're working very actively with the FAA and industry to develop a joint roadmap for the future enhancement of the initial CPDLC capabilities. It provides the foundation for a future, higher-precision Air Traffic Management System."

CAASD used resources from across the corporation for this work, including expertise in quality assurance and validation from MITRE's Software Engineering Center. For planning beyond the initial installation, CAASD brought in MITRE's Center for Acquisition and System Analysis to conduct risk and investment analysis to assess FAA and industry plans. We also coordinated with the St. Louis Operations in the Air Force Center to ensure military compatibility with the system.

The Miami Center's implementation of CPDLC has enabled the FAA and the aviation community to validate procedures and resolve technical integration issues between ground-based and aircraft-based system elements. We expect that the Miami controllers and participating airlines will begin to see the benefits of CPDLC as more airlines equip more airplanes for this service.

Current services provided by CPDLC include:

• Communications Transfer: Controllers "hand off" aircraft as they move from sector to sector throughout the system.
• Initial Contact/Confirm Assigned Altitude: Pilots "check in" when they enter a new sector with the current cleared altitude. Controllers then verify the reported altitude is the same as the assigned altitude.
• Altimeter Settings:Controllers uplink barometric pressure information.
• Menu Text: Controllers and pilots exchange preformatted text messages, for example, routine information associated with standard procedural instructions.

—by David Van Cleave

Page last updated: September 21, 2004 | Top of page