Clearing The Air: CPDLC

Clearing The Air: CPDLC

  • October
  • 02
  • 2023
  • Advanced Aircrew Academy

The Federal Aviation Administration (FAA) recently announced a plan to restore enroute domestic Controller-Pilot Data Link Communications (CPDLC) back to full availability and broaden the participation to allow additional business aircraft to use the system.

Approximately one thousand business aviation aircraft were previously in a trial program that allowed them to use enroute CPDLC communications, but the trials were closed last October to new entrants because of the disagreement on what constitutes acceptable performance criteria.

The CPDLC program is not currently allowing any General Aviation (GA) aircraft to use enroute services unless they were part of the "US Domestic En Route CPDLC Avionics Trial." If any of the aircraft in the trail were sold, they were forced to drop out of the trial. But there is now a plan for business aviation operators, who have aircraft that are properly equipped, to permanently use this system and to allow new participants to join. With this announcement comes a new conversation about the use of this technology.

CPDLC – Another Acronym

For those who have not yet been introduced, CPDLC is like text messaging. Its segments include non-urgent clearances for departure, domestic enroute, and international enroute. It is a generic term for data link communications between pilots and air traffic controllers.

You may also hear data link referred to as Performance Based Communication and Surveillance (PBCS), Future Air Navigation System (FANS) 1/A which, in addition to CPDLC, includes Automatic Dependent Surveillance–Contract (ADS-C). The messages are predefined (canned clearances and responses) but there is also a "free text" capability to exchange information that does not conform to the defined formats.

This two-way texting / digital communication system allows air traffic controllers and pilots to exchange digital messages, which eliminates time on the voice frequencies. It also allows pilots to go back and recheck the details of a clearance.

Communication Errors

Communication errors to and from the flight deck are caused by a variety of factors including quality of the audio signal, pilot workload, accents, English as a second language, nonstandard phraseology, stuck microphones, and stepping on each other's radio calls. The results are misinterpretations, readback errors, and misunderstandings. With air traffic back to pre-pandemic levels and projections indicating air traffic to continue to increase [according to the International Air Transport Association (IATA)], while the labor force is pushed to its limits, the aviation industry is taking a closer look at what can be done to prevent communication errors.

Each incident of a communication error also has unique variables of aircraft, pilot training, and experience level, but if you pull back the layers, they all come down to broken communication and misunderstanding of clearances. The goal of aviation training is to prevent accidents, but the first step beyond current training philosophy is to acknowledge that pilots will make communication mistakes. To offset a singular mistake, there must be numerous layers of correcting that error. If miscommunication continues to be a root cause, then what else can the aviation industry do to streamline transmissions? CPDLC is just one answer, but it might just be the foundation for building a better Pilot-Controller communication system.

Streamlining Communication

CPDLC is currently being used for departure clearances (-DCL) and enroute (domestic and oceanic) non-urgent messages to aircraft. Each time this platform is used, it eliminates some traditional radio conversations. This can increase ATC efficiency, reduce possible errors (especially when there are language barriers), reduce the VHF frequencies being "blocked" by simultaneous transmissions, and allow numerous communications at the same time.

One of the best uses of -DCL is when ATC has a change that they need to convey to several aircraft due to a shift of weather conditions and/or reroute requirements. Rather than contacting every aircraft and tying up the frequency, the controller can send a new route to each aircraft. This is especially beneficial if aircraft are in line waiting for takeoff with engines running. While it is just the beginning of this technology's use, if this method is refined and proven, it could be expanded—which might provide a higher safety margin and reduce communication errors.

Those who were in the trial previously will be grandfathered in and are not expected to have to make any equipment changes. Now that the ban is being lifted to allow more aircraft to participate, operators need to be aware of the new levels of demonstrated acceptable CPDLC performance.

GREEN = Aircraft with avionics that have demonstrated acceptable performance

YELLOW = All new entrants will enter at the "yellow" level until avionics have completed interoperability and route load ability testing. You must finish the minimum number of enroute transactions to demonstrate acceptable performance to move out of yellow. Or you could move from green to yellow if the avionics have identified a non-safety of flight performance issue, but you're still allowed to continue participating pending a permanent fix.

RED = Aircraft with critical CPDLC-related avionics issues and/or unacceptable air-to-ground enroute performance; however, you may still be allowed to participate in the datalink clearance program.

Aircraft And Pilots Need Approval

Above all else, both the aircraft and flight crews need to be approved to use it. Advanced Aircrew Academy's CPDLC/PBCS module is designed to meet the training requirements for Ops Spec A056 on Data Link Communications. If you operate Part 91, our module is designed to meet the training requirements for Letter of Authorization (LOA) A056 on Data Link Communications.

The module complies with the International Standard for Business Aircraft Operations (IS-BAO) training requirement for CPDLC defined in Chapter 13 of IS-BAO. The Business Aviation Safety Consortium (BASC) standard requires training when LOAs are issued for international operations.

We can also customize the content based on your operating procedures. Module content includes the following:

  • ADS-C
  • ADS-C and CPDLC
  • AOC Messages
  • Connecting with ATS
  • CPDLC Departure Clearance (DCL)
  • CPDLC Departure Clearance (DCL) and Performance Based Communication and Surveillance (PBCS)
  • CPDLC Messages
  • Emergency
  • Europe-Specific Procedures
  • Federal Aviation Administration (FAA) Advisory Circular 90-117 - Data Link Communications
  • Flight Planning
  • Human Factors - ASRS reports by pilots with lessons leaned on how to prevent errors
  • ICAO Doc 10037 Global Operational Data Link Document (GOLD)
  • ICAO Doc 9869 Performance-based Communication and Surveillance (PBCS) Manual
  • Oceanic, NATHLA, and Class II Airspace
  • Pacific-Specific Procedures

For discounted package pricing, email or purchase the module online here.


FAA CPDLC Avionics Trial

Procedures for Issuing Automated Clearances