Story ID: 045
Getting To Yes on CPDLC
By: David Hughes
Caption: The FAA has taken concrete steps to enable use of CPDLC by more business jets, but it still needs to establish performance criteria.
Word Count: 1943
The FAA plans to allow additional business aircraft to use en-route controller-pilot data link communications (CPDLC) again, ending a moratorium that began late last year. But the long-term goal of the NBAA and the General Aviation Manufacturer Association (GAMA) is to have FAA define what constitutes acceptable CPDLC performance for avionics.
About 1,000 business aircraft, mostly jets and a few turboprops, had joined a trial program that allowed them to use en route CPDLC. However, on October 25, the FAA closed the trial to new entrants, citing concerns over acceptable performance criteria.
As a result, participating aircraft started to dwindle over the next seven months. Some of that decline was due to jets that were sold and then not allowed by the FAA to remain in the trial program, according to GAMA.
Under a recent decision from the FAA, the CPDLC trial for business and general aviation will formally close. But business and general aviation aircraft involved in the trial will be able to continue to use en route CPDLC and can be joined by additional appropriately equipped business aircraft starting August 31.
That resolved the question of when new aircraft can be included in the use of domestic en route CPDLC; “Now new business aircraft won’t be frozen out,” said Heidi Williams, director of air traffic services and infrastructure for NBAA.
NBAA and GAMA see domestic U.S. en route CPDLC as having significant benefits for business and general aviation just as departure clearance with CPDLC does. The relay of clearances and non-urgent instructions via text messages increases cockpit crew situational awareness and reduces frequency congestion.
“We have seen great benefits from Data Comm [the FAA platform for digital communiations] across the board from the tower with departure clearance and en route CPDLC,” Williams said, noting it reduces readback errors and enhances safety. She anticipates business aviation will adopt CPDLC at a higher rate than was originally envisioned.
However, not all questions are resolved.
In a March letter to officials from the FAA Air Traffic Organization and Aviation Safety Organization, the two associations wrote about the FAA calling out certificated avionics as not meeting an acceptable level of CPDLC performance. This occurred without the FAA defining what constitutes acceptable performance.
Needless to say, this caused confusion in the business and general aviation industry. The associations’ letter encouraged the two FAA organizations to find a path forward for business aviation to use en route CPDLC.
In a meeting of the FAA’s Data Comm implementation team (DCIT) on May 24, a plan was presented to resolve this simmering issue and also allow new business aircraft to use en route CPDLC again. The FAA also aims to define acceptable performance criteria for all aircraft by May 2025, including those involved in business and general aviation, airline, and military operations.
“This will provide clarity for CPDLC participation for business and general aviation and airline and military aircraft for what is acceptable and unacceptable performance,” said Jens Hennig, GAMA v-p of operations. “We applaud the FAA for taking this step because this has been an area of confusion with the program for four or five years.”
The FAA has had much more data to establish criteria for the airlines but still wants to collect more data from business and general aviation en route CPDLC operations, while more of the 22 air route traffic control centers in the U.S. become equipped.
The NBAA’s Williams said she understands that the FAA wants to gather more data to make an informed decision on business aviation. “There is a strong desire to work on any avionics issues so we can get to success,” Williams said.
New Classification
As it lifts the moratorium, the FAA is rolling out a new scheme for classifying aircraft of all types using en route CPDLC, and business and general aviation aircraft that have been involved in the trial will come under two of the three new categories. They will either be rated as Yellow (aircraft with known CPDLC-related avionics issues but allowed to use CPDLC) or Green (aircraft without CPDLC issues). The Red classification is for aircraft with critical CPDLC-related avionics issues that prohibit the use of en-route CPDLC.
When the FAA decided in October 2022 to accept no new business aircraft applications for the CPDLC en route trial, it had a specific reason. “The FAA did not feel comfortable with an indefinite trial with no end point in sight,” said Hennig.
The FAA had said it needed to publish acceptable performance levels for all types of operators and until it did so, the agency would not accept any more business jets into the trial program.
As a result, GAMA members have been delivering new business jets equipped in better ways for en route CPDLC than aircraft already in the trial, and yet they were not allowed to join and participate. However, these aircraft have been allowed to use CPDLC for departure clearances. Hennig said this hiatus on en route CPDLC has been very frustrating for both GAMA and NBAA; GAMA has aircraft manufacturers with aircraft rolling off the line that can’t participate in the program while NBAA has members with new aircraft who can’t participate.
As for the new criteria, Hennig said he expects that the government will modify Advisory Circular 90-117 or another publication such as the Aeronautical Information Manual when it determines what it wants acceptable performance to be.
The approximately 1,000 aircraft, mostly business jets and some turboprops, that participated in the trial will be grandfathered and are not expected to have to make any equipment changes to continue to operate, Hennig said. Some airplanes that will return to operation with CPDLC may have non-safety items to address within a defined timeframe. En route controller-pilot data link communications (CPDLC) greatly simplify pilot and ATC communications with texting-style messaging that is unambigous and relatively easy to use. (Photo: Honeywell)
Departure Clearances
The FAA began working to provide CPDLC departure clearances (DCL) in 2012 and en route clearances in 2014. Acceptable performance has never been an issue with DCL using CPDLC and many business aviation aircraft can be equipped to use this service.
The FAA completed CPDLC departure clearance deployment to 55 towers by December 2016, 2.5 years ahead of schedule. More towers have been added since then. “We’ve been doing CPDLC departure clearances now for a while, and everybody loves it,” said Hennig. Now pilots don’t listen to clearances on voice radio and read them back to verify they are correct. Instead, they just receive a data message with the clearance they can review for accuracy, acknowledge receipt, and then push a button to load it into their flight management system.
One of the most useful applications of DCL is when something in the ATC system changes, such as when a weather event requires a new departure runway or lots of reroutes. Rather than reading each crew a new clearance, the controller can send a data message with a new route to each aircraft in the queue waiting to take off with engines running. “The burning of jet fuel, while you are waiting for a new clearance, is reduced,” Hennig said. “I think aircraft operators love it because the benefits have been so tangible. There will be a few new killer applications available as we get further into CPDLC deployment.”
Initial en-route clearance functions include the transfer of communications, initial check-in, altimeter settings, altitudes, limit speeds and crossing restrictions, airborne reroutes, limited controller initiated reroutes, and initial direct-to-fix. Additional features are planned for future implementation including some yet to be budgeted such as support of 4D trajectories, interval management, and tailored arrivals.
The Solutions
MRO Duncan Aviation has been installing FANS/CPDLC avionics for a decade. Activity started in 2013 when the first phase of FANS was mandated for the North Atlantic tracks (NAT). As these mandates were implemented, many business aircraft had to be equipped or retrofitted with new avionics to avoid being barred from the preferred tracks with the best tailwinds to Europe and the least headwinds headed to the U.S.
“There are multiple solutions depending on the aircraft,” said Justin Vena, a Duncan senior avionics installation sales representative. He has hosted a four-part video series “Understanding FANS” for Duncan that is available on YouTube and co-authored a 26-page book on the subject. Vena is based at Duncan’s Battle Creek Executive Airport facility  in Michigan.
“Not every aircraft has a CPDLC solution,” Vena added. “It is largely FANS upgrades that have been driving installations in business aviation.” The same model aircraft may have different configurations requiring different STCs.
The FAA requires FANS now for CPDLC but there may be different technology in the future, Vena said. “What we are talking about is the difference between FANS and the Aeronautical Telecommunications Network [ATN]. ATN gets into more datalink functionality in that more information is communicating with ATC and unlike FANS it is also only air-to-ground. Some ATN-capable avionics equipment is being shipped and installed now in business jets and that is going to be really good for departure and enroute clearances now and even more so in the future.”
The NAT mandates drove a lot of the FANS installations starting in 2013, which Vena said moved in a series of waves up to the present time. A basic datalink installation requires an FMS, an upgraded cockpit voice recorder to capture data link messages, a compliant datalink for FANS, and a safety services-approved satcom link.
Typically the FMS has to be modern unit on the market after the advent of RNAV approaches using localizer performance with vertical guidance (LPV) minimums. Most of the aircraft being equipped with FANS also added LPV and ADS-B at the same time. The push to get equipped with FANS/CPDLC drove other avionics upgrades in 2013 and beyond.
FANS installations dropped off during the pandemic, as did a lot of avionics modification work, while maintenance and cabin modification work picked up. Now, if a new business jet owner with sufficient range but without FANS decides he or she wants to fly to Europe, that is the big driver in getting a FANS/CPDLC upgrade.
However, departure and en route use of CPDLC in domestic U.S. airspace are becoming more of a factor, Vena said. “It is still a bonus reason to get a FANS installation done but is not the real driver to do it yet,” he said. But more aircraft operators are starting to realize the advantages of CPDLC in U.S. airspace.
Some STCs come with push-to-load of flight plans, and more customers are adding that now. Vena said CPDLC installation can cost between $150,000 and $400,000, depending in part on whether LPV capability is already installed and the required satcom system is already onboard. The aircraft will be down for two to three weeks or as much as two months if CPDLC is part of a major flight deck upgrade.
Another advantage of CPDLC is that it reduces controller workload and increases safety at a time when there is a shortage of controllers.