Story and photos by John Croft, FAA NextGen Outreach and Reporting
Pilots accustomed to receiving live ADS-B traffic updates from FAA radar through the Traffic Information Service Broadcast (TIS-B) will feel blind — and less safe if that service gets shut off. But that is exactly what might happen if their ADS-B equipment is transmitting hazardous information or performing incorrectly over a given number of flights.
Under a change to the ADS-B ground infrastructure software made in mid-December, aircraft flagged by the FAA’s ADS-B performance monitoring system as not complying with the criteria spelled out in the ADS-B rule could be placed on a No Services Aircraft List (NSAL). Once on the list, the aircraft will no longer receive traffic from FAA radar through the TIS-B uplink, and the aircraft’s ADS-B information will not be displayed on controllers’ screens.
Traffic Information Services, or TIS-B, gives a pilot equipped with ADS-B In the location of surrounding traffic under FAA radar surveillance.
While the onboard ADS-B equipment itself does not alert pilots to such errors, the FAA’s Public ADS-B Performance Report, or PAPR (pronounced “paper”) does. The agency is asking equipped pilots to check their systems regularly using the PAPR, a free check completed over the web after a flight in airspace with ADS-B coverage. Pilots receive the analysis, which rates the actual performance compared to ADS-B specifications, through email shortly after submitting the request.
“Understanding the issues we’re seeing with ADS-B avionics over the past three years, I recommend that pilots who are flying every weekend check their ADS-B performance every fourth or fifth flight,” said James Marks, the FAA’s ADS-B Focus Team lead. Typical issues include aircraft transmitting the wrong ICAO codes (a fixed number set during aircraft registration), wrong flight identification (tail number), incorrect air-ground registration (the ADS-B unit reporting that the aircraft is in the air when it is on the ground, and vice versa) and position errors.
Marks notes that an ADS-B system is more complex than a transponder and its performance is dependent not only on properly functioning and configured avionics but also dependent on the availability of GPS/WAAS services, the FAA’s ADS-B ground infrastructure and its available coverage, terrain and other factors. “Just because your ADS-B passed the initial test after installation doesn’t necessarily mean your system will comply with the rule afterward,” says Marks.
Marks has a team of nine avionics inspectors and three analysts working full time to identify and analyze errant ADS-B outputs, and when avionics problems are confirmed, they notify the aircraft owner. Marks and his team have shifted their ADS-B compliance machinery into high gear as equipage nears 50,000 aircraft and the 2020 mandate looms less than 24 months away.
Under the changes made in December, an aircraft can be placed on the NSAL if the ADS-B equipped aircraft is emitting “erroneous or hazardously misleading” information. “Over the past three years, [FAA monitoring] has identified some ADS-B Out aircraft with non-performing equipment transmitting data used by ATC and ADS-B In-equipped aircraft that present a safety hazard to the National Airspace System,” according to an FAA notification of NSAL to the public on December 20, 2017.
NSAL aircraft, those with persistent or more serious problems, are a subset of the so-called non-performing equipment (NPE) aircraft, the latter of which number in the thousands. Marks’ team is trying to reach owners of all NPE aircraft through a mass mailing of notification letters, hoping to correct the issues before having to place the aircraft on the NSAL.
As of mid-January, more than 400 aircraft were on the list, mostly foreign-registered airliners with a common ADS-B Out issue for which a fix has been developed. Marks expected the number of general aviation aircraft on the list to increase over time, but said “Our goal will always be to resolve avionics issues first when possible to avoid the need to put an aircraft on the NSAL.”
ADS-B equipped pilots can request a performance report over the internet after a flight in “ADS-B rule” airspace. Reports are sent via email, typically within 30 minutes of filling out the form.
For pilots, the FAA’s actions highlight the importance of regularly requesting a PAPR, not the least of which is that the cover page will tell you in red if you are on the NSAL. Specific issues with the unit also are highlighted in red, and anything red means the aircraft has NPE.
“A lot of pilots install the ADS-B equipment and assume everything is fine,” said Marks. “If it’s not, a member of my team will at some point contact them.”
This article was originally published in the March 2018 issue of Avionics News.