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 during 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, or 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.
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 online at ADSBPerformance.FAA.gov/PAPRRequest.aspx 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 the 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,” Marks said.
Marks has a team of nine avionics inspectors and three analysts working full time to identify and analyze errant ADS-B outputs. 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 22 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 Dec. 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.
“Our goal will always be to resolve avionics issues first when possible to avoid the need to put an aircraft on the NSAL,” he said.
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,” Marks said. “If it’s not, a member of my team will contact them at some point.”
At the FAA hangar at SnF, they had someone manning their ADS-B booth. I walk up and ask a question to which the representative gets a deer in the headlight look on his face. Nuff said.
Even with single box 1090 ADS-B transponders, most folks don’t understand that there are two parts to the transmitted signal … the normal Mode S transponder signal (carrying your ICAO code) which responds to FAA radar interrogations and normal position determination by those radars and ‘extended squitter’ bits providing ADS-B info (carrying your flight ID) in a sort of radio signal format for use by others in the clear … without encryption. So if their system detects an issue between the two, they shut off services? Airplanes on special mission flights are going to trigger mismatch issues. And, they’re now saying that aerobatic aircraft are going to trigger issues, as well. And what about UAT equipped aircraft with the ability to transmit ‘anonymous’ flight ID’s? FYI: IF you’re using a UAT solution and transmitting (manually commanded) anonymous flight ID, you have to be able to switch back to ID’ing yourself IF you request ATC services.
I’m now ADS-B equipped but not yet “in” capable … that’ll happen this summer. I look forward to being able to see traffic and weather in the cockpit. But with this new NSAL issue … I’m wondering how much I can trust the system.
And I think a can of worms is about to be unleashed. And the first time I hear that an enforcement action has been issued based solely on ADS-B information … the equipment will come out of my airplane as fast as I can remove it ! Be careful what you ask for, FAA !
As usual with the FAA, this is something they want to use as a club for enforcement. The FAA expects 30 day compliance for repairs of the most minor nit in your ADS-B output for something that isn’t currently required, and ATC doesn’t even have the equipment to see ADS-B Equipped Aircraft. You can’t get an appointment with an avionics shop in 30 days right now, and replacing equipment takes longer yet. The FAA is living in a fantasy world where they think this overblown, over complicated system will work. The fact is, that even when everything is working properly, it doesn’t work very well. There will always be failures with on board equipment. Often times multivendor equipment doesn’t work well together. So the FAA’s solution is to shut off critical flight data? It appears that they learned nothing from the collision between the ADS-B IN equipped C-150 and the F-16 a few years ago.