Houston, We Have a Problem

Not unlike the “no voice” radio problem I talked about earlier, if you are flying in an NPE condition, your ADS-B system is not communicating correctly to air traffic control (ATC) or other aircraft around you. For example, your system could be transmitting the wrong ICAO code, or the wrong aircraft category — describing your aircraft as a rotorcraft instead of a light fixed-wing aircraft, for example.

A more common, and vexing problem, is when barometric altitude is not included in the ADS-B message, then ATC and other aircraft might not know how high you are flying. This is not hazardously misleading information, but failing to broadcast barometric altitude is a safety risk.

In the most critical of cases, your system could be transmitting hazardously misleading information, with your aircraft “lying” about its position in the air or on the ground. Obvious issues here involve ATC or other aircraft reacting to traffic information from your system that just isn’t accurate. Pilots could maneuver incorrectly to avoid where they think you are, possibly causing an accident.

The FAA is constantly monitoring for critical NPEs that are “lying” about the aircraft’s positioning. Although the FAA does not come across these critical cases very often, they immediately notify the owner/operator when they do.

A Successful Failure

Keep in mind that NPEs are not always identified by ATC. Your transponder may appear to be working just fine. It’s transmitting out to the ground stations, and your broadcasted information is delivered to ATC for separation services. But the system does not always give the controller any insight into how well your ADS-B is performing or if all information elements comply with the requirements of the ADS-B rule. You should not count on ATC letting you know if you have an issue.

Likewise, your ADS-B system does not always display a caution or warning light in the cockpit to tell you if you’re flying in an NPE condition. Just because everything is greenlight ready on your screen, it doesn’t mean that you don’t have a problem, and it doesn’t confirm that your system is transmitting the correct data.

“The self-checking abilities within the equipment are limited. A fault light will only come on under a handful of circumstances, usually related to an equipment failure of some kind. Anything short of that, then the pilot is probably not even aware that there’s an issue,” says Marks.

PAPR to the Rescue

The easiest way to check your ADS-B system to ensure that you are not flying in an NPE condition is to run a PAPR report after any flight. PAPR, or Public ADS-B Performance Report, is a quick, easy, and free way to check your ADS-B system, and as many times as you’d like. Fifteen to 30 minutes after a flight, go to adsbperformance.faa.gov/PAPRRequest.aspx to request a PAPR report. It only takes a few minutes to get the report by email. Remember that flying near the surface or at the fringe of ADS-B coverage areas may negatively impact the metrics provided in your PAPR Report.

Please do yourself a favor and run a PAPR report. It will effectively identify any erroneous information that your equipment broadcasts. You can take the report straight to your avionics installer to help identify and rectify any issues.

Prevention Before the Cure

The FAA strongly recommends that you run a PAPR after installation of your ADS-B equipment and annually thereafter. It is not mandatory to run a PAPR report; however, regular requests for a PAPR will confirm whether or not your system is performing in compliance with the rule, and it will give you a heads up if your system is being red flagged as an NPE.

Mission Control

Fortunately, there’s a device inside the FAA ADS-B ground system called the ADS-B Performance Monitor (APM). The APM is designed to automatically check your ADS-B system for performance issues, red-flagging any NPE results or other non-compliance concerns. It works by capturing all broadcast information from your aircraft, including all operations within FAA ADS-B coverage from taxi to takeoff to landing automatically, and every time you fly. After your flight ends, the data collected by the APM during that operation is used to perform a compliance assessment and generate a corresponding PAPR.

“The APM completes around fifty different individual compliance checks on each ADS-B message transmitted during a flight to monitor your ADS-B system’s performance against the requirements specified by the rule,” says Marks, “and there are compliance thresholds embedded in the APM. For example, your ADS-B has to transmit a navigation integrity category, or NIC, that is equal to or greater than seven to be in compliance. If it transmits anything less than seven, at any time during your flight, the APM will flag those messages as non-compliant and when enough non-compliant messages accumulate, the operation will be flagged as a potential NPE.”

When the APM flags an aircraft as an NPE, it stores the data, which is continuously monitored and analyzed by the FAA’s ADS-B Focus Team (AFT) via the avionics trend analysis tool, created by Marks, to notify the team if an aircraft has operated at any time in an NPE condition. “Our team of aviation safety inspectors reviews this data to verify whether or not the aircraft is indeed operating with an NPE. There is always a human review of that data to validate the accuracy of what the system tells us,” explains Marks.

If your ADS-B is determined to be operating in an NPE condition, a member of the AFT will contact the owner/operator by phone, email, or certified mail to provide notification of the avionics issues and coordinate corrective action.

“What’s great about the APM is that we have a performance-based tool that generates ADS-B reports available to the public on-demand, to help determine if their ADS-B is working correctly and complies with the rule,” says Marks. He stresses that pilots will benefit from regular use of the PAPR system.