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Correct Data — The Key to ADS-B Accuracy

Source: FAA Safety Briefing Jan/Feb 2019
By: Jennifer Caron

When it comes to ensuring the proper set up of an ADS-B system, the number one, most important thing to do is to verify that the system configuration data is correct. The second most important thing to do is to verify that the system configuration data is correct, and the third? You guessed it. Verify that the system configuration data is correct!

The aircraft identification data entry task is the most important step during the installation of the ADS-B system. Why? Correct ADS-B setup requires the installed ADS-B system to accurately identify the aircraft to air traffic control (ATC) and other aircraft in the airspace.

It is the responsibility of the avionics installer to verify the data configured in the ADS-B system following installation. According to James Marks, ADS-B Team Lead in the FAA’s Flight Standards Service, “too many ADS-B-equipped aircraft are not fully compliant with the performance requirements for the equipment, and the majority of these ADS-B compliance failures result from improper configuration of the equipment.”

Three of the most common errors that we regularly see are: transmission of a wrong emitter category, an incorrect flight identification (aircraft call sign), and transmission of a wrong ICAO code,” Marks explains. These common errors can be easily avoided by making sure that the system is set up correctly during the aircraft identification data entry process.

1. Verify the Emitter Category

The ADS-B system transmits the emitter category, or aircraft category, to describe the weight class of the aircraft. This information must accurately portray the aircraft as light, small, large, rotorcraft, glider, etc., for a correct set up of the ADS-B system. Most GA aircraft are in category 1 for light fixed-wing aircraft (less than 15,500 lbs. maximum takeoff weight), or category 2 for small fixed-wing aircraft (between 15,500 lbs. and 75,000 lbs. maximum take-off weight).

Check the configuration summary or maintenance page to locate the aircraft’s emitter category information. Verify that the emitter category is correct for the maximum takeoff weight of the aircraft. See FAA Advisory Circular 20-165B, section, for more details.

2. Verify the Flight Identification

Like a Mode S transponder, the ADS-B system transmits the aircraft’s flight identification (FLT ID), or aircraft call sign, so ATC and other aircraft with ADS-B-In systems can identify the aircraft. This field must match the call sign filed in your flight plan. It is the responsibility of the installer to enter the FLT ID correctly in an ADS-B system that does not allow the FLT ID to be changed by the pilot. Unless the ADS-B unit contains a pilot-programmable call sign feature, the owner often cannot make changes to, or reconfigure, the system setup once the repair shop releases the aircraft.

FLT ID errors are ususally the result of configuration mistakes. If a FLT ID is not entered, it results in the “Missing FLT ID” or “No FLT ID” readout, another common cause of ADS-B set up error. To avoid errors, check the configuration summary page and verify that the FLT ID exactly matches the aircraft registration number or an FAA-authorized call sign if requested by the operator.

3. Verify the ICAO Code

“Fat fingering” input of the 24-bit ICAO code is another common ADS-B setup error. In most cases, the ADS-B manufacturer ships the equipment with a factory default ICAO code. The installer must change the factory default ICAO code to match the aircraft’s FAA-assigned ICAO code (also known as the “Mode S address”).

Checking for the presence of an ICAO code during a ground check is not sufficient. Marks advises avionics equipment installers to “carefully review the configuration summary, or maintenance page, to make sure that the Mode S/24-bit ICAO code you entered exactly matches the code assigned to that aircraft by the FAA, to allow proper ATC identification and tracking.”

Some manufacturers have developed fail-safes that prevent system activation until the installer enters a new ICAO code. Still, “several aircraft are flying today with the pre-assigned default ICAO factory codes,” says Marks. The bottom line: it is the installer’s responsibility to make sure that the transmitted ICAO code exactly matches the aircraft’s FAA-assigned ICAO code. There is often no way for the aircraft owner to access the ADS-B set up system to make this correction.

failed report

Finally — Test the System

After configuration, it is essential to test the ADS-B system. Most ADS-B equipment manufactur-ers provide checkout tools that an installer can use to edit and view the system configuration. “The configuration summary page verifies the data configured in the avionics, but it is not an actual test of the system,” explains Marks. You need to perform both a ground check and a post-flight check to validate the system configuration and its performance.

The ADS-B system ground check verifies what is being broadcast by the equipment. Some avionics installation shops have ramp test equipment or other system interface tools on hand to display data transmitted by the ADS-B unit. This equipment allows technicians to verify that all parameters are configured correctly prior to the first flight after the installation. Additionally, your shop can confirm a successful installation following the first flight by requesting an FAA ADS-B performance report.

After the owner completes the post-installation validation flight in airspace with ADS-B coverage, the owner and installer should request an equip-ment performance report using the FAA’s Public ADS-B Performance Report Request (PAPR) ser-vice. Visit the FAA’s PAPR request website at, fill out the required information, and submit the request. The PAPR service sends an email with all the configuration and performance details of the ADS-B Out equipment installed on the aircraft. Any equipment configuration or performance errors will show up in highlighted red, and if the report isn’t flagged red, you’re all set. Any areas of the report highlighted in red should be addressed and verified by requesting a PAPR following the next flight.

The integrity and accuracy of the ADS-B equipment itself is determined by the manufacturer. However, it is your job as the avionics installer to make sure that the ADS-B system hardware is installed and configured correctly, including having the appropriate component software loads to enable the equipment to meet regulatory performance standards. Use these techniques to keep your ADS-B installs error free.

Learn More

Visit the FAA’s Equip ADS-B Installation site at

Jennifer Caron is an assistant editor for FAA Safety Briefing. She is a certified technical writer-editor, and is currently pursuing a Sport Pilot Certificate.

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