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ADS-B: Changing flight ID

Why would you, how do you?

As of October 1,  we’re two years and three months from implementation of the FAA’s Automatic Dependent Surveillance-Broadcast Out mandate. The agency will require ADS-B Out equipage after January 1, 2020, for flight in airspace where a transponder is required today.
October P&E
The control head of this Freeflight UAT shows it is broadcasting CMF—the Compassion call sign used by authorized humanitarian organizations—as its ADS-B flight ID.

As with many new technologies, early adopters are finding occasional glitches. One emerging issue is call sign mismatch—when the flight ID transmitted by ADS-B does not match the call sign specified in the flight plan (see “ADS-B: What is an NPE? March 2017 AOPA Pilot). Initial concern focused on air carriers and commercial operators that change flight numbers frequently; for most general aviation operations, the flight ID is simply the aircraft’s N number.

However, as more GA aircraft owners equip with ADS-B Out, the incidence of call sign mismatch is increasing. And it could be a problem for pilots who fly using call signs—including pilots flying for authorized medical or humanitarian volunteer organizations, and some flight schools.

In August the FAA published a legal interpretation—requested by its own Air Traffic Organization—that requires the aircraft’s ADS-B flight ID, whether it’s a call sign or registration number, to match what’s filed on the flight plan. Noncompliance would violate FAR 91.227. “It is clear from the NPRM and final rule preambles that §91.227(d)(8) is meant to ensure that ATC is able to correlate flight plan information with information presented on the radar display,” the FAA said.

This doesn’t mean approved equipment is deficient, the Aircraft Electronics Association said in a regulatory alert. “It is a sales issue, in that ‘one-size ADS-B Out’ doesn’t fit all flight missions,” AEA said. “This places an additional knowledge burden on the installing agency to ensure that the customers are purchasing mission-appropriate equipment.”

“AOPA is working with the FAA and our industry partners to ensure pilots are informed about the differences in the various ADS-B systems,” said Rune Duke, AOPA director of airspace and air traffic. “Depending on your mission and how you fly, one solution may be more practical and effective than another. The FAA needs to provide greater clarity around the topic of flight ID to make sure pilots understand the operational implications as well as their regulatory requirements.”

Duke said information about call sign mismatch and other ADS-B topics is not consistent between the Aeronautical Information Manual and FAA Order 7110.65, the air traffic control handbook. AOPA is working with the FAA and the National Air Traffic Controllers Association to resolve the discrepancies, which should be accomplished in 2018.

What does all this mean to an aircraft owner considering ADS-B? If you fly missions requiring a call sign other than your N number—for example, the Compassion call sign (with designator CMF) used for designated humanitarian flights, or Animal Rescue (designator ARF)—buy ADS-B Out equipment that allows easy configuration of the flight ID. Most TSOed ADS-B units allow the field to be edited, although some are easier than others; a few require that editing be enabled by an avionics shop.


In the Appareo Stratus ESG transponder, press FUNC or the arrow keys until “Flight ID” appears. Press ENT, then use the number keys to overwrite the previously entered flight ID; the transponder’s pilots guide explains how to insert letters into the field. (If a new flight ID has fewer than eight digits and characters from the previous flight ID are still visible, overwrite them with spaces.) Press ENT to confirm the new flight ID.


Pressing the FUNC button on the BendixKing KT 74 transponder provides access to the flight ID, said Jay Shears, senior manager of marketing and product management. Use the numeric buttons to edit; letters are selectable through multiple button pushes. Press ENT to accept a character and advance to the next digit. When ENT is pressed for the last digit, the new ID replaces the previous value. “Pressing the VFR button when in Flight ID Edit changes the flight ID to the preprogrammed ID set up during configuration of the transponder,” he said.

On the company’s KGX series of universal access transceivers, which provide ADS-B Out on the 978 MHz frequency, Shears said the call sign/flight ID can be set using the UAT’s control head. The flight ID must be set in the configuration mode and cannot be changed in flight, he added.


The installer can configure all Garmin’s panel-mount and remote-mount Mode S Extended Squitter transponders for the flight ID to be pilot editable, said Bill Stone, senior business development manager. “Since most pilots do not need dynamic flight ID, they are defaulted to broadcast a fixed fight ID, generally the aircraft’s registration number,” he said. Pilots can edit the flight ID through the front panel controls or, for remote transponders, a connected multifunction display.

“A UAT by its nature is a remote box and thus does not have a user interface. Whether or not the UAT supports dynamic, pilot-selectable flight ID is a function of how the UAT is integrated into the aircraft,” Stone said. For example, a flight ID can be sent to a GDL 84/88 from an interfaced Garmin GPS/nav/com or Mode S transponder, but if it’s installed as a standalone—synchronizing transponder data “over the air”—the crew cannot change the flight ID broadcast by the UAT. That’s also true for Garmin’s new, low-cost GDL 82.

FreeFlight Systems

According to the FreeFlight FDL-978-TX Quick Reference Guide, pressing the FN (Function) button allows the pilot to edit the call sign/flight ID. “You may either directly rotate the code knob or press the key and the first character of the flight ID will be highlighted. Use the rotary code knob to select your choice of alpha-numeric characters. Press again and the cursor moves to the next character.” Update all eight characters to save the call sign/flight ID change.

L3 Aviation Products

For L3’s Lynx NGT-9000 ADS-B transponder, the installer must be asked to enable pilot configuration of the flight ID parameter. “It’s as simple as changing the squawk code on this unit,” said Kim Stephenson, senior manager for aftermarket business development. If it was not enabled at installation, that capability can be added any time, she added. Pilots who use any of L3’s UAT products can set the flight ID through their control heads.


The NavWorx ADS600-B UAT does not have a control head. Therefore, the only way to edit the flight ID is to connect a laptop computer to the UAT’s service port and update the field through the company’s configuration software.

It’s a good idea to request a report from the FAA’s ADS-B performance monitor at least annually to make sure your system is working properly. “The Public ADS-B Performance Report will catch flight ID issues,” AOPA’s Duke said. “Aircraft owners might want to do this at the time of their annual inspection. It can be done at any time that’s easy to remember.”

Because the FAA monitors ADS-B data on a real-time basis, no scheduled inspection is required. But an aircraft owner or pilot can verify ADS-B performance at any time by going online and entering the date of a recent flight; the report will be sent to the email address you enter. If a problem is indicated, work with your shop to resolve it; if it’s clear, consider keeping a copy with your maintenance records. 

Email [email protected]

Mike Collins

Mike Collins

Technical Editor
Mike Collins, AOPA technical editor and director of business development, died at age 59 on February 25, 2021. He was an integral part of the AOPA Media team for nearly 30 years, and held many key editorial roles at AOPA Pilot, Flight Training, and AOPA Online. He was a gifted writer, editor, photographer, audio storyteller, and videographer, and was an instrument-rated pilot and drone pilot.

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