Cover Photo by Shutterstock/ Jacob Lund

Here’s what you need to know to create your ADS-B Out compliance plan

With barely 14 months left before the January 1, 2020, mandate for ADS-B installation, it is now crunch time. Most aircraft have one more maintenance cycle before that due date to facilitate the installation of your chosen system. Assuming you haven’t equipped yet, this article will give you the information you need to make your ADS-B equipage decision.

The ADS-B Out Mandate

Both transponders and ADS-B Out are simply surveillance equipment. The transponder and corresponding radar system date back to the 1930s, relying on a radar “ping” to measure your distance and establish your location.

At a little more than a decade old, ADS-B Out is the modern version of this surveillance. It uses own-ship determination of location and then broadcasts your location to the FAA’s NextGen Traffic Management System. ADS-B will allow air traffic controllers to put more aircraft in the same space with closer margins and accuracy.

14 CFR 91.225, which sets forth the regulations for ADS-B Out equipment and use, requires that aircraft be equipped with ADS-B Out for access to rule airspace. It further defines the scope and limitation of rule airspace. You are encouraged to review 14 CFR 91.225 paragraphs (a) and (d) to become familiar with the airspace that will require ADS-B Out equipment, or see figure 1 below, which graphically shows the rule airspace.

Photo by FAA Image

For our purposes today, let’s make it simple: generally, airspace requiring a transponder today will require ADS-B Out at the start of 2020. And conversely, if you don’t fly in airspace that requires a transponder, then you probably don’t need to equip with ADS-B.

In addition to the confusion regarding who is and is not required to be equipped, many people focus on the label ADS-B and assume that ADS-B Out and ADS-B In are the same thing. They are not!

ADS-B Out is used for surveillance; ADS-B In is used to send flight information into the cockpit. They are two distinctly different systems. More importantly, these two systems are treated completely differently by the FAA. Installation of ADS-B Out is mandated because it will provide the primary source of surveillance in the NextGen Traffic Management System.

While not mandated by the FAA, ADS-B In provides pilots with a wealth of information, such as weather and traffic information. Please see Zac Noble’s article to learn more about how pilots will benefit from ADS-B In.

ADS-B In installations are treated as normal avionics work—nothing special. In general aviation, the majority of ADS-B In installations are for supplemental information. If, however, ADS-B In will be used for required information such as a Part 135 weather briefing, then approval of the system requires more FAA involvement.

Who Should Equip

There are two questions that affect your equipage decision: will the due date be extended, and do you fly in rule airspace?

Let’s first address the due date. Will the FAA extend the January 1, 2020 date? The answer is most likely no.

When he was heading the FAA, Michael Huerta had repeatedly answered that question with a resounding “No, the FAA will not extend the mandate!” Dan Elwell, the current acting administrator, has also reiterated that message on multiple occasions. Still, I live and work in Washington, D.C., and as we all know, there is no such thing as a sure thing, especially in this city.

But if you rely on your aircraft, gambling that you won’t have access to needed airspace come January 1, 2020, might be a fool’s bet. And even if you equip this year and although unlikely, they extend the mandate a year or two, you won’t gain much by delaying your installation.

As to whether you need access to airspace where ADS-B Out is mandated, remember: 14 CFR 91.225 is an airspace rule, not an aircraft rule. ADS-B Out doesn’t make your helicopter fly higher, faster, or longer—it simply gives you access to airspace. If your desired airspace requires ADS-B Out, the aircraft must be equipped. If the airspace does not require ADS-B Out, then you don’t need it.

Choosing ADS-B Out Equipment

ADS-B Out is considered a system, not just a radio. It is a system that contains a transmitter and a reliable position source (usually a WAAS (wide area augmentation system) receiver). Let’s look at some of the major decisions you will make when choosing ADS-B Out equipment (or see figure 2 below, which contains a summary of this information).

The Transmitter

In the United States, the FAA allows two different technologies for the transmitter:

  • A universal access transceiver (UAT) broadcasting on 978 MHz, or
  • A Mode S transponder with extended squitter broadcasting on 1090 MHz.

In the rotorcraft world, you don’t need to worry about class A airspace (above 18,000 feet); traffic in that airspace must use Mode S transponders. Therefore, you can utilize either UAT 978 transmitters or Mode S transponders — whichever is right for you.

The answers to a few questions can steer you in the right direction. Because ADS-B Out equipment broadcasting on 1090 MHz is normally incorporated in a mode S transponder (equipment that broadcasts on 978 MHz is normally stand-alone equipment), one factor in determining your transmitter choice is the age of your current transponder.

If you need to replace your transponder or you anticipate replacing it in the near future, upgrading to a Mode S transponder with extended squitter is a good option. Keep in mind that most legacy avionics have a useful lifespan of around 20 years. If your transponder was installed before 2000, it might be time to look to a Mode S transponder with extended squitter and solve both problems at once.

Another reason you might want to consider the Mode S transponder is that Part 135 requires all transponders replaced after January 1, 1992, to be replaced with the appropriate class of TSO-C112 (Mode S) transponder. It doesn’t matter if the aircraft was operated under Part 135 at the time of transponder change. If you are operating under Part 135 and your transponder was installed after January 1, 1992, you must install a Mode S transponder.

The United States is the only aviation authority utilizing dual frequencies for ADS-B Out, so if you are located near the northern or southern borders and anticipate flying internationally, you should choose the Mode S transponder with extended squitter solution.

And finally, if you fly with a dynamic flight ID, where you change your call sign based on your mission, you might want to consider a Mode S transponder. It allows the pilot the capability to change the flight ID from the cockpit. Changing the flight ID on most UAT systems is a ground/maintenance action. AC 120-26M, issued September 10, 2018, which clarifies requirements and procedures for the use of aircraft call signs in the National Airspace System, states that the aircraft operator’s ADS-B flight identification must correspond with the aircraft identification filed in the flight plan.

The size, space, and installation issues of either transmitter choice aren’t much of a consideration. While a transponder replacement is certainly the least real estate change, component for component, the additional wiring and antenna for Mode S solutions tend to be on par with a UAT system. In addition, UAT systems are so small that they don’t take up much space.

The Position Source

Now let’s look at position sources. The position source needs to provide an accuracy equivalent to that of primary radar while on short final. While a WAAS receiver was never required in the regulations, the practical application of the accuracy requirement drives general aviation to a WAAS receiver.

Does your aircraft already have a WAAS receiver/navigator or are you installing a new navigator with WAAS capability? If the answer is yes, then you simply need to marry that system with your chosen ADS-B transmitter. The FAA requires that all ADS-B Out transceivers be certified with approved WAAS receivers via an supplemental type certificate (STC). This is referred to as an “approved pairing.”

If you do not have a qualified navigator and don’t plan to install one, you would be looking for an ADS-B solution with a dedicated WAAS receiver, either as an internal component of the ADS-B Out transceiver or as an available approved external component.

Minimizing Installation Issues

Now that you have chosen which system to install, let’s discuss some of the issues that may arise during equipage.

Qualifications of ADS-B Installers

I suppose the first question is always, who is allowed to install ADS-B Out? And that answer is simple: anyone who is qualified.

14 CFR 65.81(a) prohibits a mechanic from approving and returning to service any maintenance or alteration unless they have “satisfactorily performed the work concerned at an earlier date.” While ADS-B Out may be contained within a transponder, it is not a transponder but rather programmable avionics. Training, experience, and qualification with ADS-B Out systems is required.

In addition, 14 CFR 43.13(a) requires the mechanic to “use the tools, equipment, and test apparatus necessary to assure completion of the work in accordance with accepted industry practices.” And “if special equipment or test apparatus is recommended by the manufacturer involved, he must use that equipment or apparatus or its equivalent acceptable to the Administrator.” So having the proper test equipment is also a regulatory requirement.

And finally, 14 CFR 91.413(b) requires that following any installation of an ATC transponder, the integrated system must be tested, inspected, and found to comply with paragraph (c), appendix E, of part 43 of this chapter. 14 CFR 91.413(c) specifies who may perform these tests and inspections and unfortunately, a certificated mechanic isn’t authorized to perform them. Only certificated repair stations, those who hold a continuous airworthiness maintenance program, or an aircraft’s OEM can conduct these tests and inspections.

Relevant Installation Guidance

The FAA has three documents that contain guidance for the installation of ADS-B equipment. Your installer—and if possible, you or your mechanic—will need to be familiar with all three of these documents:

  • FAA AC 20-165B: Airworthiness Approval of Automatic Dependent Surveillance – Broadcast Out Systems. This AC provides guidance for the installation and airworthiness approval of ADS-B Out systems in aircraft. While the AC is mostly used by ADS-B manufacturers, it contains important and needed information for the proper installation and, especially, the configuration of the ADS-B Out system. See in particular paragraph 3.2.3, Configuration of Associated Parameters, which provides guidance on setting key ADS-B Out parameters.
  • FAA Field Approval Guidance, Policy Number: AFS-360_2016-03-02. This document explains the agency’s policy regarding installation of ADS-B Out systems into civil aircraft. There are two key points. First, the policy is clear that ADS-B Out systems that have previously received FAA approval via type certificates, supplemental type certificates, or approved type certificates, and that meet certain specified conditions may be installed and returned to service on other aircraft without further data approval. And second, the policy spells out the nine specific requirements for follow-on installations.
  • FAA Technical Paper AFS-360-2017-1 (Rev 0, 09/25/2017), Installation of ADS-B Out Equipment. The companion document to the Field Approval Guidance, this technical paper explains and clarifies the FAA’s policy regarding alterations to aircraft for the installation of ADS-B equipment and, in some cases, provides guidance on how you can comply with the policy’s requirements.

Why are these documents important? Because we have been struggling for more than five years with a double-digit error rate with installed ADS-B equipment.

Prior to 2018, 11 percent of the installed ADS-B Out systems were classified as nonperforming equipment (3,253 per 28,930). Fortunately, through outreach and education, the industry has been able to reduce the NPE rate for 2018 to below 8 percent.

Common Installation Issues

The FAA is working with operators, manufacturers, and installers on eliminating common ADS-B installation errors. The most common issues associated with an ADS-B installation are:

  • Missing barometric pressure altitude
  • Air/ground determination issues
  • Flight ID issues, including missing flight ID three-letter identifier
  • Duplicate and wrong ICAO codes
  • Invalid mode 3/A code (mitigation in place)
  • Incorrect emitter category
  • Aircraft with position errors.

The best way to minimize installation errors is to:

  • Use a trained and qualified installer
  • Follow the installation manual
  • Be familiar with and follow AC 20-165B
  • Use the proper test equipment
  • Conduct an operational flight evaluation and request an FAA ADS-B compliance report.

Next Steps

When this magazine hits mailboxes, you will have approximately 280 working days until January 1, 2020. But don’t wait until the last minute. As the deadline approaches, the queue at avionics shops will continue to grow, so schedule early.

It’s now ADS-B Out decision time! How will you equip?


  • Ric Peri

    A US Coast Guard veteran, Ric Peri has more than 45 years in aviation maintenance as a mechanic, instructor, writer, consultant, and auditor. As VP of government and industry affairs with the Aircraft Electronics Association, Ric advocates for the avionics and maintenance industries before aviation authorities worldwide.

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Ric Peri

Ric Peri

A US Coast Guard veteran, Ric Peri has more than 45 years in aviation maintenance as a mechanic, instructor, writer, consultant, and auditor. As VP of government and industry affairs with the Aircraft Electronics Association, Ric advocates for the avionics and maintenance industries before aviation authorities worldwide.