Getting it Right What You Need to Know About ADS-B Installation Errors

by James Williams, FAA Safety Briefing

Do you hear that? It is the rhythmic tick-tock of time marching ever forward. Time is the one thing we are helpless to stop. By now, you’ve no doubt realized the theme of this issue of FAA Safety Briefing: being prepared for the rapidly approaching ADS-B mandate that will take effect on January 1, 2020. We can all debate the merits of the mandate, but we cannot ignore the reality. To paraphrase the George R.R. Martin novels, A Song of Ice and Fire, “January 2020 is coming.”

What’s Next?

We explain the functionality and requirements of ADS-B elsewhere in this issue, so this article will look at three specific areas regarding ADS-B installation. First, we will explore some of the things you should know when selecting a shop to do the installation work. Second, we will examine some common problems that can occur during that process. Finally, we will offer some advice as to what aircraft owners should expect before accepting an installation.

What Difference Does the Shop Make?

As it turns out, quite a bit. During the FAA’s ADS-B panel discussion at AirVenture in Oshkosh, Wisc., I heard several scary stories of shops needing multiple tries to get an ADS-B install right, which lead to many frustrated owners and extensive aircraft downtime. Anecdotes don’t make a trend, but it was still troubling. Could it really be that hard? The answer is both yes and no. “With these newer avionics, it’s as much about computer programming as it is about installing radios,” explains Dawayne Wilcox, the Avionics Manager for Capital Aviation in Manassas, Va. I visited Capital Aviation as they finished up an ADS-B In and Out installation on a Cessna 172. Wilcox recommended using a shop that is familiar with this type of installation, as there are many small details that can render an installation non-compliant (more on that later). Wilcox walked me through the test process Capital uses to ensure that an installation will be compliant. Specifically, this shop utilizes ground testing equipment that can receive and display the signal transmitted by the ADS-B unit. This test allows technicians to verify that all parameters are correct before the test flight.

The three most common installation errors are transmission of the wrong ICAO code, an incorrect flight identification, and Dual-Out boxes using different ICAO codes.

Not all shops have ADS-B testing equipment, nor is it a requirement. It is a helpful tool that can save time and aggravation, but a shop can certainly do an installation successfully without it. The main thing is to be sure the shop you select has an established process to test the installation. It could be as simple as a test flight and successful performance report. You also want to be sure the shop you select has experience working with modern avionics and the programing that comes with them, along with a proven track record when it comes to successful ADS-B installs. Experience with the process and solid procedure go a long way towards avoiding potential pitfalls. In today’s modern social media world, it’s a good idea to check not only with other aircraft owners around you, but to also seek feedback on shops with sites like Google or Yelp.

Another thing to consider is the level of support you or your avionics shop can expect from the manufacturer. Wilcox reported that while some are better than others, most major manufacturers are very responsive in addressing issues related to a particular installation. Still, it’s helpful to check with the manufacturer’s user base to see what kind of support to expect both during and after the installation.

ADS-B ground testing equipment, as shown here, can verify all parameters are correct after an ADS-B installation.

What Could Possibly Go Wrong?

Famous last words — what could possibly go wrong? In a word — lots. FAA data shows that about 5,000 of the 27,000 ADS-B Out installations have performance problems or transmit incorrect data. Most (4,100) of those are single-engine GA aircraft.

To investigate what can happen and, more importantly, how to avoid common problems, I turned to James Marks of the Flight Standards Service’s Maintenance Division. Marks is the ADS-B Focus Team Leader and, as such, he is actively working to help cut down on installation errors.

“The three most serious errors that we regularly see are: transmission of a wrong ICAO code, an incorrect flight identification (aircraft call sign), and Dual-Out boxes using different ICAO codes,” Marks explained. Here’s the story. ADS-B has an FAA-assigned 24-bit ICAO code. This code is different from the flight identification, which should match the aircraft’s N-number. The installation technician must enter this information to comply with the rule, and glitches do occur. One of the ADS-B Focus Team’s highest priorities is to quickly contact any aircraft owner with incorrect ICAO codes or flight identification. The FAA handles about 200 of these cases per month. A related issue is call sign mismatch for aircraft using a call sign instead of an N-number. This issue doesn’t arise for the vast majority of GA, but you can find more information in the article, “What’s in a Name?” in this month’s FAA Safety Briefing.

While that covers the first two issues, the third is a special twist of technology. When the rule was first proposed, the idea was that aircraft would have to equip with either a Mode S transponder (operating on 1090 MHz) or a Universal Access Transceiver or UAT (operating on 978 MHz). Both meet the requirement for an ADS-B transmitter. To ensure that their aircraft is seen in all airspace (including outside of FAA ADS-B coverage), some aircraft owners are equipping with both device types. This approach can result in a “dual out” problem.

“If the ICAO code in your Mode S transponder (reporting to the ground on 1090 MHz) and your UAT avionics (reporting on 978 MHz) are different, your aircraft may appear on a controller’s display as two aircraft in close proximity,” Marks explains. “Also, if your aircraft is equipped with ADS-B In, you may see a second aircraft displayed very close to your own position, prompting you to try to avoid an aircraft that isn’t there.”

The ADS-B Focus Team is also working a reporting issue called Air/Ground determination. That means the FAA has detected ADS-B equipped aircraft reporting in airborne mode while taxiing or stationary. This problem stems from issues with the ADS-B avionics that make the actual Air/Ground determination and relay that information to the FAA’s ADS-B system. The FAA is working with avionics manufacturers to better understand the issue and determine how to resolve it.

Other common ADS-B installation issues the FAA team has seen include:

  • Missing barometric pressure altitude
  • Invalid Mode 3/A Code
  • Incorrect emitter category
  • Aircraft with position errors

What Should You See Before You Sign the Check?

“We emphasize making sure your installation is compliant with the rule before signing off on work, because many aircraft equipped with ADS-B are operating with some type of unresolved problem,” Marks said. One way to make sure everything is good is to use ground-based testing equipment. This equipment will detect most issues, but the ultimate test is to fly the aircraft in ADS-B rule airspace and request a performance report. The FAA will provide a performance report free of charge, usually within 30 minutes of a flight. You can request your report here:

The performance report will tell you what, if anything, needs to be corrected. That, in turn, will help you figure out who needs to fix it. In most cases, the answer is your avionics shop. ICAO codes and Flight ID are set by the installer, and any conflict between 1090/978 MHz outputs should also be corrected by the installer.

The Performance Report allows you to check your installation. Failures will be highlighted in red. Also NO=Pass while YES=Fail.

As you probably noted from the discussion above, an Air/Ground determination failure is more complicated. The installer is a good first step, but the culprit could also be an issue with the avionics. If the installer verifies that everything else is correct, you will need to go to the equipment manufacturer. If this source is unable to resolve the situation, please contact the FAA via email at: to request a review. This communication should include “PAPR Review Request – Air/Ground Failure” in the subject line, and you need to attach a copy of your performance report in the body of the message.

Speaking of the ADS-B Performance Report, the FAA has prepared a user’s guide to help you understand what it all means. The guide – available at – explains what each section of the report is measuring. As you can see, getting either a copy of your performance report or the opportunity to generate one is a sound means to verify correct completion of the installation work. Think of it as an authoritative, independent review that enables you to sign off on the installation with confidence.

So We’re Done Now, Right?

Not quite. Getting the installation done correctly is the biggest challenge, but there are some lingering concerns. “ADS-B performance problems can still emerge after initial installation, so it is a good idea for aircraft owners to check performance with the PAPR service periodically, especially after maintenance or a software update to an ADS-B system component,” Marks said.

The bottom line is that while physical installation errors can occur, the FAA now sees most ADS-B problems on the “programing” of the units. Given the number of parameters that must be precisely set, it’s easy to see how a mere “typo” could botch smooth and correct operation of the equipment. That’s why it is critical to work with a shop that understands the process and has the right capabilities.

The benefits of ADS-B are huge. By arming yourself with a better understanding of ADS-B installation pitfalls, you can reap those benefits right away by ensuring that your ADS-B equipment works properly right from the start.

Learn More

James Williams is FAA Safety Briefing’s associate editor and photo editor. He is also a pilot and ground instructor.

This article was originally published in the March/April 2017 issue of FAA Safety Briefing magazine.
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