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Mandate Myth-Busting

Separating Fact from Fiction for ADS-B 2020 Equipage Requirements Part 2 of 2

Source: FAA Safety Briefing, July/Aug 2016
By Tom Hoffmann

As of the publication date of this issue (July/August 2016), there will only be 42 months remaining before the FAA’s ADS-B Out equipage deadline set for January 1, 2020. And yet, as this deadline fast approaches, there are still many aircraft owners who are unsure, undecided, or just confused about what equipment they may or may not need to comply.

To help shed light on some common ADS-B misconceptions, the FAA Safety Briefing staff sat down with two of FAA’s leading experts in the area of ADS-B equipage: James Marks from the Aircraft Maintenance Division’s Avionics branch, and Alex Rodriguez of the Aircraft Certification Service’s Communications and Surveillance Technologies section. Together they were able to tackle some important questions and debunk many of the myths about ADS-B equipment choices, specifications, and installation procedures. The following is part two of a two part series designed to clear up some of the confusion of the ADS-B Out requirement and get folks on the proper path toward compliance. For part one, see the May/June 2016 issue of FAA Safety Briefing.

ADS timeline graphic

What guidance/policy documents should I review before I purchase and/or install ADS-B Out?

Some of the technical documents you’ll want to reference include Advisory Circular (AC) 20-165B (Airworthiness Approval), AC 90-114A, Change 1 (ADS-B Operations), Technical Standard Orders C154c (UAT) and C166b (1090), and the Aeronautical Information Manual (AIM) Chapter 4, Section 5 – Surveillance Systems. Title 14 Code of Federal Regulations (14 CFR) sections 91.225 and 91.227 also contain all the details of the 2020 ADS-B Out mandate. Links to all of these and more can be found on the Equip ADS-B resource page at For additional background, have a look at the NextGen Office’s library of ADS-B related articles and resources at

What are some questions I should ask the repair shop I’m considering using to perform the install?

Most folks already have an avionics shop they go to so that might be a good starting point in your installation search. One thing you might want to check is if that shop is an approved dealer for the ADS-B Out unit you choose. You can check directly with the manufacturer for approved shops in your area. It also helps to know what the upgrade path of your existing GPS and transponder is. Your GPS might be good for navigation, but is it good enough to upgrade for ADS-B? If not, maybe an integrated unit is a good solution. Knowing your existing equipment will help you to ask the right questions.

Some owners are also taking advantage of the aircraft down time to have additional work done, like an ADS-B In or localizer performance with vertical guidance (LPV) system. Other owners are considering ADS-B installation during their next annual inspection. This will still likely involve work being done independently on two different tracks, but it might help decrease downtime and costs as access to certain parts of the aircraft will be easier. Finally, be sure to plan ahead; talk to your installation shop and set an appointment early so you’re in the queue.

Will there be any kind of scheduled maintenance or calibration requirements for my system? Will I be able to accomplish them without the aid of a technician?

ADS-B equipment is an “on condition” product and does not impose any additional tests or checks. There is no scheduled maintenance that is required (except for what your manufacturer may require) and there is no regulation for inspection intervals or operational checks. However, the FAA does continuously monitor the performance of all ADS-B equipped aircraft flying in the United States and we encourage all owners to verify their system meets the requirements of 14 CFR section 91.227. Owners can verify their ADS-B system performance for free via an email request to the FAA at Include your aircraft N-number, ADS-B transmitter make and model number, and the position source (GPS) make and model number. With that information, the FAA will provide an ADS-B performance report highlighting any areas that fail to meet required performance levels or avionics configuration settings that are incorrect for the aircraft. Expect to see a publically accessible online version of this performance report tool soon.

What are the common errors or problems that you’re seeing with some installations? How is the FAA involved in correcting and/or preventing these errors?

As mentioned earlier, we do monitor post-installation performance and identify aircraft with ADS-B systems that fail to meet required standards. We maintain a list of common installation and configuration errors that can cause performance problems after an ADS-B system is installed. These errors are also categorized by risk. Some are low risk errors, like an incorrectly configured onboard parameter, while others are considered a higher risk, like position jump errors, since that error is potentially being seen by ATC and other aircraft. The FAA is working with operators, manufacturers, and installers on eliminating common ADS-B installation errors. Here is a list of some of the most common issues we’ve seen so far:

  • Missing barometric pressure altitude
  • Air/Ground determination issues
  • Flight ID issues including missing flight ID 3-letter identifier
  • Modes S address (ICAO address) errors
  • Invalid Mode 3/A code
  • Incorrect emitter category
  • “Position jumping” errors

Installation shops should have the necessary test equipment to verify system performance and proper configuration on the ground before they give the aircraft back to the owner. However, we encourage aircraft owners and repair shops to verify system performance by requesting an ADS-B Performance Report from the FAA following initial installation or maintenance on an existing installation. This will help ensure the owner or install shop doesn’t receive a call or notification letter from the FAA when a problem missed during ground testing is detected by FAA monitoring.

Myth: The specs for ADS-In/Out are only going to change making anything I buy now obsolete and out of compliance.

In terms of the requirements for the 2020 ADS-Out mandate, those are not going to change. Moving forward, there may be enhancements to the ADS-B avionics standards, but any new standards will need to be backward compatible with the existing standards and FAA will not change the ADS-B Out mandate. And even if FAA releases subsequent versions of the ADS-B TSOs, the language in the existing rule would still be the minimum that’s required.

How can ADS-B Out system installations be approved?

Initial ADS-B Out system pairings (transmitter/GPS) must be approved for installation using the Type Certificate (TC), Amended TC (ATC), or Supplemental Type Certificate (STC) process. Consult your Aircraft Certification Office to determine the appropriate approval process for these initial installations. Once the performance of the initial pairing has been established, the FAA considers follow-on installations of the same pairing to be approved.

Approved pairings can be installed under the Field Approval process, or if certain conditions are met, installed without further approval from the FAA. Reference AVS Policy Memo, Installation Approval of ADS-B OUT Systems, dated March 2, 2016.

Is there any advantage to having a dual frequency (1090 and UAT) system?

With regard to ADS-B Out, there won’t really be any operational advantages to have a dual-frequency system. Some operators want a dual link ADS-B Out system to ensure that they are “seen” by all ADS-B-In receivers in remote areas that may not be within the coverage of FAA’s ADS-B ground stations. Some people also don’t want to deal with any of the airspace limitations that exist for UAT. The internationally agreed standard for ADS-B is 1090ES and not UAT. With regard to ADS-B In equipment, which is not required to meet the 2020 mandate, there are some operational differences between the two links pilots should be aware of. ADS-B Flight Information Service (FIS-B) that provides information on weather, pilot reports, and special use airspace (among other things), is only available over the UAT frequency and not on 1090. Another important distinction: If your aircraft is outside the range of an ADS-B radio station, which translates traffic information between the two links, you will not see anyone on the other frequency unless you receive ADS-B In on both frequencies.

Can you describe the TIS-B changes that went into effect this year? How does it affect someone looking to equip their aircraft or who may have already done so?

In 2013, the FAA learned that there were a significant number of operators using non-compliant ADS-B Out equipment to enable reception of TIS-B (traffic) services. This caused a safety concern since these aircraft using uncertified ADS-B Out were essentially “invisible” to other aircraft with TSO-certified ADS-B-In systems and the uncertified ADS-B Out information was unusable to air traffic control. To rectify this, the FAA in early 2016 put in place changes that allow TSO-certified ADS-B-In systems to see aircraft using uncertified ADS-B Out equipment. The change also removed the incentive for those who choose to equip with uncertified or otherwise non-compliant ADS-B Out by confining the transmission of TIS-B services strictly to those aircraft that meet the minimum performance requirements of TSO-C199 (Traffic Awareness Beacon System). TSO-C199 essentially defines the minimum acceptable level of performance for airborne ADS-B transmitters in the United States.

Unfortunately, there are cases of operators who are unaware that their system is non-compliant and which may have appeared problem-free after installation. We’re actively trying to reach out to people who may be in this situation so they can get it resolved. That is another reason we encourage people to email us for a free performance check.

How long does a typical ADS-B Out installation take for a small piston GA aircraft?

The time can vary based on installation complexity and the capability of particular shops, but on average a typical installation will take approximately two days if you have an existing GPS, and about three to five days if you need both GPS and an ADS-B transmitter installed.

What about Experimental/Amateur-Built (E/AB) aircraft? Do they need to meet the performance requirements of 14 CFR 91.225/27? Does their equipment need to be certified?

There is nothing in the regulations that prevent owners of E/AB aircraft from installing a non-certified ADS-B system. What we do have is policy on how they have to configure that system so it doesn’t transmit parameters that would allow data from that aircraft to be improperly displayed to an air traffic controller or to the pilots of other ADS-B In equipped aircraft. If they are not flying in airspace requiring ADS-B, they can have non-certified equipment that doesn’t meet rule performance requirements, but we’ve defined the specific avionics settings that they must transmit. If they are in airspace requiring ADS-B as defined in 14 CFR 91.225, they must meet rule performance requirements, regardless of the aircraft type [unless they meet the exceptions defined in 14 CFR 91.225(e)]. Updates to AC 90-114A, Change 1 ( address what light sport aircraft and E/AB operators will need to do to bring their systems to within certified standards.

Tom Hoffmann is the managing editor of FAA Safety Briefing. He is a commercial pilot and holds an A&P certificate.

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