30 ADS-B Questions You Should Know How to Answer

ADS-B In traffic map. Photo courtesy of Elliott Aviation

As the business and general aviation industry gathers in Las Vegas for the annual NBAA business aviation conference and exhibition the week of Oct. 9, the FAA estimates that there are still more than 100,000 general aviation aircraft requiring upgrades to become compliant with its Jan. 1, 2020, ADS-B Out airspace mandate.

Duncan Aviation recently published a report noting that as of March 31, 73% of U.S.-registered business jets were not in compliance of that mandate.

Here are answers to 30 of the most common questions pertaining to ADS-B that Avionics has encountered through webinars, trade shows and engagement with readership over the past year.

  1. Why is it still necessary to do an ADS-B flight test per AC 20-165B for supplemental type certificate (STC) approvals when all the parameters can be properly tested during ground tests?

The main purpose for the test flight is to test the avionics dynamically to assess the GPS performance during maneuvering.

  1. Is there a way to address non-performing emitter (NPE) installation issues at the point of install?

Most NPEs are a result of improper avionics configuration or wiring during installation. Others are a result of component software compatibility, all of which could be detected with appropriate ground test equipment or flight check.

  1. Has the FAA addressed the military flight ID format that is not in compliance with the performance monitoring system flight ID format?

The FAA is working with the U.S. Defense Dept. and other federal, state and local agencies to address flight ID protocol.

  1. If the FAA audits NPE data, how do you report inaccurate transmitted data to the registered owner operator?

The ADS-B Focus Team contacts owners via phone or email if able. A letter of finding is mailed to the address on the aircraft’s registration if we are unable to contact via phone or email.

  1. How is inaccurate data for N-registered aircraft flying in outside the U.S. handled?

We work through our international Flight Standards Office (AFS-50) to resolve non-U.S.-registered NPEs.

  1. Will local FAA offices treat errant transmitted code by local registered aircraft a pilot deviation or a maintenance issue?

With a few exceptions, most NPEs will be treated as airworthiness issues and the ADS-B Focus Team will resolve them directly with the owner. Resolution of NPE aircraft for certificated operators will be coordinated through the principal inspectors.

  1. What is the split of NPEs between airliners, regional transports, business jets and general aviation?

This information can be found at:

  1. What is the procedure for validating the ADS-B system once it is installed in the aircraft?

Verification of proper configuration and performance can be accomplished using appropriate ground test equipment or check flight using the Public ADS-B Performance Report service at

  1. What should be included in the statement of compliance from the manufacturer or the STC holder?

The manufacturer’s statement of compliance should include a reference to compliance of the equipment performance requirements specified in§91.227. See Notice 8900.362.

From Notice 8900.362: "c.   Compliance Statement. The installer has a statement of compliance (SOC) from the applicable manufacturer(s) or STC holder that the equipment (self-contained) or specific equipment pairing (ADS-B OUT transmitter and GNSS position sensor) have been shown, via TC, amended TC, or STC, to comply with all § 91.227 requirements. This SOC may be included in the applicable installation instructions. The installation instructions must address how the equipment is to be installed and maintained to comply with not only the applicable TSOs but also § 91.227 requirements."

  1. What is “cloaking” for special mission and military aircraft?

These are operations in which the aircraft transmit non-descript ADS-B information to prevent association of flight data to sensitive missions.

  1. Are military aircraft exempted from ADS-B compliance?

The FAA has not exempted any public or private entity from compliance to the rule.

  1. If the aircraft is only compliant to DO-260A and not DO-260B, will it still be grounded Jan. 1, 2020?

The aircraft would not be permitted to operate in the airspace identified in Federal Aviation Regulations Part 91.225 without prior authorization from ATC.

  1. Is there any plan for the FAA to mandate any Mode-S capability from transponders similar to the Eurocontrol Mode-S EHS mandate?

There are no plans to mandate additional Mode S capabilities in the U.S.

  1. Are non-U.S.-registered airplanes that fly to the U.S. that will retire by 2021-2022 also be required to equip ADS-B per DO-260B?

All aircraft operating in U.S. airspace specified in FAR 91.225 after Jan. 1, 2020, will need to equip for the mandate. As with any FAA rule, exemption requests can be submitted for consideration.

  1. Is designated engineering representative (DER) approval an option, or is ADS-B equipage only possible via an STC installation?

This would depend on the scope of the DER’s agreement with the applicable Aircraft Certification Office oversight. Initial ADS-B systems (transmitter and GPS pairing) must be approved via TC or STC.

  1. What is the FAA doing to correct all of the NPE installation errors?

The ADS-B Focus Team uses a multi-faceted mitigation strategy to reduce installation errors, including outreach, direct owner/operator coordination, repair station remediation, aircraft condition notices and letter of finding issued to owner/operator.

  1. Is a helicopter ADS-B Out message required to have a length/width code configured?

There is no language in AC 20-165B that waives the requirement for any aircraft to not transmit the length/width code when it’s on the surface. Helicopters hover-taxi and are airborne while they’re taxiing around the airport. When they’re in that configuration, they’re not required to transmit the length/width code. However, no requirement in FAA policy or guidance permits helicopters to not transmit a length/width code when it’s appropriate.

  1. How can you estimate the equipment/installation costs and down times for business jets by type?

“We need to know what kind of transponders are in the aircraft, full part numbers, we need to know what kind of FMSs are in the aircraft. Are they already WAAS receivers? If not, do you have WAAS GPS receivers in the aircraft? If it’s a Honeywell package, we need to know the RMUs. Are they RMU 850s? Are they RMU 855s? Then the RCZs, radios, we need to know the dash numbers of the RCZ radios. With that baseline information, we can generate a proposal as to what it’s going to take to get your aircraft compliant. If it’s a Collins-configured aircraft, we primarily need to know the existing transponder part number and then we know whether it’s a ProLine 4 or ProLine 21, etc. A few of those specific questions will help us put a proposal together and once we know that, we can estimate the downtime as well.” – Gary Harpster, senior avionics modification specialist, Duncan Aviation.

  1. Is there any restriction about broadcasting ADS-B out on both 1090ES and 978 UAT simultaneously?

“We kind of discourage it for obvious reasons. What we do see a lot and what we do refer to as “dual out installations” where they’ve got a 1090 UAT system installed on the same aircraft and both are transmitting is that they pick a link, most of the 1090 units now receive on both links, so you can get the traffic and the weather information from a single unit. But there is no restriction to limit broadcasts on both links. One particular item to remember in that case is that you need to make sure that your flight ID and your ICAO code are entered correctly on both units, otherwise an ADS-B In-equipped aircraft will see that as two aircraft flying very close to one another.” – James Marks, FAA ADS-B Focus Team.

  1. Is TCAS 7.1 required for ADS-B?

No it is not. 7.1 is a European mandate for aircraft traveling to Europe.

  1. Are Part 135 aircraft that operate below 18,000' still required to have 1090ES? I understood that was an early requirement, but had been revoked. I cannot find any ruling on that.

The ADS-B rule is an airspace rule. A 135 operator may or may not be required to have a Mode S transponder. But if they’re only operating below 18,000 feet, they could certainly install a 1090 or a UAT system and be in compliance of the rule.

  1. Are there any changes being made to shorten the FAA STC approval process considering ADS-B Out mandate is not too far?

“We did revise certification project procedures to authorize certain OEAs to alleviate the requirement to submit a project notification letter, and that cut off about 30 days on average from the certification timeline. But I don’t know of any work internally to do anything beyond that.” – James Marks, ADS-B Focus Team Lead, FAA.

  1. In August, the FAA proposed changing its rules for U.S.-registered ADS-B equipped aircraft operators applying for RVSM authorization. If this policy change is approved, what does this mean for ADS-B-equipped aircraft?

An aircraft must have a precise digital altimeter system and an autopilot to keep the aircraft inside RVSM airspace envelope. An aircraft equipped with ADS-B can fly in RVSM airspace immediately rather than wait for the FAA to approve its RVSM changes.

  1. Would a flight test be required if the interface GPS and transponder systems were common on a different aircraft type? i.e. same system / different aircraft type (e.g. B757 / B767)

Please submit this question to

  1. What will happen if aircraft is not compliant with the ADS-B mandate by Jan. 1, 2020? Can aircraft still fly with flying level limitation?

The aircraft cannot operate in the airspace specified in §91.225 without prior authorization from the appropriate ATC facilities.

  1. What is Exemption 12555?

According to the FAA, Exemption 12555 is “a one time, grant of exemption from 14 CFR § 91.227(c) (1)(i) and (iii) for aircraft that are ADS-B Out equipped using qualifying GPS receivers when their performance falls below the requirement and backup surveillance is available.”

The agency established this exemption to address the performance characteristics associated with the three different variants of GPS receivers that are currently found in air transport category aircraft. Operators use these receivers to meet the ADS-B Out Navigation Integrity Category (NIC) requirements found in the code of Federal Aviation Regulations (FAR), § 91.227(c).

  1. Where can I find a list of ADS-B compliant equipment for my aircraft type?

The FAA’s website features a database of available equipment designed to meet the requirements of 14 CFR 91.225 and 91.227, either as separate components or complete installation solutions. The database includes both FAA-certified equipment and equipment not yet approved.

  1. Is the European ADS-B mandate following the same timeline as the mandate for U.S.-registered aircraft?

The European Aviation Safety Agency (EASA) uses the following dates:

  • All new aircraft were required to be ADS-B equipped as of June 8, 2016.
  • Aircraft requiring retrofits need to be equipped by June 7, 2020.
  1. Where can aircraft owners obtain post-installation checks to evaluate the rule compliance status of their new ADS-B installations?

Send an email to with the following information:

  • Aircraft N-Number
  • ADS-B Manufacturer and Model #
  • Position Source Manufacturer and Model #
  1. After Jan. 1, 2020, where can non-ADS-B equipped aircraft fly?

The FAA published an extensive list of guidelines as to what airspace and areas of the National Airspace System will not require ADS-B after Jan. 1, 2020.

A shorter snippet of this article was featured in our October/November issue. It has been updated with more information.

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