Federal Aviation Administration

ADS-B Frequently Asked Questions (FAQs)


Why is the FAA deploying ADS-B technology?

ADS-B is an environmentally friendly technology that enhances safety and efficiency, and directly benefits pilots, controllers, airports, airlines, and the public. It forms the foundation for NextGen by moving from ground radar and navigational aids to precise tracking using satellite signals.

With ADS-B, pilots for the first time see what controllers see: displays showing other aircraft in the sky. Cockpit displays also pinpoint hazardous weather and terrain, and give pilots important flight information, such as temporary flight restrictions.

ADS-B reduces the risk of runway incursions with cockpit and controller displays that show the location of aircraft and equipped ground vehicles on airport surfaces – even at night or during heavy rainfall. ADS-B applications being developed now will give pilots indications or alerts of potential collisions.

ADS-B also provides greater coverage since ground stations are so much easier to place than radar. Remote areas without radar coverage, like the Gulf of Mexico and parts of Alaska, now have surveillance with ADS-B.

Relying on satellites instead of ground navigational aids also means aircraft will be able to fly more directly from Point A to B, saving time and money, and reducing fuel burn and emissions.

The improved accuracy, integrity and reliability of satellite signals over radar means controllers eventually will be able to safely reduce the minimum separation distance between aircraft and increase capacity in the nation's skies.

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How was the ADS-B ground system certified, and how will it be re-certified?

ADS-B systems are certified for aircraft and for vehicles on the ground. For aircraft, there is a requirement for continuing airworthiness certifications that include verifying the proper operation of avionics subsystems.

FAA Technical Operations personnel certify ADS-B for use on air traffic control automation platforms before ADS-B is turned on during Initial Operating Capability (IOC). FAA Technical Operations personnel also perform regularly scheduled certifications of the ADS-B service at each facility where ADS-B is used for air traffic control.

The entire ADS-B system was approved for use throughout the national airspace system when the FAA Administrator made the In-Service Decision in September 2010. Training and operating guidelines will be implemented at each air traffic facility as ADS-B is deployed. Deployment throughout the nation is targeted for completion in 2014.

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Is the FAA looking at ways to offset the relatively high cost burden and increase the benefits of ADS-B for general aviation?

The FAA believes free ADS-B broadcasts of traffic, weather, and aeronautical information yield significant safety benefits to general aviation. The agency continues to look for ways to lower costs and provide even more benefits. For instance, the FAA has tasked an Aviation Rulemaking Committee with examining all aspects of ADS-B In, including recommending new applications that have potential high-value benefits to general aviation. This committee is composed of members from major organizations within the aviation community, including Heidi Williams from AOPA (Aircraft Owners and Pilots Association), Steve Brown from NBAA (National Business Aviation Association), manufacturers, and more. The committee is slated to make a final report to the FAA by September 30, 2011, and to submit detailed recommendations on next steps for ADS-B by June 2012. In parallel, the FAA is funding avionics standards development for the "Traffic Situation Awareness with Alerts" ADS-B In application. This application is expected to yield significant safety benefits for general aviation users who do not have TCAS (Traffic Alert and Collision Avoidance System) equipment.

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Will the ADS-B system be implemented as an enforcement tool to collect user fees, carbon offsets, tax assessments, or for FAA enforcement actions?

The FAA has no plans to use ADS-B as an enforcement tool to collect fees, carbon offsets, or tax assessments. The FAA does need to ensure that ADS-B transmissions being broadcast from aircraft comply with the established performance and parameter-reporting requirements identified in the ADS-B Out rule in Title 14 CFR Part 91. The FAA Flight Standards office may take enforcement action to ensure aircraft comply with these regulations.

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What other solutions were examined for NextGen and what were the reasons for the decision to implement ADS-B over other alternatives such as Loran enhancement, ground station Mode C transceivers, or Mode S?

The FAA determined the new surveillance system would need to supply these capabilities to lay the foundation for NextGen:

  • Core Surveillance. Perform as well as or better than today's surveillance system, while also enabling multifunction capabilities. Deliver services cost-effectively.
  • Cockpit Advisory Services. Provide traffic, weather, and database products to improve pilots’ situational awareness and decision-making abilities.
  • Cockpit Critical Services. Enable advanced cockpit display applications that would improve capacity by allowing aircraft to fly safely with less separation and ultimately transfer some separation responsibility from air traffic control to the pilot.

In its analysis, the agency also considered the possibility of doing nothing and retaining all existing radar until 2035.

Two alternatives for ground and air-to-air surveillance services were considered along with ADS-B because they met two of the three above criteria (Loran, Mode S, and Mode C technologies did not). These were radar replacement and multilateration. Radar replacement could supply core surveillance and cockpit advisory services, but could not support air-to-air cockpit services and paid back only a fraction of its implementation costs in benefits. Multilateration did not support air-to-air applications. Only ADS-B supported all required and desired capabilities and was found to provide sufficient benefits to the FAA and to aircraft operators within 23 years of implementation.

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ADS-B provides altitude, aircraft number, and vertical air speed. Will it also furnish horizontal air speed?

In fact, ADS-B reports two kinds of altitudes: barometric and geometric. Barometric or pressure altitude is the one pilots know best – this is the altitude that is displayed on the altimeter in the aircraft. Geometric altitude is calculated by GPS (Global Positioning Satellites) as the height of the aircraft above the earth ellipsoid. These two altitudes are not the same, but having both allows for applications that require one or the other as an altitude source and provides a means of verifying correct pressure altitude reporting from aircraft.

ADS-B does not report vertical or horizontal airspeed. Instead, ADS-B reports horizontal and vertical velocity relative to the Earth. This velocity is useful for air traffic control functions and ADS-B applications. Airspeed can be provided by other aircraft sensors.

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The final rule mandates ADS-B Out only. Is this correct?

Yes, only ADS-B Out is mandated, and only within certain airspace. Title 14 CFR § 91.225 defines the airspace within which these requirements apply.

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How will the new ADS-B Out rule effect me?

On January 1, 2020, when operating in the airspace designated in 14 CFR § 91.225 (outlined below) you must be equipped with ADS-B Out avionics that meet the performance requirements of 14 CFR §91.227. Aircraft not complying with the requirements may be denied access to this airspace.

Under the rule, ADS-B Out performance will be required to operate in:

  1. Class A, B, and C.
  2. Class E airspace within the 48 contiguous states and the District of Columbia at and above 10,000 feet MSL, excluding the airspace at and below 2,500 feet above the surface.
  3. Class E airspace at and above 3,000 feet MSL over the Gulf of Mexico from the coastline of the United States out to 12 nautical miles.
  4. Around those airports identified in 14 CFR part 91, Appendix D.

The ADS-B Out rule does not apply in the airspace defined in items 1 and 2 above for any aircraft that was not originally certificated with an electrical system or that has not subsequently been certified with such a system installed, including balloons and gliders.

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What equipment is required by the new rule?

The rule specifies ADS-B Out equipment compliant with either Technical Standard Order (TSO)-C154c (Universal Access Transceiver) or TSO-C166b (1090 ES). However, to operate in Class A airspace, aircraft are required to equip with avionics certified to TSO-C166b.

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Do my current avionics meet the performance requirements of the rule?

Your avionics shop and equipment manufacturer can help you determine if your current equipment will meet the performance requirements of the rule and can advise you on available options and costs associated with any required upgrades. Likewise, they can advise you on equipment needed if you wish to install ADS-B In capability (e.g. FIS-B, TIS-B) – ADS-B In is not required under the current ADS-B Out rule. Advisory Circular 20-165 and 20-172 contain information about rule-compliant equipment installation and certification requirements and ADS-B In requirements.

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When do I have to equip?

The rule requires ADS-B Out performance by January 1, 2020, to operate in designated airspace. If you never fly into ADS-B-designated airspace, then there is no requirement to equip.

The ADS-B ground infrastructure is being deployed now and will be fully deployed by 2014, so those who choose to equip early will realize benefits long before the mandate.

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Will aircraft be able to fly in a non-transponder area without ADS-B?

For the most part, the ADS-B Out mandate covers the same airspace where transponders are required. However, to be sure of the regulatory requirements it is best to check 14 CFR § 91.225 for ADS-B-designated airspace and 14 CFR § 91.215 for transponder-designated airspace.

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What is the difference between ADS-B Out and ADS-B In?

ADS-B Out is the ability to transmit a properly formatted ADS-B message from the aircraft to ground stations and to ADS-B-In-equipped aircraft. ADS-B In is the ability of an aircraft to receive information transmitted from ADS-B ground stations and from other aircraft. ADS-B In is not mandated by the ADS-B Out rule. If an operator chooses to voluntarily equip an aircraft with ADS-B In avionics, a compatible display is also necessary to see the information. . Refer to AC 20-172 for information on ADS-B in installation and certification.

What are ADS-B In broadcast services?

ADS-B In pilot cockpit advisory services consist of Flight Information Service-Broadcast (FIS-B) and Traffic Information Service-Broadcast (TIS-B). These are free services transmitted automatically to aircraft equipped to receive ADS-B In.

FIS-B provides a broad range of textual/graphical weather products and other flight information to the general aviation community. FIS-B is only available on the 978MHz Universal Access Transceiver (UAT) equipment. FIS-B includes the following:

Page Last Modified: 05/13/13 12:29 EDT

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