Air Traffic Services Brief -- Automatic Dependent Surveillance-Broadcast (ADS-B)

Illustration by John Macneil

Air Traffic Services Brief

Automatic Dependent Surveillance-Broadcast (ADS-B)

The issue:

ADS-B, or Automatic Dependent Surveillance-Broadcast, is a cornerstone of NextGen air traffic modernization, and the FAA has mandated that aircraft operating in airspace that now requires a Mode C transponder must be equipped with ADS-B Out by Jan. 1, 2020.

ADS-B Out transmits information about altitude, airspeed, and location derived through GPS from an equipped aircraft to ground stations and to other equipped aircraft in the vicinity. Air traffic controllers use the information to “see” participating aircraft in real time with the goal of improving traffic management.

ADS-B in, which is not part of the mandate and requires additional equipment, allows participating aircraft to receive traffic and weather information from ADS-B ground stations and nearby aircraft broadcasting their positions through ADS-B Out. This information can be displayed in the cockpit to improve situational awareness,

The ADS-B Out rule does not affect current transponder requirements, meaning aircraft must continue to carry their transponders even after equipping for ADS-B Out.

Unlike most rulemaking activities which are safety based, the basis of the ADS-B Out mandate is to support the FAA’s Next Generation Air Transportation System (NextGen). The FAA has said that the mandate will not greatly increase or decrease safety, but is necessary to move forward with NextGen.

The Importance to our Members:

The high cost of the necessary avionics and the lack of direct benefits are the two greatest barriers to the adoption of ADS-B Out by a large segment of general aviation operators.

The current cost to install mandated ADS-B Out equipment is at least $5,000 to $6,000. An AOPA analysis of the FAA’s Aircraft Registry shows that at least 81,564, or 43 percent, of the 188,099 piston-powered, fixed-wing, certified general aviation airplanes on the FAA registry have an average retail value of $40,000 or less. The weighted average value for this segment is $25,865.

When stacked up against these numbers, the price to meet the mandate is excessive and unreasonable for a large segment of the GA fleet, especially when the operator does not derive any benefit for equipping beyond the ability to continue to fly in the same airspace used today. In order to receive the added situational awareness benefits of traffic and weather information in the cockpit, aircraft owners must also install ADS-B In equipment.

Largely as a result of this high cost/low value equation, the FAA estimated that just 10 percent of the general aviation fleet was equipped for ADS-B Out at the end of the 2014 fiscal year. This puts the FAA’s current ADS-B implementation strategy at risk and jeopardizes the agency’s goal of meeting the 2020 mandate for fleet-wide equipage.


Since 1990 AOPA members have embraced Global Positioning System (GPS) technology and ADS-B has been part of the FAA’s long-term modernization plans. Since 1999, AOPA has carefully evaluated ADS-B in an effort to confirm the technology’s potential benefits. By working closely with general aviation pilots in a widespread ADS-B trial and demonstration in Alaska, and by equipping AOPA-owned aircraft with ADS-B, we have seen first-hand the safety and efficiency improvements that are possible, if the system is designed and implemented correctly.

In 2007, the FAA began deploying ADS-B infrastructure and proposed mandatory aircraft equipage. AOPA immediately identified a number of significant issues that would likely reduce or eliminate the benefits of ADS-B for general aviation. In 2008, when the FAA issued its proposed rule concerning the mandatory adoption of ADS-B Out, AOPA outlined the barriers to ADS-B equipage, including the high cost and lack of benefits, and proposed alternatives in formal comments.

Now, with five years remaining until the Jan.1, 2020, deadline, the FAA has made it clear that it will not delay the mandate. AOPA is disappointed with the agency’s failure to address the cost issue, and the association continues to advocate for low-cost alternatives to the current ADS-B Out certification standard.

Technology has changed significantly since the mandate was announced in 2010. The widespread use of the iPad, introduced in 2010, and the proliferation of useful aviation apps have made it much easier and less expensive to bring weather and other information into the cockpit. At the same time, innovations in the non-certified marketplace have changed the technological landscape. While these may not be solutions in themselves, AOPA believes they may point to a strategic direction that could offer ADS-B Out equipage at a significantly lower cost.

AOPA’s Position

For nearly 20 years AOPA has supported the transition from ground-based infrastructure to satellite based systems. AOPA generally supports the ADS-B concept and recognizes the importance of near-universal participation. Aircraft operators who can identify clear benefits to their operations and can afford to do so are encouraged to equip ahead of the ADS-B Out mandate.

However, it is difficult to identify adequate benefits in the ADS-B implementation strategy for some operators, particularly the owners of low-value piston-powered aircraft. AOPA expects many of its members to delay equipage as long as possible and anticipates some will be forced to ground their aircraft in 2020 unless a lower cost solution can be found. As noted in comments to the FAA, AOPA continues to have a number of concerns with FAA’s implementation strategy to include:

  • Affordability. AOPA has recommended several technical changes that would reduce the price of ADS-B systems. AOPA has also called on the FAA to permit pilots to use hand-held ADS-B receivers that can obtain free traffic, weather, and airspace status content from the ADS-B infrastructure.
  • Collision risk. The FAA is implementing ADS-B on two independent, non-compatible frequencies. Unless general aviation pilots equip aircraft in such a way that they receive the ADS-B transmissions on both frequencies, they will likely see only one-half of the ADS-B equipped fleet. The costs and availability of dual-frequency ADS-B receivers is not known. The FAA could address this concern in two ways: 1) either provide a re-broadcast service at all general aviation airports or 2) require all aircraft to transmit on the same frequency.
  • Mandate not necessary. AOPA recommended that the FAA exclude low-altitude operators from the mandate because the financial benefits all stem from operations in high altitude airspace, over the Gulf of Mexico, or when operating to and from the largest airline airports. An independent FAA-sanctioned rulemaking committee confirmed the AOPA recommendation would achieve most of the benefits without the widespread mandate on general aviation.
  • Transponder removal. AOPA recommended that because the FAA plans to transition from radar and transponders to ADS-B, that general aviation aircraft should be allowed to remove their transponders. However, the FAA has rejected that proposal, primarily because they have not adapted Traffic Collision Avoidance System (TCAS) to support ADS-B.
  • ADS-B infrastructure. The FAA has installed the ADS-B infrastructure to provide the same coverage as radar. Except for overwater, deep in the Gulf of Mexico, no new airspace or airports are expected to receive surveillance as a result of the ADS-B infrastructure installation.

Status / Next Steps for ADS-B

In September 2014, the Department of Transportation’s Inspector General released a report identifying numerous problems with the ADS-B implementation process, including many that were raised previously by AOPA. The problems included delays, cost overrruns, the high cost to equip, lack of benefits, issues with data integrity, coverage gaps, and more.

On Oct. 28, 2014, AOPA President Mark Baker sent a letter to the FAA administrator urging the agency to address the negative economic impact of the mandate on general aviation, the logistical challenges of meeting the mandate, the potential to lower the cost of compliance through the use of alternative equipment standards, and the findings of  the Inspector General’s report.

The letter noted that the minimum investment of $5,000 to $6,000 to install ADS-B-Out equipment is “far too high” for many GA operators, especially given that the general aviation fleet includes at least 81,564 certified, piston-powered, fixed-wing aircraft that are valued at $40,000 or less, and that GA owners have no way to recoup their costs.

Also in October 2014, AOPA participated in an FAA-sponsored Call to Action to identify the barriers to meeting the ADS-B Out mandate. AOPA is now working with the FAA, avionics manufacturers, and industry experts to develop solutions to overcome those barriers as part of the Equip 2020 group.

AOPA is pleased that the FAA is prepared to address the barriers to compliance with the mandate and confident that the cost issue can be effectively addressed so that all segments of the general aviation community can participate in ADS-B Out and the FAA can meet its goal of modernizing the nation’s air traffic system.