ADS-B and the NextGen Air Traffic System

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As the national airspace system evolves, the FAA will be utilizing many new technologies. One of the primary systems that is being implemented within the FAA’s NextGen program is ADS-B, which stands for Automatic Dependent Surveillance-Broadcast. In an effort to streamline operations, the FAA is implementing ADS-B as the primary source of navigation for all aircraft within the national airspace system. While ADS-B is already operational in most o the United States, there are still questions about the risks and costs involved.


The Role of ADS-B

In the near future, the aviation industry will be asked to accept the idea of free flight, a method of reducing air traffic congestion through the use of ADS-B. The ADS-B system also reduces pilot and controller workload and provides more direct routing for aircraft, saving money and time across the board.

For years, the air traffic control system in the United States has suffered from inefficiencies. The system continues to see an increase in consumer demand as well as delays. 

In a 2009 report, the FAA stated, “Without NextGen there will be a gridlock in the skies. By 2022, FAA estimates that this failure would cost the U.S. economy $22 billion annually in lost economic activity. That number grows to more than $40 billion by 2033 if the air transportation system is not transformed.”

The role of the ADS-B system is an extensive one. The system uses highly accurate GPS-based ground and air surveillance to provide controllers and pilots with precise, real-time data. This data, more accurate than radar itself, can be used to reduce separation between aircraft, increase safety and provide more direct routes for airplanes. In addition, real-time traffic and weather functions will be provided in the flight deck, in some cases at no cost to the operator. 

ADS-B uses an aircraft-based transponder (Mode S), the global navigation satellite system (GNSS), and ground stations to determine altitude, speed and track for aircraft. The information is then relayed from aircraft to aircraft and from aircraft to controller or ground station, along with any other participating parties. 

Safety Risks

Overall, the ADS-B system is a major improvement for the future of our airspace system. But it’s not without risk. With the current radar system being a mostly risk-free, accurate navigational system, a move to a completely new system brings up questions of reliability, safety risks and cost. What are those questions and risks, and have they been mitigated to an acceptable level?

While the FAA has demonstrated that the final result will be an unequivocally safer, more efficient air travel system, and they’ve conducted research to back up their stance, they’ll need to continue to examine and re-examine the program from a safety perspective. The implementation of any new system is likely to bring unknown errors and hazards. For ADS-B, these hazards include:

  • Training and human factors
  • GPS failure
  • Avionics malfunctions
  • Security issues

These issues have yet to be resolved entirely, but they’ve been identified as risks and measures have been taken to minimize their risk as much as possible. A 2000 study completed a typical system safety precedence sequence with regards to the system as a whole, and found the residual risk to be “controlled to an acceptable level.”

Early in the development of ADS-B, the Capstone System Safety Working Group was established in partnership with the FAA to provide the necessary research and preliminary hazard analysis of ADS-B. The hazards determined include the following: 

Human Factors

  • Confusion and loss of situational awareness
  • Inappropriate use of avionics
  • Pilot procedural errors
  • Coordination issues with ATC
  • Loss of situational awareness due to too much “heads-down” time

Ground System Risks

  • Calibration errors
  • Loss of communication
  • Malfunction

Avionics Failure

GPS Errors 

Weather, traffic and terrain malfunctions

  • Lack of coverage
  • Limited forecasts
  • Limited reporting stations

Security vulnerabilities

  • Spoofing, jamming and masking

For the most part, these risks have been researched, analyzed, mitigated and accepted. But one of the biggest hazards associated with ADS-B still remains: Human error. If the pilot doesn’t fully understand the equipment he or she is using, the system becomes a hazard instead of a benefit. Studies suggest that advanced avionics systems require in-depth training and understanding for operators to use safely, and many operators will not voluntarily receive the training they need to safely fly with ADS-B.

And the FAA’s ADS-B mandate for all aircraft to be equipped with ADS-B by 2020 will intensify the costs and hazards associated with advanced avionics and human error.

The Capstone project determined that excessive heads-down time while using ADS-B would potentially result in a frequent loss of situational awareness and that although an accident might be rare in this case, a resulting accident would likely be catastrophic. This is a constant risk that will continue to be a problem for ADS-B users as it becomes a familiar addition to the flying world. Pilots must accept responsibility for mitigating this risk as much as possible through training and awareness.

When all is said and done, ADS-B is a safe, efficient addition to the nation's airspace system. But like any navigation aid or avionics system, it's only as safe as its operator.