When the FAA mandated Automatic Dependent Surveillance-Broadcast (ADS-B Out) for most aircraft by January 2020, there were the predictable complaints from various segments of the aviation community regarding acquisition and installation costs as well as the limited time available for operators to comply with the rule.

In time, the opposition turned to benign acceptance of ADS-B Out an integral part of the Next Generation Air Transportation System (NextGen), which aims to transition the National Airspace System (NAS) from ground-based radar and navigational aids to a spaced-based Global Positioning System (GPS). Now, interest is shifting toward the possible adoption of ADS-B In, the companion technology that enhances the baseline technology.

Improved situational awareness in domestic and international airspace along with enhanced traffic and weather data are a few of the surface benefits of ADS-B In. However, some of the more promising uses for ADS-B In are in developing standards for Interval Management and In-Trail Procedures (ITP). Those standards, which the FAA is developing presently and aims to release within the next 24 months, will create a template for avionics manufacturers and aircraft systems integrators to build and install ADS-B In on aircraft.

For General Aviation (GA) aircraft operators, ADS-B In is considered the “poor man’s TCAS [Traffic Collision Avoidance System]” and considered a vital piece of equipment. Equally important, the technology allows GA planes to operate almost autonomously in the NAS. ADS-B In provides additional capabilities beyond the safety and situational awareness benefits of the TCAS, however.

“There is a sea change occurring in general aviation as it relates to ADS-B In acceptance,” says John Uczekaj, president and CEO of Aspen Avionics. “Once ADS-B becomes more proliferated in the industry, people will come to the realization that the technology is a safety enhancing tool.”

At present, there are 10,000 aircraft, mostly GA planes, equipped with ADS-B In. “ADS-B In technology is here and those with it don’t ever want to be without it,” says Jens Hennig, vice president operations for the General Aviation Manufacturers Association (GAMA), and the organization’s primary voice on Air Traffic Control (ATC) modernization. Hennig also notes that the situational awareness enhancements gleaned from ADS-B In technology “are fantastic.” Noteworthy, is that the GA community — not commercial airlines — are leading the drive toward ADS-B In acceptance, says Uczekaj. He notes that in the past, that role was reversed, as airlines lead the effort to equip with ADS-B Out, mostly through necessity.

Avionics makers and associations such as the GAMA and the National Aviation Business Association (NBAA) have reported that GA aircraft operators find ADS-B In beneficial, in part, because of the numerous free services available to the aircraft via the Universal Access Transceiver (UAT). Originally developed as the single ADS-B data link for the NAS, UAT is now the preferred data link for all GA aircraft that fly below 18,000 feet.

The ADS-B Flight Information Services-Broadcast (FIS-B) weather and flight information service is only available to UAT-equipped aircraft. All larger commercial and business aircraft that operate at higher altitudes are required to have a Mode-S transponder operating on a 1090 MHz frequency with extended squitter.

Larger aircraft can still receive full ADS-B In services through the addition of a UAT receiver. It should be noted that UAT is only permissible as the sole ADS-B equipment up to 18,000 feet. However, aircraft can have a combined receiver that listens to both the UAT and 1090 link. If flying above 18,000 feet, an aircraft equipped with both receivers would comply with the mandate based on the 1090 link and would also receive the benefits of FIS-B services up to 24,000 feet.

For these aircraft, ADS-B Out is required to be part of that system. ADS-B In systems receive FIS-B weather and data services only on the 978 MHz frequency. Traffic Information Services-Broadcast (TIS-B), provides ADS-B Out/In-equipped aircraft with surveillance information about aircraft that are not ADS-B equipped. To qualify as a TIS-B target, an aircraft must be equipped with a transponder and be within radar coverage.

Tim Taylor, president of FreeFlight Systems, the company that produced the first rule-compliant UAT ADS-B system, believes ADS-B In “has become one of our fastest growing segments, for all aircraft types.” FreeFlight produces two UAT products for Part 23 GA aircraft and rotorcraft: the Rangr Blue ADS-B system, and the entry-level Rangr Lite. Both systems work with an iPad and other tablets. The Lite is available as an ADS-B transmitter and transceiver, and the Blue is available as an ADS-B transceiver or receiver. The FAA’s SC-186 technical group, the group of engineers chartered by the FAA to develop standards for avionics for ADS-B, has recently begun work to update the FIS-B standard to accommodate the new weather services offered in the ADS-B In Minimum Operational Performance Standards (MOPS). Harris is currently developing the new FIS-B products, and the avionics standards for these products are in parallel development within the RTCA SC-206 Committee, regarding Aeronautical Information and Meteorological Data Link Services (AIS).

Not on Board

For airlines, even those that have proven the benefits of the technology, ADS-B In is a tough sell. Airlines won’t spend money on any technology historically unless there is a compelling safety and business case. Several airlines told Avionics they have no immediate plans to outfit their fleet with ADS-B In. “ADS-B In is not yet mature enough for airlines to invest in,” says Joe Bertapelle, director of the strategic airspace program at JetBlue Airways. “The current status is on hold and future status is yet to be determined.” JetBlue obtained a Supplemental Type Certificate (STC) for ADS-B In with Astronautics and ACSS, but as of yet the airline hasn’t equipped any airliners with the technology.

UPS Airlines, an ADS-B pioneer, is in the process of removing obsolete ADS-B In equipment from its fleet of Boeing 767s and 757s, according to Christian Kast, advanced flight systems manager at UPS. The move is not because the carrier doesn’t believe in the potential value of ADS-B In. The avionics are more than 15 years old and were a product of its former UPS Aviation Technologies (UPS AT) subsidiary, which Garmin purchased in 2003 and has since stopped supporting the equipment.

Despite the potential, UPS’ interest in ADS-B In seems to have waned. “UPS has no current plans to equip for ADS-B In,” says Kast. “As UPS makes decisions on upgrading avionics for retrofit, ADS-B In is a consideration for provisioning. This capability must show demonstrable benefit versus the cost of equipping our aircraft.” UPS remains a strong advocate for ADS-B Out, however. The company’s Boeing 747, MD-11, 767, and Airbus A-300 freighter fleets have ADS-B Out already and Kast notes that the 757 fleet will install the technology as the aircraft cycle through their C-checks. Kast also says UPS would be ADS-B Out compliant well in advance of the

FAA’s 2020 mandate deadline.

FedEx is another carrier that sees the potential value of ADS-B In, but did not elaborate on its testing or current views on the technology. “FedEx is following the development of ADS-B In applications closely, and we are actively participating in benefits validation,” says Dan Allen, senior manager of air traffic operations at FedEx.

Still, Matthew W. Beres, airborne repair and maintenance analyst with Forecast International, an aerospace consultancy, believes that airlines may never equip their fleets with ADS-B In unless the government mandates the equipment. The why-do-I-need-this-technology mentality among upper airline management remains.
“If it is not mandated, most commercial aircraft operators aren’t going to install the technology,” says Beres. “It’s on their radar, but ADS-B In isn’t a priority.” Others believe operators cannot determine the long-term value of ADS-B In until ADS-B Out becomes fully operational and organizations can gather enough data to determine its effectiveness. “The industry push toward ADS-B Out is the baseline requirement to gaining the full ADS-B In situational awareness and operational advantages,” says Craig Peterson, senior director of commercial systems marketing at Rockwell Collins. “We don’t believe a mandate is necessary for operators to initiate ADS-B In applications as the implementation will provide the benefit that meets their financial requirements.”

Rockwell Collins has fielded numerous TCAS units that have a traffic computer that can add ADS-B In software. The company has certified its Integrated Surveillance Systems (ISS) to provide ADS-B In as an airline-selectable option. In another bid for the technology, all Honeywell Epic glass cockpits are capable of ADS-B In functions.

Mandated or not, Tom Dooling, senior manager of technical sales at Honeywell Aerospace says ADS-B In could help save airlines millions of dollars in fuel costs annually because of better sequencing of arriving aircraft. ADS-B In would be helpful particularly at facilities like San Francisco International Airport (SFO), which serves many wide-body long-haul aircraft daily, says Dooling. SFO’s two parallel runways can be tricky for pilots on approach from a weather and logistics standpoint. The airport could classify one runway for ADS-B-equipped aircraft, which could sequence aircraft more efficiently, while the airport could designate the other runway for non-ADS-B-equipped aircraft. At present, SFO only allows simultaneous landings on the parallel runways in ideal weather conditions.

Memory Lane

To understand the limbo in which ADS-B In finds itself requires an historical review. Between 2006 and 2007, an Aviation Rulemaking Committee (ARC) developed ideas for the ADS-B Out mandate. The committee developed a 10-year transition period from final rule publication to compliance date along with recommendations, which were submitted to FAA.

After the FAA published the ADS-B Out final rule in May 2010, the agency formed a separate ARC to develop a strategy surrounding how to develop ADS-B In as well as to consider advanced applications for the technology. The FAA published a 300-page report containing both immediate and long-term benefits of ADS-B In. It also took a look at other advanced applications, such as the ability to use ADS-B In as a tool to help initiate an altitude climb in oceanic airspace, as well as a way to enhance the flow and sequencing of aircraft into airports. The ARC report listed 10 applications for ADS-B In and recommended a phased-in approach for adopting the technology.

In 2009, the Radio Technical Commission for Aeronautics’ (RTCA) Task Force 5, which included airline representatives, stated unequivocally that it wanted to slow down certain elements of NextGen, including ADS-B In. “The task force report really slowed down a lot of the work on ADS-B In,” says GAMA’s Hennig. The report advised FAA to re-baseline and re-prioritize a number of ADS-B related programs as well as initiate more incremental improvements to enhance the air transportation system, with an eye toward the bottom line. Elsewhere, worldwide testing and development of ADS-B In is limited. ADS-B In is under development with the RTCA/ European Organization for Civil Aviation Equipment (EUROCAE) standards group but, at present, the only work to deploy ADS-B In is by way of the U.S. Government for applications, such as ITP.

While NATS, the United Kingdom’s air navigation service provider, does not currently rely currently on ADS-B to detect and track aircraft, the organization is studying the technology through Project Electronic Visibility via ADS-B, or Project EVA. With the study, NATS aims to enhance flight safety by improving the visibility of GA pilots to each other, and to air traffic control through the transmission and reception of ADS-B data, including gathering ADS-B In data. According to Project EVA material on the NATS website, the project aims to “show that innovative devices enhance situational and traffic awareness for the GA community.”

NATS is also conducting another trial in Southeast England to assess the quality of data produced by other non-certified GPS sources connected to Mode S transponders. Steve Fulton, a senior advisor and test pilot for Sandel Avionics, believes that while there are numerous discussions taking place regarding the pros and cons of investing in ADS-B In, the discussions are somewhat shortsighted.

When NextGen was launched, the FAA envisaged the program as a four-dimensional, trajectory-based operation. “The current operations are fairly tactical, and if we look at ADS-B In from that perspective, we can see how it has a lot of value,” says Fulton. “But if you make the jump to developing a more organized system, the individual airplane-to -airplane coordination is done in a more strategic manner through the use of Performance Based Navigation (PBN) procedures.”

According to Fulton, this requires time, speed and spacing tools to manage the flow of aircraft on PBN routes. Fulton co-chairs an RTCA Task Group that is developing recommendations for the FAA plans on the development of those tools. Flight interval management spacing, an application of ADS-B In, provides a unique performance increment in minimizing the variance in inter-aircraft spacing and is under review by the task group. Final recommendations are due in October 2016.

Will ADS-B In ever be on par with its Out counterpart? The GA community has embraced the technology, but Hennig says the airlines need to get onboard for the technology to become an integral part of NextGen. “FAA must precede any ADS-B In deployment with policies and revisions to the ATC Controller Handbook that would accommodate use in the NAS,” says Kast of UPS.

ADS-B In will, for now, likely remain a part of NextGen and other modernization efforts worldwide. Seasoning and acceptance of its sister technology must come first before In is in. “Fifteen years ago, people couldn’t dream that we would have three-dimensional synthetic vision and now we do,” says Uczekaj. “I think ADS-B In has a similar parallel. With extra data available, FAA’s ability to stimulate innovation by certification reform, and aircraft manufacturers wanting to differentiate themselves, you’re going to see its acceptance.” AVS