ATM Modernization

FAA Considers Reduced Separation Minima in Oceanic Airspace

By Woodrow Bellamy III | July 18, 2017

Boeing 787-10. Photo: Boeing.

Boeing 787-10. Photo courtesy of Boeing

The FAA is  developing a business case to establish reduced separation requirements for airplanes flying in U.S. controlled oceanic airspace. A government-industry body, the Enhanced Surveillance Task Group (ESTG) has determined the way to do this is by introducing space-based ADS-B into oceanic airspace controlled by the FAA. The questions now — how to pay for that and how to prove it would be effective, considering the mixed avionics equipage status of aircraft flying in U.S. oceanic airspace.

According to a new ESTG report, the Radio Technical Commission for Aeronautics (RTCA) NextGen Advisory Committee was tasked in July 2016 with developing a plan to assist the FAA in introducing better surveillance methods for U.S. controlled oceanic airspace. Over the past 12 months, the group received briefings from satellite service providers, air navigation service providers and operators.

Collectively, the enhanced surveillance working group concluded that the introduction of space-based ADS-B technology in U.S. controlled airspace could produce a reduced separation minima of 15/15. In order to produce this level of reduced separation minima, ESTG determined that space-based ADS-B would need to be coupled with Future Air Navigation System (FANS), controller-pilot data link, Automatic Dependent Surveillance – Contract (ADS-C) and Required Navigation Performance Level 4 (RNP4) capabilities.

The two specific surveillance technologies considered by ESTG for improving oceanic air traffic flows include space-based ADS-B and ADS-C technologies. ADS-C is a surveillance technique that uses onboard aircraft systems to automatically provide position, altitude, speed, intent and meteorological data sent in a report to an air traffic service unit or airline operational center ground system for surveillance and route conformance monitoring.

ADS-C has been in use in oceanic airspace for two decades, but the group was considering the use of classic ADS-C with higher update rates and increased equipage. But according to the report, there was a “a fundamental disagreement between the industry and the FAA about the nature of ADS-C as surveillance using via HF.”

“Reduced separation, resulting in increased capacity, increased availability of optimal altitudes, and optimal routings, while continuing to support cost index speeds, are the primary benefits from spaced based ADS-B,” the report says.

In February, Vitaly S. Guzhva, a professor at Embry Riddle Aeronautical University, and Kenny Martin, managing director at air traffic management software company ISA Software, produced an operational analysis of reduced separation in FAA-controlled oceanic airspace for the ETSG. Using ISA’s “RAMS Plus” gate-to-gate air traffic fast time simulation model, the analysis evaluated how the use of space-based ADS-B combined with assumed increased FANS equipage could provide benefits for U.S. airlines. Their analysis found that annual benefits for airlines operating in Atlantic and Pacific U.S. controlled oceanic airspace could reach up to $440.5 million in fuel burn and other operational savings, and a reduction of up to 1.2 million metric tons of carbon dioxide.

The task group also analyzed how space-based ADS-B could benefit aircraft flying in specific oceanic regions, including the North Pacific, Central Pacific, and West Atlantic Route System, among others. One issue that was found when examining specific regions was the variation in the number of aircraft equipped with ADS-B, FANS/RNP4 and other advanced avionics.

“An aircraft equipped with FANS/RNP 4 cannot receive the benefit of reduced separation standards if all the aircraft surrounding it are equipped with HF communications and surveillance limited to significant waypoints because this type of equipage is limited to 50 nm lateral separation and 10 minutes longitudinal separation,” the report says. This would raise the need to establish special consideration to separate aircraft featuring advanced equipage from aircraft with less advanced equipage. The biggest problem areas identified by the group were the WATRS region and the airspace between the West Coast and Hawaii.

Finally, the cost of introducing space-based ADS-B is also a major consideration for enhanced surveillance in oceanic airspace. The report featured two possibilities for covering the cost of introducing space-based ADS-B in U.S.-controlled oceanic airspace. These two options include a cost model in which operators would contract directly with the service provider — a model similar to that used for the provision of ADS-C services. ESTG opposes this option, saying having operators bear the financial burden introduces “an unwarranted and unneeded level of financial and operational complexity.”

The other option is for the FAA to pay for the provision of space-based ADS-B itself. It would be dependent on the FAA receiving funding to provide the new service.

According to data provided by Aireon, which started seeing its first space-based ADS-B messages in January 2017, 10 total air navigation service providers from around the world have signed up for space-based ADS-B service once it becomes fully operational next year. Among them include NAV Canada, the U.K.'s NATS and the Civil Aviation Authority of Singapore. Another 20 countries have established memoranda of understanding with Aireon.

View the ESTG report in its entirety here.

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