Editor’s Note: ADS-B: Its Time Has Come

It was quietly disclosed, with little fanfare. Had you not read an article by Charles Keegan, vice president, operations planning, with FAA's Air Traffic Organization, in an RTCA newsletter, you probably wouldn't know the decision was made. "We consider it an internal milestone," says Paul Fontaine, FAA's manager of future surveillance systems, explaining the agency's low-key disclosure.

And a milestone it is. Keegan announced that FAA's Joint Resources Council has decided to begin developing the Next Generation Air Transportation System (NGATS) by selecting automatic dependent surveillance-broadcast (ADS-B) as the preferred option for the future surveillance system in U.S. airspace. In coming months, with input from the aviation industry, the agency will enter a second phase in ADS-B development, working out details toward a final decision on the technology, at which point a true milestone will exist.

And, yes, that Phase 2 could involve equipage mandates. As a result of FAA's recent decision, says Keegan, "the agency will be examining options for rulemaking, including a timetable for requiring ADS-B equipage within various classes of airspace." FAA plans to begin work on the second phase this month and have it completed by July 2006.

Beginning NGATS development with ADS-B makes sense. For its initial decision, in addition to ADS-B, FAA looked at other options for future surveillance. They include maintaining the current ground radar infrastructure, which would be very expensive, and establishing a nationwide multilateration system, which is less expensive than ground radar but is more costly than ADS-B. All three options "have comparable capabilities," says Fontaine.

Cost savings are the key benefit that ADS-B delivers to FAA. The new surveillance system would allow the agency to phase out its 328 beacon radars, 43 airport surface detection equipment (ASDE) radars, and seven precision runway monitoring systems. "We would expect attrition of these systems, starting in 2018," says Fontaine.

But the agency also believes ADS-B technology has proven its worth to pilots and aircraft operators. Alaskan pilots, flying in an environment with a quite limited ground surveillance infrastructure, have seen improved safety from ADS-B, which is part of FAA's Alaskan Capstone project. ADS-B is largely an airborne system, requiring an airborne GPS receiver for aircraft positioning, an airborne transceiver/transponder to broadcast the aircraft's position information and receive the positioning data of other aircraft, and a cockpit display of traffic information (CDTI).

U.S.-based freight carriers have long been evaluating applications of ADS-B, including enhanced visual approaches. And, at its Tech Center, FAA has demonstrated that weather and temporary flight restrictions can be uploaded to pilots via ADS-B.

In short, Fontaine proclaims, "We've refined ADS-B and brought it to a decision point--and we made the decision [to make ADS-B an approved option] because we don't want open-ended R&D."

During Phase 2 the agency also will be looking at future applications of ADS-B--what Fontaine calls "transformational capabilities." These include using ADS-B as a surface movement tool in order to help prevent runway incursions. The agency will flesh out its plans for TIS-B (traffic information service-broadcast) and for a nationwide network of ground transceivers that ensures wide coverage of broadcast position data. Currently, 30 ground stations deliver the ADS-B service along the U.S. East Coast and parts of Arizona, North Dakota, Ohio and Wisconsin. These transmit and receive via a universal access transceiver (UAT) data link, but FAA plans to install dual-link transceivers that also include Mode S with 1090ES (extended squitter) capability. FAA envisions 420 ground stations positioned in the U.S., Gulf of Mexico and Caribbean, says Fontaine, adding, "We don't have the specs [for the transceiver] yet. That, too, will be part of the next phase."

ADS-B is the initial enabling technology for NGATS, but it won't be the last. Fontaine hinted that other technologies may soon be announced, including a system-wide information network.