Although a demonstration in Alaska of “automatic dependant surveillance-broadcast” (ADS-B) has hit a temporary snag, both the Federal Aviation Administration (FAA) and the local aviation community believe that the technology has a huge role to play in improving aviation safety.
On March 24, FAA decided to turn off the display of ADS-B targets on air traffic controller screens in the southwest part of Alaska around the city of Bethel, also referred to as the Yukon-Kuskokwin delta region. At the time, FAA expressed the concern that controllers’ use of the ADS-B targets was “exceeding current authorization to provide services in a mixed (radar & ADS-B) environment.” Since then, the agency has been conducting an extensive investigation, and a decision to restore the ADS-B targets is expected any day.
The Yukon-Kuskokwin delta has been the “phase one” location of a multi-system safety demonstration program known as the “Capstone,” and is directly managed by the FAA Alaskan Region. While this part of Capstone is temporarily down, all other elements of the program — including others that also use ADS-B — remain fully operational. Then again, everyone involved in Alaskan aviation — including national and regional FAA staff, the Alaska Aviation Coordination Council (AACC), and the National Air Traffic Controllers Association (NATCA) — expects the ATS-B system to come back online soon, albeit with some procedural adjustments.
Overall, FAA credits Capstone with reducing accidents in the Bethel region by 47 percent. Partly because of Alaska’s mountainous terrain, its often extreme environmental conditions, as well as a history of aviation mishaps, Alaska has recently evolved into something of a test bed for various aviation modernizations and safety initiatives. In essence, Capstone is an effort to integrate the latest of those modernizations.
Speaking of the interruption in controllers’ ADS-B displays, AACC Chairman Skip Nelson says, “Most of us feel what’s happened in the last couple of months is no more than a small technical correction. Nobody’s talking about fatal flaws or the death of a program.” Moreover, the lessons learned in Alaska will probably be seen someday as an important part of the technology’s growth, Nelson tells Air Safety Week.
Nelson, who also is president of ADS-B Technologies, Inc., is among many aviation officials in Alaska who speak strongly of FAA’s commitment to resolving the current difficulties.
Indeed, the agency refers to ADS-B as “the future of air traffic control” in a new May 2 fact sheet on the technology, which also serves to remind the aviation community that FAA has requested $80 million in fiscal year 2007 for supporting ADS-B infrastructure installation on the East Coast.
As recently as May 4, FAA Administrator Marion Blakey testified before the Senate Transportation Committee that ADS-B and another technology known as “system wide information management” (SWIM) are the “two cornerstones to the next generation air transportation system.” ADS-B, in particular, she testified, “will reduce infrastructure costs, increase capacity, and can have significant safety benefits as shown in the Alaska context.”
Instead of pilots and controllers having to rely on radar signals to spot another aircraft’s approximate location, an ADS-B transponder installed on each craft uses signals from GPS satellites to determine a more precise position. The GPS signal also is combined with other information from a craft’s flight monitoring system, such as the type of craft, its speed, direction, and flight number. The result is real-time displays of local air traffic within 200 miles for both controllers and pilots, FAA says.
The high expectations for ADS-B at FAA and in the U.S. aviation community is hardly news. Last September, for example, FAA declared that ATSB is a key part of the agency’s effective and safe future management of the national airspace system (NAS). What will come as more of a surprise to the aviation community is that ADS-B by itself could generate some safety concerns.
At least it has according to NATCA, the main national union for FAA’s controllers. Around the middle of last year, Rick Thompson, NATCA Alaskan regional vice president, started sending a series of letters and emails to Rick Day, FAA’s vice president for en route and oceanic services, with certain concerns about the safe operation of ADS-B and the professional conflicts it was creating for controllers. That resulted in the first brief shutdown of ADS-B targets last August, instigated by the acting air traffic manager in Anchorage. But the union didn’t think much had changed after the targets were restored to controllers’ screens that first time, and continued pressing its concerns on FAA. This resulted in the current shutdown starting on March 24, followed by a team of about 20 FAA officials and technicians visiting Alaska in April for a first-hand look.
A principle concern for the union was that some aircraft operating in the Yukon-Kuskokwin delta were equipped with ADS-B, while others weren’t. Those other craft were still sometimes picked up on conventional radar, and controllers were having difficulty keeping the two types of signals separate on their screens, says Doug Fralig, NATCA’s director of technology.
As long as the ADS-B-equipped craft remained in the trial area — where no radar was possible — there wasn’t a problem, Fralig explains to Air Safety Week. But that changed whenever such a craft left the area’s boundaries or climbed to a higher altitude, and could then be picked up on radar. Moreover, controllers had no capability for turning off one of the signal sources.
NATCA also has said repeatedly that it is fully supportive of ADS-B as a tool for safe air traffic management, but insists that some glitches have to be ironed out before the technology sees common use.
After the initial ADS-B shutdown last August, NATCA’s Thompson complained to FAA ADS-B was turned back on Aug. 9 with “no fixes to the equipment … identified.” That placed the burden squarely on the controller to identify and report new problems, and to decide whether to instruct a pilot to shut off the ADS-B equipment. Also, the same aircraft could go out on a later flight, with “the same or different controller … left to re-identify the problem again.”
To those concerns, FAA’s Day replied to Thompson (in a copy of Day’s return message forwarded by NATCA) that FAA “took steps” to address controllers’ concerns. Moreover, “as an ADS-B displayed target can only be used in non-radar areas and not in a mixed environment, there should not be any degradation in our safety margins provided [FAA] procedures are followed…”
NATCA’s Thompson tried to dispel FAA of the notion that ADS-B signals weren’t getting mixed in with radar. As Thompson’s March 22 message to Day reads, “It is a fact that [Anchorage Center] controllers on a daily basis separate numerous aircraft.” Furthermore, Thompson felt that controllers were jeopardizing their careers by helping FAA try out the new technology “with no clear direction” from the agency. If an accident occurred, he continued, FAA would surely blame the controller, and not its own procedures.
Two days after that message, FAA decided to pull the plug — at least for a while. But why it did is subject to interpretation. According to a March 8 letter to AACC’s Nelson, FAA Administrator Marion Blakey said the decision was made because of a possible “improper separation standard” being used by Anchorage controllers monitoring aircraft either through ADS-B or radar.
At any rate, FAA’s actions had nothing to do with NATCA, insists Patrick Poe, administrator for the FAA Alaskan Region.
Nelson believes that “controllers and perhaps FAA do not have a good feeling for exactly how to separate ADS-B from radar.”
There was hope that FAA was going to announce a resolution to the matter by May 12. The hope arose from what Poe and others characterized as an “unprecedented” meeting two days before on May 10 among FAA national and regional staff, as well as Alaska aviation officials, where FAA affirmed its strong support of restoring the ADS-B display targets.
Nelson, who was part of the May 10 meeting, says there’s a general feeling that there will be some type of announcement or service restoration by June 1.
A chief issue in managing the “mixed environment” of both radar and ADS-B signals is the fact while the former takes a few seconds to ping back and forth, the latter is based on digital technology and is updated every second, Nelson says. Ultimately, it is up to FAA’s technicians to develop the algorithms that will keep the signals separate.
Also, when FAA turned off ADS-B targets on controllers’ screens at the Bethel control tower in late March, the agency inadvertently turned off several other ADS-B services. As AACC’s Nelson wrote to Blakey on March 29, this occurred without any notice as the Alaska aviation industry was entering its busy spring-summer travel season.
FAA quickly restored the other interrupted services, including operational fleet monitoring and the display of traffic information in the Bethel control tower.Still other ADS-B services, including flight information services-broadcast (FIS-B), air-to-air situation awareness, and search and rescue have continued to function without disruption, FAA says.
Meanwhile, Capstone already is proceeding from “phase one” in the Yukon-Kuskokwin delta region into “phase two” in the southeast area of the state around the capital of Juneau, Poe says. Phase two also will have a slightly different, and somewhat “more sophisticated” suite of technologies, Poe adds. This will include Chevron Flight Systems‘ Electronic Flight Information System, which includes real-time 3D terrain modeling, airspeed, groundspeed, altitude data, and many other types of information, FAA says.
>>Contacts: Patrick Poe, Alaska Regional FAA, (907) 271-5645; Doug Fralig, NATCA, (202) 628-5451; Skip Nelson, AACC, (907) 264-6798, [email protected]<<