It’s now less than two years until January 2, 2020—when the FAA has mandated installation of Automatic Dependent Surveillance-Broadcast (ADS-B) Out to fly in airspace where a transponder is required today. ADS-B uses satellites instead of ground-based radar to determine aircraft location, and is a key technology behind the FAA’s Next Generation Air Transportation System.
According to FAA data, as of December 1, 2017, 46,968 U.S.-registered aircraft had equipped with ADS-B Out. Of that total, 34,400 are certificated fixed-wing general aviation aircraft, and another 1,542 are registered to U.S. air carriers.
It’s hard to say how many more must equip by 2020, because nobody knows how many aircraft require ADS-B capability. The FAA and Aircraft Electronics Association have talked about equipage requirements of 120,000 to 160,000 aircraft, but those forecasts are based on aircraft with transponders. The actual number on January 2, 2020, will be much lower—maybe 70,000 or 80,000.
Why? Not all GA aircraft have to equip. If you don’t fly in Class A airspace; in and above the 30-nautical-mile Mode C veils surrounding Class B; in and above Class C; or Class E airspace at and above 10,000 feet msl, excluding airspace at and below 2,500 feet agl—or at and above 3,000 feet msl over the Gulf of Mexico, within 12 nm of the U.S. coastline—ADS-B is not required.
But the airlines can’t choose not to equip, or delay installations until 2020. Their turbine aircraft can’t fly efficiently below 10,000 feet msl, and few can avoid Class B and Class C airspace.
You may have heard about an exemption for the airlines. They do have a five-year grace period, but it applies only to upgrading GPS position sources to fully comply with ADS-B rules—airliners still have to equip with ADS-B Out by January 2020.
Why aren’t the airlines further along? Some have made significant strides—United Parcel Service’s fleet is 99 percent equipped, FedEx is at about 37 percent, and United and JetBlue both are at about 35 percent.
Southwest Airlines currently operates 700 Boeing 737s. Only its 14 newest jets, 737 MAXs, are ADS-B Out-equipped. “The airlines can only buy things that are for sale. Until three months ago, there was nothing for us to buy,” explained David Bunin, a Southwest avionics engineer. There were no certified ADS-B transponders or rule-compliant GPS receivers. Like many GA aircraft, airliners are not WAAS GPS-equipped—with multisensor flight management computers that combine inertial navigation, DME, GPS, and other position sources, WAAS wasn’t needed.
Changes to DO-260, the RTCA specification for Mode S Extended Squitter/ADS-B transponders, partially caused the delay in hardware availability. Europe’s ADS-B rules use the DO-260A standard, and the FAA mandated DO-260B while DO-260C was being discussed. “There were so many changes, the industry wasn’t confident there wouldn’t be another change,” Bunin said.
As a result, Air Transport hardware providers such as Boeing, Collins, and Honeywell didn’t have solutions. “Not only did they have to develop the transponder, but they had to develop a WAAS GPS—which they’d never done before—and get it certified.” That’s the primary reason behind the airlines’ ADS-B position source exemption, he added.
Now there’s a 1090ES transponder for Southwest’s fleet, but the company is waiting for a service bulletin authorizing its installation. “What we’ve been doing is installing the wiring. We’ve been working on that for the last year,” Bunin said. “Once we get the authorization and get the physical parts, we’ll be doing the upgrades aggressively. We don’t object to the mandate—we want to comply.”
Beginning this summer, Southwest will have 18 months to install nearly 1,400 new transponders (each jet carries two). With the wiring in place, that can be accomplished during an overnight layover, said Bunin, who is confident the airline will meet the 2020 deadline. The total cost to the company will be in the hundreds of millions of dollars. “I fly a Cessna 172—it’s a Hawk XP,” he said. “The first transponder on the jet, alone, costs more than my whole airplane. And there’s two of them.”
Ankit Nanda, director of engineering for Allegiant Air, presented a similar perspective at Avionics magazine’s Avionics for NextGen conference in Herndon, Virginia, in November. Allegiant has a mixed fleet and although it’s been discussing ADS-B for a couple of years, even for its Airbus jets there is not a universal equipage solution, he said. Another challenge is making ADS-B seamless to pilots, and training implications also must be considered.
“We’re trying to figure out what ADS-B brings to us from a flight operations perspective,” Nanda said. “We’re looking at what benefits we can implement sooner rather than later.” Opportunities such as optimized flight profiles and fuel-efficient routings all have training implications.
Allegiant plans to retire its McDonnell Douglas MD–80 jets before 2020. “Part of [that decision] is the cost it would take to make them 2020-compliant,” Nanda said. The company also has a diverse fleet of Airbus A319 and A320 jets that have two different equipment requirements. “On the Airbus side of things, for some reason, there is not a lot of equipment available out there. It’s a very tight timeline.”
While the larger group awaits approval of an STC, a solution identified for the other Airbuses was too costly. “When two aircraft are going to cost the same as the rest of my fleet, that’s not an acceptable solution,” said Nanda, who discovered that he could pair a GPS receiver with ADS-B Out transponders. The aircraft with older avionics will be his first two equipped.
The Department of Defense is not exempt from the ADS-B Out mandate, U.S. Air Force Capt. Devin Borden, a NextGen analyst, said at Avionics for NextGen. “However, it is well known that DoD will be late to the party,” he said, adding the military will need airspace access and is working with the FAA to facilitate that.
“We’ve known about this since 2010 and we still have issues with equipping,” Borden said. One concern involves the security of some ADS-B data. “We don’t want that seen by the public or bad actors,” he explained. And the military is transitioning to a new military- or M-code GPS receiver designed to improve positioning, timing, and security; an interim transition to an ADS-B-compliant position source would be very expensive. But M-code keeps getting pushed back, with deployment currently scheduled in 2021.
“We’re not fighting NextGen,” Borden said. “We’re working diligently with the FAA to not disrupt the [National Airspace System].”
And the military is beginning to equip. Textron Aviation in Wichita recently received an $8 million contract to add ADS-B to 255 U.S. Navy and Army T–6 Texan II turboprop trainers—that’s $31,373 per aircraft. The project requires replacing the Mode S transponder and GPS antenna, and upgrading the GPS receiver in the aircraft’s integrated avionics computer with a new Space Based Augmentation System (SBAS)/WAAS receiver. Textron also will update the T–6 flight management system software and the aircraft’s ground-based training system.
In early December, Global Aviation Technologies in Wichita received the first of 19 C–21A jets—military Learjet 35As delivered in 1984 and 1985—that it is updating with ADS-B, glass panels, and controller-pilot data link communications. The $32.2 million contract—about $1.7 million per jet—does far more than meet the ADS-B mandate, and acknowledges the benefits of bundling ADS-B with other avionics upgrades.
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