P&E: ADS-B

Important clarifications, with a connection

Australia. 1090ES required today above Flight Level 290, and February 4, 2016, for operations in specified airspace. Beginning February 2, 2017, required for all IFR flights.

Canada. Currently no mandate, but operators who voluntarily equip with 1090ES (particularly in the Hudson Bay and nearby oceanic airspace) can receive a higher level of service. Nav Canada is part of a joint air traffic surveillance venture, Aireon, installing ADS-B equipment on low-Earth-orbit satellites. Nav Canada will be the launch customer when the service becomes available in 2018, and initially intends to incorporate ADS-B into North Atlantic airspace.

Europe. 1090ES required for IFR aircraft with a maximum takeoff weight exceeding 12,566 pounds or maximum cruise airspeed faster than 250 KTAS. Mandatory for new-production aircraft beginning June 8, 2016, and must be retrofitted into all aircraft by June 7, 2020. (Dates slipped from original timetable.)

Hong Kong. 1090ES required on specified airways, FL290 and above; in all airspace, FL290 and above, beginning December 8, 2016.

Indonesia. 1090ES required, FL290 and above, beginning January 1, 2018.

Mexico. A proposal would require 1090ES January 1, 2020, in Class A, B, C, E above 10,000 feet msl, and other specified airspace; possibly sooner in some airspace over the Gulf of Mexico.

Singapore. 1090ES required on specified airways.

Sri Lanka. 1090ES required within the Colombo Terminal Control Area (TMA), FL290 and above.

Taiwan. 1090ES required on specified airways, FL290 and above; in all airspace, FL290 and above, December 31, 2016.

Vietnam. 1090ES required on specified airways.

See AOPA’s new online ADS-B resources and ADS-B selection tool.

There is a lot of confusion among aircraft owners regarding ADS-B Out requirements for international operations. There’s also some confusion—maybe it’s more curiosity—about diversity as it relates to Automatic Dependent Surveillance-Broadcast.

ADS-B is a key technology behind the FAA’s Next Generation Air Transportation System. The FAA has mandated ADS-B Out equipage beginning January 1, 2020, for most operations in airspace where a transponder is required today. Antenna diversity is required for certain aircraft and may benefit others—and it may eventually prove a component of equipping for certain international operations.

Two antennas, better signal

What diversity means in the world of ADS-B is simply this: The system is able to transmit and receive on two different antennas, with one mounted on the bottom of the airframe and the other mounted on top. There’s more to it than just a second antenna, however; the aircraft’s ADS-B hardware, whether 978 UAT or 1090ES, must be diversity-capable. Not all products are.

Why—and where—is diversity necessary? “Due to the line-of-sight nature of transponder and UAT signals, a single antenna on the bottom of the aircraft can experience signal shading from aircraft structure during aircraft maneuvering, and of course for aircraft flying above you,” said Bill Stone, Garmin’s senior business development manager. “Antenna diversity adds a second receiver to the equipment, as well as installing an antenna on top of the aircraft to help ensure continuous broadcast and reception of ADS-B signals while maneuvering—and for other aircraft flying above your own ship.”

“If diversity is enabled, transmit of ADS-B data is sent on alternating periods to the top or bottom antenna,” said Gary Watson, senior director of business development at L-3 Avionics Systems.

“Diversity is an option for Part 23 aircraft in the United States,” noted Pete Ring, director of sales and marketing for FreeFlight Systems. “Where it becomes a requirement is when the aircraft is required to have a TCAS II system.” Such a traffic alert and collision avoidance system interrogates the transponders of nearby aircraft; based on the data included in their replies, it provides the pilot of the TCAS II-equipped aircraft with a traffic advisory or, if the target is close enough to be a threat, instructions to the flight crew for maneuvering to avoid a collision.

Diversity transponders must be used with TCAS II-equipped aircraft in the United States. “The aircraft that are required to, or voluntarily, carry TCAS II also typically fly above FL180—so their ADS-B Out path will be 1090ES,” Stone said. (The FAA does not authorize the use of 978-MHz universal access transceivers above 18,000 feet.) “And by virtue of the TCAS II requirement, they will also be diversity.”

Garmin recommends diversity for other aircraft, as well, Stone added. “It simply performs better for both ADS-B Out and ADS-B In by addressing antenna shading, but there is no regulatory requirement—it is strictly optional.”

L-3 doesn’t recommend diversity, Watson said. “There’s not a requirement for it. Whether you choose to have diversity is up to you.”

The Notes column of AOPA’s online Mode S ADS-B products page (www.aopa.org/adsb/ModeS) indicates 1090ES transponders for which diversity is available.

International operations

Let’s move to ADS-B and international operations. “Do I need a 1090ES ADS-B Out solution to fly to the Bahamas in January 2020?” was asked at one of AOPA’s ADS-B forums at EAA AirVenture last summer. The answer? No—as of right now, you won’t need any ADS-B capability. To date the Bahamas have not announced any ADS-B Out requirement. The Bahamas could decide to require ADS-B Out with an effective date sometime before the FAA’s January 1, 2020, mandate—or afterward. But until there’s a mandate, there’s no requirement.

So why is 1090ES ADS-B Out required for international operations? For most of the world, recommended might be a better term. So far the United States is the only country to approve 978 UAT for ADS-B Out—anywhere else in the world with an ADS-B mandate, the requirement is for 1090ES. If there’s no mandate, there’s no requirement.

Will any other countries adopt the 978 UAT datalink? It’s possible, but because of the cost of ground infrastructure, combined with lower levels of civilian traffic, it’s not likely. That said, there is some 978 UAT infrastructure in China—installed specifically to support domestic flight training operations within a limited geographical area.

For now, everywhere outside the United States that has an ADS-B Out mandate requires the 1090ES datalink. A Mexican proposal to require 1090ES in Class B, C, E above 10,000 feet msl, and other specified airspace has already been through public comment; a requirement could become effective January 1, 2020—earlier over the Gulf of Mexico. Therefore, 1090ES equipage is strongly recommended for any pilot who plans to operate outside U.S. borders.

The intersection

Diversity and international operations intersect with satellite ADS-B. While it’s too early to say how and when Canada might approach an ADS-B mandate over the country’s lower airspace levels, its investment in Aireon should be considered.

“We are aware of and have been following Aireon’s proposal of space-based ADS-B tracking using the Iridium Next satellite network, scheduled to become first operational in 2018,” said Garmin’s Stone. “The Aireon system has not yet been tested, but the concept would not require any additional equipment onboard the aircraft.” A 1090ES transponder with antenna diversity and a suitable position source should do the job.

“Currently, we are not in a position to speculate what Canada or other nations may be considering as required equipage until such a time that they initiate their own rulemaking processes,” he noted.

“Without details on the specific system, this answer could change, but in previous tests with satellite-based ADS-B systems, a diverse 1090ES system will be satisfactory,” L-3’s Watson agreed.

“In my opinion it’s a little early to speculate what additional equipment may be needed for operations in Canada due to the low maturity level of their pending regulation. As it progresses I am sure that picture will become more clear as to what is needed,” FreeFlight’s Ring said. On first glance, however, he said a simple 1090ES installation with diversity probably would meet such a requirement.

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