AIN Blog: ADS-B: It’s Herd Immunity

Michael Huerta

The FAA mandate to equip with ADS-B OUT avionics is coming in fewer than 5.5 years, and many owners and operators are still waiting to upgrade their aircraft, either because they’re hoping prices will drop and technology will improve or they aren’t sure they’ll be keeping their aircraft beyond the deadline.

While the FAA and industry keep talking about the Jan. 1, 2020 deadline, I’m going to change that slightly because 2020 seems like a long way away. If the deadline is written as “midnight Dec. 31, 2019,” then it seems closer, and maybe that will galvanize people into action.

Current estimates by Ric Peri, vice president of government and industry affairs for the Aircraft Electronics Association (AEA), put the number of aircraft needing to comply with the ADS-B OUT mandate at about 186,000. Only 2,000 or so have been upgraded thus far. Given the number of workdays left before the deadline, about 130 aircraft per workday will need updating, Peri noted. The avionics shops that will be installing ADS-B equipment are understandably nervous about a last-minute rush, although also happy to have another mandate to keep customers coming in the hangar doors.

One of the problems for some owners is that there is no clear pathway for ADS-B equipage in their older airplanes. Some older Cessna Citations, for example, still have no solution available. And some solutions may end up very expensive, which could leave owners deciding not to keep flying their older aircraft.

Another more important problem is that many owners question the need to upgrade, wondering how installing ADS-B OUT equipment will benefit them.

ADS-B stands for automatic dependent surveillance-broadcast. It is not complicated: all it does is transmit an aircraft’s position, velocity, heading, altitude and other information to any nearby ADS-B receiver. The FAA’s network of more than 630 ADS-B ground stations is now in place, and air traffic controllers are already seeing ADS-B-transmitting targets on their screens.

ADS-B installations require an accurate position source. Although the rules don’t specify a Waas-compatible GPS receiver, a receiver with that level of accuracy meets the requirements and thus most installations are using Waas as a minimum standard. A non-Waas GPS receiver can be qualified for ADS-B if sufficiently accurate, but that would likely require extra expense and it’s easier to default to the Waas standard.

Because controllers can “see” ADS-B traffic better than aircraft that are transmitting their position using an ordinary transponder, there are tremendous benefits, for both the equipped aircraft as well as ATC and other aircraft. The reason that controllers get better reception of ADS-B traffic is because the 630 ground stations cover the entire U.S. in much more detail than far more expensive radar systems. And radar is slower to update because the antenna takes up to 12 seconds to sweep the sky, while ADS-B broadcasts position data at least once per second.

This helps controllers see updates of traffic much sooner and could help controllers know in far more detail where an aircraft reported its last position in case of an accident. As FAA Administrator Michael Huerta said during the Meet the Administrator session at the EAA AirVenture Oshkosh show in late July, “This highly precise surveillance is improving our ability to perform lifesaving search-and-rescue operations; it’s helping to take the search out of search-and-rescue.”

ADS-B OUT doesn’t just benefit air traffic controllers and lost pilots. Many pilots are enjoying much better services when flying IFR from airports where radar coverage is spotty. Some airports are near enough to ADS-B ground stations to get coverage on the ground, but many more airports have ADS-B coverage at much lower altitudes than radar, and pilots thus are able to get into the IFR system more quickly. “What this does is it makes flying safer,” Huerta said.

For pilots flying in the U.S., there is an added bonus, the ability to receive free weather and traffic information via ADS-B IN. Note that the midnight Dec. 31, 2019 mandate does not require ADS-B IN.

With ADS-B IN there are two frequency and receiver choices, 978 MHz (Universal Access Transceiver) and 1090 MHz (Extended Squitter). With a 1090ES receiver, an aircraft can receive traffic information displayed either on a suitable cockpit display (many avionics manufacturers have designed or are designing ways to show traffic on cockpit MFDs) or on an electronic flight bag (EFB) or iPad or Android tablet. The 978UAT frequency receives both traffic and weather information, all for no extra cost. Of course, one can keep the cost of ADS-B IN low with a portable receiver, available in 978, 1090 or both configurations, and by displaying weather and traffic on a tablet. ADS-B IN traffic is better, by the way, if you have ADS-B OUT in your airplane, because the ADS-B ground station needs to be “woken up” before it will send traffic information.

However, note that no ADS-B IN equipment, whether permanently installed or portable, meets the ADS-B OUT mandate.

For those who are still wondering whether ADS-B OUT makes sense, there are other considerations. First of all, in the U.S. ADS-B OUT capability is required only in airspace where transponders are currently required. There are ADS-B OUT mandates in other parts of the world, now active at higher altitudes in many Asia-Pacific countries, part of Canada and soon in European airspace. But if you aren’t planning to fly in controlled airspace where transponders are required, then no need to spend the money on ADS-B OUT.

Ultimately, however, what ADS-B compliance is about is herd immunity. There is a medical analogy: some people are so worried about the effects of immunizations that they forego having their children immunized. The harm caused by this isn’t just to the non-immunized kid, the harm is the larger effect on the human population. When groups of people aren’t immunized, then certain diseases grow and spread, but when most people are immunized, the entire human herd is more protected.

The same is true of ADS-B. The more aircraft are equipped with ADS-B OUT, the greater the benefits for all aircraft in the air (someday this will include drones; in fact drones ought to be required to be fitted with ADS-B OUT). It’s like herd immunity for aircraft.

AEA’s Peri has another way of explaining why we need to equip for ADS-B: It’s a one-time price we have to pay to help upgrade the National Airspace System, he explained, which hasn’t seen major upgrades to its radar-based technology for many decades.

As Huerta put it, “When everyone is ADS-B-compliant it will truly be a different world.”

August 8, 2014, 2:54 PM

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