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ADS-B privacy inches forward

Anonymous mode allowed for VFR flight plans

An AOPA petition to expand pilots’ ability to use certain Automatic Dependent Surveillance-Broadcast (ADS-B) Out equipment in anonymous mode has resulted in the FAA clarifying that what AOPA sought actually is what the agency intended when it wrote the ADS-B requirements.

The Federal Aviation Administration is one of the many government agencies that have influence over general aviation. Photo by David Tulis.

In November 2018, Rune Duke, AOPA senior director of airspace and air traffic, petitioned the FAA for an exemption from 14 CFR 91.227(d)(8) and (11). He asked that pilots of aircraft equipped with 978 MHz Universal Access Transceiver (UAT) ADS-B systems be allowed to operate utilizing their UATs’ anonymous mode when (1) the pilot has filed a VFR flight plan; (2) the pilot has not requested air traffic control services; and (3) the operation is outside of 14 CFR 91.225 ADS-B rule airspace. This was because Paragraph 4-5-7(c)(3) of the Aeronautical Information Manual states that a UAT’s anonymous mode can only be used “when the operator has not filed a flight plan and is not requesting ATC services”—excluding aircraft on VFR flight plans, he said.

A UAT is one of the two ADS-B datalink technologies established by the FAA in the United States, where the agency will require ADS-B Out for flights after Jan. 1, 2020, generally in airspace where a transponder is required today (the other is the 1090 MHz Mode S Extended Squitter transponder). In the anonymous mode, a UAT creates a randomized address that does not match the actual, unique International Civil Aviation Organization (ICAO) code assigned to that aircraft, protecting the privacy of the aircraft operator. ADS-B broadcasts an aircraft’s ICAO code and call sign, which can be captured by anyone with a suitable receiver and then used to determine who owns and operates the aircraft.

AOPA had been told in June that this concern would be resolved through clarification in the Aeronautical Information Manual. “In pushing the issue we were able to achieve our goal and ensure pilots can fly on a VFR flight plan and utilize anonymous mode, while also ensuring this capability is available in rule airspace,” Duke said. “I was told by air traffic that the petition request was probably the fastest path to an answer, as legal interpretations must go through several levels of external oversight right now and are delayed. I am happy to see that we were able to get a good answer for pilots.”

The FAA response noted that a pilot conducting a VFR operation may file a VFR flight plan to obtain search and rescue protection. “When a pilot files a VFR flight plan, he or she does not receive ATC services unless he or she requests flight following. Therefore, a pilot conducting a VFR operation may file a VFR flight plan without requesting ATC services…. It appears that the FAA intended to allow persons conducting VFR operations, including those on a VFR flight plan, to use the anonymity mode so long as they did not request ATC services (i.e., flight following).”

The AIM provisions clarifying UAT anonymous mode operations will be published on Jan. 30, 2020. The FAA also noted that it will consider revising 14 CFR 91.227(d)(8) and (11) in the future to eliminate any confusion regarding whether anonymous mode can be used while on a VFR flight plan.

1090ES privacy

Privacy options are moving more slowly for aircraft equipped with 1090 MHz Extended Squitter for ADS-B Out. AOPA has been actively engaged in collaborative conversations with the FAA, the National Business Aviation Association, and other industry partners to find an anonymity solution for operators using 1090 MHz ADS-B systems, as well as those utilizing air traffic services, Duke said. The FAA has proposed a concept called “rolling ICAO codes,” in which a participating aircraft would emit randomly assigned ICAO codes that are periodically changed; combined with an anonymous call sign, aircraft would be harder to track. The idea has also been called “private ICAO addresses.”

“This is a promising approach to increasing anonymity for general aviation operators, but we are still waiting for the FAA to take the necessary steps to begin a demonstration effort,” he said.

The next step in the process is for the FAA to publish a request for proposals from the third-party providers that would be involved—but this has not happened, he added. “I understand we can expect an update at the next Equip 2020 meeting on Sept. 11. However, the FAA can't give us much of a timeline, as they are still conducting internal reviews,” Duke said.

“Work must be expedited on the long-term solution: encryption of ADS-B data,” he added. “It is understood that to facilitate privacy, anonymity must be initiated at the source—the aircraft—as the many privately operated ground receiver networks do not rely on an FAA data stream to feed their tracking websites. Encryption at the source will allow an automated solution that will reduce the workload for operators and the agency, and this solution could become a global standard.”

Mike Collins

Mike Collins

Technical Editor
Mike Collins, AOPA technical editor and director of business development, died at age 59 on February 25, 2021. He was an integral part of the AOPA Media team for nearly 30 years, and held many key editorial roles at AOPA Pilot, Flight Training, and AOPA Online. He was a gifted writer, editor, photographer, audio storyteller, and videographer, and was an instrument-rated pilot and drone pilot.
Topics: Advocacy, NextGen, Avionics

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