FAA Exploring Possible Privacy Protections for ADS-B

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FAA Exploring Possible Privacy Protections for ADS-B

Post by Albert »

The FAA is weighing proposals to tackle one of business aviation’s chief concerns surrounding the implementation of automatic dependent surveillance-broadcast (ADS-B) and the Jan. 1, 2020 ADS-B equipage mandate: privacy. A general aviation working group that was part of the larger ADS-B Equip 2020 panel recently delivered a white paper to the agency outlining potential approaches to handling aircraft and operator privacy and security concerns surrounding mode-S transponders. According to the white paper, “The core concern of the operator community is real-time tracking of the geographic location of a specific aircraft.”

ADS-B-equipped aircraft transmit unique identification and position information either through the 1090-MHz extended squitter mode-S transponder (for all altitudes) or the 978-MHz Universal Access Transceiver (UAT) below 18,000 feet. The extended squitter or ES format can carry up to 49 parameters compared with three for mode-C and seven for ordinary mode-S. “The extended squitter message is broadcast rather than response to an interrogation and includes the ICAO address in each broadcast message,” the white paper noted, hence the key difference between an ordinary mode-S transponder and ADS-B out equipment.

Business aviation leaders have expressed reservations about the mandate because the 1090 MHz mode-S transponder identification codes can easily be detected, tracked online and traced to the operator, bypassing protections established in the former Block Aircraft Registration Request program.

The code, a 24-bit address assigned to each U.S. aircraft registration number, is sometimes referred to as the aircraft’s ICAO address.

The tracking ability has been available for some time, in any mode S-equipped aircraft whether ADS-B enabled or not, but that ability has grown in recent years as the number of ground stations (or listening stations) has increased, noted Jens Hennig, vice president of operations for the General Aviation Manufacturers Association (GAMA). These stations can be acquired for about $100, and hobbyists and flight-tracking companies have strung together a global network that can keep track of any mode-S-emitting aircraft. The information gathered from the so-called listening stations is readily accessible on the Internet.


NBAA has called privacy and security concerns one of the chief stumbling blocks for ADS-B equipage. “In transitioning to satellite-based navigation and surveillance, we need to find a way to make accommodations for privacy, security and competitiveness, and we want to ensure that concern is addressed as ADS-B moves toward implementation,” president and CEO Ed Bolen told a NextGen Advisory Committee meeting earlier this year. “When it comes to ADS-B, we continue to believe that people should not have to surrender their security just because they board an airplane.”

The working group looked at several possibilities for addressing these concerns. These included making the FAA’s Aircraft Registry private. NBAA had offered that as a solution late last year, but the FAA responded that might not be possible given Freedom of Information Act requirements. Also, the agency was concerned that it is signatory to the Cape Town Convention that established the International Aircraft Registry. This registry is important for financial interests.

A second solution was to step up the anonymity of registered aircraft owners through LLCs or trust corporations. FAA data shows approximately 10,000 aircraft are registered through trust corporations. But even with the veiled names of a trust corporation or LLC, careful mining of public records can unearth the ultimate owner.

Another possibility discussed was developing an anonymity mode for the 1090ES datalink. The anonymity mode exists for the 978UAT standard, but is not part of the 1090ES standard. This was purposefully omitted for 1090ES after objections were raised by Europe, the working group said in the white paper.

But other options presented by the working group might gain more traction. A longer-term option would be encrypting the mode-S 1090ES datalink. The FAA is looking at potential future changes to the operational performance standard (RTCA DO-260B), such as expanding the bandwidth, which might enable functions such as encryption. The changes, which would be under DO-260C, are not expected to be completed until after 2020. Also, it is uncertain whether encryption will require fundamental design changes, whether it would be practical and whether it would truly achieve the privacy goal. The RTCA is looking into the technical feasibility of this option, said Doug Carr, NBAA vice president of regulatory and international affairs.

To address concerns in the shorter term the working group discussed the establishment of a “privacy office” to administer the mode-S address codes and possible anonymous flight identifications. The group suggested that aircraft could regularly (daily or monthly) change codes if necessary; at present the codes in the U.S. are static. NBAA has agreed to review mechanisms for making such changes and the frequency with which the codes would need to be changed.

Several technical questions raised by this option need to be ironed out, including the capability of existing transponders to change their assigned address and whether this would require a maintenance or pilot action. GAMA is exploring potential prospects for this option. Also, the FAA would need to determine whether frequently changing an aircraft’s code has system implications.

Many unknowns remain for these options, including the cost to the operator or to the government. Carr stressed that the industry doesn’t have enough information yet to determine whether they are feasible. “We’re not there yet,” he said, adding that privacy could always be an issue because as one solution develops another technology may arise to encroach upon it.

Having said that, Carr added that changing the code or encryption “could be very effective.”

In the interim, the FAA has been open to suggestions, eager to encourage equipage. The number of aircraft equipping has accelerated. More than 13,000 are now ADS-B out compliant, and all but 200 to 300 of those are business and general aviation aircraft. That is up from just a few thousand a year ago. But how many thousands more that have yet to equip is unknown. Estimates vary but all exceed 100,000.

The costs to equip have come down significantly, but many owners continue to are wait to make sure the standards don’t change, to see if outstanding issues get resolved, to ensure that a solution is available for their aircraft or to see if prices drop further. Hennig advised those opting to wait to at least block a time slot with a repair station. Installers are already reporting bookings in 2017, 2018 and 2019, he said. The 2020 deadline is not going to change, he reiterated.
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