March 3 is the final date by which the user community can file its comments on the FAA’s Oct. 1, 2007, Notice of Proposed Rulemaking (NPRM) regarding the agency’s $2+ billion transition plan to the Automatic Dependent Surveillance-Broadcast (ADS-B) system. FAA officials might be slightly apprehensive as the deadline approaches, since users are expected to raise cost-benefit concerns about a system that likely won’t be fully operational for two decades.

Industry associations have been generally guarded about the positions they will take, but concerns about costs and benefits are likely to be common themes. This could, according to an official of one of the leading aviation associations, speaking off the record to AIN, be the result of the way the FAA has presented its program, which he characterized as “expectations versus reality.”

He explained that eventually, ADS-B will provide all the benefits that it promises, but legislators and the media have gotten the impression that the system will “hit the ground running” with its full capabilities within the next few years. In other words, they expect that all aircraft will be equipped with cockpit displays showing the position of all aircraft in the vicinity, allowing the separation between aircraft to be safely reduced, thereby increasing airspace capacity, reducing delays and preventing midairs. “That won’t happen for another 20 years,” he said.

But the popular expectation of ADS-B is one where, in the near future, all aircraft will broadcast their identification, GPS position, altitude, heading, speed and other data once per second–a process called “ads-b out.” In turn, their avionics will receive this data–through their “ADS-B in” mode–from all other aircraft, for flight-deck display via their “full” or “full featured” ADS-B equipment. The ADS-B out data will also be received by local ground stations that transmit them to controllers’ screens at local ARTCCs. “Full featured” general aviation ADS-B units will also receive weather and other data, although aircraft flying above 24,000 feet must use different-frequency airline-type units that do not receive weather broadcasts.

Airspace where all aircraft are equipped with “full” ADS-B capabilities would be a major step forward in safety and efficiency. But the reality is that the NPRM mandates only that aircraft install the “out” capability by 2020, with carriage of “in” capability and cockpit displays being optional. Many operators view this scenario as a disadvantage, since “out” operation brings them little or no benefit, although it does improve the picture on controller screens. But “out” retrofits are costly, and the add-on “in” equipment even more so. In its early response to the NPRM, British Airways stated “As yet no business case can be made for ADS-B in.”

In addition, some operators reasonably expect that over the next 12 years, technology advances could significantly lower equipment costs, potentially discouraging early installations. Also, the Department of Homeland Security’s recent adoption of eLoran as a GPS backup to protect critical national infrastructure, and the possibility of a mandated eLoran backup to ADS-B raises further cost questions.
Should large numbers of users opt not to install “out” equipment until much closer to 2020, there could be a correspondingly reduced incentive for operators to voluntarily install “in” avionics to receive their signals. In that light, another 20 years might not be unrealistic.

On the other hand, the contract to install the continental U.S.-wide network of 794 ADS-B ground stations is under way. Initial installations are forecast for 2010 around the Gulf of Mexico; Louisville, Ky.; Philadelphia; and Juneau, Alaska, with the remaining stations to be installed gradually throughout the National Airspace System by 2013.

In the Gulf, helicopters serving the several hundred offshore oil and gas platforms have long suffered from inadequate weather data, limited ATC surveillance and IFR restrictions. At Louisville and Philadelphia, UPS can use the system for advanced merging and spacing of its inbound jets. And the Juneau stations will extend the coverage of the Capstone ADS-B network. At all these locations, users will carry “full” ADS-B avionics to obtain maximum benefit.

Yet system uncertainties remain, including overall security, which the FAA appears unwilling to acknowledge. Protection against such things as malicious “spoofing” of
the aircraft data to produce multiple false targets on controllers’ screens; signal interference or jamming; undetectable “eavesdropping” of transmitted aircraft data; and other infringements are concerns that still remain unanswered.