When the idea was initially being explored a number of years ago, FAA planners saw a use for automatic dependent surveillance-broadcast (ADS-B) only in Alaska, where the technology would allow aircraft operating beyond the reach of radar to develop their own position data using onboard GPS equipment, and then transmit that data to others in the region through either a microwave satellite uplink and downlink or ground-based VHF network.
Now that the agency is starting to view ADS-B as among the most important technological advances under development, it is busily devising the standards that would bring the surveillance concept to aircraft operating in the lower 48 states. The question for business jet operators is how the introduction of ADS-B will help them–and possibly hurt them.
Nobody yet knows when ADS-B will be implemented or what form the requirements will eventually take, but most experts in the field seem to agree that the idea will be adopted throughout much of the world in the next decade. The basic concept behind ADS-B traces its roots back to at least the 1970s and evolved from several key technologies in the 1980s and 1990s. The first of these, developed in Sweden, was VHF Datalink Mode 4, a concept for both surveillance and communications capability still under review in Europe.
Researchers later began to take a serious look at 1090-MHz extended squitter, an outgrowth of mode-S radar standards and technology. In the early 1990s the FAA and Mitre Corp. explored technology that would make possible the so-called universal access transceiver (UAT), a two-way digital datalink developed from the ground up solely for the emerging surveillance concept. The FAA eventually decided that ADS-B would use the 1090-MHz extended squitter (1090ES) surveillance link for air carrier and private/commercial operators of high-performance aircraft, and the UAT surveillance link for the typical general aviation user.
The FAA’s link selection jibes with a joint strategy being coordinated with Eurocontrol for implementing ADS-B-enabled applications, the goal being a high degree of interoperability between systems fielded on both sides of the Atlantic. It also meets a request from the RTCA Free Flight Steering Committee to evaluate operational enhancements supported by ADS-B.
ADS-B is considered a cornerstone of Free Flight because it provides applications that let pilots and controllers view a common picture of airspace and traffic. The airborne systems transmit an aircraft’s identity, position, velocity and intent to other aircraft and to ATC systems on the ground, thereby providing situational awareness to pilots of all appropriately equipped aircraft.
How will ADS-B benefit the typical crew of a corporate jet or turboprop? From a safety standpoint, the technology will improve situational awareness by acting as an extension to TCAS. Instead of just seeing targets on a cockpit display, now the pilots would have additional information about each to give them a clearer tactical picture of traffic. ADS-B will also be useful on the ground at busy airports. It is the FAA’s hope that ground vehicles can be equipped with ADS-B transceivers so that they too would appear on the cockpit display.
The FAA also thinks that ADS-B will facilitate the introduction of closely spaced parallel approaches and so-called enhanced visual approaches (not to be confused with enhanced vision systems), as well as allow reduced spacing on final approach and reduced spacing en route.
Eventually, some within the FAA believe that ADS-B technology will allow for VMC-like operations in IMC conditions, where pilots would use their ADS-B displays in the cockpit to see and avoid other aircraft just as they do now by looking out the window when flying VFR.
The FAA is currently concentrating on deploying ADS-B in select areas, such as Alaska for the Capstone program and in the Gulf of Mexico for offshore helicopter operators. By 2007 the agency hopes to begin rolling out the nationwide ground infrastructure to support the technology. In the beginning, airlines will most likely use ADS-B on some high-density routes, while GA users will begin equipping with low-cost TIS-B (traffic information service-broadcast) avionics.
Because the airlines and business aviation will equip with 1090ES and GA users will install UAT avionics, interoperability between the links is an important concern. Further studies will determine how the two systems can safely coexist, and if long-range air-to-air applications that cannot be satisfied by 1090ES alone might be supplemented by UAT.
Now for the bad news. If this all sounds eerily similar to recent FAA requirements for RVSM, TAWS, ELTs and so forth, it is with good reason. ADS-B will likely be another in a long list of mandated technologies intended to transform aviation from its present state to the far-reaching Free Flight ideal. The obvious concern for business aircraft operators is the equipage cost of the expected ADS-B mandate.
According to FAA officials, the airlines would need to equip with 1090ES avionics by a certain date, while typical GA operators would have the option of installing UAT gear. In the long term, the FAA thinks that between 40 and 70 percent of GA aircraft will opt for UAT avionics. Business aircraft, meanwhile, will be required to carry 1090ES equipment, but because this unique segment flies at high altitudes with the airlines and also into non-radar fields where GA aircraft are based, the FAA will suggest, or possibly even mandate, that business aircraft carry both 1090ES and UAT avionics.