Traffic Tech for GA
Recognizing a need for traffic awareness technology for the general aviation market, avionics makers and the FAA worked together in the late 1990s to create a new class of safety avionics known as the traffic alerting system. Priced lower than TCAS I, a TAS typically consists of a low-power, remote-mounted traffic receiver, antennas mounted on the top and bottom of the fuselage (or sometimes only on the top or bottom) and a cockpit display.
The lowest priced TAS products typically can detect traffic out to a distance of about six nautical miles, while at the top end, these systems can track targets out beyond 20 nautical miles. In general, the faster your airplane, the longer-range TAS you should consider buying. At the low end of the TAS market are the Avidyne TAS 600 ($8,490 list price) and Garmin GTS 800 ($9,995 list). Both are superb choices for light piston airplanes and helicopters, with the TAS 600 able to track targets to a range of seven nautical miles in all directions and the GTS 800 to a range of 12 nautical miles ahead of the aircraft and fewer behind. For higher-performance piston singles, twins and turboprops, Bendix/King sells the KTA 870 ($14,995 list), Garmin the GTS 820 ($19,995), L-3 the Sky899 SkyWatch ($20,990), and Avidyne the TAS 620 ($20,990), with several other models filling gaps between.
TAS products display traffic using standard TCAS symbology, the major difference being no RAs are issued by such systems. The same is true for fliers on a tighter budget who opt for TIS-compatible Mode S transponders capable of displaying traffic targets broadcast by certain ground radar stations. Unfortunately, TIS coverage is restricted to a little more than 100 radar sites around the country, a number of which are scheduled for decommissioning as the ADS-B mandate approaches. Still, the FAA plans to keep scores of these sites operational for the next decade or more, meaning there is value in TIS technology if you often fly in areas covered by the service.
The ADS-B Mandate
Clearly, you can see ADS-B is the common denominator in any discussion you’re likely to have about purchasing a new transponder over the next several years. In May 2010, after thousands of hours of flight trials, the FAA formalized its mandate for ADS-B compliance as the “backbone” of the Next Generation Air Transportation System (NextGen). The “dependent” part of ADS-B simply means that everybody operating in the ATC environment will ultimately depend on everybody else to broadcast their identity, position, track, airspeed and so forth via ADS-B “Out” technology. Put plainly, traffic surveillance is going interactive, with NextGen air navigation transitioning from ground-based radar systems to a space-based, satellite-driven aircraft tracking system. Those radars will remain online in case of emergency and for use by the Transportation Security Administration, but for the most part satnav will be the norm in the future.
And that’s a good thing, really. The benefit of NextGen surveillance is that it’s more precise and widely available than radar. Currently, it takes 12 seconds for a long-range radar station to complete one sweep versus about five seconds for a terminal-area radar. That’s a long time, and as a result, controllers must maintain wider separation among aircraft for safety’s sake. ADS-B technology updates about once a second, allowing closer separation. Hence, NextGen will offer growth capability to accommodate future air traffic demands, which will be high.
Who will need ADS-B equipment? The short answer is, just about everybody who flies in controlled airspace. Even if you don’t fly IFR, your ability to obtain VFR traffic advisories and transition through most ATC-controlled airspace will still require that you have ADS-B “Out” capability on board. Basically, wherever you need a transponder now, you’ll need ADS-B in the future.
