Waypoints: Traffic dead ahead?

The ADS-B traffic debate

May 12, 2014

Thomas B. HainesThe callout jolted me from a zone of concentration while intercepting a radial off of the Westminster, Maryland, VOR. “Traffic. 12 o’clock. Same altitude. One mile,” came the loud voice in the headset. The yellow caution screen was flashing on the Garmin GTN 750 showing the traffic dead ahead. My safety pilot in the right seat was scanning the sky as I flipped the instrument hood out of the way and tried to see the traffic in the haze of the setting sun. “There,” he said, pointing. “Turn right.” I banked the airplane sharply in time to see the Cessna 172 pass just below us. He didn’t appear to be maneuvering, so most likely he never saw us.

Even at our leisurely approach speed and his likely speed, our closure rate was some 220 knots, meaning less than 20 seconds to cover the one-mile distance.

The incident, one of three close calls over the past year since I upgraded the panel in my 42-year-old Bonanza to include traffic information, reminded me of the benefits of ADS-B available now, more than five years ahead of the FAA’s mandate for everyone to be equipped (see “Safety Pilot Landmark Accident: See and Avoid?” page 70). While the new means of controlling air traffic is controversial and not what we all thought it was going to be when first envisioned 20 years ago, the benefits of in-cockpit weather and traffic are real. For those who already have equipped with a WAAS GPS for the benefit of LPV approaches, the step to ADS-B In and Out can be relatively inexpensive. A Mode S transponder with extended squitter (ES) connected to the WAAS signal can serve as an Out solution. With that, a portable system—such as the Stratus, Garmin GDL 39, or any of a number of other ADS-B receivers—can serve as the conduit for traffic and weather into the cockpit to be displayed on a portable device, such as an iPad. Even without ADS-B Out equipage, those portable systems can provide weather and limited traffic into the cockpit.

Most airplanes capable of LPV approaches have a panel-mount display also capable of depicting weather and traffic. For that, a built-in ADS-B solution, such as the Garmin GDL 88, is an option, which is what I chose. For use in the United States and below 18,000 feet, the GDL 88 can be the entire ADS-B In and Out package.

In any case, one must still maintain a transponder, whether Mode C or S—mostly to satisfy the Traffic/Collision Avoidance System (TCAS) needs of airliners. As originally envisioned, ADS-B would obviate the need for transponders, at least for flights in the United States. However, when the FAA issued rulemaking in 2007 requiring all aircraft be equipped with ADS-B Out by January 1, 2020, the rule also required the continued use of transponders indefinitely.

The transponder mandate and the stubbornly high cost of equipage for those who don’t already have panel-mount displays and a WAAS receiver have caused many pilots to wait to equip with ADS-B Out. While portable solutions can provide excellent ADS-B weather information, the problem is that without ADS-B Out, the traffic shown on the portable devices is less than complete. It takes an ADS-B Out position to trigger the FAA ground stations to transmit the traffic information back up the datalink to the participating aircraft. Without that, the only traffic a portable ADS-B In system can see is nearby ADS-B Out-equipped aircraft (each of which is broadcasting its position). If an ADS-B Out aircraft is within about 15 miles, an airplane with ADS-B In only may be able to display traffic sent up to the other aircraft, but the information will be referenced to the other aircraft, making position determination difficult.

The cost to equip an airplane for ADS-B Out when it doesn’t already have a WAAS position on board can run $6,000 to $8,000, a big hit for casual fliers.

The frustration is in the waiting for lower cost options, which many believe are coming. Meanwhile, the 2020 mandate moves ever closer. With every passing day, the likelihood of finding an avionics shop able to handle the influx of work needed to install the systems by then diminishes. Few FAA equipage mandates in the past have been met by their original date. But so far, the agency has shown no signs of pushing the date back. It has, after all, been a 13-year window.

For me, with WAAS and displays already installed, paying about $4,000 for the GDL 88 was a cost-effective way to get a traffic system. Otherwise, active traffic systems start at about $10,000 and go upward to $25,000. And although I flew safely for decades without a traffic system, I appreciate how many airplanes are out there—some nearby—that I never saw before. Some suggest traffic systems cause pilots to be lazy in looking for traffic. I find it just the opposite. With the help of the system, I find myself working harder to spot traffic.

Editor in Chief Tom Haines flies his Beechcraft Bonanza A36 for business and pleasure.

Email thomas.haines@aopa.org