Enhancing contract tower safety, capability

Air traffic controllers are trained to account for uncertainty. At airports without radar coverage, pilots’ reported positions can be delayed, imprecise, or simply wrong. Controllers learn to build buffers into every decision and, much like pilots, build a mental picture of where aircraft should be, which then gets revised based on observation.

Of the 265 contract ATC towers nationwide, 91 operate without radar or surface surveillance. At these facilities, controllers rely on binoculars, radio calls, and pilot position reports to sequence aircraft and manage ground movement. It’s a system that depends heavily on experience, judgment, and trust—one where the margin for error is thinner than many realize. That margin is reduced even further by weather; congested radio frequencies, and human errors such as misidentified taxiways, missed calls, or inaccurate distance estimates.

For decades, that approach has been accepted as sufficient. But incursions, near-misses, and low-visibility events at smaller airports—without tools comparable to those at larger airports—have exposed limits of an outdated operating model, accelerating the FAA’s shift toward ADS-B-based situational awareness—using aircraft-broadcast position, speed, and altitude data—at towers that operate without radar.

Cyriel Kronenburg, vice president of airports and air traffic management at uAvionix, knows these challenges firsthand. As a former dispatcher and global head of ATC at the International Air Transport Association, he understands how the gap in situational awareness has become increasingly difficult to ignore.

Built on ADS-B data and delivered through a secure, cloud-based architecture, uAvionix’s FlightLine Airborne Position Reference Tool (APRT) provides controllers with a real-time visual representation of aircraft positions, including traffic not in radio communication with the tower, delivering a clearer picture of the local airspace, while FlightLine Surface Awareness System (designed to support the FAA Surface Awareness Initiative) extends that view to the airport surface—displaying both ground and airborne traffic. Together, the systems create a continuously updated operating picture that reduces reliance on pilot position reports alone.

With recent FAA approval, the airspace and ground awareness systems developed by uAvionix have moved from concept to operational reality—without the cost, complex infrastructure, or lengthy deployment timelines of traditional radar systems. It changes not only how controllers work, but what they can see.

As a result: Both federal and non-federal contract towers gain a new level of situational awareness and a clearer, more consistent picture of the airspace they manage.

For APRT and SAI to be successful at general aviation airports, reliability and completeness of data are critical. One of the most common shortcomings is incomplete frequency coverage, particularly the inability to capture both ADS-B frequencies used in the United States.

“Our receivers are all dual mode. So, we see both,” Kronenburg said, referring to both 1090 megahertz (MHz) and 978 MHz universal access transceivers. To meet FAA expectations, uAvionix systems use monitored ground-based receivers with redundancy built into both sensors and communications. Latency, uptime, and data integrity are continuously tracked. “We have to monitor our sensors. We have to monitor latency on the data through timestamps. You have to show that the system is actually functional.”

That professional-grade reliability is one reason the FAA adopted SAI as a service rather than agency-owned infrastructure. Since its initial rollout, SAI has become operational at 14 airports and is accelerating rapidly. By the end of this year, approximately 50 sites are expected to be operational.

APRT, approved for use at federal and non-federal contract towers with substantial operations, is currently the only FAA-certified ADS-B based service awareness system deployed under the FAA’s service-based model.

“We’re currently the only company that has a certified system,” Kronenburg said.

Controller feedback from both programs has been positive. Initial skepticism, often rooted in the belief that visual scanning is sufficient, fades once controllers begin using the system in daily operations, and training requirements are minimal.

“Procedurally, nothing changes for the controllers,” Kronenburg explained. “It is a non certified radar, in a VFR tower. So, they still have to look out of the window.”

Beyond tower operations, expanded deployment of ADS-B surveillance has delivered an additional benefit: improved coverage across the United States. According to Kronenburg, ADS-B equipage across the country is already very high—nearly 90 percent of commercial aircraft are equipped, and among the GA fleet the rate is similarly strong, with Alaska standing out as the primary area where adoption remains lower. As ground-based surveillance and service-based systems expand, their impact goes beyond the control tower. This raises new questions for the owners of aircraft that are not yet equipped with ADS-B.

For pilots without ADS-B—or who have delayed adopting it—the lack of visibility is becoming harder to ignore. As airspace where ADS-B is not required becomes more congested and surveillance tools become common in both towers and cockpits, aircraft without ADS-B risk being the only ones not clearly seen in an increasingly difficult traffic picture. That affects more than air traffic controllers; it also limits what nearby pilots can see, particularly in areas where visual and instrument traffic overlap.

uAvionix offers aircraft equipment solutions that have evolved beyond complex or intrusive installations. Its ADS-B systems are engineered to be pilot-friendly and adaptable to ;nearly any GA cockpit, reducing barriers to compliance without requiring major panel upgrades. For example, the tailBeacon ($2,199) is designed to replace the rear position light and has approved GPS built in, so it can work with a Mode C transponder to comply with the 2020 ADS-B Out mandate.

Globally, regulators are also moving in similar—but not identical directions. Australia, for example, is expanding ADS-B requirements through a phased approach that reflects the range of aviation operations. While full ADS-B is required for IFR and higher-altitude flight, approved portable electronic conspicuity (EC) devices are permitted as an alternative or supplement. In contrast, U.S. regulators currently view EC devices primarily as a collision-avoidance aid (including with drones). At present, there is no indication that EC devices in the country will be accepted as a substitute for ADS-B for airspace access or as a source of surveillance data for ATC.

Whether through certified ADS-B installations or EC devices, the direction is clear: Increased visibility benefits everyone sharing the airspace. 

However, cost remains one of the last major barriers. APRT is delivered as a managed service, with annual costs for contract towers averaging around $30,000. For a mission-critical system under FAA oversight, it’s not a “set it and forget it” solution—it comes with ongoing support and monitoring.

As installations expand to more airports, the goal is clear: Managing complex operations with limited tools should give way to a future where safety enhancements aren’t constrained by the cost or complexity of legacy systems but driven by scalable technologies that meet airports—and pilots—where they are.