By: Dawn Zoldi
The skies continue to get increasingly crowded. Uncrewed aircraft, helicopters, business jets, air taxis and legacy airliners are all converging in the same low‑ and mid‑altitude corridors where most operations for emerging aviation will take place. At the same time, regulators feel the pressure to approve more beyond visual line of sight (BVLOS) drone missions for inspections, public safety, cargo and defense. Airspace safety has never mattered more and the airspace itself has never been more complex.
In this exclusive interview, Tom Furey, CEO of Sagetech Avionics advocates that the only credible path forward is a layered approach to collision prevention and avoidance that mirrors how safety has historically advanced in aviation. “No single means of safety is sufficient to eliminate midair collisions,” he said, particularly in a world where communication links fail, traffic density spikes and noncooperative actors share the sky with certified aircraft.
From Strategic Separation to Real‑Time Detect and Avoid
For decades, crewed aviation has depended on a hierarchy of tools to keep aircraft apart: procedural rules, strategic separation, air traffic control and pilot see and avoid. “In the uncrewed BVLOS environment, these building blocks still matter, but they are no longer enough,” Furey warns.
Traditional methods, he says, now sit at the base of a wider stack. Strategic separation and airspace management is where helicopters, drones and other aircraft are scheduled or restricted so they are never authorized in the same place at the same time. Air traffic control (ATC) and air traffic management (ATM) keeps human controllers in the loop for instrument flight rules and complex terminal areas. Unmanned traffic management (UTM) systems orchestrate UAS flows using ground‑based services and electronic communications to maintain separation.
On top of these sit cooperative collision avoidance systems like TCAS II and its successor, ACAS X, along with detect‑and‑avoid (DAA) capabilities that fuse cooperative and noncooperative sensing. Together, they promise a safety net that is both more robust and more flexible than any single layer could provide.
Why Layered Collision Avoidance Is Non‑Negotiable
Commercial air transport offers a useful case study on why layering collision avoidance is key to airspace safety. Today’s airliners rely on a three‑layer structure: ATC, pilot visual scanning and TCAS II. Each has distinct strengths and weaknesses. Controllers can get overloaded, humans can miss threats and TCAS II was never designed for dense low‑altitude operations. When combined, however, they deliver the track record that has made global air travel the safest of all modes of transportation.
Furey believes uncrewed aircraft systems (UAS) must adopt an analogous architecture: ATM/UTM to manage flows and onboard DAA to safeguard the aircraft when something upstream goes wrong. UTM and ATM rely on radios and command‑and‑control (C2) links to maintain safe separation. If those links fail or become degraded, onboard collision avoidance provides a backup layer that can still detect threats and issue guidance.
In practical terms, he said, this layered approach does three things particularly well. It reduces dependence on any single system or entity, whether that is a ground controller, a network service supplier or a radar feed. It allows each layer to be optimized for its domain, for example, UTM for strategic route management and ACAS X for last‑resort collision avoidance.It creates a credible “safety case” for BVLOS approvals in increasingly congested airspace by showing regulators that failures are anticipated and mitigated, not ignored.
ACAS X vs. TCAS II: Collision Avoidance for Drone Ubiquity
TCAS II was built for large commercial transports flying at higher altitudes. Its algorithms were designed for the speed and climb rates of those aircraft, so it is generally not suited for the flight dynamics of drones or rotorcraft. In addition, it comes with size, weight and power penalties that make it a poor fit for anything other than large fixed wing aircraft. It does not use ADS‑B data and depends on directional interrogation with a large, heavy antenna to locate other aircraft.
ACAS X, by contrast, is a family of next‑generation algorithms designed from the ground up for multiple classes of aircraft:
- ACAS Xa for commercial transport.
- ACAS Xu for large fixed‑wing UAS.
- ACAS Xr for rotorcraft, crewed or uncrewed.
- ACAS sXu for small uncrewed aircraft.
Instead of relying solely on directional interrogation, ACAS X employs hybrid surveillance that fuses validated ADS‑B with transponder interrogations. The reduced frequency of transponder interrogations opens the door to omnidirectional interrogation, which can dramatically reduce system cost, size, weight and integration complexity while maintaining performance, without negatively impacting spectrum use.
Sagetech has leaned into this opportunity under Furey’s leadership. His own background as a former Naval Flight Officer and long‑time industry executive, has informed his role at Sagetech Avionics since its carve‑out in 2019. He has guided the company’s focus on certified, mission critical avionics for both civil and defense customers. Under his direction, Sagetech has fielded situational awareness solutions across drones and crewed aircraft, supported defense programs with IFF Mode 5 upgrades, and partnered on advanced detection efforts with organizations like MatrixSpace and AATI. In each of those efforts, the mission remains the same: safety in depth, not safety by slogan.
Along those lines, the company developed a patented omnidirectional interrogation approach and in 2025 completed flight research with the FAA showing that omnidirectional hybrid surveillance can match the effectiveness of directional TCAS II, with less burden on the transponder/ADS‑B spectrum. Omnidirectional interrogators also simplify installation on rotorcraft and UAS, platforms that often cannot accommodate large directional antennas without major structural changes.
Completing the Picture: Cooperative and Noncooperative DAA
Cooperative systems like ACAS X and TCAS II excel at tracking aircraft that “play by the rules,” cooperative aircraft that broadcast via transponder or ADS‑B. But a complete detect‑and‑avoid picture must also account for noncooperative traffic, from general aviation aircraft without active equipment to drones and other unknowns.
Here again, a layered sensor strategy matters. Ground‑based radar can provide long‑range detection, which offloads hardware from the aircraft and feeds surveillance data over the C2 link. Onboard radar, particularly on medium and larger UAS, can deliver continuous sensing across all phases of flight, including outside terminal areas, where ground‑based radar is sparse.
In a 2025 FAA project, Sagetech demonstrated how this multi‑sensor model works in practice. When available, ground‑based radar offered reliable noncooperative surveillance over the C2 link to the onboard ACAS X system. Outside radar coverage areas, ACAS X still provided traffic alerting and collision avoidance guidance based on ADS‑B and other cooperative inputs. For larger UAVs equipped with onboard radar, the aircraft could maintain full detect‑and‑avoid capability even beyond the reach of ground‑based infrastructure.
For smaller UAS where every gram and watt counts, Sagetech’s approach enables detect and avoid without the burden of onboard radar by leveraging offboard sensors and transmitting their data into ACAS X over the C2 link. The result is a flexible architecture that can scale from Group 2 sUAS to larger Group 4 or 5 platforms without rewriting the safety playbook.
Inside Sagetech’s ACX‑3200: ACAS X in a Transponder
All of this would be academic if the hardware couldn’t meet real‑world size, weight, power and cost demands. Sagetech’s answer is the ACX‑3200 series, which integrates ACAS X directly into the transponder hardware to deliver a compact, certifiable DAA solution.
Sagetech has spent years refining low‑SWaP transponders and ADS‑B solutions, including its TSO‑approved MXS micro transponder used on platforms like American Aerospace Technologies’ AiRanger. Those products are now paired with ACAS X processors to enable BVLOS waivers and exemptions. The ACX‑3200 builds on that lineage, collapsing previously separate boxes into a single unit while adding the logic necessary for well‑clear and collision avoidance functions.
For operators, that integration matters in three ways. It reduces installation complexity and potential failure points by consolidating surveillance and avoidance functions. It lowers SWaP enough to make certified DAA realistic on more UAS types, not just the biggest and most expensive. It accelerates time to operations by aligning with FAA and international ACAS X standards rather than bespoke, one‑off solutions.
Building the BVLOS Safety Case with Layered Technologies
Regulators have been clear that meaningful BVLOS at scale will require demonstrable, repeatable safety mitigations for air risk. Layered collision prevention and avoidance technologies give operators a structured way to make that case.
A credible BVLOS safety stack increasingly looks like this:
- Strategic deconfliction and airspace management via UTM/ATM and concept of operations design.
- Cooperative surveillance through transponders and ADS‑B, feeding ACAS X logic onboard the aircraft.
- Noncooperative sensing via ground‑based and/or onboard radar, with data fused into the DAA computer.
- Certified, low‑SWaP ACAS X implementations such as Sagetech’s ACX‑3200, providing real‑time guidance when other layers fall short.
Safety on the Edge: What Comes Next
As BVLOS approvals expand and advanced air mobility prototypes move from test campaigns to limited commercial service, the airspace will sit on a knife‑edge between opportunity and risk. Operators, OEMs and regulators will have to prove that large numbers of uncrewed and crewed aircraft can share the sky without an unacceptable rise in incidents. Onboard ACAS X, particularly when implemented in low‑SWaP architectures with omnidirectional hybrid surveillance, can meet the demanding requirements of many medium‑ to large‑class UAS. Paired with UTM, ground‑based radar and robust C2 links, it becomes a key pillar in a layered safety architecture that can adapt to different missions and airspace environments.
The industry has learned this lesson before. Aviation safety has always advanced in layers: first radar, then transponders, then collision‑avoidance systems that became standard in the jet age. With uncrewed systems, the same principle applies, but this time, the layers must extend all the way from cloud‑based traffic management services to the ACAS X logic running inside a transponder at the edge of the network. That is what it means to pursue safety on the edge: designing for failure, planning for density and building systems that can still keep aircraft apart when everything else is going wrong.