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US Airborne Collision Avoidance System (ACAS sXu) applicability for Drones in Europe: Not sure just yet... cf EUROCAE report

Updated: 11 minutes ago


ACAS

Since 2008, the United States Federal Aviation Administration (FAA) has been funding the research and development of a next-generation Airborne Collision Avoidance System (ACAS). This initiative is the successor to the widely used Traffic Collision Avoidance System (TCAS) and aims to serve both crewed and uncrewed aviation, addressing the evolving complexities of modern airspace.


Several tailored versions of ACAS have been developed:

  • ACAS Xa for commercial aircraft

  • ACAS Xr for helicopters

  • ACAS Xu for large drones, such as military UAVs

  • ACAS sXu for small unmanned aerial vehicles (sUAVs)


In December 2022, developers from MIT Lincoln Laboratory and MITRE Corporation were recognized with the prestigious R&D 100 Award, often referred to as "the Oscars of Innovation." This accolade highlights their groundbreaking work on ACAS sXu, underscoring its potential to revolutionize small UAV operations.


Why a New System?

As the National Airspace System (NAS) becomes increasingly congested—with small aircraft, commercial space travel, and UAVs complementing traditional aviation—TCAS is no longer sufficient. Originally designed for larger private, military, and commercial aircraft, TCAS lacks the adaptability needed for modern airspace dynamics.

“TCAS, while a good system, is limited in what it can do and doesn’t expand very well,” says Brian Patterson, an engineer at MITRE. “ACAS covers everything the old system has been plus more.”

ACAS X employs machine learning to generate adaptive logic and determine optimal maneuvers based on the aircraft's unique performance capabilities, ensuring effective collision avoidance in real-time.


ACAS sXu adaptability to Europe: not sure, work in progress

The EUROCAE ER-032 European Industry Report analysed the feasibility of implementing the RTCA DO-396 ACAS sXu solution within European airspace. While the report, available for purchase, provides valuable insights, it also raises critical unanswered questions about the adaptability of ACAS sXu to Europe’s complex airspace structure.


Looking Ahead

Despite two decades of research, airborne collision avoidance for drones and Beyond Visual Line of Sight (BVLOS) operations remains an emerging field. ACAS sXu could become a key enabler for these operations, however there is no “silver bullet” solution available yet. However, with increasing market recognition of its importance, investment in this critical area is expected to accelerate.


About EUROCAE

EUROCAE is a non-profit organisation, created in 1963 as the “The European Organisation for Civil Aviation Equipment", with the objective to develop standards for European civil aviation.

EUROCAE currently has over 450 members, including industry, service providers, regulators, research institutes and international organizations. EUROCAE has become the European leader in the development of worldwide recognized industry standards for aviation. EUROCAE membership is open to organisations and industries worldwide.





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