Strategic Deconfliction Increases Operational Safety in Simulation

Air traffic is expected to increase significantly in the next two decades with the advancement of Unmanned Aircraft System (UAS) technology. While this will undoubtedly lead to exciting breakthroughs in drone delivery and urban transport, it also raises concerns regarding safety, especially as traffic increases in urban environments. However, UAS Traffic Management (UTM) approaches are already being explored with the goal of safely meeting expected traffic demands.

Strategic Deconfliction

One approach is strategic deconfliction, which involves resolving operational conflicts pre-flight. New research from Airbus UTM and The Johns Hopkins Applied Physics Laboratory (APL), published in the paper “Safety Assessment of UTM Strategic Deconfliction,” shows that cooperative strategic deconfliction dramatically reduced the risk of mid-air collisions in simulated operations, including complex, high-density traffic scenarios.

While UAS operations may not present immediate safety concerns in rural or relatively unpopulated areas, the expected UAS congestion in urban areas presents concerns that may be addressed by cooperative strategic deconfliction.

ASTM Standard

In response to the developing UTM ecosystem, ASTM International (ASTM) has published a standard addressing UTM interoperability and strategic deconfliction to mitigate conflicts that may result in losses of separation or mid-air collisions between UAS operations. With these standards in mind, Airbus UTM and Johns Hopkins APL ran simulations that used prototype UTM services from USim — Airbus UTM’s proprietary simulation environment to examine the impact of strategic deconfliction on UAS operational safety.

Airbus UTM previously collaborated with Johns Hopkins APL on the paper “Evaluation of UTM Strategic Deconfliction Through End-to-End Simulation.” At the same time, Airbus UTM collaborated with MIT’s DINaMo Research Group on the paper “Protocol-Based Congestion Management for Advanced Air Mobility.” The papers were important explorations of strategic deconfliction and congestion management in UTM, and they won Best in Session and Best in Conference, respectively, at the USA/Europe ATM R&D Seminar.

Simulation Scenarios

This new strategic deconfliction research builds on the previous work, increasing complexity in the simulated operations to better reflect real-world scenarios and take steps to further explore the safety benefit as defined by the ASTM standard. The research also demonstrates USim’s simulation-as-a-service capabilities, as researchers at Johns Hopkins APL were able to access USim to use Airbus UTM’s strategic deconfliction services and examine their impact on operational safety.

Notably, the scenarios tested showed significant safety benefits — reducing mid-air collisions by 99% — when participation in strategic deconfliction remained high and was in accordance with the ASTM standard’s required operational intent conformance rates, even as operational complexity and density increased.

To test strategic deconfliction’s impact on UAS operational safety, Airbus UTM and Johns Hopkins APL simulated operations across the Denver metropolitan area. The simulations examined both low-complexity and high-complexity operational scenarios. The low-complexity scenario involved uniformly distributed out-and-back operations. The high-complexity scenario was more varied, including hub-and-spoke operations, like those in package delivery services; point-to-point operations, like medical deliveries; and long-linear-inspection operations simulating road or railway inspections, as well as out-and-back operations.

In both scenarios, Airbus UTM and Johns Hopkins APL ran simulations with 95% operational intent conformance rates — flights that largely followed their submitted flight plans — in accordance with the ASTM Standard. Researchers incorporated a degree of system error (e.g., noise in the navigation and guidance systems) to model this simulated 95% conformance rate. The results showed that strategic deconfliction improved operational safety, and the safety benefit remained approximately constant, even at increased operational densities.

Importance of Participation

The rate of participation in strategic deconfliction has a significant impact on the safety benefit. When simulated participation was reduced to 75% in both the low- and high-complexity scenarios, the safety benefit — based on the mid-air collision rate — dropped by 25% and 41%, respectively.

These results demonstrate that, while high-complexity scenarios do increase risk, when operational conformance remains high, in accordance with the ASTM Standard, increased participation in strategic deconfliction increases the safety benefit, even in complex, high-density scenarios.

This research is significant in exploring the safety benefit derived from cooperative strategic deconfliction in UAS operations, as defined by the ASTM standard. Constraints like restricted airspace and external variables like weather remain to be studied, and these may impact traffic density and operational conformance, possibly increasing the risk of conflicts. The work is nonetheless significant in demonstrating the impact cooperative strategic deconfliction may have on traffic safety in real-world operations, from simple flights to complex package delivery services.

- Tony Evans and Sebastian Zanlongo