Operational benefits of LDACS-APNT in continental en-route operations

Abstract

While providing essential capabilities, that enable safe and efficient operations for modern air transport, satellite-based positioning, navigation and timing functions are also becoming an increasingly vulnerable single-point of failure. This vulnerability has the potential to mitigate the advantages for both terminal and en-route operations. Therefore, ground-based alternative positioning, navigation and timing (APNT) systems are brought to the focus of attention of current research and development to increase safety and reliability in such cases. APNT systems can complement their satellite counterparts during nominal operations and provide for a fall-back option in case of technical failures or functional cutbacks caused by third parties. Two candidates for such ground-based APNT-systems are either using the distance measuring equipment (DME) or the L-Band Digital Aeronautical Communication System (LDACS). While the DME infrastructure is already established, the placement and design of LDACS-APNT stations is still in consideration. To support this process and identify key drivers for system performance an initial technical-operational assessment is needed. In our work we apply a previously demonstrated method for the assessment of APNT navigation performance impact on a suitable safety metric based on the aircraft horizontal collision rate, for a representative LDACS APNT setup. Also, we provide a comparison with a representative DME-setup, establish initial overall operational implications and limitations with regard to infrastructure footprint and air traffic flow and discuss implementation options.