Evaluation of the Four-Dimensional Trajectory Live Flight Demonstration (4DT LFD) Project

Current operations in the National Airspace System (NAS) primarily rely on voice communication designed to minimize lengthy conversations as well as simple data exchanges intended to supplement voice communication without adding additional fidelity to instructions. Advances in communication, data processing capabilities, and cultural acceptance of technology-enabled procedural changes are paving the way for implementation of Air Traffic Management (ATM) concepts based on Four-Dimensional Trajectories (4DT). Exchanging Four-Dimensional (4D) data (latitude, longitude, altitude, and time) and trajectories via an internet- based infrastructure is part of the Federal Aviation Administration (FAA) Next Generation Air Transportation System (NextGen) Office's vision for Trajectory Based Operations (TBO). In 2020, the FAA successfully completed the 4DT Live Flight Demonstration (4DT LFD) project to demonstrate how 4DT-based operations in the NAS can be implemented with current technologies and to inform future research.The FAA partnered with key industry participants to conduct two live flights in the NAS using 4DT for controller-pilot negotiations, clearances, and aircraft intent information. The 4DT LFD leveraged a connected aircraft with an Internet Protocol (IP) data link that enabled Air-to-Ground (A/G) SWIM and Demo IP-based Clearance connectivity as the aircraft traversed the NAS. The project maximized use of current infrastructure while leveraging NextGen capabilities at the FAA's Florida NextGen Test Bed (FTB) and communication systems available from industry partners.The 4DT LFD elaborated procedures, validated existing technology, and began to socialize the feasibility of TBO in the NAS to ATM stakeholders including the FAA, airspace users, and system providers. The project focused on new data exchange mechanisms for trajectory negotiations in the NAS enroute environment, leveraging commonly used avionics equipment with emphasis on Electronic Flight Bag (EFB) and Flight Management System (FMS). The project also leveraged ongoing FAA NextGen investments, such as System Wide Information Management (SWIM), Performance Based Navigation (PBN), and research into Flight and Flow - Information for a Collaborative Environment (FF-ICE). Lessons learned from the project will inform future FAA system requirements and airspace users' development of their own procedures and technologies. These lessons will help refine global concepts, standards, recommended practices, and implementation guidance.