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TI Researchers Provide Safety Case Leading To FAA Approval of First-Ever Small UAS BVLOS Operations Over Land
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TI Researchers Provide Safety Case Leading To FAA Approval of First-Ever Small UAS BVLOS Operations Over Land

The Unmanned Aircraft Systems (UAS) Traffic Management (UTM) concept is being engineered by NASA to usher in a paradigm that will lower the threshold of access to the National Airspace System (NAS) for Small Unmanned Aircraft Systems (sUAS) whose operations will occur in low altitude uncontrolled airspace, whilst maintaining (or improving) the prevailing level of safety. UTM is being developed as a series of progressively more capable Technical Capability Levels (TCLs), whose functionality will be showcased through proof-of-concept flight demonstrations in the NAS.

Previous demonstrations have occurred within Visual Line of Sight (VLOS) and Extended VLOS (EVLOS), but future operations will be conducted Beyond Visual Line of Sight (BVLOS) over sparsely populated areas, and where there may be manned aircraft in the vicinity of the area of operations. A key capability to be utilized for achieving safety in true BVLOS operations is Ground-Based Detect and Avoid (GBDAA), which will be deployed in lieu of visual observers as an Alternative Means Of Compliance (AMOC) to the see-and-avoid regulation. To conduct BVLOS sUAS operations with GBDAA, NASA needed Federal Aviation Administration (FAA) operational approval in the form of a Certificate of Waiver or Authorization (COA).

That, in turn, required supplying a safety justification to the FAA, which was submitted as a safety case by Code TI researchers Ewen Denney and Ganesh Pai. Safety cases subsume traditional safety analysis and safety risk management documents: they organize the analysis and gather the necessary evidence to provide explicit and compelling rationale as to why regulators must find that a system and its operations will be safe. Thus, it provides a framework both for independent assessment and for systematically reasoning about deficiencies, if any, in the analysis and/or the evidence. The safety case submitted to the FAA was such a compendium of engineering data and analysis, which provided the evidence and rationale that they needed to conclude that NASA's intended BVLOS operations will meet the existing level of safety. The FAA subsequently approved the safety case and awarded a COA.

BACKGROUND: Two key concepts formed the core of the safety case: structured arguments, which provided the safety justification for using specific capabilities (such as GBDAA); and barrier models, which provided the means for visualizing and managing safety risk. The Assurance Case Automation Toolset (AdvoCATE), developed in Code TI, was used to create the associated structured arguments and barrier models.

Ongoing research seeks to develop techniques to architect safety cases, so that they are maintainable with the system under consideration, are comprehensible to a variety of stakeholders, including system designers, regulators, operators and end-users, and to exploit a diversity of formal/non-formal reasoning and analyses for automating their creation to the extent possible.

NASA PROGRAM FUNDING: Airspace Operations and Safety Program (AOSP), Aeronautics Research Mission Directorate (ARMD)

TEAM: Ewen Denney and Ganesh Pai

POINT OF CONTACT:Guillaume Brat,

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