Making a Risk Informed Safety Case for Small Unmanned Aircraft System Operations

Clothier, Reece; Denney, Ewen; Pai, Ganesh

doi:10.2514/6.2017-3275

Cited by 15 publications

(7 citation statements)

References 15 publications

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“…Since sNMAC is proposed to be a functional analog to NMAC, any of the potential sNMAC candidates should also be compatible with any regulatory or standards process that leveraged NMAC. The community adoption of final sNMAC criteria could lead to risk-based minimum operating performance standards (MOPS) for DAA systems [59,60] Assessment (SORA) 14 . Upon selection of final singular sNMAC metric, it can be a "drop-in" replacement for NMAC, enabling the generation of a set of metrics used to train and evaluate ACAS sXu [53].…”

Section: Nomentioning

confidence: 99%

A Quantitatively Derived NMAC Analog for Smaller Unmanned Aircraft Systems Based on Unmitigated Collision Risk

Weinert¹,

Alvarez²,

Owen³

et al. 2020

Preprint

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The capability to avoid other air traffic is a fundamental component of the layered conflict management system to ensure safe and efficient operations in the National Airspace System. The evaluation of systems designed to mitigate the risk of midair collisions of manned aircraft are based on large-scale modeling and simulation efforts and a quantitative volume defined as a near midair collision (NMAC). Since midair collisions are difficult to observe in simulation and are inherently rare events, basing evaluations on NMAC enables a more robust statistical analysis. However, an NMAC and its underlying assumptions for assessing close encounters with manned aircraft do not adequately consider the different characteristics of smaller UAS-only encounters. The primary contribution of this paper is to explore quantitative criteria to use when simulating two or more smaller UASs in sufficiently close proximity that a midair collision might reasonably occur and without any mitigations to reduce the likelihood of a midair collision. The criteria assumes a historically motivated upper bound for the collision likelihood and subsequently identify the smallest possible NMAC analogs. We also demonstrate the NMAC analogs can be used to support modeling and simulation activities.

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Section: Nomentioning

confidence: 99%

A Quantitatively Derived NMAC Analog for Smaller Unmanned Aircraft Systems Based on Unmitigated Collision Risk

Weinert¹,

Alvarez²,

Owen³

et al. 2020

Preprint

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“…Bow tie diagrams (BTDs), which realize a barrier model of safety, provide a graphical means to visualize and assess the risk scenarios associated with a given hazard [7]. Fig.…”

Section: Background a Bow Tie Diagramsmentioning

confidence: 99%

Towards a Rigorous Basis for Specific Operations Risk Assessment of UAS

Denney

Pai

Johnson

2018

2018 IEEE/AIAA 37th Digital Avionics Systems Conference (DASC)

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The Specific Operations Risk Assessment (SORA) guidance represents the consensus of various national aviation authorities on a common process to identify, qualitatively assess, and manage the safety risk posed by unmanned aircraft systems (UAS), when preparing the safety case required for regulatory approval to conduct certain types of operations. As such, it can be considered a de facto standard, being increasingly adopted by various relevant stakeholders. This paper first gives an overview of the SORA process and associated methods, identifying a number of inconsistencies in risk identification and assessment, also discussing plausible strategies to close the associated gaps. Then, we give a well-founded basis for the applicable concepts, such as barrier integrity, assurance, and robustness, following which we present a preliminary and simple probabilistic formalization of the underpinning barrier-based safety model. We illustrate our overall approach through a worked example, also discussing how a Bayesian framework can facilitate extending and enhancing our initial formalization. We conclude with a discussion of the opportunities afforded by our approach, such as a well-founded basis for barrier selection, whilst addressing the associated challenges. The main objective of this work is to complement the current SORA guidance through a principled, mathematicallybased approach to risk assessment, particularly when it is applied to higher-risk operational concepts that warrant greater rigor in safety assessment and assurance.

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“…Based upon the argument development process (Section 2.3), our experiences in creating real safety cases [6,13,15,24], as well as from feedback from other users and projects within NASA, we have identified a core set of needs, which we believe can be met by providing tool support along with the appropriate automation. Amongst the stakeholders who would benefit from such a capability are safety engineers, systems engineers and developers, managers who are required to make safety-relevant decisions (such as those concerning risk acceptance, effort allocation towards risk reduction measures, etc.)…”

Section: Motivating the Need For Automationmentioning

confidence: 99%

“…Towards addressing the general needs for safety case development identified earlier (Section 3.1), and the more specific needs to support our process (Section 2.3), we have defined a number of high-level requirements 13 to implement automation support in AdvoCATE (Fig. 4).…”

Section: Requirements Specificationmentioning

confidence: 99%

Tool support for assurance case development

Denney

Pai

2017

Autom Softw Eng

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Argument-based assurance cases, often represented and organized using graphical argument structures, are increasingly being used in practice to provide assurance to stakeholders, e.g., regulatory authorities, that a system is acceptable for its intended use with respect to dependability and safety concerns. In general, comprehensive system-wide assurance arguments aggregate a substantial amount of diverse information, such as the results of safety analysis, requirements analysis, design, verification and other engineering activities. Although a variety of assurance case tools exist, many desirable operations on argument structures such as hierarchical and modular abstraction, argument pattern instantiation, and inclusion/extraction of richly structured information have limited to no automation support. To close this automation gap, over the past four years we have been developing a toolset for assurance case automation, AdvoCATE, at the NASA Ames Research Center. This paper describes how AdvoCATE is being engineered atop formal foundations for assurance case argument structures, to provide unique capabilities for: a) automated creation and assembly of assurance arguments, b) integration of formal methods into wider assurance arguments, c) automated pattern instantiation, d) hierarchical abstraction, e) queries and views, and f) verification of arguments. We (and our colleagues) have used AdvoCATE in real projects for safety assurance, in the context of unmanned aircraft systems.

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Making a Risk Informed Safety Case for Small Unmanned Aircraft System Operations

Cited by 15 publications

References 15 publications

A Quantitatively Derived NMAC Analog for Smaller Unmanned Aircraft Systems Based on Unmitigated Collision Risk

A Quantitatively Derived NMAC Analog for Smaller Unmanned Aircraft Systems Based on Unmitigated Collision Risk

Towards a Rigorous Basis for Specific Operations Risk Assessment of UAS

Tool support for assurance case development

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