ADS-B: Probabilistic Safety Assessment

In the effort to quantify Automatic Dependent Surveillance Broadcast (ADS-B) system safety, the authors have identified potential ADS-B failure modes in Syd Ali et al. (2014). Based on the findings, six potential hazards of ADS-B are identified in this paper. The authors then applied the Probabilistic Safety Assessment approach which includes Fault Tree Analysis (FTA) and Importance Analysis methods to quantify the system safety. FTA is applied to measure ADS-B system availability for each identified hazard while Importance Analysis is conducted to identify the most significant failure modes that may lead to the occurrence of the hazards. In addition, risk significance and safety significance of each failure mode are also identified. The result shows that the availability for the ADS-B system as a sole surveillance means is low at 0·898 in comparison to the availability of ADS-B system as supplemental or as primary means of surveillance at 0·95 and 0·999 respectively. The latter availability values are obtained from Minimum Aviation System Performance Standards (MASPS) for Automatic Dependent Surveillance-Broadcast (DO-242A).

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Probabilistic Safety Assessment for UAS Separation Assurance and Collision Avoidance Systems

Aerospace ◽

10.3390/aerospace6020019 ◽

2019 ◽

Vol 6 (2) ◽

pp. 19 ◽

Cited By ~ 2

Author(s):

Asma Tabassum ◽

Roberto Sabatini ◽

Alessandro Gardi

Keyword(s):

Safety Assessment ◽

Fault Tree Analysis ◽

Analytical Framework ◽

Unmanned Aircraft ◽

Surveillance Systems ◽

Probabilistic Safety Assessment ◽

Importance Analysis ◽

Cooperative Tracking ◽

Traffic Detection ◽

Probabilistic Safety

The airworthiness certification of aerospace cyber-physical systems traditionally relies on the probabilistic safety assessment as a standard engineering methodology to quantify the potential risks associated with faults in system components. This paper presents and discusses the probabilistic safety assessment of detect and avoid (DAA) systems relying on multiple cooperative and non-cooperative tracking technologies to identify the risk of collision of unmanned aircraft systems (UAS) with other flight vehicles. In particular, fault tree analysis (FTA) is utilized to measure the overall system unavailability for each basic component failure. Considering the inter-dependencies of navigation and surveillance systems, the common cause failure (CCF)-beta model is applied to calculate the system risk associated with common failures. Additionally, an importance analysis is conducted to quantify the safety measures and identify the most significant component failures. Results indicate that the failure in traffic detection by cooperative surveillance systems contribute more to the overall DAA system functionality and that the probability of failure for ownship locatability in cooperative surveillance is greater than its traffic detection function. Although all the sensors individually yield 99.9% operational availability, the implementation of adequate multi-sensor DAA system relying on both cooperative and non-cooperative technologies is shown to be necessary to achieve the desired levels of safety in all possible encounters. These results strongly support the adoption of a unified analytical framework for cooperative/non-cooperative UAS DAA and elicits an evolution of the current certification framework to properly account for artificial intelligence and machine-learning based systems.

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Preliminary Probabilistic Safety Assessment of the IRIS Plant

10th International Conference on Nuclear Engineering, Volume 2 ◽

10.1115/icone10-22095 ◽

2002 ◽

Author(s):

Yuko O. Mizuno ◽

Katsunori Ogura ◽

Hisashi Ninokata ◽

Lawrence E. Conway

Keyword(s):

Safety Assessment ◽

Fault Tree ◽

Fault Tree Analysis ◽

Heat Removal ◽

Primary System ◽

Event Tree ◽

Secondary System ◽

Probabilistic Safety Assessment ◽

Loss Of Coolant Accident ◽

Probabilistic Safety

A preliminary level-1 probabilistic safety assessment of the IRIS plant has been performed. The first focus is on five internal initiating events, such as primary system break (loss-of-coolant accident and steam generator tube rupture) and transients (secondary system line break and loss-of-off-site power). In this study, the event tree for each initiating event was developed and the fault tree analysis of the event tree headings was carried out. In particular, since one of the IRIS safety systems, the passive emergency heat removal system, is unique to the IRIS plant and its reliability is key to the core damage frequency evaluation, it received more extensive fault-tree development. Finally the dominant sequences that lead to severe accidents and the failures in the main and support systems are identified.

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