Fault Tree Analysis (FTA) is a top-down, deductive root cause analysis method widely used in safety and reliability engineering. Using Boolean logic and visual tree diagrams, FTA identifies system failures by breaking down a major "top event" into its underlying component causes and basic events.

What is ALD Fault Tree Analysis (FTA) Software?
ALD FTA is an enterprise Fault Tree Analysis software designed for RAMS (Reliability, Availability, Maintainability, Safety) and System Safety engineers. It performs both qualitative and quantitative risk analysis, automatically calculates Minimal Cut Sets (MCS), failure rates, and system unreliability, and strictly complies with international standards such as ARP4761, ARP4754A, ISO 26262, MIL-STD-1629 and MIL-STD-882E  

Safety Commander's FTA (Fault Tree Analysis) software module is one of the unique features of Safety Commander. It is a simplified FTAnalyzer, fully integrated with Safety Commander's product tree and FMECA. It implements and summarizes the first-hand experience gained by the ALD FTA experts in hundreds of projects using Safety Commander and other ALD software tools. 

 

Safety Commander Fault Tree Analysis module has been initially developed for Aircraft (civil and military, helicopter, UAV, space ) which is a large and complex system, and a specific example of a System of Systems. Many different systems and devices have to work together to operate different parts of the aircraft but can only work when all the essential systems work together. Safety Commander allows organizations /programs / projects to resolve all challenges of assuring Safety of highly integrated systems.  A/C or System of Systems structure can be imported from external applications or built manually in RAM Commander or Safety Commander.

 

Fault Tree Analysis Module Features

 

• Modern Fault Tree editor with zoom, panning, overview functionality
• Creation of integrated fault trees using developed events
• Events import/export to and from MS Excel
• Fault Trees Import from CAFTA, Isograph, RAM Commander, PTC, OPSA format (MCS)
• Control over codification of FT elements - trees, gates, events
• Printing fault trees with automatic separation to multiple pages
• Multiple calculation types, including average probability calculation
• Link between FTA and the product tree
• Calculation of very large fault trees with fine-grained control over MCS truncation
• Loop Fault Trees resolution
• True/False Propagation
• Events Importance Calculation
• Repeated Events Indication
• Generation of multiple types of reports
• Aircraft Safety Assessment Dashboard
• Probability Diagram
• Probability Distribution Diagram
• Version / Revision Control for the history of A/C or System of Systems Safety
• Safety Commander Fault Tree Navigator resolves intersystem dependencies and ensures the real integration of entire aircraft or systems of systems safety assessment

Fault Tree Analysis is one of the most widely used methods in system reliability and failure probability analysis. A fault tree is a graphical representation of a logical structure depicting undesired events ("failures") and their causes. You create the logical structure by using gates and represent undesired incidents by using basic events. Reliability parameters are assigned to each basic event. Widely used in system reliability studies, fault tree analysis offers the ability to focus on an event of importance, such as a highly critical safety issue, and work to minimize its occurrence or consequence. The probability of a top-level event can then be determined by applying appropriate mathematical techniques. The resulting fault tree diagram is a graphical representation of the chain of events in your system or process, built using events and logical gate configurations.

FTA Basic Event data

Two types of analysis can be conducted using Fault Tree Analysis Software:

• Qualitative Analysis: performed by means of Minimal Cut Sets (MCS) building
• Quantitative Analysis: calculating the Absolute probabilities, i.e. the probabilities of system failures

Example of FTA Unavailability and MCS Analysis report

 

 

After Unavailability calculation and MCS analysis, Importance and Sensitivity Analysis may be performed. Results of Importance analysis help select those fault tree events, which contribute most to the system's unavailability. Sensitivity analysis helps choose those events, for which a relatively small change will lead to a relatively large system unavailability changes. Calculated values are Fussell-Vesely importance (FV Imp), Risk Decrease Factor (RDF), Fractional Contribution (FC), Risk Increase Factor (RIF) and Sensitivity Value for each Basic or Undeveloped Event.

 

Example of FTA Importance and Sensitivity Analysis report

 

 

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