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 An Introduction to Tools and Techniques Minimize

This table summarises some of the Safety Assessment Tools and Techniques available to the safety assessor. Each of these tools has its own advantages and disadvantages and the extent to which these can be used during various phases of the product lifecycle, and the degree to which they can be applied to safety assessments, vary. For a list of Advantages and Limitations of each, see Appendix A to Aircraft System Safety: Military and Civil Aeronautical Applications.

It is extremely important to note that as the complexity of the tool increases so does the degree of training required for the user and/or the need for an experienced evaluation team to conduct the evaluation. On the plus side, the data derived from the more complex methodologies may be more supportable. Unfortunately, the primary disadvantage of such tools is that "trained subject matter experts" may have limited experience in the actual operational environment and, therefore, their evaluations may not be entirely applicable to the certification process.

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 Tools and Techniques Minimize
 NameSorted By Name In Ascending OrderDescription
Fire Hazards AnalysisFire Hazards Analysis is applied to evaluate the risks associated with fire exposures. There are several firehazard analysis techniques, i.e. load analysis, hazard inventory, fire spread, scenario method. Any fire risk can be evaluated. [Tarrents, 1980]
Flow AnalysisThe analysis evaluates confined or unconfined flow of fluids or energy, intentional or unintentional, from one component/sub-system/ system to another. The technique is applicable to all systems which transport or which control the flow of fluids or energy. [Tarrents, 1980]
Function and Task AnalysisHuman error reliability assessment technique. Detailed analysis of the functions to be accomplished by the human/machine/environment system and the tasks performed by the human to achieve those functions.
  • Function Analysis: An analysis of basic functions performed by the "system" (which may be defined as human-machine, human-software, human-equipment-environment, etc.). The functional description lists the general categories of functions served by the system. Functions represent general transformations of information and system state that help people achieve their goals, but do not specify particular tasks.
  • Task Analysis: Task analysis is one of the most important tools to understand the user and can vary substantially in its level of detail and completeness. The preliminary task analysis traditionally specifies the jobs, duties, tasks, and actions that a person will be doing.
Functional Analysis System Technique (FAST)This tool is used in the early stages of design to investigate system functions in a hierarchical format and to analyse and structure problems (e.g., in allocation of function).

The aim of FAST is to understand how systems work and how cost effective modification can be incorporated. It asks 'how' a sub-tasks link to tasks higher up the task hierarchy, and 'why' the super-ordinate tasks are dependent one the sub-tasks [Creasy, 1980; Kirwan and Ainsworth, 1992; Adams and Lenzer, 1997].
Functional Failure Analysis (FFA)See Functional Hazard Analysis.
Functional Failure Path AnalysisA method of determining the safety critical aspects of an implementation.

A structured, top-down, iterative analysis which identifies functional paths and associated failures.
Functional Hazard Analysis (FHA)A systematic, comprehensive examination of a system's functions to identify and classify failure conditions (conditions which the system can cause or contribute to, not only if it malfunctions or fails to function, but also in its normal response to unusual or abnormal external factors) of those functions according to their severity.

The FHA provides a top-level analysis of the functions performed by the system and the risks presented by these functions following failure or misuse. These hazards produced by the system are categorized according to their level of severity. Potential effects on the aircraft or on crew workload determine each hazard's associated severity.
Gathered Fault Tree CombinationFormalised extension of FMES (developed in France, used on Airbus and Concorde).
Generic Error Modelling System (GEMS)GEMS is an error classification model that is designed to provide insight as to why an operator may move between skill-based or automatic rule based behaviour and rule or knowledge-based diagnosis. Errors are categorised as slips/lapses (frequently skill-based errors) and mistakes (usually knowledge based errors). The result of GEMS is a taxonomy of error types that can be used to identify cognitive determinants in error sensitive environments. GEMS relies on the analyst either having insight to the tasks under scrutiny or the collaboration of a subject matter expert, and an appreciation of the psychological determinants of error [Reason, 1990].

See Eurocontrol.
Goals, Operators, Methods and Systems (GOMS)GOMS is a task modelling method to describe how operators interact with their systems. Goals and sub-goals are described in a hierarchy. Operations describe the perceptual, motor and cognitive acts required to complete the tasks. The methods describe the procedures expected to complete the tasks. The selection rules predict which method will be selected by the operator in completing the task in a given environment. GOMS is mainly used in addressing human-computer interaction and considers only sequential tasks [Card, Moran and Newell, 1983].

See Usability First and Eurocontrol.
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