Safety factors associated with engine failures or malfunctions

Safety factors associated with engine failures or malfunctions

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  the individual reporting the occurrence
  
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  the type of failure mechanism
  
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  whether an engineering inspection was carried out.
  

Despite being reasonably consistent, there is up to a 26 per cent difference in the proportion of occurrences with safety factors between the manufacturers. These differences in the proportions of safety factors introduce inherent errors in any further comparison and analysis of safety factors. Accordingly, when comparing rates of safety factors, such as in Figure 7, the proportion of occurrences with unknown safety factors are used to generate error bars.

For safety factors relating to engine failure or malfunctions, technical failure mechanisms can include:

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  fracture - physical separation of parts of a component. Action of stress created by a single load application or the action of repeated stressing created by alternating loading
  
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  wear - surface interactions involving the removal of material from the surface of a component or transfer of material from one surface to another
  
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  corrosion - loss of material through a chemical action between a component and its environment. May be a localised reaction or a general surface reaction at low or high temperatures
  
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  deformation - physical distortion. Plastic deformation (permanent), elastic deformation (recoverable after force removed)
  
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  electrical discontinuity - disruption of an electrical connection at wiring level, circuit level, integrated circuit level
  
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  mechanical discontinuity - disruption of a physical connection in a mechanical, hydraulic or pneumatic system
  
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  software/firmware anomaly - computer or microprocessor program malfunction
  
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  other technical failure mechanism - any other type of failure mechanism.
  

Figure 7 shows the rates of technical failure mechanisms safety factors per 10,000 hours flown for the four major engine manufacturers. (Note that this figure is using safety factors, not occurrences, and some occurrences have multiple safety factors.)