ONE of the things which led mo to develop the idea of “fixed period renewal”, was 12 months' experience of Quality Control with a famous aero‐engine firm. During that time I kept life‐charts and quality data in regard to numerous interesting variables relating to the failures and use‐characteristics of components within the power‐plant structure as a whole. Despite failure percentages of rarely more than 5 per cent, as a proportion of total production, I was absolutely amazed at the utter uncertainty as to failure probability, cither in terms of timing or quantity. It was equally appalling to realize what a low life‐expectation there is for all components. During the war the comparative lack of reliability in many minor components, within important assemblies, has led, in my personal and it is true restricted experience, to a terrible wastage of man‐power. Even though material weaknesses and shortages have to some extent excused this (with regard for example to the repair schemes) the result has not infrequently been to endanger or actually to end human life. When a component would be expected, Tor both safety and economic reasons to last χ hours, it has been found to last instead perhaps χ/3 or χ/4 hours.
Phillips, H.S. (1945), "Quality Control: Some Advantages of a System of Fixed Period Renewal", Aircraft Engineering and Aerospace Technology, Vol. 17 No. 6, pp. 179-182. https://doi.org/10.1108/eb031257
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