Editing Fail-safe (section)

{{Short description|Design feature or practice}}
{{Other uses}}
In [[engineering]], a '''fail-safe''' is a design feature or practice that, in the event of a [[failure causes|failure]] of the design feature, inherently responds in a way that will cause minimal or no harm to other equipment, to the environment or to people. Unlike [[inherent safety]] to a particular hazard, a system being "fail-safe" does not mean that failure is naturally inconsequential, but rather that the system's design prevents or mitigates unsafe consequences of the system's failure. If and when a "fail-safe" system fails, it remains at least as safe as it was before the failure.<ref>"[http://www.audioenglish.net/dictionary/fail-safe.htm Fail-safe]". AudioEnglich.net. Accessed 2009.12.31</ref><ref>''e.g.'', David B. Rutherford Jr., [https://web.archive.org/web/20111008021648/http://www.billpetit.com/Papers/Petit017.pdf What Do You Mean It\'s Fail Safe?] . 1990 Rapid Transit Conference</ref> Since many types of failure are possible, [[failure mode and effects analysis]] is used to examine failure situations and recommend safety design and procedures.<ref>Force V: The history of Britain's airborne deterrent, by Andrew Brookes. Jane's Publishing Co Ltd; First Edition 1 Jan. 1982, {{ISBN|0710602383}}, p.144.</ref>

Some systems can never be made fail-safe, as continuous availability is needed. [[Redundancy (engineering)|Redundancy]], [[fault tolerance]], or [[contingency plan]]s are used for these situations (e.g. multiple independently controlled and fuel-fed engines).<ref>{{cite book
 |last         = Bornschlegl
 |first        = Susanne
 |title        = Ready for SIL 4: Modular Computers for Safety-Critical Mobile Applications
 |publisher    = MEN Mikro Elektronik
 |year         = 2012
 |url          = https://www.menmicro.com/downloads/search/dl/sk/%22White%20Paper%3A%20Ready%20for%20SIL4%3A%20Modular%20Computers%20for%20Safety-Critical%20Mobile%20Applications%22/dx/1/
 |format       = pdf
 |access-date  = 2015-09-21
 |archive-date = 2019-06-09
 |archive-url  = https://web.archive.org/web/20190609205912/https://www.menmicro.com/downloads/search/dl/sk/%22White%20Paper%3A%20Ready%20for%20SIL4%3A%20Modular%20Computers%20for%20Safety-Critical%20Mobile%20Applications%22/dx/1/
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}}</ref>