Accident Precursor Analysis and Management Reducing Technological Risk Through Diligence (2004) / Chapter Skim
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5 Defining and Analyzing Precursors
5 Defining and Analyzing Precursors
Pages 79-88
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From page 79... ...
We now know that every shuttle launch that included an 0- log blow-by before the Challenger explosion was a precursor to m explosion m that if the pre-launch ambient temperature had been sufficiently low the O-rings would have failed and the vehicle would have been lost. In the case of the supersonic airplane Concorde, m exammation of the accident history indicates about a half-dozen recorded precursors to the fatal encoumter with a foreign object.
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From page 80... ...
Thus, a precursor is an event or situation that, if a small set of behaviors or conditions had been slightly different, would have led to a consequential adverse event. Has there ever been a consequential event, near miss, or infraction/deviation that did not have a precursor?
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From page 81... ...
Real McCoys might also be considered precursors using Equation 4a: tWorse Real McCoy+ = ~ Real McCoy J(N) + ~ Nothmg J + ~ Tome J + ~ Exacerbaring Factor(s)
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From page 82... ...
The near miss concept suggests the following: I Real McCoy I = {Near Miss} +/- I Not Much I (5) Many people believe that investigations of near misses should be commensurate with investigations of the corresponding averted consequential events.
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From page 83... ...
At Davi i-Beti is, as reported in local newspapers, there were many precursors: · leaky conhol-rod drive-mechanism joints that encouraged tolerance of leakage · boric acid deposits in the reactor vessel head area from leaks · the presence of alloy bO0, which is subject to cracking · time, temperature, and stress · criticism by the Nuclear Regulatory Commission (that was ignored) of the boric acid corrosion-control program · predictions by an indu it y group that cracks were likely IFor Intentet access to a large community of root cause analysis pracotioners, as well as links, files, database tables, and other resources, see htip//ttroupr.yahootortitroup/ Root Catuse_State_af the_Prattite/
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From page 84... ...
The investigation, however, did not result in advising submarine commanders to choose test sites sufficiently deep to achieve test objectives but shallow enough to avoid collapsing unwooded compartments. This is a special case of an important safety principle that tells us not to take risks in excess of those for which there is some benefit (see Corcoran [2002]
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From page 85... ...
And, investigations of consequential events md near misses show that higher seventy events include m accumulation of lower level events md causes. Hence, root-cause malyses of dhe precursors to accidents should help reduce accident rates.
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From page 86... ...
To avert the consequences of the future real McCoys indicated, suggested, or ar,nounced by precursors, corrective actions must include not only controlling the precursor behaviors and conditions, but also controlling the processes that produce them. In detennining corrective actions, the chains of causation must be interrupted.
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From page 87... ...
Detailed investigations of most adverse events reveal precursors that is, accidents have been preceded by events, behaviors, and conditions that were ingredients of the recipe for the adverse consequences. Adverse events that seem to come out of the blue are events whose precursors were not recognized.
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From page 88... ...
The Phoenix Handbook. Windsor, Comt.: Nttciear Safety Review Concepts Cotp or at ion .
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