LATENT FAULT EXPOSURE
It has been broken for months and nothing needed it until now.
01 DEFINITION
Condition in which a part that acts only under conditions that rarely arise can be unavailable indefinitely without any sign, so its failure and its first use are discovered at the same moment.
02 CONDITIONS
UNCERTAINTY
UNRECORDED
Whether it works is not established by anything that happens in ordinary running.
TIME PRESSURE
SHORT
When it is finally called on there is no interval in which to discover it is unavailable.
ERROR ASYMMETRY
ASYMMETRIC
Testing it and not testing it carry costs of very different size and timing.
OPERATOR STATE
SUPERVISORY
The people answerable for it are not the people who would use it.
03 WHERE IT APPEARS
ENERGYA protective function has been unavailable for months and nothing has called on it.
MEDICALA backup mode has not worked for some time and has not been needed for longer.
MANUFACTURINGA safety interlock has been inoperative since a change nobody connected it to.
CONSTRUCTIONA fall arrest provision has been compromised since an alteration and has not been loaded.
TELECOMA failover path has been broken since a reconfiguration and has not been asked for.
AI EXP.A fallback has been failing silently because nothing has fallen back to it.
04 WHERE THIS IS SURFACING
This surfaces wherever a capability is held for a condition that seldom comes. Nothing about ordinary running touches it, so ordinary running says nothing about it.
What stays unresolved is how something that does nothing proves it could — exercising it regularly is an intervention on a working system, and leaving it alone makes its readiness an assumption that grows older.