Page 60 - RCM - A practical Guide_V1

RCM - A Practical Guide

GLOSSARY

Age exploration (AE). The process of determining age-reliability relationships through controlled testing and analysis
for safety items and from operating experience for non-safety items.
Age-reliability characteristics. The characteristics exhibited by the relationship between the operating age of an item and its
conditional probability of failure.
Conditional probability of The probability that an item will fail during a particular age interval, given that it survives to
failure (CpF). enter that interval.
Consequences of failure. The results of a given functional failure at the equipment level, classified in RCM analysis as
safety/environmental consequences, operational/economic consequences,
safety/environmental hidden failure consequences and non-safety hidden failure consequences.
Crack detection threshold. The minimum life to the first detectable appearance of a fatigue crack in an item subject to a
predictable loading spectrum.
Crack propagation life. The period it takes a crack to grow from the crack detection threshold to the critical crack
length.
Crew. Personnel normally assigned to operate equipment.
Critical crack length. The crack length at which the residual strength of the item is no longer sufficient to withstand
80% of the Design Ultimate Load (DUL).

Damage tolerant structure. Refer to MRP RA5720.
Effectiveness criteria. The criteria for judging whether a specific task is capable of reducing the failure rate or
probability of failure to the required level.
End Item (EI). An aircraft or major item of equipment to which an RCM study is directed.
Failure effects. The impact a failure mode has on the operation, function, or status of an item. Failure effects
are often classified as local effect, next higher level, and end effect.
Failure finding (FF) task. Scheduled maintenance of a hidden function item to find functional failures that have already
occurred but were not evident to the operating crew.

Failure mode. The specific engineering mechanism of failure that leads to a particular functional failure.
Failure rate. The total number of failures within an item population, divided by the total number of life units
expended by that population, during a particular measurement interval under stated conditions.
Failure symptom. An identifiable physical condition by which a potential failure can be recognized.
Fatigue. Reduction in resistance to failure of a material over time, as a result of repeated or cyclic applied
loads.
Fatigue life. For an item subject to fatigue, the total time to functional failure of the item.

60
© ASPIRE CONSULTING LTD +44 (0) 1827 723820