Rules for Planned Replacement of Aircraft and Missile Parts.
Abstract
The appropriate replacement policy for a part depends on its failure characteristics and the relative costs of an in-service failure and of a planned replacement (replacement before failure). For planned replacement to be worthwhile, the part must display a wearout characteristic (a failure rate increasing with time); and the cost of an in-service failure must be greater than the cost of a planned replacement. Failure-data analysis has shown that many aircraft and missile parts fail exponentially; that is, they have a constant failure rate. In these cases, a new part is no better than a used but serviceable part of any age. The optimum replacement policy for these parts -- optimum in the sense of minimizing expected cost per unit time -- is a simple one: Never plan to replace before failure, regardless of how expensive or inconvenient an in-service failure becomes. On the other hand, analysis of failure data has also uncovered many parts with non-exponential failure characteristics. Substantial numbers of these parts exhibit an increasing failure rate over time. In this situation the age at which the part should be replaced depends on the relative cost of an in-service failure. In general, for a given aging effect, the higher the relative cost of an in-service failure, the shorter should be the planned-replacement interval. Similarly, for a given in-service failure cost, the more severe the aging effect the shorter the replacement interval.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1962
- Accession Number
- ADA081363
Entities
People
- M. Kamins
Organizations
- RAND Corporation