The Nature of the Aircraft Component Failure Process: A Working Note

Abstract

The physics of component failures is normally assumed to follow a Poisson process. However, many studies have shown that the component demands in the U.S. Air Force supply system have a variance-to-mean ratio (VMR) much higher than 1.0, the VMR of a Poisson process. This apparent contradiction is resolved by modeling component failures as a Poisson process whose demand rate is not fixed, but rather is itself a stochastic process, wandering over time as a result of various causes such as weather, flying intensity, reliability growth, and, presumably, other unknown factors. Component and program data for the F-16 and A-10 aircraft show that demand over short time periods is Poisson. This is even more apparent when demands per flying hours are used instead of demands per day. However, when demands are aggregated over longer periods of time or more flying hours, the VMR increases. A gamma-Poisson model for future demands as a function of past observations fits the measured data. We call this process 'planetary Poisson' to distinguish it from the general class of nonstationary Poisson models.

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Document Details

Document Type
Technical Report
Publication Date
Feb 01, 1988
Accession Number
ADA197979

Entities

People

  • Craig C. Sherbrooke
  • F. M. Slay

Organizations

  • LMI

Tags

Communities of Interest

  • Air Platforms
  • Materials and Manufacturing Processes

DTIC Thesaurus Topics

  • Air Force
  • Aircraft Equipment
  • Aircrafts
  • Availability
  • Chi Square Test
  • Classification
  • Data Analysis
  • Databases
  • Delphi Method
  • Information Science
  • Intensity
  • Logistics Management
  • Observation
  • Probability
  • Probability Distributions
  • Random Variables
  • Stochastic Processes

Readers

  • Logistics and Supply Chain Management.
  • Statistical inference.
  • Theoretical Analysis.