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Quantifying the Impact of Aircraft Cannibalization Task MM0206. Principal Investigator C. Richard Cassady, Ph.d., P.E. Co-Principal Investigators Scott J. Mason, Ph.D., P.E.

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Quantifying the impact of aircraft cannibalization task mm0206

Quantifying the Impact of Aircraft Cannibalization Task MM0206

Principal Investigator C. Richard Cassady, Ph.d., P.E.

Co-Principal Investigators Scott J. Mason, Ph.D., P.E.

Justin R. Chimka, Ph.D.

Graduate Research Assistants Kellie Schneider

Stephen Ormon

Undergraduate Research Assistants Chase Rainwater

Mauricio Carrasco

Jason Honeycutt

ASC PA 03-2420 9/15/03

Project motivation
Project Motivation

  • extensive use of cannibalization in fleet maintenance

  • existing mathematical models of cannibalization do not address USAF issues

Project objectives and activities
Project Objectives and Activities

  • project objectives

    • to develop a mathematical modeling methodology for assessing the impact of cannibalization on fleet performance

    • to identify policies for making cost-effective, dynamic cannibalization decisions

    • to study the impact of these policies on management of the spare parts supply chain

  • project activities

    • generic scenario definition

    • generic simulation modeling

    • application

    • future work

Generic scenario definition
Generic Scenario Definition

  • set of n independent and identical aircraft

  • each aircraft

    • two parts connected in series

    • part i has a constant failure rate λi

  • aircraft operation

    • continuous until failure

  • aircraft failure – caused by failure of part j

    • immediately routed to base of operations for Mx

  • sj part j “spares” in the system





Maintenance logic
Maintenance Logic

failure – remove part j (time Rj) – send removed part off for repair (time Lj)

spare part j available?



install part j (time Ij)

cannibalization allowed?



cannibalization possible?



cannibalize (time Cj) – cannibalized aircraft now needs both parts

aircraft departs

aircraft waits

Maintenance logic cont
Maintenance Logic (cont.)

repaired part j returned to base

failed aircraft waiting for only part j?



install part j on failed aircraft

failed aircraft waiting for both parts?



spare of other part available?



aircraft departs

restore aircraft

add part to inventory

Generic simulation modeling
Generic Simulation Modeling

  • simulation model of defined scenario constructed in Arena

  • performance measures estimated from model include:

    • average readiness (R)

    • Mx-man-hours per flying hour (MMH/FH)

    • average “experience” of a failed aircraft

Performance analysis example
Performance Analysis – Example

(min, mode, max) in hr

Performance analysis cont
Performance Analysis (cont.)

  • suppose target average readiness is 80%

  • suppose no cannibalization is permitted

    • R = 78.8%

    • MMH/FH = 0.0035

  • suppose cannibalization is permitted

    • R = 81.9%

    • MMH/FH = 0.0042

  • cannibalization satisfied the readiness issue but increased requirements for Mx resources

  • what are some other options?

    • 1. add a spare for part 2

    • 2. reduce the repair delay for part 2 by two days

  • option 1: R = 84.2%, MMH/FH = 0.0036

  • option 2: R = 81.2%, MMH/FH = 0.0036

Performance analysis cont1
Performance Analysis (cont.)

  • suppose all three options are implemented

    • R = 86.6%

    • MMH/FH = 0.0039

    • average “experience” of a failed aircraft

      • 23.5% receive a spare immediately

      • 11.9% are restored via cannibalization

      • 64.6% must wait

        • average time waiting for a single part = 70 hr

        • 11.9% become cannibalized

        • average waiting time after cannibalization = 174 hr

Application outline
Application Outline

  • Hill AFB visit

  • motivating questions

    • should cannibalization be consolidated?

    • how many technicians should be assigned to the CANN-dock?

    • how many aircraft should be designated as CANN-birds?

    • how long should aircraft remain in CANN-bird status?

  • simulation modeling

Simulation modeling application
Simulation Modeling – Application

  • based on the cannibalization activities that take place at Hill AFB

  • modeling concepts

    • one wing, three squadrons

    • cannibalization, slaving

    • AMU-level or consolidated cannibalization

    • fixed number of CANN-birds

    • rebuilds after specified number of days

    • rework and testing after rebuilds

    • limited number of maintenance technicians

    • various technician skill sets

    • technicians pulled from AMU to CANN-dock