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Mathematical models of the logistics system are used to determine spares requirements, and they play an important role in evaluating logistics policies. The kernel of many, if not most, of these models is the modeling of the failure process and the resulting series of random demands on supply and maintenance. This report describes the assumptions of these models and quantifies ways in which the behavior of the data differs from the assumptions of the models. The differences are pervasive and important. In addition, an examination of the number of parts in the repair pipeline over time reveals even more variability than does the number of demands over time. These observations have two important consequences: (1) excessive demand variability substantially reduces the confidence we can put in our requirements and capability assessment models, and (2) highly variable repair pipelines with means larger than assumed by requirements models have a damaging effect on aircraft availability and wartime readiness. Depot policies, decisions, and goals should be aimed at reducing the number of parts in these pipelines and increasing aircraft availability and wartime readiness.

United States. --- Aviation supplies and stores.

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The Dyna-METRIC model was developed to study and predict the readiness of groups of aircraft squadrons as determined by a major subset of logistics resources, namely, those associated with component repair and resupply. This report describes the mathematical approaches to modeling the effects of spare parts supply, component repair, and related processes on combat capability. It does not describe the implementation of any specific version of Dyna-METRIC. Section II reviews the time-dependent pipeline equations. Section III describes time-dependent stockage and component-repair measures of performance. Section IV combines these measures to give aircraft capability measures. Section V introduces the pipeline model for indentured components, while Sec. VI describes the pipeline equations for the time-dependent, multiple-echelon model. Section VII describes the optimization techniques for supply requirements, and Sec. VIII describes the approach for limited service facilities.

Airplanes, Military --- Maintenance and repair --- Mathematical models. --- United States. --- Aviation supplies and stores --- Procurement

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This report describes and demonstrates a new methodology for increasing the effectiveness of future fighters that must face growing enemy threats in Europe and the Third World. Unlike traditional methods, this new methodology integrates changes in the design of air vehicles with changes in the basing and support systems they will use. The methodology calls not only for such conventional measures as the speed, acceleration, altitude, payload, and maneuverability of the air vehicle, but also for such new measures as the flexibility, mobility, sortie generation capability, aircraft ground survivability, and cost of the air vehicle, as well as its basing methods and support structure.

Fighter plane combat --- Air bases, American. --- Fighter planes --- United States. --- Aviation supplies and stores.

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This report documents a briefing that presents a method for examining the effect that various stockage policies have on the length of time weapon replaceable assemblies (WRAs) spend waiting for parts. The authors argue that the current stockage policies--which emphasize descriptors of parts and rarely include information about the end-item that needs them--likely contribute to the simultaneous problems of long repair turnaround times (TATs) and excesses of repair parts. The report discusses an algorithm which incorporates both parts descriptors and output measures and which minimizes the expected length of time an end-item spends in repair. The authors' research suggests that through effective stockage of repair parts, the Services may be able to achieve large savings from shortening the TAT at depot, which allows more end-items to be in circulation. Furthermore, the authors' evaluations suggest that their calculations can identify weapons systems where it would make sense to stock parts and those where it would not. The calculations can be used to balance investment strategies between spending money on parts and spending it on other segments of the repair pipeline.

United States. --- Aviation supplies and stores. --- Equipment --- Maintenance and repair. --- Cost control.

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The U.S. Air Force is grappling with the challenge of aging fleets and when it might be optimal to replace those fleets. This monograph examines commercial aviation data with the goal of drawing inferences and lessons about aging aircraft that may be relevant to the Air Force. It focuses on "aging effects"-i.e., how commercial aircraft maintenance costs change as aircraft grow older. Although commercial aircraft clearly differ from military aircraft, commercial aviation aging-effect estimates might help the Air Force to project how its maintenance costs will change over time and how those costs might evolve for new commercially analogous aircraft not yet in its inventory. This study found that commercial-airline inflation-adjusted total aircraft maintenance costs, per flight hour, rise substantially as aircraft come off the manufacturer's warranty after a few years of operation, and then rise at about a 3.5 percent annual rate for aircraft six to 12 years old, but are nearly unchanged for aircraft 12 to 25 years old.

Airplanes, Military --- Maintenance and repair. --- United States. --- Aviation supplies and stores.