Research for Spare Parts

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Improving Navy's Buying Power Through Cost Savings
October 1, 2006

The Department of the Navy wants to recapitalize but finds that it does not have as much buying power as it used to. Last year, CNA examined the trends in the Navy's budgets and prices to understand why the Navy could not buy as many weapons platforms as it used to: the study found that the Navy had less to spend on procurement than before and that the Navy's mix of ships and aircraft cost more on average now than before. To reverse the trend and buy more platforms, the Navy needs to devote more money for procurement and/or buy less expensive platforms. This study examined various initiatives or savings opportunities (total of 17) that would allow the Navy to allocate more money for procurement. Taken together, the total savings from these initiatives are about $7 billion to $10 billion (or 5 to 8 percent of the Navy’s annual budget). We assessed the risk associated with these initiatives and deemed most to be minimal to moderate risk in terms of cost uncertainty, effects on readiness, or other effectiveness measures. Nonetheless, tough decisions must be made and cultural and other barriers must be overcome before the Navy may reap the savings.

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A Model to Study: Cannibalization, FMC, and Customer Waiting Time
February 1, 2002
The military services, the Department of Defense, and the U.S. Congress have all expressed concern about the shortages of spare parts for aviation units and about the workarounds, including the cannibalization of parts, that are required to achieve readiness goals. In this paper, we provide a theoretical framework that should help decision-makers understand why cannibalizations occur; what factors influence cannibalization rates; and, given the interaction of those factors, how to predict cannibalization rates. We start with a description of the theoretical model and then provide a numerical example. Next, we examine several policy implications and offer some suggestions for future research. Upon request, we will provide a spreadsheet calculator that will allow users in the Navy and Air Force to derive simulation results using their own parametric values.
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USS Nimitz and Carrier Airwing Nine Surge Demonstration
April 1, 1998
This paper is the first of a two-volume report in which the analysis of the USS Nimitz and Carrier Airwing Nine Surge operations of July 1997 are documented. This paper focuses on three areas: operational issues, aircraft and ship maintenance and supply issues, and personnel issues. The analysis is a combination of descriptive (narrative of what happened), qualitative (documentation of knowledgeable individual's insights), and quantitative (measured data, such as time expended, amount expended, and sorties generated) assessments. Special attention is paid to the generation and support of strike/fighter sorties.
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Aviation Logistics Support: Retail Sparing Issues
June 1, 1993

The main objective of this study is to develop the cost-versus-readiness relationship for alternative aviation supply inventories (called AVCALs). This analysis will help the Navy develop future inventory policy by answering questions like: (1) what are the alternative supply support options and (2) what is th e expected loss in readiness when supply support costs are reduced.

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'Awaiting Parts Time' in a Multi-Indenture, Readiness-Based Sparing Model
November 1, 1990
This research memorandum presents a means of calculating the expected length of 'awaiting-parts time' of weapon replaceable assemblies, which are needed to calculate aircraft readiness in a multi-indenture, readiness-based sparing model. The method presented is appropriate for any other level of indenture. Although full scale application of the model is not feasible at this time, the model aids in comparing and evaluating existing models.
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AVCAL's Effectiveness in Supporting Operations Without Resupply of Aviation Parts
April 1, 1989
This research memorandum examines the capability of a deployed aircraft carrier's Aviation Consolidated Allowance List (AVCAL) to meet the goal of supporting wartime operations for 90 days without resupply.
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A Comparison of Models for Determining Spares Requirements for Aircraft Battle Damage Repair
October 1, 1988
As part of the Aircraft Battle Damage Repair (ABDR) Project, CNA analysts performed research into finding an appropriate model for determining ABDR spares requirements. The analysis focuses on the relative performance of four spares requirements models, given uncertainties associated with predicting battle damage rates.
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A Sparing Model for Sea-Based Aircraft Parts
November 1, 1987
When an aircraft is being repaired or inspected and a certain part is found to have failed, the part is replaced immediately, if a spare part is available. This research memorandum describes a queueing model used to analyze a sparing decision for a part with general probabilistic demand. It also describes an extension of the model to include discriminating treatment of the repair and resupply pipelines. The final section applies the model to an example.
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AIRCRAFT ENGINE MAINTENANCE STUDY
June 1, 1976
This study reviews three problem areas of aircraft engine maintenance in the Navy: the setting of maximum operating times, the performance of overhauls for cause instead of repairs, and the site of engine repair. All of the problem areas affect in some way the number of engine overhauls performed annually. The study assesses the effectiveness of engine overhaul from a safety and reliability standpoint by analyzing Navy data on engine-related aircraft mishaps and engine removals. The analysis revealed that within the current range of operations engines wear in but under current policies of continued repair/replacement and relatively short times between overhauls, engines as a system do not wear out. Consequently, policies which would decrease the number of overhauls performed annually and increase the time between overhauls appear to be reasonable from a reliability and safety standpoint. Using a model of the engine repair and overhaul pipeline, the study finds that three new policies, two of which would increase the time between overhauls, result in lower annual maintenance costs and improved spare engine availability.
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A PHASED - PROCUREMENT MODEL FOR APPLICATION TO F-14 SPARE PARTS PROVISIONING
August 1, 1974
When a new aircraft, such as the F-14, is being bought, decisions on the quantities of spare parts to be bought are made even though information on expected demands, operating programs, and the final configuration of the aircraft is limited. For high-value, low-usage parts, which are those considered, the minimum-cost strategy might be to defer procurement until demands occur. During the period of deferral, the Navy would buy the needed spare parts from a stock carried by the manufacturer or from the production line if no stock is held. This paper describes an algorithm for determining in what cases this would be the best policy.
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