Air Force Inventory Research Articles

The efficiency of using a tailored inventory management system in the military aviation industry

IntroductionMilitary aviation inventory management systems are a vital tool for air forces to reduce operating costs whilst improving fleet readiness, aircraft serviceability, and availability, and the safety measurements of the country. ObjectiveThis paper aims to establish a local, affordable, high quality, reliable, and adaptive inventory management system which manages and improves inventory in the military aviation industry (Air forces). The aim of the new system is to improve aircraft fleet serviceability, reliability, and readiness in order to enhance the operational status and level of readiness at the least possible costs. MethodsThis study designs, proposes, and implements a highly reliable customized Microsoft Access software as a powerful, simple, user-friendly. Affordable software that supports the on-time availability of the air force inventory of spare parts. The system will have full capability of integrating maintenance management systems (M.M.S.) and will address aircraft inventory challenges. ResultsThe proposed system provides high-quality reports that improve supply chain management and processes that help collate maintenance, supply chain, and logistics information that reduces stock to the minimum. This will result in improved components, increased serviceability, availability, and reliability, decreased costs, and decreased Aircraft on Ground (A.O.G.).

Numerical modelling as a cost-reduction tool for probability of detection of bolt hole eddy current testing

Probability of detection (PoD) studies are broadly used to determine the reliability of specific nondestructive inspection procedures, as well as to provide data for damage tolerance life estimations and calculation of inspection intervals for critical components. They require inspections on a large set of samples, a fact that makes these statistical assessments time- and cost-consuming. Physics-based numerical simulations of nondestructive testing inspections could be used as a cost-effective alternative to empirical investigations. They realistically predict the inspection outputs as functions of the input characteristics related to the test piece, transducer and instrument settings, which are subsequently used to partially substitute and/or complement inspection data in PoD analysis. This work focuses on the numerical modelling aspects of eddy current testing for the bolt hole inspections of wing box structures typical of the Lockheed Martin C-130 Hercules and P-3 Orion aircraft, found in the air force inventory of many countries. Boundary element-based numerical modelling software was employed to predict the eddy current signal responses when varying inspection parameters related to probe characteristics, crack geometry and test piece properties. Two demonstrator exercises were used for eddy current signal prediction when lowering the driver probe frequency and changing the material's electrical conductivity, followed by subsequent discussions and examination of the implications on using simulated data in the PoD analysis. Despite some simplifying assumptions, the modelled eddy current signals were found to provide similar results to the actual inspections. It is concluded that physics-based numerical simulations have the potential to partially substitute or complement inspection data required for PoD studies, reducing the cost, time, effort and resources necessary for a full empirical PoD assessment.

9.3.1 A Vector Approach to Assessing Modularity

AbstractA method to assess product modularity using a vector approach is presented and demonstrated using two precision guided munitions. Modularity has several fundamental benefits agreed upon by industry including reusability, flexibility, reconfigurability and extensibility. Current modularity measures focus on interfaces within or between modules in provide/depend relationships. A new method that assesses the module interfaces as well as captures and addresses each of the recognized modularity benefits is presented in a Vector Modularity Measure (VMM). Components of the VMM include terms for degree of coupling, reusability, and flexibility. Flexibility is assessed in terms of reconfigurability and extensibility. The overall evaluation method is then summarized, followed by an application using two similar precision guided munitions in the U.S. Air Force inventory: the Guided Bomb Unit‐24 (GBU‐24), referred to as the laser guided bomb (LGB); and the Guided Bomb Unit‐31 (GBU‐31), referred to as the Joint Direct Attack Munition (JDAM).

Empirical Evidence Relating Aircraft Age and Operating and Support Cost Growth

Abstract Since the mid-1990's, senior Air Force leaders have pointed to an aging fleet for justification to procure new aircraft. They believe rising Operating and Support (O&S) costs are inhibiting new investments and leading the Air Force into a ‘death spiral’ (Tirpak 2006). Using 11 years of data from the Air Force Total Ownership Cost (AFTOC) database, this study investigates the relationship between aircraft age and ownership Cost Per Flying Hour (CPFH) cost growth from seventy four different airframes in the Air Force's inventory. The analysis reveals that cost growth follows a ‘bathtub’ curve where the burn-in, steady-state, and end-life display cost growth rates of 6.6%, 3.1%, and 6.9% respectively. Furthermore, the variability associated with this increase follows the same functional form as the cost growth. This research suggests that very young and very old aircraft exhibit significantly higher levels of cost growth and variability, but the magnitude of the cost growth and variability for old a...

Test and Evaluation of an Air Force Non-Developmental Item (NDI) Computer System

The Air Force is fielding a computer-based command and control system to support fighter base mission requirements. The acquisition strategy for this system was to purchase it as a Non-Developmental Item (NDI). Since the hardware and software were in the Air Force inventory, it was determined that system development was not necessary. Initial implementation and installation occurred without system-level specifications or performance requirements. This paper presents the results of a Human Factors Engineering evaluation of the system from three perspectives: an Expert's view, a Military Standard view, and a User's view. Two primary lessons resulted from the evaluation: First, the multi-perspective evaluation technique is valuable and highly recommended for use in other HFE evluations. Second, the purchase of NDI or commercial off-the-shelf (COTS) items should be viewed from the systems perspective, i.e., even though subsystems may be NDI, the system may be developmental.

Mechanistic Design Concepts for Heavyweight F‐15 Aircraft on Flexible Pavement

A new F‐15 aircraft is now the heaviest fighter aircraft in the United States Air Force inventory. A mechanistic design procedure is developed for flexible pavements to accommodate the heavyweight F‐15 loading. The ILLI‐PAVE finite element computer program is used as the structural model to compute pavement structural responses. Design algorithms are developed from an ILLI‐PAVE data base and are demonstrated in an example problem. The proposed design procedure is then compared with the present U.S. Department of Defense (DOD) procedure. The DOD procedure does not adequately consider asphaltconcrete fatigue effects. DOD minimum surface thickness requirements may not be sufficient to prevent premature cracking of pavements subjected to long‐term use by the heavyweight F‐15 aircraft. However, the DOD procedure may be overly conservative for subgrade rutting.

EM Transient Protection Requirements for Avionics LRUs

Avionics and electronic equipment installed in aircraft and air breathing missiles are required to operate without upset or damage when subjected to EM environments caused by lightning, NEMP, and Intrasystems transients. To simplify the design effort required to protect electronic equipment and minimize overlapping transient requirements and qualification tests, unified test requirements and procedures are needed. The goal of these unified test procedures would be to insure a known susceptibility level for each newly designed electronic Line Replaceable Unit (LRU). Ten avionics equipments in current Air Force inventory were tested for the purpose of developing unified procedure test methods. Operating LRUs were subjected to transients using common mode cable current (CMCC), groung potentials and chatteriing relay cable injection methods. Based on observed test results and review of current test requirements, test methods and test levels for unified test procedures for power-on transient tests of avionics equipment have been formulated.

Fuel Property Effects on Air Force Gas Turbine Engines-Program Genesis

The Air Force has conducted a series of investigations to quantify the effects of certain fuel properties on the operability and durability of its aircraft gas turbine engines. Initially these efforts were conducted on a small number of engines intended to be representative of the majority of gas turbine engines in the Air Force inventory. The testing was conducted exclusively in rigs representing the combustor and fuel nozzle components of these engines of interest. Test fuels for these programs were blended to achieve specific property variations. Based on results of these evaluations, a second generation of test activity in the fuel effects area was formulated. Engine system selection was broadened to include more considerations. Test fuels were reduced in number and priorities for modification of certain fuel properties were adjusted. This paper presents the primary test results of early fuel effects programs and the background which dictated the structure of the second, more comprehensive program.

A Field Study of the Maintainability and Reliability of an Interceptor Squadron

This paper analyzes in terms of flight operations the maintenance and reliability data collected by RAND during a field study of interceptor squadron effectiveness. This study was made several years ago, but the limited availability of this type of information makes worth-while its availability in an unclassified document, even though the aircraft is no longer in the Air Force inventory. The results are primarily useful in that they indicate the importance of certain parameters on maintenance and reliability. In particular, the validity of the Poisson distribution for predicting both the failures generated by system operation and the time required for repair was examined. The effect of periodic inspection on reliability was also of concern. This paper presents some highlights of the study. More detailed results are discussed in the authors' original RAND paper. <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup>

Military-Civilian Teamwork

IN THE heart of California's Central Valley, ten miles northeast of the capital city of Sacramento, is McClellan Air Force Base, headquarters of the Sacramento Air Materiel Area. This base was constructed twenty years ago as the principal West Coast Air Force Depot for the repair of aircraft and equipment and the storage and distribution of materiel. As the nation's air power has grown, so has this installation. At its dedication in 1939, its employees were numbered in the hundreds. Today 20,000 people, three-fourths of them civilians, are at work on various Air Force missions. Most of them are assigned to the Sacramento Air Materiel Area which is part of the worldwide operation of the Air Materiel Command engaged in procurement, supply, and maintenance activities for the entire Air Force. The managerial responsibilities of the Sacramento Air Materiel Area, measured by normal business standards, are enormous. They include the management and control of an inventory of over $0.5 billion of materiel, the assurance of effective supply and maintenance support to nearly half the aircraft in the Air Force inventory, and the administration of contracts with major Air Force suppliers totaling in excess of $2 billion per year. Top management of the Sacramento Air Materiel Area includes Major General George E. Price, commander, Colonel H. H. Tellman, his deputy, and the senior Air Force commissioned officers who head the major departments and staff offices. These officers assume responsibility for results, provide policy direction, assure responsiveness of logistics to military operational requirements, and bring their extensive military tactical and logistical experience to the accomplishment of the Command mission. Each military department head has, assisting and advising him, a technical associate who is a member of the federal civil service. The technical associates are men with extensive experience in their particular fields. Most of them have risen up through the ranks of the Sacramento Air Materiel Area to their positions of responsibility. Thus they provide continuity in management and technical advice in their respective fields.