Depot Level Maintenance Research Articles

Effect of noise and ototoxicants on developing standard threshold shifts at a U.S. Air Force depot level maintenance facility

Noise exposure has traditionally been considered the primary risk factor for hearing loss. However, ototoxicants commonly found in occupational settings could affect hearing loss independently, additively, or synergistically when combined with noise exposures. The purpose of this investigation was to determine the combined effect of metal and solvent ototoxicants, continuous noise, and impulse noise on hearing loss. Noise and ototoxicant exposure and pure-tone audiometry results were analyzed for U.S. Air Force personnel (n = 2,372) at a depot-level aircraft maintenance activity at Tinker Air Force Base, Oklahoma. Eight similar exposure groups based on combinations of ototoxicant and noise exposure were created including: (1) Continuous noise (reference group); (2) Continuous noise + Impulse noise; (3) Metal exposures + Continuous noise; (4) Metal exposures + Continuous noise + Impulse noise; (5) Solvent exposure + Continuous noise; (6) Solvent exposures + Continuous noise + Impulse noise; (7) Metal exposure + Solvent exposures + Continuous noise; and (8) Metal exposure + Solvent exposures + Continuous noise + Impulse noise. Hearing loss was assessed at center octave band frequencies of 500–6,000 Hz and using National Institute for Occupational Safety and Health Standard Threshold Shift (STS) criteria. Hearing changes were significantly worse at 2,000 Hz in the Metal exposure + Solvent exposure + Continuous noise group compared to the Continuous noise only reference group (p = 0.023). The Metal exposure + Solvent exposure + Continuous noise group had a significantly greater relative risk (RR) of 2.44; 95% CI [1.24, 4.83] for developing an STS at 2,000 Hz. While not statistically significant, the Solvent exposure + Continuous noise group had a RR of 2.32; 95%CI [1.00, 5.34] for developing an STS at 1,000 Hz. These results indicate that noise exposure may dominate hearing loss at ≥3,000 Hz while combined effects of concomitant exposure to ototoxic substances and noise are only noticeable at ≤2,000 Hz. These results also suggest combined exposures to ototoxicants and noise presents a greater hearing loss risk than just noise.

Approaches to F-35 Depot-Level Maintenance: Insights from Other Systems

Approaches to F-35 Depot-Level Maintenance: Insights from Other Systems

A Study on the Applying Improvement Method of Guide for efficient depot level maintenance

A Study on the Applying Improvement Method of Guide for efficient depot level maintenance

A Study on the Necessity of Verification about depot level maintenance plan through the Weapons System cases analysis

A Study on the Necessity of Verification about depot level maintenance plan through the Weapons System cases analysis

Optimisation of military aircraft engine maintenance subject to engine part shortages using asynchronous metamodel-assisted particle swarm optimisation and Monte-Carlo simulations

ABSTRACTComprising the coordination of various maintenance levels, flight maintenance planning (FMP) constitutes an appealing and hard-to-solve optimisation problem. In this article, a modified version of the typical FMP problem is studied for a typical-size military fleet, focusing on engine maintenance: a disruption of the depot level maintenance (DLM) facilities is considered, causing long-term shortage of serviceable engine parts. In this context, an optimisation strategy is proposed to schedule engine and part exploitation so that engine availability be retained until the recovery of the DLM supply lines, and flight and maintenance requirements be fulfilled to the maximum possible extent. To incorporate the effects of stochastic events, model their interaction with the capacity of the available maintenance resources and assess the outcome of the proposed plans, Monte-Carlo simulations are employed. A computationally efficient variant of the asynchronous particle swarm optimisation method is introduced to find the optimal solutions, combining parallelisation of the evaluation calls with a metamodel-based pre-evaluation strategy to reduce the optimisation turnaround time. Tested on a full-scale application, the proposed method is shown to be capable of producing robust FMP solutions and, also, quantifying the maintenance chain's operating status to aid in long-term planning.

Collaborative Development of a Functional Trivalent Chromium Electroplating Process

Faraday has been working for over 20 years on the development of a functional chromium plating process from a trivalent-based electrolyte to replace hexavalent chromium plating. Hexavalent chromium plating has been used for many decades to provide hard, durable coatings with excellent wear and corrosion resistance properties. However, hexavalent chromium has come under increasing scrutiny due to the toxic nature of the bath, effects on the environment, and workers’ health. Faraday has demonstrated that the chrome coatings prepared using the FARADAYIC(R) Process have equivalent functional properties to the coatings produced with a hexavalent chromium bath. The data demonstrates equivalent or superior: 1) plating rate, 2) Knoop hardness, 3) current efficiency, 4) hydrogen embrittlement behavior, 5) adhesion, 6) corrosion resistance, 7) porosity, 8) thickness, 9) Taber Abrasion, Ball on Flat Reciprocating and Dithering wear resistance, and with no hexavalent chromium formation in the bath. The data that will be presented demonstrate the feasibility of the process and have provided the basis for further technical qualification and prototype design. Of note, due to the promise of this technology, Faraday’s team received a 2013 Presidential Green Chemistry Challenge Award. The long development time frame of 20+ years for development, testing and adoption of a new coating process is not uncommon in the aerospace industry, the primary target of Faraday’s trivalent chromium plating process. This is due, in part, to rigorous testing requirements. In addition, the development of a paradigm shifting innovation can be an arduous and lengthy process. The initial phases of this development process were conducted by Faraday under EPA SBIR funding, with some input from academic and government laboratory sources for plating chemistry development. As we presented the data at technical conferences showing the demonstration of feasibility, we began to garner interest from OEMs such as The Boeing Company and depot-level maintenance communities within the Department of Defense. Such interest is vital to furthering technology development, by better understanding the industrial and military needs with respect to testing requirements, as well as implementation restrictions. We obtained funding through a government/industry consortium, the National Center for Manufacturing Sciences, to pass some general tests that needed to be passed to show the functional performance of the coating. During this program, we determined that there are also specific tests for each application, e.g., aerospace versus automotive, and within each application, tests that are specific to each entity, e.g., from one OEM to another and the various services within the Department of Defense. These specific technical hurdles needed to be passed before additional interest, and funding, could be obtained. Furthermore, realizing that plating industry sales are made mostly through chemical vendors, we identified and partnered with a vendor, Coventya, that has the requisite market channels and expertise to sell our trivalent chromium plating process. Coventya is working with us to stabilize the bath chemistry and determine bath lifetime and reliability. We recently began working on a US Army program for an expanded testing matrix working on a fully REACH-compliant trivalent chromium plating chemistry, developed in conjunction with Coventya, that does not contain boric-acid. Acknowledgements: This study is supported by the US EPA SBIR Program (EP-D-11-044), the US Army (W911NF-11-2-0014) and private sources. The financial support of Faraday Technology, Inc. corporate R&D is also gratefully acknowledged.

New Pretreatments and Non-Chromated Chemfilm for Magnesium Alloys

A new environmentally friendly non-chromated chemfilm with different pretreatments was studied as a replacement to conventional hexavalent chromium-based chemfilm technologies for magnesium alloys. Anti-corrosion and paint adhesion properties of conversion-coated sand-cast AZ92A-T6 magnesium alloy were investigated. Open-circuit potential (Eoc), potentiodynamic polarization, neutral salt spray and gravimetric methods were employed to evaluate the corrosion resistance of this novel conversion coating. Surface morphology and the presence of the coating were investigated by scanning electron microscopy (SEM) technique. Tape adhesion and pull-off adhesion studies were performed to characterize the paint adhesion properties. Rework along with the Touch-Up application and turbine-oil immersion studies was performed in order to simulate the depot-level maintenance. The results of corrosion and paint adhesion studies revealed that the new non-chromated conversion coating technology could be a drop-in replacement to the conventional hexavalent chromium-based conversion coatings.

Performance Measurement of Depot Level Maintenance in Military Aviation Environment

Performance Measurement of Depot Level Maintenance in Military Aviation Environment

Processing and Environmental Effects on Composite Repairs

The scarf-joint technique is one of the latest techniques used for repairing composite aircraft structures. But this technique is mostly used at depot level repairing activities since it requires autoclave and other equipments. This article focuses on scarf joint comprised of vacuum and autoclave precured and co-cured composite patches bonded to autoclave and vacuum precured parent laminates. Autoclave and vacuum cured parent laminates and scarf joints were prepared and exposed to the same temperature and moisture environment for comparison. All specimens were loaded in tension at three temperatures. Interlaminar shear strength (ILSS) tests were also carried out for the parent materials. As noted, the tensile strength and ILSS decrease when the material has been exposed to moisture and tested at elevated temperature. But, no significant difference was reported for either tensile strength or ILSS between autoclave and vacuum cured materials. The room temperature repair efficiencies are reported for single scarf repairs comprised of vacuum co-cured and precured patches. These vacuum cured repair efficiencies were found to be similar to the efficiency of the autoclave precured patch repair. This result supports the feasibility of scarf joint repairs with precured or co-cured patches under vacuum curing conditions in field level facilities. Therefore, repairs with vacuum precured or vacuum co-cured patches requiring less equipment seems to be a serious potential alternative to the composite patch repair requiring autoclave conditions which might be only available at depot level maintenance centers.

A study on curing processes and environmental effects for rapid composite repair

This article focuses on scarf joint comprised of vacuum-precured, vacuum-cocured, autoclave-procured, and autoclave-cocured composite patches bonded to autoclave- and vacuum-precured parent laminates. Autoclave- and vacuum-cured parent laminates and scarf joints were prepared and exposed to the same temperature and moisture environment for comparison. All specimens were loaded in tension at three temperatures. Interlaminar shear strength (ILSS) tests were also carried out for the parent materials. As noted, the tensile strength and ILSS decrease when the material has been exposed to moisture and tested at elevated temperature. But, no significant difference was reported for either tensile strength or ILSS between autoclave- and vacuum-cured materials. The room temperature repair efficiencies are reported for single-scarf repairs comprised of vacuum-cocured and vacuum-precured patches. These vacuum-cured repair efficiencies were found to be similar to the efficiency of the autoclave-precured patch repair. This result supports the feasibility of scarf joint repairs with precured or cocured patches under vacuum curing conditions in field-level facilities. Therefore, repairs with vacuum-precured or vacuum-cocured patches requiring less equipments seem to be a serious potential alternative to the composite patch repair requiring autoclave conditions which might be only available at depot-level maintenance centers.

Passenger rail vehicle depot-level electronic maintenance

Capital-intensive companies and organizations that purchase long-life industrial equipment, such as the transit agencies and railroad companies, often have language in their procurement specifications that define the useful life of the equipment and the necessary tools and equipment to maintain their defined life-cycle. However, if the organization is not structured around life-cycle maintenance then these long-term objectives will surely become just an unrealistic hope.

Depot-Level Maintenance Planning for Marine Corps Ground Equipment

Depot-Level Maintenance Planning for Marine Corps Ground Equipment

AN APPROACH TO INTRA‐CYCLE MAINTENANCE MATERIAL MANAGEMENT

ABSTRACTThe Implementation of the Navy's Destroyer Engineered Operating Cycle (DDEOC) and LO‐MIX Programs involves the extension of the overhaul cycle from the standard 37 months to a minimum 54 months. To provide for the intermediate and depot level maintenance required under the extended operating cycle, Selected Restricted Availabilities (SRA's) and Intermediate Maintenance Activity Availabilities (IMAV's) were initiated. The SRA's are scheduled for six to eight weeks length between deployments, and the IMAV's for periods of approximately four weeks. The relatively short time frame for accomplishment of SRA's and IMAV's makes it essential to have a system of maintenance material management which will provide positive response to the repair parts needs of the accomplishing maintenance activity. The system must, in additions to other important elements, identify maintenance material requirements in sufficient time to be utilized in the budget cycle and to facilitate planning for long lead time buys at the inventory control point level.This paper presents a mechanized system of material management which is designed to identify, forecast, track and control maintenance material, and to provide availability and status reporting. It has the capability of being updated for technical changes (pricing information, part numbers, etc.), and other revisions which will improve management effectiveness. The system provides a reliable means of managing maintenance material, as well as a means for review and analysis of the effectiveness of material procedures.