On-board Vibrations and Health Monitoring Systems: an Approach to Achieve Condition-based Maintenance (cbm)

The objectives of our program are 1) to evaluate the cost and effectiveness of the AH-64 (Apache) and UH-60 (Blackhawk) helicopters’ on-board Vibration Monitoring (VM) System, to provide an annual cost savings analysis of the Vibration Management Enhancement Program (VMEP), and to initially correlate vibration signals with the ULLS-A (logistics) database to create a Costs Benefits Analysis (CBA) model, 2) to extend our activities in data collection and analysis to achieve the condition-based maintenance (CBM) principles, and 3) to develop diagnosis and prognosis models based on scientific knowledge and laboratory experimentations. In order to provide a timely and sufficient cost and economic analysis to support the effective allocation and management of resources for Army programs, a CBA model has been developed. As of today, our activities have been highlighted by savings in parts cost, operational support, an increase in mission capability rates, a decrease in maintenance, and an increase in total flight time. Other highlights of non-tangible benefits include an increase in confidence for early diagnosis, an increase in attention and performance, an increase in personnel morale, and an increase in safety and sense of safety. Our second objective has begun to extend our On-Board Vibration Monitoring System (VMEP, MSPU, HUMS) activities to meet the objectives and goals of the Condition-Based Maintenance (CBM) concept. At the conclusion of this program we are going to deliver a methodology and the needed technologies for the CBM concept (using logistics (ULLS-A), maintenance (MDR) and vibrations (VMU) databases) to complete a qualified prognosis model(s) and an analytical tool to relate usage and condition indicators to the aforementioned data in order to predict the remaining life as a function of CI’s and usage profile; and a simulation model to demonstrate flight regimes and flight profile. HISTORY AND BACKGROUND 1. The On-Board Vibration Monitoring (VM) System: The specific objectives of this task were to 1) reduce rotor track and balance maintenance test flights, 2) reduce aircraft operation costs, 3) increase aircraft availability, and 4) increase aircraft safety. The University of South Carolina and SCARNG have established a model to measure the cost effectiveness of the VMEP program. VMEP has been mitigated to other Apache Readiness Improvement Program (ARIP) problems, such as APU clutch failures (believed to cause fires), shaft-driven compressor (SDC) component failures, nose gearbox seal failures, pitch-change bearing wear, tail boom cracking, vertical stabilizer ribs cracking, engine nacelle bulkhead cracks, generator failure due to bearing faults, and main rotor blade debonding. The method and approach of this program are to 1) measure and record in-flight vibrations, 2) process vibration data, apply signal analysis methods, and identify “hot-spots,” 3) fine-tune the track and balance of the aircraft to reduce vibrations, and 4) identify and address incipient failures through repair and/or replacements. 2. Costs-Benefits Models: Costs and benefits are considered at 4 levels: (a) On-Aircraft, (b) At-Aircraft, (c) at Unit-Level, and (d) in the Sustainment Base/Above Unit Level. The costs and benefits for on-aircraft and at-aircraft levels were covered by a HUMS costs-benefits model. The costs and benefits at unit-level and at sustainment base levels were covered by an Activity-Based Costing (ABC) model. The HUMS and ABC model interpenetrate at unit level. 2.i. On-Aircraft Costs and Benefits The investment costs occur primarily at the platform level and consists of the on-board VM equipment. Benefits are delivered to the mission and to the direct support personnel, and may percolate up through successively higher levels of Army personnel. Quantifiable benefits from on-aircraft investments may include 1) reduced flight hour costs and returned maintenance man-hours, 2) better RAM status: mean time between failures (MTBF), mean time between maintenance actions (MTBMA), mean time to repair/replacement (MTTR), and operational stability, 3) improved mission completion rates (lower mission abort rates), and 4) improved safety of flight statistics. 2.ii. At-Aircraft Costs and Benefits Investment costs relate to tools designed to improve performance of “hands on” aircraft maintainers. Benefits are delivered initially to hands-on maintainers, and flow up to the Army Aviation Logistics network. It is expected that investments will be done in products that complement what is being done at the on-aircraft level. The at-aircraft investment products magnify and complement the on-aircraft investments. A table similar to Table 1 will be compiled to correlation of investment products and perceived benefits for the DAL-P project in the on-aircraft, ataircraft CBA framework. These benefits begin at platform level and ripple up to the higher levels of Army Aviation organization. Cost benefits will also be realized in parts reliability with a resulting extension in parts life (Time before replacement – TBR) 2.iii. Unit-Level Costs and Benefits Unit-level costs and benefits are estimated using a combination of HUMS and ABC models. The HUMS model will provide the initial data. The ABC model will provide further estimates of man-hour reductions complementing those estimated by the HUMS model. Investment costs are related to the tools designed to improve the performance of unit-level maintenance managers. Benefits of the VM system, felt initially by the maintenance managers, will flow up and down through the Army Aviation Logistics network. Investments at the Unit-Level will enable process changes in the way maintenance managers and maintainers do their jobs. Process improvements at the unit level (and below) are fundamental benefits delivered by the VM system. Reduced direct operating costs (DOC), returned man-hours, and higher availability are the results of improved resource utilization. 2.iv. Above Unit Level and Sustainment Base Costs and Benefits The investment costs at above unit level and sustainment base framework relate to the VM “building blocks” designed to improve upper elements of Army Aviation Logistics. Benefits are rendered to elements of the sustainment base and to the Operational Army. Benefits will flow down through the Army Aviation Logistics network. Operational commanders will directly benefit from reduced cost, improved availability, and enhanced safety of flight enabled by the VM investments. 2.v. Review of Cost-Benefit Analysis Method Currently, cost-benefit analysis (CBA) is largely used by government agencies. This is mainly due to the strong legislative actions taken by the Reagan and Clinton Administrations that issued Executive Orders endorsing the use of CBA. Executive Order 12886 on Regulatory Planning and Review, signed by President Clinton .on September 30, 1993 requires agencies to perform cost-benefit analysis of proposed and final regulations. It revoked and replaced two executive orders issued under Reagan Administration: Executive Order 12911 requiring Regulatory Impact Assessment and Executive Order 12498 establishing the regulatory planning process. Moreover, the use of CBA by government agencies was enforced by Congress who enacted numerous statutes requiring agencies to perform CBA analyses. When used by governmental agencies, CBA attempts to measure, over a relevant time period, the change in societal well being resulting from the implementation of a governmental project or the imposition of governmental regulations. It can provide information to decision makers on the merits of the current project or regulation as well as offer a framework for comparing a variety of project or regulatory alternatives. Agencies' project or regulation evaluations are subject to the review of the Office of Management and Budget (OMB). In 1992 OMB issued the Circular No. A-94, which recommends the use of CBA in formal economic analyses of government programs or projects and provides general guidance for conducting CBA Its goal, is to "promote efficient resource allocation through well-informed decision-making by the Federal government." CBA aims to present categories of costs and benefits in terms of dollars (so that the cost-benefit comparison can be performed with a common unit of measurement); therefore, agencies have to define and monetize all categories of costs and benefits determined by the project implementation. Sometimes practical problems appear such as obtaining data, evaluating benefits and costs, etc. Monetization of some benefits categories may be controversial because indirect methods are often employed to estimate a value for goods that are not generally traded in the marketplace (e.g. estimate the monetary value of a reduction in risk of premature mortality). In this sense OMB stipulated, "Analyses should include comprehensive estimates of the expected benefits and costs to society based on established definitions and practices for program and policy evaluation. Social net benefits, and not the benefits and costs to the Federal Government, should be the basis for evaluating government programs or policies that have effects on private citizens or other levels of government. Both intangible and tangible benefits and costs should be recognized. Costs should reflect the opportunity cost of any resources used, measured by the return to those resources in their most productive application elsewhere"(OMB -A-94). Despite its recognized merit in providing important information and transparency in the governmental decisionmaking process, CBA was often criticized, especially by American academics who claim that CBA is an analytical technique that deals only with economic efficiency without considering who receives the benefits and who bears the costs. They also claim that CBA sometimes produces morally unjustified outcomes or it is not correctly used. Yet, it is important to highlight that CBA is a decision procedure or a method for achieving desirable results, and "some decision procedures are more accurate or less costly than others" .As long as it is used in the right way, meaning that under certain conditions agencies may need to modify the traditional approach of CBA, this decision procedure is justified if it is less costly than other procedures. e.g. risk-risk analysis, feasibility based assessment. Some remarks have to be made. First, budgetary and time constraints may impede EPA, as well as other governmental agencies, from collecting all the necessary data. Second, when all data are available and easy to collect, agencies should try to monetize all costs and benefits and include them in their final CBA. This helps agencies to clearly present the effects of governmental projects and alert affected groups. Third, CBA is an important way for governmental agencies to defend their projects against critics coming from other agencies, as well as against legal and political challenges from affected groups. Finally, given its relative cheapness and transparency, CBA is considered the best procedure for agencies to use in evaluating their projects. The use of CBA is not limited to governmental agencies. The U.S. Army also employs this technique in estimating whether its projects achieve an improvement in the allocation of resources. CBA can provide valuable perspectives on the best ways to manage projects concerning the army infrastructure, labor force, capital stock etc. This approach is consistent with the Department of Defense and Army guidance and with the Army Regulation 11-18 establishing responsibilities and policy for the Army's Cost and Economic Analysis Program. For the design and manufacturing of the helicopter AH-64D Apache Longbow, Boeing Helicopter of Mesa, Arizona put up a multidisciplinary team focused on meeting the Army's cost and performance requirements. This Integrated Product Development (IPD) team incorporated a manufacturing engineer, a design engineer, a tool engineer, a stress engineer, and later on a material process engineer, purchasing personnel, and an industrial engineer who was called in to perform a CBA. During the project development, the team used the costing software Design for Manufacture and Assembly (DFMA) that provided "a means of before-and-after comparison not only against the previous models [six Apache Prototypes] but for individual redesign ideas that are part of the iterative process" (Parker, 1997). Thus through continuous CBA the best alternative was chosen and the new Apache Longbow innovative production strategies not only proved better performance and quality, but also brought savings of $1.3 billion over the life of the program. 3. Condition-Based Maintenance (CBM) and the On-Board Vibration Monitoring (VM) System: At present, a number of important projects are directed at reducing the Army aviation costs through improved logistics technology, better data management, and prompt/timely actions. As we embark on Aviation Maintenance Transformation, producing higher operational readiness using fewer, more capable resources (reducing the logistics footprint), connecting the logisticians to an Integrated Enterprise-wide logistics system, provide commanders with relevant maintenance-based readiness information at every level, achieve operating capability by 2011 IAW CSA intent, and shift from preventative and reactive processes to Condition-Based proactive analytical maintenance processes; i.e. Condition Based Maintenance (CBM). Behind homeland security, the next priority for the Commander of the Aviation and Missile Life Cycle Management Command (AMLCMC) is Condition Based Maintenance (CBM). Per the Office of the Secretary of Defense (OSD), CBM is defined as “set of maintenance processes and capabilities derived, in large part, from the real-time assessment of weapon system condition obtained from embedded sensors and/or external tests and measures using portable equipment.” Future maintenance action and instructions will be based on aircraft condition and usage data. The AMLCMC is sponsoring a “CBM Proof of Principle” using data from AH-64, UH-60, and CH-47 platforms. The CBM prototype conclusions and recommendations will be delivered by July 2005 with a strategic plan to meet FY11 objectives. PM Apache along with the UH60 and CH47 PMOs are part of an exciting initiative to transform Army Aviation maintenance. The initiative, Conditioned Based Maintenance (CBM) will use on-board diagnostics and remote prognostics to convert data into maintenance action. Our soldiers might see little change inside their electronic logbooks but the maintenance leaders and logisticians could see dramatic change over the next several years CBM requires at least four kinds of data that stem from Apache systems; namely 1) vibration for analysis of dynamic components from VMEP (Vibration Maintenance Enhancement Program), 2) state data for regime recognition, fatigue, and flight visualization from the MDR (Maintenance Data Recorder), 3) parts tracking and usage history from AMATS/CMB (Aviation Maintenance Automated Tracking System/Contact Memory Buttons), and maintenance activity – from ELAS (Enhanced Logbook Automation System). The CBM objectives as cited in several communications [ 21-26] are to 1) reduce unscheduled maintenance & maintenance workload, 2) decrease maintenance and logistics footprints, 3) perform maintenance only upon evidence of need, 4) improve diagnosis and prognosis capabilities, 5) integrate advanced engineering, maintenance, and information technologies (condition indicators, usage and health indicators, data warehousing and mining), 6) use real-time assessments of material condition obtained from embedded sensors and/or external tests and measurements using portable equipment, and 7) increase Operational Availability.