This guide addresses RAM as essential elements of mission capability. It focuses on what can be done to achieve satisfactory levels of RAM and how to assess RAM. This Background Brief introduced RAM, what it is, why it is important, current RAM problems in the DoD, and activities appropriate to achieving satisfactory levels.
RAM refers to three related characteristics of a system and its operational support: reliability, availability, and maintainability.
Reliability is the probability of an item to perform a required function under stated conditions for a specified period of time. Reliability is further divided into mission reliability and logistics reliability.
Availability is a measure of the degree to which an item is in an operable state and can be committed at the start of a mission when the mission is called for at an unknown/random point in time. Availability as measured by the user is a function of how often failures occur and corrective maintenance is required, how often preventative maintenance is performed, how quickly indicated failures can be isolated and repaired, how quickly preventive maintenance tasks can be performed, and how long logistics support delays contribute to down time.
Maintainability is the ability of an item to be retained in, or restored to, a specified condition when maintenance is performed by troops having specified skill levels, using prescribed procedures and resources, at each prescribed level of maintenance and repair.
Many factors are important to RAM: system design; manufacturing quality; the mission space which the system is transported, handled, stored, and operated; the design and development of the support system; the level of training and skills of troops operating and maintaining the system; the availability of materiel required to repair the system; and diagnosis tools. available.
All these factors must be understood to achieve a system with a desired level of RAM. During pre-systems acquisition, the most important activity is to understand the users’ needs and constraints.
During system development, the most important RAM activity is to identify potential failure mechanisms and to make design changes to remove them. During production, the most important RAM activity is to ensure quality in manufacturing so that the inherent RAM qualities of the design are not degraded.
In operations/support phase, the most important RAM activity is to monitor performance in order to facilitate retention of RAM capability, to enable improvements in design if there is to be a new design increment, or of the support system to included support concept, spare parts storage, etc.
Although significant improvements have been made in increasing the reliability of basic components, these have not always been accompanied by corresponding gains in the reliability of equipment or systems. In some cases, equipment and system complexity and functionality have progressed so rapidly that they negate, in part, the increased reliability expected from use of the higher reliability basic component.
In other cases, the basic components have been misapplied or overstressed so that their potentially high reliability is not realised. In still other cases, past Site Visit Executives have been reluctant or unable, due to program budget shortfalls or highly aggressive schedules, to devote the time and attention necessary to ensure that the potentially high reliability is achieved.
However, in many areas of the commercial sector, increased system complexity has not negated system reliability. In fact, often products with increased system complexity are provided with increased system reliability. This is an area the defense sector must also strive to improve.
Achieving specified levels of RAM for a system is important for many reasons, specifically the affect RAM has on readiness, mission success, and logistics footprint.
“Why does System RAM disappear over time?”
1. Change in operating concept
If system is used in a manner different from that originally allowed for in the design, new failure modes can occur, and the overall frequency of failures can increase.
2. What effect does Change in Scenario Have on Mission?
In such cases, corrective actions can be expensive or impractical. If the system must operate in the new scenario, decreased RAM levels may have to be accepted.
3. What are the consequences of Inadequate training?
Inadequate operating or maintenance training usually increases the number of failures induced by improper operation or maintenance. The corrective action is to improve the training.
4. Why do systems fall apart later in Service Life
Reliability Centered Maintenance Program overhaul such parts will prevent wearout from becoming a problem. Ideally the preventive maintenance program is based on the reliability characteristics of the parts i.e., a reliability-centered maintenance program based on the field info
5. Why do design/test assessments fall short?
All engineering models, assessment tools, and test methods are imperfect. It is also impossible to perfectly model or simulate the actual operational environment during design and test. The time and funds available for testing are limited. For all of these reasons, failure mechanisms may go undetected until after the system is fielded.
6. Why do teams exhibit Lack of understanding?
Most modern weapons systems are digital in design. The mission success, available adequate he number of failures per unit time for parts having wearout characteristics will increase. A preventive maintenance program to replace or ability, and supportability. Previously, classical RAM levels were component failure intensive. Currently, software plays a more important role. Personnel labour developing, and producing these new systems need to understand some systems require a different approach to failure detection, isolation and ultimate repair or corrective action.
7. What are the effects of Change in supplier?
If a supplier chooses to stop manufacturing a part or material, goes out of business, or no longer maintains the necessary levels of quality, an alternate source of supply is needed. If RAM is not a major consideration in selecting the new supplier, system reliability may degrade. If there are a limited number of new suppliers to select from, lower RAM levels may have to be accepted.
8. Why are there deficits in configuration control?
Over a system’s life, there is the temptation to reduce costs by substituting lower-priced parts and materials for those originally specified by the designer. Although the purchase price may be lower, service lifecosts will increase, and the mission will suffer if the “suitable subs” do not have the necessary RAM characteristics. Strong configuration management and a change control process that addresses all factors, including RAM performance, are essential throughout the life of the system.
9. What are Prevalent Manufacturing problems?
Although the manufacturing processes may have been qualified and statistical processes implemented at the start of production, changes can occur during the production line that degrade RAM. This possibility increases as the length of the production run increases; therefore, constant quality control is essential.
10.What are the consequences of Inadequate funding?
“Create Assess Record Define What System Supports RAM Requirements”
Provides progressive assurance that RAM requirements are being developed, implemented, verified, enforced and that the requirements can be achieved. The case evolves between the customer and supplier as the project evolves. Initially the customer is acquisition organisation; eventually, it is subsequently the user. Reliability analyses are not an after-the-fact documentation of what resulted during the design process, but an active integral part of the design process. Immediate action should be taken if unacceptable analysis results are found.
1. Document the user needs and inform the subsequent activities. Documentation of the model provides the baseline for subsequent assessments.
2. Initial RAM projections provide the basis for technology development, fault mitigation, and risk reduction activities in pre-systems acquisition.
3. The RAM Rationale describes the level of reliability user needs in order to achieve system readiness, and mission performance goals. In DoD acquisition framework, the RAM Rationale is summarised and later updated in the Capability Development Document and the Capability Production Document .
4. The RAM Program Plan describes the structured series of RAM related activities that will achieve the needed RAM levels. accumulated evidence, at any point in the program, of demonstrated progress toward achieving the users’ RAM needs. Examine the design and its detail.
5. Examine subsystems, assemblies, subassemblies, and components: identify “knowns” and “unknowns” about each indenture level within the system to mitigate risk to success. Find, assess, and mitigate failure modes and failure mechanisms.
6. Avoid delaying corrective action in development.. Account for manufacturing. The design can contribute to minimising quality control problems that will cause mission failures in the field.
7. Evaluate the maintainability and supportability of the system such as the accessibility of components that might need to be replaced, the completeness of the built-in test equipment, the presence of on-board instrumentation, or consider issues of sparing and support
8. Develop ground maintenance support system to support maintenance decisions in the User's environment using recorders to support tasks such as maintenance planning, scheduling, configuration control, operator debrief, and usage processcollection such as operating hours or cycles. Some modern designs must be supported in the Automated Maintenance Scenario and must be designed for this support concept.
9. Develop a representative prototype of the system, and, where possible, identify composition of subsystems, assemblies, subassemblies, and components.
10. Verify that RAM is achieved in representative conditions, using developmental testing or similar activities.
“Design/Production Phase Shift to Process Control, Quality & Stress Screen”
1. Stress Screening: Defined as the removal of latent part and manufacturing process defects through application of scenario stimuli prior to fielding the equipment. Stress screen will be used to ensure that reliable, available, and maintainable systems are produced and deployed that will be devoid of latent part and manufacturing process defects.
2. Production Reliability Assurance Testing : Performed to ensure that the reliability of the components is not degraded as the result of changes in tooling, processes, workflow, design, parts quality, or any other variables affecting production.
3. Continuation of Growth/Test, assess & Fix-Test: The process of growing reliability & tech performance, and testing the system to ensure that corrective actions are effective was started-- focus becomes ensuring that the corrective actions are producible and equate to improved RAM in the produced system.
4. Reliability Growth Testing Methodology monitors improvements in reliability while deficiencies are being identified and fixed. This methodology also can assess the impact of design changes and corrective actions on the reliability growth rate of the system, specifically during O&S production design or that the system has not been degraded by component updates. Overall system maturation is important to achieve OT&E goals.
5. Continued Reliability Quality Testing and Acceptance Testing: The RAM activities shift from qualifying the proposed design to ensuring that the manufacturing process
6. The biggest change in the process where process status is captured. Instead of developmental testing being the primary source of data, information can be captured from OT&E, other field sources.
7. System Verification Review: The purpose of Functional Configuration Assessment is to evaluate the system under review to determine if it can proceed into Low-Rate Initial Production and Full-Rate Production requirements, including RAM, documented in the Functional, Allocated, and Product Baselines.
8. Production Readiness Review planning to ensure designed-in RAM levels are not degraded. At this review, the Integrated Product Team should review the readiness of the manufacturing processes, the Quality Management System, and the production planning i.e., facilities, tooling and test equipment capacity, personnel development and certification, process documentation, inventory management, supplier track
9. Operational Test Readiness Review conduct another review prior to Initial Operational Test and Evaluation focuses on ensuring that the “production configuration” system can proceed into IOT&E with a high Production Decision may hinge on this successful determination. assesses the ability of operational tests to confirm RAM requirements.
10. Physical Configuration Audit: Rate Production Decision examines the actual configuration of an item being produced to verify that the related design documentation matches the item as specified in the contract. also confirms that the manufacturing processes, quality control system, measurement and test equipment, and training are adequately planned, tracked, and controlled in order to ensure that RAM is not degraded in the production process. Additional assessments should be performed throughout the system life cycle as necessitated by changes in item design, manufacturing process and source of supply dictate.
“Monitor Field Performance in Service Review Assure RAM During Operations & Sustainment Phase?
1. Backbone of assurance technologies reliability, availability, maintainability as it provides info needed to monitor system performance and identify corrective actions to ensure RAM is not degraded after system is deployed
2. Reliability growth testing monitors improvements in reliability while deficiencies are being identified and fixed. This methodology also can assess the impact of design changes and corrective actions on the reliability growth rate of the system, specifically during O&S design changes to the deployed system.
3. Service Life factor Review: Supports overhaul decisions, changes to the maintenance concept, and risk mitigation activities through stats of component, assembly, or system info
4. Repair Strategy: Continually reviews maintenance and support concepts to ensure that repair strategy is not introducing defects into the deployed system that degrade its inherent RAM. This includes refinement of the on and off equipment maintenance processes including the automated maintenance environment support strategy.
5. Maturation: Defines the continuous process of eliminating false alarms and improving fault detection and isolation as the system matures.
6. Reliability centered maintenance logically determines if preventive maintenance makes sense for a given item and, if so, determining the appropriate time and manner in which to conduct the preventive maintenance. As field performance is monitored during O&S
7. Condition-Based Maintenance: Defines optimal maintenance point that maximises the expected results in terms of increased product output, decreased maintenance costs, etc. with the short-term and long-term of implementing the maintenance
8. It is important during O&S to verify that condition-based maintenance program is acceptable based on the monitored field performance
9. Discontinued Parts Sources Attempts to avoid potentially expensive and time-consuming problem of searching for suitable replacement parts
10. Parts that are no longer manufactured or are no longer viable to produce according to the current specification
“Translate RAM into Budget/Readiness Goals for Specs Ensure System Perform”
1. Allocate the system-level requirements down to a level i.e., subsystem, component, or assembly level meaningful to the design and manufacturing engineers.
2. Inherent factors are a function of the time and money available for design and test, the robustness of design analyses, the available technology, and other competing requirements
3. Other Performance Factors: Trade-offs between competing requirements are made to reach “optimal compromises.” For example, it is extremely difficult to optimise both of two inversely related engine requirements for an aircraft, such as high reliability and high thrust-to-weight ratio
4. Trade-off is made that produces an engine design that is reliable enough to ensure safety and an acceptable aircraft availability, but which still has an adequate thrust-to-weight ratio.
5. Support Infrastructure Factors: The operating and support concepts will affect RAM performance. Specialisation of skills and other personnel policies will affect the operating and support concepts
6. The number of required spares as well as pipeline times within the support concept can be directly affected by the maintenance concept i.e., levels of repair, a single location/base performing maintenance for several locations, etc. and inspection
7. Spares buys are determined not only on the basis of the maintenance concept and available funding, economic order quantities, and other factors.
8. Operating Concept Factors: The RAM performance of any system can and will be affected by the operations concept that will govern the system when it is deployed.
9. Must accurately account for the types of mission that the system will be subjected to, deployment requirements, the need for operations at austere bases, etc.
10. Operating Scenario Factors: RAM performance is obviously a function of the type and scenario operated in. Different Operations Locations will impose different stresses on a system than others