5.3. Supportability Design Considerations
Logistics Infrastructure and Footprint Reduction. Programs can best support evolving military strategy by providing forces with the best possible system capabilities while minimizing the logistics footprint. Consequently, programs are responsible for achieving program objectives throughout the life cycle while minimizing cost and logistics footprint (see DoD Directive 5000.01, E1.17 and E1.29). To achieve these goals, the support posture of a system needs to be designed-in up front (i.e., logistics and availability degraders are designed out) since the opportunities for decreasing the logistics footprint decline significantly as the system evolves from design to production to deployment. Minimizing the logistics footprint through deliberate and integrated logistics/engineering design efforts means that a deployed system will require fewer quantities of support resources especially:
- Spares and the supply chain
- Test, support and calibration equipment
- Manpower and personnel requirements (including highly specialized or unique skill/ training requirements)
- System documentation/technical data
Sustainment analyses should include a basic understanding of the concept of operations, system missions, mission profiles, and system capabilities to understand the rationale behind functional and performance priorities. Understanding the rationale paves the way for decisions about necessary trade offs between system performance, availability, and LCC, with impact on the cost effectiveness of system operation, maintenance, and logistics support. There is no single list of sustainment considerations or specific way of grouping them as they are highly inter-related. They range from: compatibility, interoperability; transportability; reliability; maintainability; manpower; human factors; safety; natural environment effects (including occupational health; habitability); diagnostics & prognostics (including real-time maintenance data collection); and corrosion protection & mitigation. The following are key considerations that should be considered for the System Specification.
5.3.1. Architecture Considerations
Figure 5.3.1.F1 lists key system architecture attributes which can provide a solid sustainment foundation. The focus on openness, modularity, scalability, and upgradeability is critical to implementing an incremental acquisition strategy. In addition, the architecture attributes that expand system flexibility and affordability can pay dividends later when obsolescence and end-of-life issues are resolved through a concerted technology refreshment strategy. However trade-offs are required relative to the extent each attribute is used as illustrated in the Commercial Off-the-Shelf (COTS) case.
Figure 5.3.1.F1. Illustrative attributes for System Architecture Supportability Assessments
Maturity and use of Commercial Off-the-Shelf (COTS) Items. Technology risk should receive consideration as the system is developed. Maximum use of mature technology (including non-developmental and/or standards based COTS software or computer hardware) provides the greatest opportunity to adhere to program cost, schedule, and performance requirements by leveraging industry's research & development and is consistent with an incremental acquisition approach. However, this is not a one time activity. Unanticipated changes and the natural evolution of commercial items may drive reconsideration of engineering decisions throughout the life cycle. In addition, the program must consider the logistics implications of supporting commercial items in a military environment. Finally, because COTS items have a relatively short manufacturing life, a proactive diminishing manufacturing sources and material shortages / obsolescence approach should also be considered. Consequently, care must be taken to assess the long term sustainability of COTS options and to avoid or minimize single source options.
Modular Open Systems Approach (MOSA). Open system architectures help mitigate the risks associated with technology obsolescence and promote subsequent technology infusion. MOSA can also help to provide interoperability, maintainability, and compatibility when developing the support strategy and follow-on logistics planning for sustainment. It can also enable continued access to cutting edge technologies and products and prevent being locked into proprietary technology. Applying MOSA should be considered as an integrated business and technical strategy when examining alternatives to meet user needs. PMs should assess the feasibility of using widely supported commercial interface standards in developing systems. Closely related to MOSA is the Open System Architecture (OSA) approach to software development. This concept, which relys upon the sharing of software code can significantly enhance affordability. For a detailed discussion of OSA see the Open Systems Archecture Guide (insert hyperlink here to the Guide and BCA). MOSA should be an integral part of the overall acquisition strategy to enable rapid acquisition with demonstrated technology, incremental and conventional development, interoperability, life-cycle sustainment, and incremental system upgradeability without major redesign during initial procurement and re-procurement.
Standardization. Parts management is a design strategy that seeks to reduce the number of unique, specialized, and defined problem parts used in a system (or across systems) to enhance standardization, commonality, reliability, maintainability, and supportability. In addition to reducing the need and development of new logistics requirements (e.g. documentation, spares, etc.) it reduces the logistics footprint and also mitigates parts obsolescence occurrences due to diminishing manufacturing sources and material shortages.
Materiel and Interoperability/Joint Architecture. The Materiel and Interoperability/Joint Architecture concept can be used to help reduce the logistics footprint. (For further discussion on this topic see Chapter 7.)
5.3.2. Reliability
Reliability is critical because it contributes to a system's war fighting effectiveness as well as its suitability in terms of logistics burden and the cost to fix failures. For each system, there is a level of basic reliability that must be achieved for the system to be militarily useful, given the intended CONOPS. Reliability is also one of the most critical elements in determining the logistics infrastructure and footprint. Consequently, system reliability should be a primary focus during design (along with system technical performance, functions, and capabilities). The primary objective is to achieve the necessary probability of mission success and minimize the risk of failure within defined availability, cost, schedule, weight, power, and volume constraints. While performing such analyses, trade-offs should be conducted and dependencies should be explored with system maintainability and integrated with the supportability analysis that addresses support event frequency (i.e. Reliability), event duration and event cost. Such a focus will play a significant role in minimizing the necessary logistics footprint, while maximizing system survivability and availability.
The requirements determination process offers the first opportunity to positively influence a system from a reliability perspective. Trade-offs among "time to failure," system performance, and system life-cycle cost are necessary to ensure the correct balance and to maximize materiel availability. Options that should be considered and implemented to enhance system reliability and achieve the Materiel Reliability KSA include:
- Over-designing to allow a safety margin;
- Redundancy and/or automatic reconfiguration upon failure allowing graceful degradation;
- Fail safe features (e.g., in the event of a failure, systems revert to a safe mode or state to avoid additional damage and secondary failures). Features include real time reprogrammable software, or rerouting of mission critical functions during a mission;
- Calibration requirements; and
- Reliability Growth Program.
Reliability estimates evolve over time. Generally, the initial estimates are based on parametric analyses and analogies with like or similar systems operating in the same environment and adjusted via engineering analysis. As the design evolves and as hardware is prototyped and developed, the engineering analysis becomes more detailed. In addition to estimates and modeling, testing at the component, subsystem, or system level may be necessary to assess or improve reliability. Approaches such as accelerated life testing, environmental stress screening, and formal reliability development/growth testing, should be considered and incorporated into program planning as necessary. To assure the delivery of a system that will achieve the level of reliability demanded in field use, a methodical approach to reliability assessment and improvement should be a part of every well-engineered system development effort. The Reliability Availability and Maintainability (RAM) Guidance provides a structure, references, and resources to aide in implementing a sound strategy. It is crucial the reliability approach be planned to produce high confidence the system has been developed with some margin beyond the minimum (threshold) reliability. This will allow for the inevitable unknowns that result in a decrease between the reliability observed during development and that observed during operational testing and in-service. In addition to reliability, the Reliability, Availability, Maintainability & Cost (RAM-C) Rationale Report Manual provides guidance in how to develop and document realistic sustainment Key Performance Parameter (KPP)/Key System Attribute (KSA) requirements with their related supporting rationale; measure and test the requirements; and manage the processes to ensure key stakeholders are involved when developing the sustainment requirements.
5.3.3. Maintainability
The design emphasis on maintainability is to reduce the maintenance burden and supply chain by reducing the time, personnel, tools, test equipment, training, facilities and cost to maintain the system. Maintainability engineering includes the activities, methods, and practices used to design minimal system maintenance requirements (designing out unnecessary and inefficient processes) and associated costs for preventive and corrective maintenance as well as servicing or calibration activities. Maintainability should be a designed-in capability and not an add on option because good maintenance procedures cannot overcome poor system and equipment maintainability design. The primary objective is to reduce the time it takes for a properly trained maintainer to detect and isolate the failure (coverage and efficiency) and affect repair. Intrinsic factors contributing to maintainability are:
- Modularity: Packaging of components such that they can be repaired via remove and replace action vs. on-board repair. Care should be taken not to "over modularize" and trade-offs to evaluate replacement, transportation, and repair costs should be accomplished to determine the most cost effective approach.
- Interoperability: The compatibility of components with standard interface protocols to facilitate rapid repair and enhancement/upgrade through black box technology using common interfaces. Physical interfaces should be designed so that mating between components can only happen correctly.
- Physical accessibility: The designed-in structural assurance that components requiring more frequent monitoring, checkout, and maintenance can be easily accessed. This is especially important in Low Observable platforms. Maintenance points should be directly visible and accessible to maintainers, including access for corrosion inspection and mitigation.
- Designs that require minimum preventative maintenance including corrosion prevention and mitigation. Emphasis should be on balancing the maintenance requirement over the life cycle with minimal user workload.
- Embedded training and testing, with a preference for approved DoD Automatic Test Systems (ATS) Families when it is determined to be the optimal solution from a LCC and Materiel Availability perspective.
- Human Systems Integration (HSI) to optimize total system performance and minimize life-cycle costs. (For further discussion, see Chapter 6 and section 4.3.18.10.) This includes all HSI domains (Manpower, Personnel, Training, Human Factors Engineering, Environment, Safety, Occupational Health, Survivability, and Habitability) to design systems and incorporate technologies that require minimal manpower, provide effective training, can be operated and maintained by users, are suitable (habitable and safe with minimal environmental and occupational health hazards), and survivable (for both the crew and the equipment).
Condition Based Maintenance Plus. When it can support the materiel availability, prognostics & diagnostics capabilities/technologies should be embedded within the system when feasible (or off equipment if more cost-effective) to support condition based maintenance and reduce scheduled and unscheduled maintenance. Health management techniques can be very effective in providing maintainers with knowledge, skill sets, and tools for timely maintenance and help reduce the logistics footprint. Condition based maintenance plus (CBM+) (the application of technologies, processes, and procedures to determine maintenance requirements based, in large part, on real time assessment of system condition obtained from embedded sensors), coupled with reliability centered maintenance can reduce maintenance requirements and reduce the system down time. (CBM+ references include the DoDI 4151.22, the CBM+ Guidebook, and the CBM+ DAU Continuous Learning Module (CLL029).) The goal is to perform as much maintenance as possible based on tests and measurements or at pre-determined trigger events. A trigger event can be physical evidence of an impending failure provided by diagnostic or prognostics technology or inspection. An event can also be operating hours completed, elapsed calendar days, or other periodically occurring situation (i.e., classical scheduled maintenance). Key considerations in implementing this concept include:
- Use of diagnostics monitoring/recording devices and software (e.g., built-in test (BIT) and built-in-self-test (BIST) mechanisms) providing the capability for fault detection and isolation, (including false alarm mitigation) to signal the need for maintenance. It should include user friendly features to convey system status and the effect on mission capabilities to the operator and maintainer.
- Use of prognostics monitoring/recording devices and software monitoring various components and indicate out of range conditions, imminent failure probability, and similar proactive maintenance optimization actions to increase the probability of mission success and anticipate the need for maintenance. (As in the case for diagnostics prognostics includes BIT and BIST mechanisms with user friendly features and false alarm mitigation.)
- Maintenance strategies that balance scheduled (preventive) maintenance and minimize unscheduled corrective maintenance with risks.
Key characteristics in implementing the CBM+ concept include:
- Hardware—system health monitoring and management using embedded sensors; integrated data
- Software—decision support and analysis capabilities both on and off equipment; appropriate use of diagnostics and prognostics; automated maintenance information generation and retrieval
- Design—open system architecture; integration of maintenance and logistics information systems; interface with operational systems; designing systems that require minimum maintenance; enabling maintenance decisions based on equipment condition
- Processes—RCM analysis; a balance of corrective, preventive, and predictive maintenance processes; trend-based reliability and process improvements; integrated information systems providing logistics system response; CPI; Serialized Item Management (SIM)
- Communications—databases; off-board interactive communication links
- Tools—integrated electronic technical manuals (i.e., digitized data) (IETMs); automatic identification technology (AIT); item-unique identification (IUID); portable maintenance aids (PMAs); embedded, data-based, interactive training
- Functionality—low ambiguity fault detection, isolation, and prediction; optimized maintenance requirements and reduced logistics support footprints; configuration management and asset visibility.
In accordance with DoDI 4151.22, it is envisioned that elements of CBM+ should be revisited as the life cycle progresses, conditions change, and technologies advance. Consequently CBM+ should be considered and revisited in each life-cycle phase. See CBM+ Guidebook, Section 4 which provides basic steps for planning and implementing CBM+ throughout the life cycle.
5.3.4. Other Logistics Technologies
Program managers can minimize life-cycle cost while achieving readiness and sustainability objectives through a variety of methods in the design of the system and its maintenance / sustainment program. Below are technologies that should be considered to improve maintenance agility and responsiveness, increase materiel availability, and reduce the logistics footprint:
- Serialized Item Management (SIM). SIM (DoDI 4151.19) can be used to aid asset visibility and the collection and analysis of failure and maintenance data. (Also see section 4.3.18.14) The SIM program should be structured to provide accurate and timely item related data that is easy to create and use. While SIM is a DoD wide initiative, the primary function for the program is in ensuring the marking of the population of select items (parts, components, and end items) with a universal item unique identifier (IUID) (DoDI 8320.04). IUID should be used on tangible property, including new equipment, major modifications, and re-procurement of equipment and spares. As a minimum populations from the following categories should be considered for marking:
- Repairable items down to and including sub-component repairable unit level;
- Life limited, time controlled, or items with records (e.g., logbooks, equipment service records, Safety Critical Items); and
- Items that require technical directive tracking at the part number level.
Serialized item management techniques including the use of automatic identification technologies (AIT) such as item unique identification (IUID) technology, and radio frequency identification (RFID) using data syntax and semantics should conform to International Organization for Standardization (ISO) 15418 and ISO 15434.
- Automatic Identification Technology. AIT is an integral element of serialized item management programs. IUID markings and accompanying AIT capabilities facilitate paperless identification, automatic data entry, and digital retrieval of supply and maintenance related information. The program has a wide range of technologies from which to choose, ranging from simple bar codes to radio frequency identification technology. In choosing the specific technology, the PM should consider that the technology will change over the life cycle both for the program and the supply chain management information systems using the information. Consequently, it is important the PM take into account the need to plan for and implement an iterative technology refreshment strategy. In addition, since AIT is used by supply and maintenance management information systems it is important that items selected for serialized item management be marked in conformance with MIL STD 129.
- Need for special handling or supportability factors. This includes the need for special facilities or packaging, handling, storage, and transportation (PHS&T) considerations. This is usually driven by physical needs (e.g., size, weight, special materials) but can also include eliminating excessive set up and teardown times or the in ability to transport systems without disassembly and reassembly.
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