Form, Fit, Function, and Interface - An Element of an Open System Strategy

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T h e J o u r n a l o f t h e R e l i a b i l i t y A n a l y s i s C e n t e r F i r s t Q u a r t e r - 2 0 0 5 7 (Continued on page 10) Introduction Parts obsolescence and diminishing sources of manufacturing are two problems that the commercial and defense sectors alike face on a daily and increasing basis. The problem has reached seri- ous proportions over the past decade or so, as the pace of tech- nological improvements and innovation has steadily accelerated. An approach to solving the problem that enjoys broad support within the defense management community is that of open sys- tems. The term is bound to be heard at nearly every conference and symposium even remotely related to logistics and support. What is the open systems approach? Federal Standard 1037C defines open system as follows: "A system with characteristics that comply with specified, publicly maintained, readily available standards and that therefore can be connected to other systems that comply with these same standards." The Software Engineering Institute defines an open system in a similar fashion: "An open system is a collection of interacting software, hardware, and human components: · Designed to satisfy stated needs · With interface specifications of its components that are: · Fully defined · Available to the public · Maintained according to group consensus · In which the implementations of the components con- form to the interface specifications" The Department of Defense (DoD) Open Systems Joint Task Force defines the Open System Approach (OSA) as: "A means to assess and implement when feasible widely sup- ported commercial interface standards in developing systems using modular design concepts. It is a significant part of the toolset that will help meet DoD's goals of modernizing weapon systems, developing and deploying new systems required for 21st century warfare, and supporting these sys- tems over their total life cycle. DoD 5000 series documents call for an OSA as an integral part of the overall acquisition strategy." The Task Force goes on to state that an OSA is also an integrat- ed technical and business strategy that defines key system or equipment interfaces by widely used consensus-based standards. According to the Task Force, the open systems strategy is an enabler to achieve the objectives listed in Table 1. Table 1. Objectives of an Open Systems Strategy Form, Fit, Function, and Interface (F3I) Although the concept of open systems has become a top priority issue within DoD over the last 10-15 years, the military services were considering the use of form, fit, function, interface (F3I)1 standards in the 1970s and even earlier. F3I supports but is not exactly equivalent to the open system concept. F3I are types of essential technical requirements in a performance-based specifi- cation and are defined as follows. Form. The term form addresses the physical characteristics of an end item. For hardware items, form includes the product envelope (which could include both internal and external envelopes), weight or mass, center of gravity, moments of iner- tia. The term has less significance for software items but could include memory storage requirements, throughput requirements, etc. For training materials, it would include characteristics such as the delivery media. Fit. The term fit is primarily applicable to hardware end items and addresses the "mating" characteristics with other hardware items and with the user and operator. Fit includes such character- istics as the location relative to a defined datum of mating sur- faces/features; the location relative to a defined datum of features designed to facilitate handling, assembly, and installation; and mat- ing surface and feature requirements such as flatness or contour. Function. Function addresses what the end item must be capable of doing under a defined set of conditions. Function includes power, speed, reliability, useful life, maintainability, supportability, and other "-ilities" in general. Interface. Interface is defined as the functional and physical requirements and constraints at a common boundary between two Form, Fit, Function, and Interface - An Element of an Open System Strategy By: Ned H. Criscimagna, Alion Science and Technology · Promote transition from science and technology into acquisition and deployment · Adapt to evolving requirements and threats · Facilitate systems integration · Leverage commercial investment · Reduce the development cycle time/total life-cycle cost · Ensure that the system will be fully interoperable with all the systems which it must interface, without major modification of existing components · Enhance commonality and reuse of components among systems · Enhance access to cutting edge technologies and products from multiple suppliers · Mitigate the risks associated with technology obsolescence · Mitigate risk of single source of supply over system life · Enhance life-cycle supportability · Increase competition 1 Often written as F3I. T h e J o u r n a l o f t h e R e l i a b i l i t y A n a l y s i s C e n t e r F i r s t Q u a r t e r - 2 0 0 5 10 Form, Fit, and Function . . . (Continued from page 7) or more functions or items. Interfaces result from the interaction between functions, items, products of an item, or collateral effects of operating an item. Functional interfaces are the relationships between characteristic internal or external actions. Physical interfaces are the relationships between internal parts of the solu- tion as well as between the solution and external elements. Under the F3I concept, only the form, fit, function, and interface requirements, most commonly at the Line Replaceable Unit (LRU) level, are stipulated; no requirements are levied below the LRU level. A supplier can use any approach for designing the internal workings of an LRU, and retain proprietary rights to the internal design, as long as the F3I requirements are met. This approach allows suppliers to implement new technology as LRUs are returned for repair. These changes are transparent to the customer but the new technology may manifest itself as improved reliability, lower power consumption, lighter weight, etc. F3I has the benefits listed in Table 2. Table 2. Benefits of F3I These benefits are similar to those listed in Table 1 because F3I is similar to the open systems approach but the latter places more emphasis on specifying interfaces based on broadly accepted stan- dards to allow for as many suppliers as possible over the long term. The F3I concept is an important consideration in Reliability- Based Logistics, Flexible Sustainment, and other processes and initiatives within the DoD. Accepting the F3I Concept A common problem encountered in accepting the F3I concept is the reluctance to yield configuration control of the inside of a "box" (i.e., below the LRU level) to the manufacturer. The rea- son? Logisticians and maintenance managers are accustomed to repairing boxes at the shop or depot level. To perform mainte- nance below the box level, one must have configuration control. Otherwise, keeping the maintenance people trained, the repair manuals and schematics up to date, and having the right test equipment available would be impossible. On the other hand, if the customer retains configuration control, then the manufacturer is not free to change the internal design as new or improved tech- nology becomes available, to reduce costs, improve reliability, etc. The ARINC Standards Long before the military was debating the pros and cons of F3I, the concept had found a home in the commercial airlines com- munity. The first standards that were developed on an F3I basis are known as the ARINC Standards. The standards are actually developed by the Airlines Electronic Engineering Committee (AEEC). The AEEC is an international standards organization, comprising major airline operators and other airspace users. The AEEC began developing standards in 1949. The AEEC estab- lishes consensus-based, voluntary form, fit, function, and inter- face standards that are published by ARINC2 and are known as ARINC Standards. ARINC Standards specify the air transport avionics equipment and systems used by more than 10,000 com- mercial aircraft worldwide. A brief description of the three classes of ARINC Standards, Characteristics, Specifications, and Reports, follows. 1. ARINC Characteristics Define the form, fit, function, and interfaces of avionics equipment. 2. ARINC Specifications Principally used to define the physical packaging or mounting of avionics equipment, data communication standards, or a high-level computer language 3. ARINC Reports Provide guidelines or general informa- tion found by the airlines to be good practices, often relat- ed to avionics maintenance and support · Promotes competition · Increases supplier base · Reduces cost · Leverages commercial investment · Facilitates technology refreshment · Eliminates need for customer repair of LRUs · Supports standardization, thereby enhancing commonality and reuse of LRUs among systems · Enhances life-cycle supportability · Supports interoperability · Eliminates parts obsolescence problems for customer Example of an ARINC Standard: ARINC 429 The ARINC 429 specification defines how avionics equipment and sys- tems should communicate with each other, interconnected by wires in twisted pairs. The specification defines the electrical and data charac- teristics and protocols,. ARINC 429 employs a unidirectional data bus standard known as Mark 33 Digital Information Transfer System (DITS). Messages are transmitted at a bit rate of either 12.5 or 100 kilobits per second to other system elements, which are monitoring the bus messages. Transmission and reception is on separate ports so that many wires may be needed on aircraft. ARINC 429 has been installed on most commercial transport aircraft including Airbus A310/A320 and A330/A340; Bell Helicopters; Boeing 727, 737, 747, 757, and 767; and McDonnell Douglas MD-11. Boeing installed a newer system specified as ARINC 629 on the 777. The uni- directional ARINC 429 system provides high reliability at the cost of wire weight and limited data rates. Military aircraft generally use a high-speed, bi-directional protocol IAW Military Specifications MIL- STD-1553. Source: Condor Engineering - 2 Incorporated December 2, 1929, Aeronautical Radio, Inc., was chartered by the Federal Radio Commission to serve as the airline industry's "single licensee and coordinator of radio communication outside of the government." Soon the company, widely known as ARINC, took on responsibility for all ground-based, aeronautical radio stations and for ensuring sta- tion compliance with FRC rules and regulations. Today, ARINC serves the aviation, airports, defense, government, and transportation industries with products and services. T h e J o u r n a l o f t h e R e l i a b i l i t y A n a l y s i s C e n t e r F i r s t Q u a r t e r - 2 0 0 5 11 The use of ARINC standards for purchasing their air transport avionics equipment and systems results in substantial benefits to airlines by allowing avionics interchangeability and commonali- ty and reducing avionics cost by promoting competition. Furthermore, for new aircraft and avionics installations, ARINC standards provide the starting point for avionics development and allow aircraft manufacturers to pre-wire aircraft, thus ensur- ing that cost-effective avionics for air transport aircraft are ready when needed. The airlines also benefit from suppliers transparently incorporat- ing new technology, avoid the problems of parts obsolescence and diminishing manufacturing sources, and eliminate the need for any maintenance below the LRU level. Given the volume of avionics bought by the airlines and airliner manufacturers, avion- ics firms readily accept the ARINC standards and competition in this market is alive and well. This competition helps keep costs down and drives the competing companies to continually improve their products. According to Georgia State University in a 2000 study "The Economic Impact of Avionics Standardization on the Airline Industry," use of ARINC Standards to foster a competitive avionics marketplace alone saves the airline industry nearly $300 million annually. An August 2002 article of Avionics Magazine, Reference 1, pro- vides a current perspective on the ARINC standards. Three Military Applications The military has had some experience in applying the F3I con- cept. Take the case of the AN/FPS-108 (COBRA DANE) ground radar system. When support of three components of the system became difficult and expensive, state-of-the-art F3I replacements were developed. Development was accomplished using state-of- the-art design tools, leveraging the evolution of Commercial- Off-The-Shelf (COTS) microwave components and tools that have resulted from developments in the cellular communication and other microwave industries. Using these replacements, the life cycle of the components and system has been increased and there has been a dramatic savings in cost, space, and downtime, and improved maintainability. In another case, and in response to its strategy of Flexible Sustainment, the Air Forces implemented the F3I Lifetime Contractor Sustainment (FLICS) program for the F-15 APG-63 V1 radar. Under the program, the radar developer, Raytheon, has systems engineering responsibility of the radar: and configuration control below the LRU level. Raytheon has the responsibility and authority to manage technology insertion and parts obsolescence. The Air Force's responsibility is to remove and replace LRUs and ship bad LRUs to Raytheon within 24 hours of removal. Figure 1 illustrates the support concept for aircraft stationed at Base X. Another F3I application is the Generalized Emulation of Microcircuits (GEM). GEM technology was developed by the Defense Logistics Agency (DLA) as a long-term solution to the problem of diminishing manufacturing sources (DMS). DMS becomes a significant problem as systems are operated over ever-increasing life spans and a continually faster rate of change in technology. Using gate arrays and single line processing tech- nology, F3I microcircuits are manufactured to replace non- procurable microcircuits originally designed with RTL, NMOS, CMOS, and other technologies. COTS and F3I A broad military application of the F3I concept is the acquisition on COTS items as end products or to integrate into military sys- tems. The decision to use a COTS item is essentially a decision Figure 1. Support Concept for the F-15 APG-(63) V1 Radar T h e J o u r n a l o f t h e R e l i a b i l i t y A n a l y s i s C e n t e r F i r s t Q u a r t e r - 2 0 0 5 12 to make an F3I purchase. The advantages of buying COTS are similar to those for buying F3I and are shown in Table 2. If the item is modified in any way, then some of these advantages may be lost. These lost advantages can include warranty coverage and technology updates. Table 2. Advantages of COTS When a COTS item must be modified, either to address a more severe environment or for some other reason, the item is no longer a pure COTS item. Terms such as Ruggedized-Off-the- Shelf (ROTS) and Militarized-Off-the-Shelf (MOTS) are used to refer to such modified COTS items. Definitions of COTS, MOTS, and ROTS follow. COTS A COTS product is one that is bought and used "as is." Nearly all software bought for a desktop or laptop comput- er is COTS, including Word, WordPerfect, Excel, and Windows. MOTS A MOTS product is a COTS product customized by the buyer or the supplier to meet customer requirements that are different from those of the original COTS market. ROTS A ROTS product is a COTS product customized to meet harsher or more severe environments than originally envi- sioned by the designers. Again, the customization may be per- formed by either the buyer or the supplier. An important difference between a COTS item and one bought using an F3I specification is that the form, fit, and function of a COTS item are determined by suppliers based on the needs of a commercial market. An F3I specification can be tailored to the needs of a specific customer. Thus, although a COTS item may not meet all of the environmental and operating requirements of the user, an item bought using an F3I specification will (or should, if the specification is accurate and complete). Table 3 compares COTS and F3I items. The Importance of Reliability to F3I A critical performance requirement for items bought on an F3I basis is reliability. The reason is fairly simple as can be deduced from studying Figure 1. Note that organic maintenance consists of removal and replacement (R&R) of the failed unit. The failed unit is then shipped to Raytheon. To make this maintenance concept viable, some minimum value of reliability is needed. That level is the one that will ensure that the supply pipeline is not constantly full of avionics boxes. If the reliability is insufficient, not only will a great number of boxes be required to keep a reasonable stock of good spares at the base, but availability will suffer. Even though R&R, as opposed to repair in place, is the fastest way to "repair" an aircraft, too many R&R actions will affect availability. They also increase the need for maintenance and, hence, increase ownership costs. Obstacles to Implementing F3I Despite the long and successful history of F3I in the airline indus- try, and the success with which it has been used in military sys- tems, the concept has found limited application in military acqui- sition and modernization programs. Several related reasons could account for this limited application. 1. Tradition and Lack of Trust. Traditional approaches to specifying requirements have involved customer oversight, if not specific control, of all aspects of design down to the part level. · Reduces cost · Leverages commercial investment · Facilitates technology refreshment · Eliminates need for customer to repair LRUs · Can support standardization · Eliminates parts obsolescence problems · Enhances life-cycle supportability · Can support interoperability · Usually warranted Table 3. Comparing COTS and F3I Items in Military Applications Basis for Comparison COTS3 F3I How bought "As is" To F3I specification Designed to Satisfy commercial customers Meet F3I specification Source Original equipment manufacturer (OEM) Any supplier who can design & build to F3I spec Configuration control None At F3I ("box") level Suitability Buyer must assess to determine if item can meet require- ments Item must meet F3I specification Repair Provided by OEM Provided by supplier Warranty: Usually; may be voided by operation in different environ- ment/for different application Only if provided for by contract with supplier Obsolescence OEM can make technology updates transparently to user, but may choose to stop production of the item at any time OEM can make technology updates transparently to user; production can continue as long as buyer willing to pay sup- pliers to "build to [F3I] print" Investment No R&D or other up-front investment; purchase and repair costs Some up-front investment may be needed plus purchase and repair costs Market Usually large depending on product and whims of commer- cial marketplace Depends on military application; can be very small or very large 3 Un-modified. MOTS and ROTS items, as discussed in the text, are different from pure COTS items. T h e J o u r n a l o f t h e R e l i a b i l i t y A n a l y s i s C e n t e r F i r s t Q u a r t e r - 2 0 0 5 13 It is difficult for some to shift their thinking from a parts per- spective to a box perspective. They question the wisdom of relin- quishing control at lower indentures of design, fearing that doing so will compromise meeting requirements at the higher levels of design. For example, unless they know what is inside the box, how can they be sure reliability requirements for the LRU will be met? Although relationships between customer and contractor have improved markedly in military acquisition over the past decade, a level of customer distrust of contractors still exists. Those who most have this distrust are unwilling to let the contractor dictate the internal specification and design of LRUs. They believe that only by controlling the design to the piece part level can they be assured that the end product will meet their requirements. 2. Vested Financial Interests. The military services have developed an extensive logistics infrastructure. Military depots employ thousands of people. Managers of these depots control millions of dollars in assets. A considerable amount of the work done by depots involves repair and replacement of shop-replace- able units (SRUs) that make up the LRUs. The move to an F3I concept means that repair of LRUs now becomes the sole pre- rogative of a contractor. The loss of work could mean that the depots need fewer people and smaller budgets. Although the benefits accruing to the military from F3I may outweigh any neg- ative impact on the depots, it is only natural for those directly affected to be less than enthusiastic about the concept. 3. Dominance of Legacy Systems. It has become the norm for military systems to continue in operational use far beyond what was originally planned or even envisioned. Today, the bulk of the military's support dollars go to keep legacy systems up and running. Consequently, some may conclude that since embracing the F3I concept in new system development will have little impact on total operating and support costs, why bother. Overcoming the Obstacles The obstacles just discussed are certainly not insurmountable. Let's look at the obstacles presented in the previous section, working from the last obstacle to the first. Dominance of Legacy Systems. Consider the view that since the support of legacy systems dominates the budget, and will proba- bly do so for years to come, why bother with F3I for new sys- tems. The fallacy of this line of reasoning is that F3I is a perfect approach to modernizing and extending the life of legacy sys- tems. The examples of the F-15 radar and COBRA DANE radar, discussed earlier, clearly substantiate this claim. Legacy systems usually have size, space, power, cooling, and shape factor constraints. For these systems, the open systems approach provides F3I solutions within existing packaging, power, and environmental constraints. In such cases, the open systems solution frequently requires less system resources by using newer, more efficient technologies. By replacing older technology legacy system LRUs, that are repaired by the military services, with F3I LRUs, performance can be improved and costs reduced. In fact, the payoff for applying the F3I concept to modernization and life extension programs is greater than for new system, due to the sheer number of legacy systems. Vested Financial Interests. As for the affect of F3I on depot workload, management and personnel policies can minimize the impact on the workforce. Given the impact of outsourcing and private competition for depot work, the effect of a wider appli- cation of F3I should be less dramatic by comparison. Tradition and Lack of Trust. This obstacle really boils down to the issue of requirements. Requirements, whether or not an open sys- tems approach is being used in a specific program, must be realis- tic, achievable, and appropriate. They must be derived from the warfighter's needs. A program must start with good requirements and then have effective means of verifying if the requirements have been met. These means include analysis, simulation, and testing. Certainly the government has the responsibility to ensure that a contractor is implementing good configuration management practices, an effective process for selecting parts and suppliers, and has effective design, analysis, and test methods for achiev- ing the F3I requirements. However, the government's focus must be on the F3I requirements, whether the LRU has the required form, fit, and function, and can interface with the other elements of the system and not on the internal design, i.e., parts selection and specific design. References 1. ANSI/EIA 649-1998, National Consensus Standard for Configuration Management, Approved July 10, 1998. 2. Charles, Richard A. and Arthur C. Brooks, "The Economic Impact of Avionics Standardization on the Airline Industry," Georgia State University, 2000. 3. Criscimagna, Ned H., "Commercial Off-the-Shelf Equipment and Non-Developmental Items," RAC START Sheet 98-4. 4. Hanratty, Michael, Robed H. Lightsey, and Arvid G. Larson, "Open Systems and The Systems Engineering Process," Acquisition Review Quarterly, Winter, 1999. 5. Jensen, David, "ARINC Standards: Where They Come From. Why We Need Them," Avionics Magazine, Access Intelligence, LLC, Potomac, MD, August 2002. 6. OS Computer Resources Acquisition Guide & Supportability Guide, Next Generation Computer Resources Document No. AST 003, Version 1.0 31, Space and Naval Warfare Systems Command, December 1996. About the Author Ned H. Criscimagna is a Science Advisor with Alion Science and Technology Corporation and Deputy Director of the Reliability Analysis Center. Prior to joining Alion, he worked for ARINC Research Corporation. Before entering industry, Mr. Criscimagna served for 20 years in the U.S. Air Force and retired with the rank of Lieutenant Colonel. Over his 39-year career, he has been T h e J o u r n a l o f t h e R e l i a b i l i t y A n a l y s i s C e n t e r F i r s t Q u a r t e r - 2 0 0 5 14 involved in a wide variety of projects related to Department of Defense acquisition, reliability, logistics, reliability and maintain- ability (R&M), and availability. He led the development of the last version of MIL-HDBK-470 and the last update to MIL-HDBK- 338. He has experience in project management, aircraft mainte- nance, system acquisition, logistics, R&M, and availability. He instructs the RAC's Mechanical Design Reliability Course. Mr. Criscimagna earned his B.S. in Mechanical Engineering from the University of Nebraska-Lincoln in 1965 and his M.S. in Systems Engineering with an emphasis on reliability from the USAF Institute of Technology in 1971. In addition, he earned graduate credits in Systems Management from the University of Southern California in 1976-77. He is a member of the American Society for Quality (ASQ), the National Defense Industries Association (NDIA), and the Society of Automotive Engineers (SAE), and is a Senior Member of the International Society of Logistics (SOLE). He is a SOLE Certified Professional Logistician and an ASQ Certified Reliability Engineer. He is a member of the ASQ/ANSI Z-1 Dependability Subcommittee, the US TAG to IEC TC56, and the SAE G-11 Division. He is listed in the 27th Edition of Who's Who in the East, the 54th, 56th, and 57th, Editions of Who's Who in America, and in the 8th Edition of Who's Who in Science and Engineering. System Level Clues for Detailed Part Issues Abstract With the renewed emphasis on reliability within industry comes the desire to diagnose potential reliability problems of fielded sys- tems, before they become either a warranty or life cycle cost issue. In the world of six-sigma, many techniques are available for deter- mining the main issue or root cause of a problem, so it can be fixed. However, many such techniques are applied after a prob- lem arises. This is especially true in the world of reliability, where the high-failure items tend to warrant most of the problem-solving focus. This article presents a drill-down method useful in the world of six-sigma for early detection of reliability issues in field- ed systems. More specifically, the article describes research on a hypothesized relationship between a key parameter of the Weibull distribution and the Crow-AMSAA reliability growth model. This relationship has proven to be strong at both the component and functional levels of systems indenture. Actual data from GE Transportation Systems (GETS) were used in the research. Examples of how the relationship may be used to help detect upcoming reliability issues on GETS products are presented. Introduction One of the key objectives of a six-sigma company is to develop and maintain high quality products and processes, as measured using statistical methods. For products designed by General Electric's Transportation Rail Division (GE Rail) not only is it necessary to deliver high quality, but also to sustain high relia- bility over the full life cycle of the equipment. GE Rail current- ly has several long-term service agreements with many of its major North American customers. Because of the known impact that product reliability has on services and maintainability, GE Rail continuously monitors the reliability of its products that are maintained under such agreements. GE Rail controls the management of product maintenance under the aforementioned service agreements, making it easier to col- lect field reliability data and store it in on-line database systems. GE Rail engineers use this reliability database system to track product performance for each customer, by product model and fleet. Whenever adverse trends in product reliability are detect- ed in the data, project teams are created to determine the root cause of such trends and, if necessary, to develop improvements that are then cut in on the affected fleets. In all cases, six-sigma methods are used to determine the root cause and help develop a viable solution to the problem. While this process has proven to be effective, project teams are too often reactive in nature. That is, problem investigation and resolution sometimes occur after the problem has become signif- icant enough to be noticeable. To be more effective and to reduce the amount of time and dollars required to make improve- ments, proactive methods need to be developed. Such methods would include the ability to detect problems in their early stages, prior to the point in time that they are affecting an entire stage and prior to the point in time that they are affecting an entire fleet of locomotives. One such method being researched and pro- posed by the author involves the use of two well-known reliabil- ity analysis tools, Crow-AMSAA (CA) and Weibull. Tracking Field Reliability Several methods are used today in tracking and assessing the reliability of fielded systems. At GE Rail, many of the historical methods have included both Pareto analysis at the component level and trending of monthly mission failure rates. Projects are then created that target the poorest performing components for upgrades and improvement. More specialized techniques, such as Weibull analysis are also used on an as-needed basis. While such techniques have been sufficient to improve the over- all reliability of GE Rail products, other methods are being researched that can provide more advanced warning of reliabili- ty problems. Often, projects are defined after the problem is large enough to impact system reliability. It would certainly be better and less costly to find and fix such problems before they become large enough to be "felt" by the customer. One method of accomplishing early detection of reliability problems would be to perform a Weibull analysis on each and every compo- nent in the system. Such analysis could be used to detect early wearout failure modes that could adversely impact a fleet of loco- motives prior to overhaul, for example. However, even if such a By: C. Richard Unkle, Senior Reliability Engineer, GE Transportation Rail Division, Erie, Pennsylvania