Designing for maintainability–not just lip service anymore
Enslen, William J Jr
Maintainability is an inherent characteristic of system design. It pertains to the ease, accuracy, safety and economy in performing maintenance actions. A system should be designed such that it can be maintained without large investments of time, cost or other resources (e.g., personnel, materials, facilities, test equipment) and without adversely affecting system mission success. Maintainability is a measure of the ability of an item to be maintained, whereas maintenance constitutes a series of actions taken to restore or retain an item in an effective operational state.
Maintainability is a design parameter. Maintenance is a result of design.”1 Maintainability is an engineering discipline that, in the minimum, interfaces with all facets of an engineering development program for the purpose of integrating and influencing life cycle support features of the system.
Program statements of work (SOWs) typically contain the necessary language to require maintainability analyses and predictions, but they too often tend to be little more than words on paper during program execution. Statements of work maintainability requirements typically read: “implement a maintainability program tailored for the development program to ensure the specified maintainability requirements are achieved, and perform maintainability predictions to estimate subsystem and system mean-time-to-repair (MTTR).” Maintainability task requirements seem to be generically handed down from program to program, from SOW to SOW, often with limited effectiveness. Shortly after contract execution, maintainability design guidelines are usually written to satisfy a contractual or implied data requirement, but designers may not read them. Specialty engineering personnel then typically spend the bulk of their effort generating and manipulating numbers until it can be claimed that specification requirements are met. Typically, too little interaction occurs among specialty engineers, logisticians and design engineers, especially during the time between preliminary and critical design reviews. This may result in failure to optimize the design for maintainability and accessibility.
Adding to the problem, designers and program personnel too often don’t understand that specialty-engineering functions (e.g., maintainability) are engineering functions and not integrated logistics support (ILS) functions. They tend to wrongly group maintainability, reliability, safety and human factors under the ILS umbrella. This misunderstanding contributes to the designer’s tendency to treat maintainability as a secondary consideration. It is evident that the balance among functional performance, cost and supportability as design considerations is tipped in favor of functional performance and cost. An explanation may be that, during times of tight schedules and reduced funding, pressures to develop a functional system within budget and schedule cause designers to focus on making it work, with less attention paid to making it supportable. However, this must not be used as an excuse to diminish supportability as a design influence.
Why don’t designers, as a normal practice, design the product to meet the proper goals, including supportability and life cycle cost, themselves? Why do we have separate specialty engineering disciplines? The answer is a reflection on the growth and development of all the professions in our modern society. Technology is advancing so rapidly, and the products being designed are so complex that specialty-engineering disciplines have evolved because no single discipline can do the entire job. This specialty approach is similar to the approach taken by lawyers and doctors. Although basic backgrounds in law and medicine are required in these professions, further education in a specialty, such as patent law, criminal law, corporate law, or for doctors, surgery, dermatology, obstetrics, is usual because the time required to maintain proficiency in all areas is prohibitive. Maintainability is a specialty in the engineering profession, which when added to an acquisition program performs specific and needed functions.2
Fault for failing to optimize the design for supportability doesn’t lie entirely with designers. Specialty engineers and logisticians must share much of the blame. Even in today’s environment of integrated product teams, meaningful interaction of specialty engineers and logisticians with designers occurs too seldom. These disciplines may, indeed, routinely meet at regularly scheduled informal design or in-process reviews, but too often effective discussion in terms of supportability characteristics of the detailed design is limited. Such routine reviews are often little more than program reviews or focuses on functional performance. This happens usually because a high-level program sponsor or contractor manager attends the review. As a result, program management and top-level design information (dog-and-pony) are presented instead of the detailed design. Because of schedule and funding constraints, specialty engineers leave the meeting and continue focusing their efforts on the specific SOW tasks of generating numbers to show specifications are met. Logisticians are also at fault. Design interface is one of the ILS elements that too often receives little more than lip service during system design and development, Again, because of schedule and funding constraints, the logistician typically focuses on completing the SOW tasks for provisioning, technical manuals, training and the other ILS elements, instead of that nebulous, hard-tomeasure requirement for design interface. Although the Department of Defense (DoD) proclaims the need for ILS personnel to be active participants in the design process, in reality it seldom occurs. Most often the logistician merely surveys the design and develops support alternatives that best fit it while meeting program readiness, supportability and life cycle cost requirements – thus rarely making significant contributions to design synthesis. Another factor hampering the logistician’s ability to effectively interface with designers is lack of training or experience in the specialty engineering functions, such as maintainability. This lack of understanding tends to cause the logistician to shy away from dealing routinely one-on-one with the designers.
The hardware repair level and repair site working group (HWRL & RS WG) process is an ideal instrument for the specialty engineers, logisticians and designers to identify major improvements in design concepts. It not only provides a means for the logisticians and specialty engineers to accomplish one of their highly promoted goals (i.e., influence design for supportability), but it also enhances the relationship among the logistics, specialty engineering and design engineering organizations. When engineers are brought together with logisticians in a working, concurrent engineering atmosphere, they begin to develop a remarkably increased understanding and appreciation of the logistician’s goals. It’s the beginning of the integration among the groups that is so critical to ensuring a system is developed that not only meets performance and cost requirements, but also meets or exceeds supportability goals.
This article briefly describes the HWRL & RS WG process by explaining the approach used to implement it during design development of the remote minehunting vehicle (RMV), a prime component of the U.S. Navy’s remote minehunting system (RMS), AN/WLD-I(V)1. The HWRL & RS WG focuses on system maintainability and accessibility characteristics. The basic principles of implementing the HWRL & RS WG apply to all types of end item or component acquisitions, whether large or small, complex or simple. The process relies heavily on using concurrent engineering principles to encourage interaction among design engineering, specialty engineering and logistics personnel. This integrated approach ensures design organizations truly recognize the logistics consequences of their designs.
The objective of this article is not to provide an abundance of details on a U.S. Navy mine countermeasures system – most readers would find them meaningless and of little interest. The reader must look beyond the equipment being described and recognize the fundamental steps of a universal approach to implementing a HWRL & RS WG. Use of the process is limited only by the imagination of the engineers and logisticians.
HWRL & RS WG Development and Implementation
The AN/WLD- 1 (V) 1 RMS is a remotely controlled acoustic mine reconnaissance system designed for detecting, classifying and localizing bottom, close-tethered and moored targets in shallow and deep water. It’s a fully integrated system comprised of an unmanned surface-piercing underwater vehicle carrying various hull-mounted and towed variable-depth sensors. Lineof-sight and over-the-horizon telemetry systems provide vehicle command and control and mine reconnaissance sensor data transmission to/from a control center aboard U.S. Navy combatants. The AN/WLD- 1 (V) 1 will be integrated on the Flight IIA DDG-51 Class ships, with shipboard control, display and processing integrated as a functional segment of the AN/SQQ-89(V)15 surface ship undersea warfare combat system. The vehicle is the most complex of the four major RMS subsystems (i.e., vehicle, data link, variable depth sonar, and launch and recovery) and presents the biggest development challenges. Because the HWRL & RS WG was formed to support vehicle development, a brief vehicle description is provided.
The RMV is an unmanned dieselpowered semi-submersible vehicle used to conduct off-board mine reconnaissance at extended ranges from the host ship. The RMV deploys and recovers a towed variable-depth sonar using a winch system located in the hull and keel. The RMV is equipped with obstacle avoidance sensors comprised of a forward-looking sonar and a mast– mounted video camera. The global positioning system, RMV electronics module, data recorder and radio data links are supported by a majority of commercial off-the-shelf/non-developmental equipment. The RMV can be manually controlled from consoles in the DDG-51 sonar control room or combat information center, or by using a portable remote operator pack from the deck for launch and recovery or near-ship operations.
At the RMV preliminary design review (PDR) it was apparent that all designers weren’t fully aware of program maintainability and accessibility requirements. As a result, an action item was assigned for the contractor reliability and maintainability (R&M) responsible individual (RI) to provide the RMV design team with maintainability and accessibility guidance in addition to the R&M Design Guidelines document. Although the R&M Design Guidelines document contained many detailed R&M design requirements unique to the RMS program (instead of lengthy generic guidance that often isn’t read or implemented), it was an ineffective means to convey specific RMS R&M design requirements to the designers. Among other reasons, schedule and funding constraints caused the designers to disregard the R&M document. They were under pressure to design and demonstrate a vehicle that primarily met functional performance and cost requirements. Additionally, RMV subsystem lowest replaceable unit (LRU) repair level/site were issues too complex to rely solely on design guidelines.
The reliability, maintainability, availability working group (RMA WG) met to brainstorm approaches and select an alternative that most effectively provided maintainability and accessibility guidance to the designers. The challenge was to find an approach that didn’t get in the designers’ way of meeting schedule, and didn’t turn them off because of the need for design interface discussions and tradeoffs with specialty engineers and logisticians. The RMA WG decided that an informal, roll– your-sleeves-up working meeting with each designer was the answer. To minimize the designers’ reluctance to meet with supportability people, the RMA WG established strict rules that briefing slides would be forbidden, formally assigned action items would be forbidden and anything resembling a dog-and-pony would be forbidden regardless of rank or position of guest attendees (e.g., program sponsor, contractor management or Fleet personnel). These rules helped build the designers’ confidence that meeting with supportability people wouldn’t bog them down with additional paperwork or tasks other than those directly involved with completing the design.
A RMV hardware repair level and repair site working group (HWRL & RS WG) was established under the authority of the supportability integrated product team. Its charter was simply to review the evolving hardware designs for maintainability and accessibility, potential component remove-and-replace (R&R) location and the likelihood of component repair onboard ship. It provided a forum to discuss component reparability with the objective of influencing design for supportability. Because results of the discussions would be used as source data for the level of repair analysis (LORA), all RMA WG members agreed that the contractor RMV ILS RI would cochair the HWRL&RS WG with the Government Coastal Systems Station (CSS) R&M RI. Permanent members included the contractor R&M RI, ILS specialist, system safety RI, performance monitoring/fault detection/fault localization RI, the Government CSS R&M RI and a Government CSS mechanical engineer. Additionally, an independent contractor R&M expert participated as a permanent WG member.
The first meeting of the HWRL&RS WG included only the permanent members. Its purpose was to organize the team, define its goals and schedule, and define the process for conducting the WG with the designers. The team reviewed the system maintenance concept to ensure each team member understood it fully.
Because of its complexity, the RMV went through four detailed design reviews (DDRs) as the design progressed between PDR and critical design review (CDR). Each DDR focused on detailed design of selected components, which was based on a variety of factors including component type and design progress to date. The HWRL & RS WG decided to have four meetings. Each meeting was scheduled three to four weeks prior to each DDR. This served two purposes: (1) It allowed the HWRL&RS WG to review the hardware design prior to its formal DDR (the designer could incorporate design changes resulting from the HWRL & RS WG meeting prior to DDR) and (2) It provided an opportunity for the designer to prepare for his/her DDR presentation.
A subtle aspect of the maintenance concept that the HWRL & RS WG cochairs emphasized to all WG members and designers was the program’s strong desire to minimize the frequency of occurrence that the design dictates removing the RMV from the ship to accomplish repair. Typically, a program focuses on organizational level (0-Level) accessibility to attain the specified MTTR requirement. A key HWRL & RS WG objective was to influence design to maximize accessibility and reparability regardless of the maintenance level. The objective was to design-in shipboard R&R capabilities, thereby reducing total ownership costs and increasing operational availability. The co-chairs made it clear that final LORA results will determine the level at which repair will be done and stressed to the designers that the design normally should not dictate a LORA decision by being a pre-empting factor in the LORA. The design should allow for the capability to perform maximum repair onboard ship, regardless of any economic decision the final LORA may recommend. This was a critical condition that the HWRL & RS WG wanted to ingrain into the designers’ minds. Therefore, the WG members agreed that, during the meetings with designers, distinction between 0Level, intermediate level (I-Level) and depot level (D-Level) would not be made. Instead, discussion would focus on onboard repair capability versus off-board. Emphasis was placed on simply whether repair could be accomplished onboard, instead of requiring the RMV to be removed off-ship (e.g., shore activity) for repair. The advantage of this philosophy is obvious in that readiness and sustainability are seriously degraded when the RMV is removed from the ship for repair. If ship personnel can’t perform the repair because of lack of training or support equipment, then an I- or D– Level maintenance team can be dispatched to the ship and complete the repair in much less time than if the RMV were taken off-ship. The WG co-chairs used the following analogy to drive home this point: A car engine oil change is typically done at an auto shop (i.e., an I-Level maintenance facility); however, if the owner chooses, the design allows him/her to change the oil himself/herself at home. Although the maintenance decision in this example is for the auto shop (i.e., off-board at an I-Level facility) to do the maintenance, the design doesn’t preclude maintenance from being performed at home by the user (i.e., O-Level onboard) if the user so chooses.
This same philosophy is what the HWRL & RS WG wanted to continually emphasize to the designers – to the maximum extent, don’t allow the design to dictate whether the RMV is repaired onboard or off-board. The goal was to design for shipboard repair so LORA decisions could be made primarily based on economics. With this philosophy, even if the Navy initially decides to perform a component repair at I-Level, the design can allow for onboard repair should circumstances ever warrant the need for it.
The HWRL & RS WG members defined guidelines for conducting the meetings with designers. Candid and open exchanges of needs, ideas and experiences were desired. A working group atmosphere would be maintained at all times. Designers would use whatever tools were available to present his/her design, from handdrawn sketches to Pro-E drawings. Everyone present would participate in design discussions. To minimize causing additional workload for the designers, formal action items wouldn’t be assigned. However, the Government co-chair wanted a means to track the design-change recommendations made by the WG. A tracking method was developed and used at subsequent DDRs to verify whether the changes were incorporated, and if they weren’t, an explanation from the designer could be solicited. Formal minutes of each HWRL & RS WG meeting would be issued and distributed program-wide. An agenda would be developed for each WG meeting, coordinated with the designers. The meetings were held at the contractor’s design facility so designers could be brought into the meeting when their components were ready for review. This avoided having all designers sitting in a room listening to discussions that had nothing to do with them (their time wasn’t wasted).
Conduct of the HWRL & RS WG Meetings and DDR Influence
The first HWRL & RS WG meeting with designers included review of mechanical and electrical/electronics components. All permanent WG members attended, as well as the RMV lead mechanical and electrical design engineers, and selected component designers. The co-chairs began the meeting by emphasizing the philosophy of designing for onboard repair to the maximum extent. Designers were told up front that, for every component presented, the WG would ask, at a minimum, “Can it be removed onboard the ship, and how?”
Most component designs had progressed where they were documented in Pro-E, which allowed the designers to display their hardware in three-dimensional (3-D) images on a large screen for easy viewing by all attendees. The 3-D images could be flipped and rotated in any direction, making it easy for everyone to understand the designer’s presentation.
Pro-E allowed the designer to illustrate the component’s location within the RMV. Using Pro-E the designer described the component, its func– tion, and its maintainability and accessibility characteristics. At any time during the discussion, participants could ask questions. Extensive “what if’ discussions were key factors in identifying design improvements, especially for components that were initially thought of as not capable of being removed and replaced onboard ship. Every aspect of the component design was scrutinized for maintainability and accessibility. Designers frequently found themselves saying, “That’s a good idea,” “I never thought of that” and “Yeah, we should do that.” The following are just a few examples of the design improvements resulting from the first HWRL & RS WG meeting:
*Modified fuel and variable ballast system (VBS) bladders for onboard R&R by shipboard personnel. Added top access panel on RMV. Onboard bladder repair kit would allow onboard repair without R&R.
*Modified launch and recovery capture device to enable access to top access panel. Connectorized forward looking sonar projector and Doppler to facilitate onboard R&R by shipboard personnel.
* Added drain plug to engine muffler.
*Redesigned pylon dunnage bumpers for onboard R&R by shipboard personnel.
*Relocated nitrogen fill port for easy access and standardized fill port fittings throughout RMV.
* Developed rationale for onboard replaceable propulsor blades (a change that was later incorporated into design).
Shortly after the HWRL & RS WG meeting, the RMV DDR#I for those same components was conducted at the program level. Design presentations included identifying improvements resulting from the HWRL & RS WG meeting. When designers failed to address recommendations made by the HWRL & RS WG, they were asked to provide justification for not incorporating the design change. If a supportability representative didn’t understand the justification or felt dissatisfied with the justification, further discussion ensued among the entire Government/contractor team of designers, supportability personnel and program personnel. As a result, some recommended design changes remained unincorporated, but some that the designer initially excluded were subsequently included.
About a month later HWRL & RS WG #2 was conducted. The same format was used. Something different happened at this meeting. Formally uninvited, but welcomed, guests such as the contractor’s chief RMV design engineer and RMV program manager popped in and out of the meeting to observe and offer thanks for spending time with the designers. The WG members didn’t immediately perceive the significance of this. Realization would soon come. The following are a few examples of the design improvements resulting from the HWRL & RS WG #2 meeting:
* Relocated hydraulic compensator vent to allow access with capture device installed.
*Relocated manifold compensator and added flex hoses to improve access to traction drives.
*Resized sonar tow cable connector and enlarged hole in latch bracket to allow for onboard tow cable replacement (this interference would have prevented onboard tow cable replacement).
* Re-plumbed latch lube fittings for improved access.
* Encouraged development of common tool for use with all RMV ball valves (common %-inch socket design was incorporated).
* Developed rationale for additional maintenance access panels in propulsion section (a change that was later incorporated into design).
DDR #2 occurred shortly after the HWRL & RS WG #2 meeting. Heightened awareness of component maintainability characteristics on the designers’ part was apparent.
Design presentations included increased discussion of maintainability and accessibility. Component reliability and potential reliability improvements also steadily worked their way into discussions, oftentimes presented by the designers without prompting from the R&M attendees. HWRL & RS WG members now realized that word was getting out to the designers of the value added by the supportability people during the HWRL & RS WG meetings. Designers began to rethink their stereotypes of supportability people. Attitudes began shifting from “nuisance” to “these people can actually help improve my design.”
HWRL & RS WG #3 and #4 meetings were conducted, again using the same format as previous meetings. The remarkable success of the first three WG meetings made it possible to consider inviting Fleet personnel to the fourth WG meeting. Such invitations were unthinkable prior to the first WG meeting because of funding constraints. The program office encouraged the co-chairs’ request for Fleet attendance and funding was put in place. As a result, representatives from Naval Undersea Warfare Center, Newport, Rhode Island; Fleet Technical Support Center Atlantic (FTSCLANT), Norfolk, Virginia; and FTSCLANT Ingleside, Texas, attended the fourth WG meeting. Discussions on all aspects of supportability were enhanced by input from these Fleet representatives. In-service personnel identified design improvements based on their field experience and extensive knowledge of shipboard practices. The following are a few examples of the design improvements resulting from the HWRL & RS WG #3 and #4 meetings:
* Added an access port to pressurize the emergency recovery system for troubleshooting.
* Added a means to swing the propulsion system junction box to gain access to the back connectors.
* Changed attaching method of pylon nosepiece to enable unobstructed access to the forward-looking sonar and Doppler.
*Added secondary filter over masthead exhaust.
*Identified need for additional tooling to R&R control surfaces.
*Identified maintainability issues with the masthead antenna design that resulted in a new, simpler and more easily maintained design.
*Recommended camera improvements based on experience with cameras used in similar applications.
* Created mock-up to analyze harness routing and bending limits.
Modified capture device for probe adjustment to ensure good stab fit.
DDR#3 and #4 followed the HWRL & RS WG meetings. At the final DDR something astonishing happened. Component detailed design presentations included lengthy discussions of R&M characteristics. Other designers in the audience asked how various items could be maintained, how they could be accessed, whether they could be removed and replaced onboard ship, and how they could be made more reliable. For the supportability attendees it felt truly rewarding to sit back and listen to the design engineers taking ownership and spending so much time talking about maintenance, maintainability, accessibility and reliability.
The HWRL & RS WG concept is a resounding success. The RMV designers’ mindsets have been changed with supportability no longer a secondary thought. For them supportability is an equal to functional performance and cost. The approach is unique in that, while it requires minimal additional effort for the designers, it maximizes the capability to perform maintenance at the shipboard level. This concept of design for shipboard-level maintenance provides such a significant opportunity for enhancing system operational availability and supportability that it should be implemented as a standard best practice on other programs. It also provides a valuable opportunity for supportability personnel to provide meaningful design influence. Typically, the relationship between designers and supportability personnel is fragmented. The HWRL & RS WG approach fosters teamwork across all functional disciplines to truly optimize design.
The HWRL & RS WG concept offers another enormous benefit not yet addressed. Such thorough and easy-to-understand design reviews help supportability personnel better understand hardware. This translates to an improved support system because of a better understanding of requirements for maintenance procedures, spares, tools and test equipment. Too often logisticians who’ve never even seen the hardware, let alone understand it, develop maintenance procedures and other supportability requirements. These one-on-one discussions with designers are extremely effective in helping logisticians understand hardware and how best to support it.
Any program can achieve the remarkable success that the HWRL & RS WG concept offers. It’s easy. It’s a simple matter of doing it. All Navy programs, large or small, should implement it, without question and without hesitation.
The author acknowledges the help given by Mr. Wesley C. Hood of Lockheed Martin Naval Electronics and Surveillance Systems, Syracuse, New York (the RMS program R&M RI); Mr. Toshio Oishi of Greybeard Consulting LLC, Herndon, Virginia (expert R&M support to CSS for the RMS program); and Mr. Edward L. Pipkin of Perry Technologies Division of Lockheed Martin, Riviera Beach, Florida (the RMV ILS RI).
1. Blanchard, Benjamin S., Logistics Engineering and Management, 1986.
2. NAVSEA Product Assurance
Division, Fleet Analysis Center, Student Guide Introduction to Reliability, Maintainability and Availability, October 1990.
By William J. Enslen, Jr., CPL
William Enslen, Jr., CPL is a Logistics Management Specialist with the Coastal Systems Station Dahlgren Division, Naval Surface Warfare
Center in Panama City, Florida. He received a B.S. degree from the U.S. Naval Academy in 1979 and his Certified Professional Logistician (CPL)
credential through SOLE – The International Society of Logistics in 1992. He received certification as a lead ISO 9000 quality management system auditor from Stat-a-Matrix in 1995. He was a Ground Supply Officer in the U.S. Marine Corps and served a four-year tour at Headquarters Marine Corps in the Materiel Acquisition Support Branch. He was actively involved in integrated logistics support efforts on the U.S. Air Force B2 Bomber and Peacekeeper Missile programs. He currently performs a variety of logistics functions on Navy mine countermeasures programs, and provides specialty and life cycle engineering support to the Navy’s new DD(X) Destroyer program. v
Copyright Society of Logistics Engineers Apr-Jun 2002
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