RCM Comes Home to Boeing

Reliability-centered maintenance moves from airplanes to the production machinery that builds and assembles them

01-00boeing
This Ingersol 7-axis spar mill is one of 11 identical mills on the production line at the Frederickson facility
Boeing Commercial Airplane (BCA) has undertaken a major revamping of its facility maintenance activities over the past three years. Reliability-centered maintenance has played a major role in moving from a reactive to a proactive maintenance program.

This story begins in the early 1960s when the Type Certification process for the 747-100 airplane was initiated by the Federal Aviation Administration (FAA). The process required that Boeing define an acceptable preventive maintenance program for the 747-100. The FAA initially envisioned this program to be three times more extensive than the 707 program under the rationale that the 747 would carry three times more passengers. United Airlines (UA), one of the first of two buyers, and Boeing realized that such a requirement was so costly that the airplane could not operate in an economically viable fashion. This problem was amplified by the fact that the existing 707 maintenance philosophy was built on the premise that an airplane periodically wore out, and required a major (and costly) overhaul in order to retain airworthiness stature.

UA and Boeing decided to return to ground zero with a clean sheet of paper, and to challenge the validity of the wearout premise. Tom Matteson, vice president, maintenance planning, and his maintenance analysts at UA played a key role in this evaluation, and were able to use their extensive historical database to prove that, in reality, only about 10 percent of the nonstructural equipment in their jet fleet showed an end-of-life or wearout characteristic. As a result, they structured a common sense decision process to systematically determine where, when, and what kind of preventive maintenance (PM) actions were really needed to preserve airworthiness.

This new look evolved into what is known as the Maintenance Steering Group (MSG). The MSG defined an acceptable and economical PM program for the 747-100, which received FAA approval. This MSG process became the standard for commercial aviation and still exists today. In 1970, the process was labeled reliability-centered maintenance or RCM by the Department of Defense (specifically, the Navy), and is now a recognized maintenance process which is practiced in many industries worldwide.

The airplane design side of BCA, which was instrumental in the development of RCM, did not communicate this finding to the production side of the house. Rather, it took more than 30 years for RCM to grow its roots in other industries before the Boeing facilities maintenance people learned about RCM in their best practices investigation. This is what brought RCM home to Boeing.

Organization and approach
Within BCA, six major regions containing all of the commercial airplane production plants have been combined under one facility organization for maintenance purposes. This organization is known as Facilities Services. The six regions are located in Washington State, Oregon, Kansas, and California. The manufacturing centers in these regions are the main customers for the organization's services.

Region leaders report to the vice president of facilities services, and they have group and team leaders as their management structure. While there is autonomy within each region, for the most part, each of the various teams consists of mechanical and electrical craft personnel, maintenance analysts, and reliability engineers. Additional core resource groups include planning as well as equipment and plant engineering capabilities.

A key element of the Facilities Services strategy was the establishment of an Asset Management Initiative in conjunction with production customers. This initiative is a formal partnership with production with the stated objective to significantly improve how BCA manages all of its assets in order to achieve lean manufacturing, process improvements, and dependable measures of asset utilization.

Facilities Services has developed a long-range strategy to optimize the application of its resources, i.e., people, material, equipment, and specialty tools. Customer (production) involvement in its execution is essential to assure that the plans align with the customer's business commitments. To achieve these goals, various state-of-the-art maintenance concepts have been deployed through an Advanced Maintenance Process program (AMAP).

BCA is investing in today's best maintenance practices, such as tactical planning and scheduling (including a new computerized maintenance management system), a continuing program of craft skills development, advanced preventive and predictive maintenance technologies, TPM, and RCM. There is also an equal focus on safety and regulatory issues. One essential element of AMAP is the inclusion of the reliability parameter. Within Facilities Services, reliability is defined as asset availability and performance, and thus encompasses every aspect of what the organization does on a day-to-day basis to prevent the loss of critical facility systems while preserving, first and foremost, employee safety.

In a review of industry best practices, it was learned that the RCM process used on the airplanes has been employed increasingly throughout U.S. industry as an effective decision technique to optimize the application of maintenance resources. The RCM focus has provided dramatic results in reducing equipment corrective maintenance actions and loss of system availability (i.e., less downtime). Further, when different RCM solutions on the market were evaluated, it was discovered that the most effective programs used the classical RCM process that followed the original airplane methodology. After it was decided to use the classical RCM process, the first pilot project was the Spar Mills at the Wing Responsibility Center in Frederickson, our newest commercial factory located south of Seattle.

Plant and equipment overview
This project was conducted at the Frederickson production facility. Two major production capabilities are located here: one is dedicated to building the vertical and horizontal composite tail sections for the 777 airplane; the other is dedicated to producing the wing spar and skin kits that are used in all airplane types currently produced by BCA at its Renton and Everett, WA, final assembly lines. It is this latter facility where we conducted the first RCM pilot project.

The spar and skin facility is a 550-person organization with an annual operating budget of about $300 million. The Facilities Services personnel are composed of skilled machinists, mechanical and electrical technicians, numerical control (NC) specialists, equipment and reliability engineers, and other support personnel. This facility opened for production in April 1992. It has 21 acres of floor space that produce both spar and skin wing sections in continuous aluminum pieces up to 110 ft in length. The spar production line includes automated stringer handling, overhead crane, spar mill, drill router, deburr, paint, chip collection, shot-peen and bending/forming systems.

For the RCM project, the spar mill was divided into three subsystems: cutting, control, and auxiliary support. The cutting subsystem was chosen for a detailed RCM analysis.

The RCM team
Based on past success, the RCM team was composed of craft personnel (operator, mechanic, electrician), supported by a reliability engineer and maintenance analyst. The RCM consultant, Mac Smith, was the team trainer and facilitator. This combination of experience and hands-on knowledge of the spar mill was the key to project success since their contributions were reflective of the technical details of the equipment, how it was used in the daily operations, and how it applied to the RCM methodology.

Initially, fear of change, suspicion of goals, ingrained viewpoints, skepticism about the new process, and individual agendas were all present. But, as the project moved on, the team felt a real sense of satisfaction because they were direct participants in an opportunity to provide meaningful value added content to their daily work.

Classical RCM
Four basic features define and characterize the RCM process:

  • Preserve system function.
  • Define functional failures and specific component failure modes that can defeat required functions.
  • Prioritize the importance of the failure modes.
  • Select applicable and effective PM tasks for high-priority failure modes. Applicable tasks include those that will prevent, mitigate, detect the onset of, or discover hidden equipment failure modes. Effective tasks are the lowest cost tasks among competing options.

The RCM system analysis process consists of seven steps.

1. System selection and information collection. In a large facility or plant, certain systems tend to have a higher impact on plant operation and maintenance than others (higher maintenance cost, more forced outage contributions, etc.). Boeing focused the effort by selecting the systems that have the highest potential for improvement of the maintenance process, where the best return from an RCM program can be obtained. This selection essentially follows the 80-20 rule where 80 percent of the unexpected costs and production losses derive from 20 percent of the systems.

2. System boundary definition. Each system selected must have well-defined physical boundaries to prevent overlaps with adjoining systems or voids in the analysis, and to precisely define what moves back and forth across the boundary in step 3.

3. System description and functional block diagram. Complex systems are usually subdivided into two or three functional subsystems. Detailed descriptions and component equipment lists are developed for each subsystem. The system is represented in a functional block diagram and all in and out interfaces at the system boundary are carefully listed. The out interfaces become the key data for understanding the functions that must be preserved.

4. System functions and functional failures. The information developed in steps 2 and 3 provides the basis to precisely define the system functions and then the functional failures associated with each.

5. Failure mode and effects analysis (FMEA). The functional failures and components for each subsystem are arrayed in a matrix to reveal intersections where a potential component failure could produce the functional failure. This matrix is used as a road map to develop the FMEA for each critical point in the matrix.

6. Logic (decision) tree analysis. Any component failure mode that produces a system or plant level effect in the FMEA is tagged for logic tree analysis (LTA) and further refinement as to its significance and priority. By using three simple yes or no gates, each failure mode is categorized as safety related (Category A), outage related (Category B), or minor economic disadvantage (Category C); each is also designated as evident or hidden (Category D) relative to the normal operations process. As a general rule, all Category C failure modes are designated as run to failure, and the focus becomes the Category A and B failure modes.

7. Task selection. The safety and outage component failure modes from the LTA are evaluated to select an applicable and effective PM task. All failure modes that had been designated as run to failure (RTF) are put through a second evaluation called a sanity check before any final RTF decision is reached.

Analysis results
The existing PM program at project initiation was essentially a one-shot overhaul activity scheduled to be done on 9-month intervals. It was discovered that over a 5-yr period since their installation, this interval exceeded 9 months about 80 percent of the time, and extended to 18 months or more 40 percent of the time. This resulted in an excessive trouble call history that had then caused major downtime problems, elevating the spar mill to one of the 80-20 systems at Frederickson.

A statistical overview of the team's analysis and results for the cutting subsystem are shown in Figs. 1-3.

RCM Systems Analysis Profile Spar Mill #6 - Cutting Subsystem

Number of subsystem functions

8

 

Number of subsystem functional failures

14

 

Number of components within the subsystem boundary

58

 

Number of failure modes analyzed

172

 

Number of hidden failure modes

72

(42%)

Number of critical failure modes

150

(87%)

Number of RCM-based PM tasks identified
(including run to failure)

197

Figure 1. Systems analysis profile showed that there were a large number of hidden failure modes, and that most of the failure modes were high on the criticality list.

The systems analysis profile (Fig. 1) provides a feel for the scope of the project that took 32 days to complete, and was spread in one-week efforts over a six-month period. Perhaps the biggest surprise was that almost half of the failure modes (42 percent) were hidden if they occurred, thus the operator was unaware that any problem was developing with the spar mill until later, when the consequence finally would show, often in a detrimental way. Not surprising was the fact that most of the failure modes were high on the criticality list, and could cause personnel injury or downtime. The team made 197 decisions on what to do with the 172 failure modes (some failure modes received multiple PM actions).

RCM-PM Task Type Profile Spar Mill #6 - Cutting Subsystem

RCM

Current

Time Directed

 

 

Intrusive

32 (16%)

34 (17%)

Nonintrusive

16 (8%)

30 (15%)

Condition-directed

34 (17%)

2 (1%)

Failure finding

21 (11%)

11(6%)

Run to failure

84 (43%)

0

None

0

120 (61%)

Design modification

10 (5%)

0 (0%)

Total

197

197**

**There are currently 22 additional PM tasks for which no failure mode could be identified in the system analysis.

Figure 2. RCM results in the task type profile along with a comparison to the existing maintenance system.

Fig. 2 shows the makeup of the RCM results in the task type profile, and its comparison to the existing maintenance system. The outstanding point is that the number of failure modes receiving no attention currently was reduced by one-third, and the nonintrusive actions with condition directed (including predictive maintenance) and failure finding tasks were increased by a factor of four.

The real impact of the RCM results is seen in Fig. 3, the task similarity profile, where the similarities and differences between the RCM and current PM tasks were examined. Because the analysis showed where the critical failure modes were located, appropriate PM actions were developed where needed and PM work that was not needed was eliminated. Overall, the RCM results changed 71 percent of the current maintenance practices on the spar mill. Because there are 11 spar mills at Frederickson, the multiplying effect is quite dramatic.

RCM-PM Task Familiarity Profile Spar Mill #6 - Cutting Subsystem

 

 

Number

Percent

1

RCM task = current task

0

0%

2

RCM task = modified current task

45

21%

3A

RCM specifies task, currently no task exists

56

21%*

3B

RCM specifies RTF, currently no task exists

64

29%

4

RCM specifies RTF, currently a PM task exists

18

8%

5A

Currently a PM task exists, but no failure mode was identified

22

10%

5B

Currently a PM task exists but the selected RCM task is entirely different

14

6%

Total

 

219

 

*RCM changed 71% of the current PM program.

Figure 3. Analysis showed where critical failure modes were located. Appropriate PM actions were developed where needed and PM work that was not needed was eliminated.

Finally, the intensity of the RCM process enabled the team to discover a number of nonmaintenance related findings, items of interest (IOI), which also provide a significant portion of the benefit achieved. There were 36 IOIs recorded that affected design, operations, reliability, safety, and logistics.

Implementing the results
Implementation of the PM task findings that were developed in step 7 of the system analysis process proved to be challenging, because:

  • A general understanding of the RCM process and a buy-in to the results of the analysis from a broad group of personnel who were peers of the team members was needed for implementation. Nothing new on a factory floor is ever successfully deployed by simply announcing that it will happen!
  • Several of the new tasks required a more direct participation on the part of the operators, and this had to be carefully integrated with the production shift supervisors.
  • With the substantive changes being made to current procedures, time was needed to develop several new procedures and coordinate their review and approval with all affected parties.
  • Several of the condition-directed tasks required some exploratory work to ascertain their suitability for the failure mode(s) in question. Some of this work is still on-going.

All of the above required extensive communication across organizational lines and among the disciplines that are resident in the production and maintenance work force. Involvement of production personnel, and a close integration of their viewpoints and experiences with Facilities Services was a key ingredient in the entire project.

Currently, 21 RCM-based PM procedures have been deployed on the spar mill. These procedures essentially encompass all of the analysis findings, except for a few condition-directed tasks still under evaluation. The new PM format being used includes additional descriptions of the work to be performed plus references to the specific failure modes and failure causes that triggered the PM tasks. Deployment to the factory floor was done step by step to introduce the shift from traditional to RCM tasks without disruption. Again, open communication was essential to successful implementation. Giving honest and positive feedback to the questions that were asked was crucial to creating a positive paradigm shift.

The IOIs are in the process of being evaluated and, where appropriate, implemented. To date, several have been accomplished, including:

  • Pressure wash of the entire machine has been eliminated in favor of selective washing of a few components. This has virtually eliminated severe corrosion and chip contamination damage caused by the pressure wash.
  • Spindle vibration analysis is being closely correlated with the as-produced part quality (tolerance) to obtain the maximum spindle life before changeout.
  • A&B axis rack covers have been removed, since they trap chips and cause pinion seal damage, rather than prevent chip entrance to the racks.
  • All 7 axis drive motors will be replaced with brushless motors, eliminating five specific failure modes of concern.
  • Counter-balances have been added to all W and Z axes to eliminate failure of the thrust bearing.

Return on investment considerations
The objective of the RCM program is to focus PM resources to reduce costly corrective maintenance actions and resulting loss of machine uptime. While no hard measurements are yet available, the following observations can be made:

  • While the PM program has changed significantly, its cost is virtually unchanged. Costly time directed tasks have been replaced by expensive condition directed and failure finding tasks, and the task frequencies have been extended.
  • With the program now focusing on the critical failure modes, a reduction in unexpected corrective maintenance actions (trouble calls) of at least 50 percent is expected. Downtime should also decrease by at least 50 percent.
  • From preliminary analyses, IOIs have the ability to produce annual savings in excess of $3 million when implemented. Of those incorporated to date, annual savings in excess of $500,000 are expected.

Future directions
With the experience gained and success achieved at Frederickson, two additional RCM pilot projects at Everett and Wichita have been initiated and recently completed. These projects were performed on a Cincinnati 5-axis router and Modig extrusion mill, respectively, and are currently in the transition to implementation. ROI benefits simlar to the spar mill are expected to accrue from these projects.

Currently, six other RCM projects are in progress, two at Everett, WA, and four at Wichita. Several additional RCM progress are contemplated in the schedule for 2000.

The RCM Living Program will be applied to all completed projects in order to periodically update the PM tasks as may be required and to effectively measure the results of the RCM program.

The classical RCM process will continue to be used on critical systems because the actual benefits have exceeded our original expectations. MT


Dennis Westbrook is Maintenance Process Focal and Robert Ladner is Facilities Maintenance Analyst, Fredrickson Site, for Boeing Commercial Airplane. Anthony M.(Mac) Smith is principal at AMS Associates, San Jose, CA. The authors can be contacted by email at This e-mail address is being protected from spambots. You need JavaScript enabled to view it , This e-mail address is being protected from spambots. You need JavaScript enabled to view it , and This e-mail address is being protected from spambots. You need JavaScript enabled to view it