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2:12 pm
March 1, 2001
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U.S. Naval Aviation Implements RCM

A reliability centered maintenance program is a key tool in achieving the U.S. Navy’s goal of Affordable Readiness providing large reductions in scheduled maintenance, use of consumable materials, and disposal of hazardous materials.

The U.S. Navy faces the great challenge of becoming the Navy of Tomorrow. However, in this age of shrinking defense budgets, it has been shown that there simply are not enough funds available to maintain the current degree of readiness and modernize the Fleet for the future. As reported by Naval Air Systems Command (NAVAIR), current operation and support (O&S) costs for naval aviation weapon systems consume 50 to 60 percent of the Navy’s total operating account and it has been shown that these O&S costs will increase if they are not arrested. As a result, Vice Admiral John A. Lockard, former Commander, NAVAIR, has mandated Affordable Readiness to reduce the total cost of ownership of naval aviation weapons systems now in order to provide funding for modernization and recapitalization of the Fleet.

In an effort to reduce the total operating cost of common support equipment (CSE) and aircraft launch and recovery equipment (ALRE), the NAVAIR CSE program manager, the ALRE program manager, and Naval Air Warfare Center, Aircraft Division, Lakehurst (NAWCADLKE), together with the Fleet, have instituted Reliability Centered Maintenance (RCM). RCM is a process used to determine the maintenance requirements of any physical asset in its operating context. RCM has been applied to various end items of CSE as well as ALRE equipment such as recovery, assist, securing, and traversing (RAST) equipment. As a result, maintenance plans have been re-established. In addition, numerous changes/improvements to the equipment and various processes have been identified that, when implemented, will significantly reduce O&S costs.

Need for a standard
RCM, when carried out properly, offers a method to develop the most safe and cost-effective maintenance policies for physical assets. However, RCM is a time- and resource-intensive process. In this age of do more with less, there is a problem that has infected the discipline of physical asset management. In the interest of saving time and money, corrupted versions of RCM, versions that irresponsibly shorten the process, continue to flood the market; these tools are incorrectly called RCM. They boast that they are quicker and cheaper, yielding dependable results. This simply is not true.

A group of asset management professionals dedicated to the proper use of RCM (including representatives from NAVAIR and the Naval Sea Systems Command) developed a standard for RCM. In September 1999, the Society of Automotive Engineers (SAE) approved SAE JA1011, “Evaluation Criteria for Reliability-Centered Maintenance.” The standard does not detail how to perform RCM, but it sets out criteria that any process must comply with in order to be called RCM. The standard is not yet legally enforceable but offers a tool to evaluate any process that purports to be RCM.

Too many maintenance managers do not understand what RCM is and believe they cannot bear the expense to do it properly. On the contrary, they cannot afford not to; lives depend on it.

Why RCM?
CSE encompasses a range of equipment including tow tractors, mobile electric power plants, mobile air conditioners, avionic test systems, hydraulic test stands, weapon loaders, and bomb trailers. CSE serves several functions such as handling, servicing, maintaining, inspecting, and testing aircraft; aircraft components; and other end items of support equipment. The equipment, located ashore and afloat, is used throughout the Navy providing critical support to naval aviation operations.

RAST equipment is used to traverse SH-60 helicopters in and out of aircraft hangars and to aid in recovering the aircraft to the decks of nearly 100 air capable ships, such as frigates and cruisers in foul weather conditions.

Scheduled maintenance for CSE and RAST is a huge cost driver within naval aviation. NAVAIR reports that O&S costs increase at a rate of 5 percent per year. With the ever-increasing need to reduce O&S costs, one solution is obvious. A re-establishment of maintenance plans is compulsory. By direction of Vice Admiral Lockard, RCM was implemented to accomplish this goal.

What type of RCM?
Because there are many methods of RCM available, an appropriate RCM strategy, and one that complies with the criteria set forth by SAE Standard JA1011, had to be identified. First, it was necessary to distinguish the qualities desired in the process used.

However, perceived shortcomings of the CSE and RAST maintenance management systems’ circumstances impeded the initiation of an RCM program. First, it was believed that a previously prepared failure modes and effects analysis (FMEA) was mandatory to perform RCM. Additionally, adequate detailed failure data is virtually nonexistent.

Taking into account what was desired in the chosen RCM process and the perceived obstacles to initiating an RCM program, research into the various methods of RCM revealed that RCM2, a modern derivative of RCM developed by John Moubray of Aladon, Ltd., was the ideal method to use. Its strengths lay in many areas:

  • The RCM2 philosophy is consistent with the message of Vice Admiral Lockard. It requires that rather than relying solely on a single analyst or engineer to perform the RCM analysis, it must be executed by a team of equipment experts, under strict guidance of a highly trained RCM facilitator. The CSE and RAST RCM teams recognize the absurdity of expecting one individual to know all of the failure characteristics of a complex system. The CSE and RAST RCM analyses are completely team oriented and cannot be performed without the Fleet.
  • RCM2 recognizes that most historical data, with respect to maintenance planning, is typically inadequate. The analysis can be performed without extensive failure data.
  • The RCM2 analysis is zero-based. The analysis is conducted as if no maintenance (including pre-operational inspections) is being conducted. As a result, the new maintenance schedule is not biased by current practices that may not be technically appropriate.
  • RCM2 focuses on identifying the equipment functions that the user wants the equipment to do—not what it was designed to do (as the two are often drastically different).
  • The completed RCM2 database provides a legally defensible audit trail for all decisions.
  • RCM2 has a proven track record with other military organizations, namely the Royal Navy, and is used extensively throughout industry.
  • RCM2 does not require that a previously prepared FMEA exist before the analysis is initiated.

 

RCM process
In order to complete the RCM analysis, a team of equipment experts called the Review Group answers seven questions about the equipment being analyzed. The first four questions make up the FMEA.

  1. What are the functions and associated performance standards of the asset in its present operating context?
  2. In what ways does it fail to perform its functions?
  3. What causes each functional failure?
  4. What happens when each failure occurs?
  5. In what way does each failure matter?
  6. What can be done to predict or prevent each failure?
  7. What should be done if a suitable proactive task cannot be found?

RCM focuses on identifying what must be done to ensure safe system functions. Therefore, the first step in the RCM process is to clearly identify the functions of the unit from the point of view of the user.

One of the most distinguishing features of the RCM2 process is that functions and performance standards are recorded as what the user wants the asset to do rather than what it was designed to do. In some cases, what the Fleet needs equipment to do and what it was designed to do are very different. This may have a large impact on the maintenance requirements.

Consider a mobile electric power plant that has been in service for 16 years yet has considerable service time remaining. It is equipped with both ac and dc power supplies. When the unit was first commissioned, the dc power supply was required Fleet-wide.

Today, with the emergence of newer aircraft, the dc power supply is required at limited sites only yet it is still maintained. Using the careful identification of functions, it is often noted that the user’s expectations of the equipment and its original design capabilities are different. By identifying what the user needs the unit to do, superfluous equipment functions and the corresponding maintenance may be eliminated.

Functional failures, or the ways in which the asset can fail to meet the expectations of the user, are identified. Both total and partial functional failures must be documented. For ex- ample, the primary function of a mobile air conditioning unit may be to deliver conditioned air at the required performance parameters. The total failure of this function is to be completely unable to cool aircraft compartments.

However, a partial failure may occur—the unit may continue to produce cool air but not at the rate required, thus still cooling the aircraft compartment but not in as timely a fashion as required. It is important to list total and partial functional failures because the consequences of total and partial failures may be drastically different.

The third step in the RCM process is to identify failure modes. A failure mode is defined as an event that causes a functional failure. Examples of failure modes are “bearing seizes due to lack of lubrication” or “thermostat fails closed due to corrosion.”

All failure modes that are reasonably likely to happen are recorded. Specifically, failure modes that should be recorded are:

  • Failures that have happened in the past
  • Failures that have not occurred but have severe consequences
  • Failures that are currently prevented by existing maintenance schedules

Typically, in RCM analyses that are conducted solely by an RCM analyst or engineer, only failure modes associated with normal wear and tear and deterioration are recorded. Little emphasis is placed on failure modes that may result from human error or design flaws. Because equipment experts conduct the RCM2 analyses—personnel who have intimate knowledge and experience with the equipment and the operating environment, up to 30 percent of the failure modes identified in some CSE and RAST RCM analyses are attributed to human error.

The purpose of recording such failure modes is not to place blame but rather to identify and address impediments to preserving safe system functions of the equipment. Most of the “mistakes” are not the fault of the user/maintainer but can be traced to confusion or deficiencies in the maintenance process. Properly identifying the failure modes that are reasonably likely to occur is a crucial step in the RCM process.

The failure effects of each failure mode are documented. A properly written failure effect should:

  • Be written as if nothing is done to detect or prevent the failure
  • Describe the failure to the first point of evidence to the operating crew
  • Identify how, if so, someone could be killed
  • Identify how, if so, an environmental standard may be breached
  • Record any secondary damage to the equipment as a result of the failure
  • State what must be done to repair the failure

Only with a properly written failure effect may the consequences of a failure be appropriately assessed.

A great strength of RCM2 is that it recognizes that the consequences of failures are far more important than their technical characteristics. In fact, it recognizes that the only reason for doing any kind of proactive maintenance is not to avoid failures per se, but to avoid or at least to reduce the consequences of failure.

Using the RCM algorithm, one of five failure consequences is identified:

  1. The failure mode is first considered to be either hidden or evident. A failure mode is hidden if the loss of function caused by that failure mode does not become evident to the operating crew under normal circumstances. Examples of components that have hidden functions are smoke detection systems, over-speed governors, and over-temperature switches. For example, the user of the mobile air conditioning unit does not know that the over-speed governor is in a failed state unless the engine over-speeds and the engine is not automatically shut down. In other words, two failures have to occur for the first one to become evident.

    If the failure mode is evident to the operating crew under normal circumstances, it is documented as having:

  2. Safety consequences if someone could be injured or killed
  3. Environmental consequences if an environmental standard may be breached
  4. Operational consequences if operations may be adversely affected
  5. Nonoperational consequences if only the direct cost of repair is involved

It is important to note that the RCM2 process considers the safety and environmental implications of each evident failure mode first.

The sixth question in the RCM process addresses the establishment of proactive (predictive and preventive) maintenance tasks. One of the following types of tasks, if technically feasible and worth doing, is assigned.

On-condition task.
Assignment of on-condition tasks is condition-based maintenance (CBM). The subject of CBM and RCM is grossly misunderstood. Many believe that the two are stand-alone processes. Properly applied, they are not. RCM offers very powerful tools for determining if a CBM task is technically feasible and worth doing and, if so, how often it should be performed.

It has been explained that there is seldom a relationship between equipment reliability and age. However, many failures give an early indication that failure is imminent. For example, if Point P is the point where the potential of a failure can be detected and Point F is functional failure of the component (failure as identified by the user), the P-F interval, or the time between when a potential failure can be detected and the time actual failure occurs, must be long enough to be of use in order to prescribe an on-condition task. The on-condition task must be performed at intervals less than the P-F interval.

On-condition tasks have nothing to do with how often a failure occurs but rather how quickly it happens. As an example, a variable-flow axial piston pump is used to deliver hydraulic fluid to the RAST system. One of the failure modes associated with the pump is “Traverse pump wears internally due to normal use.” The RCM team established that the on-condition maintenance task of performing a leakage rate test was technically feasible and worth doing. In this case, the P-F interval was recorded as 2 mon. Therefore, the task was assigned to be performed every month, which leaves ample time (the remaining 1 mon) to schedule and complete replacement of the pump. Note that the task periodicity has nothing to do with how often the pump has failed in the past.

This example explains why using technical history information such as mean time between failure is inappropriate for determining the periodicity of on-condition tasks. In nearly all cases, the information needed to determine the periodicity of on-condition tasks does not exist in technical history data. But, in most cases, it is very clear in the minds of equipment experts.

The identification of the P-F interval allows inspection periodicity to be sensibly assigned. Further, CBM allows components to be replaced only on the condition that they require it. One of the advantages of CBM is that it allows a component to stay in service as long as technically possible thus realizing its maximum life. Other examples of on-condition tasks are inspecting tires and brake pads for wear.

Scheduled restoration and scheduled discard tasks.
Scheduled restoration and scheduled discard tasks are appropriate only for those items that exhibit an age-related failure pattern. Regardless of their condition at the time, components are restored to their original resistance to failure or completely replaced. Examples of scheduled restoration and scheduled discard tasks are lubrication routines and the replacement of components, respectively.

RCM provides three default actions if an appropriate proactive task cannot be identified.

Failure finding.
A failure-finding task involves checking a hidden function at regular intervals to find out if it is in a failed state. Proactive tasks (on-condition or scheduled restoration/discard) are performed to prevent failures. Failure-finding tasks are performed to check if the item is in a failed state. For example, while the engine is idling, an emergency stop switch may be activated. If the engine is shut down, the switch is functional. RCM2 offers robust tools for determining if a failure-finding task is technically appropriate, and, if so, how often the task should be performed.

Redesign.
A redesign may be a physical change to equipment. However, redesigns may include such tasks as changes in operating, training, or supply procedures. Likewise, a redesign may entail a change to a technical publication or a recommendation for a better tool.

No scheduled maintenance.
For those failures that do not have safety or environmental consequences, there may be no form of scheduled maintenance that is technically feasible and worth doing and, thus, the equipment may be deliberately run to failure.

CSE RCM analyses
Each CSE RCM analysis lasts, on average, two weeks. During that time, a Review Group convenes to perform the analysis. Every CSE RCM Review Group comprises Navy CSE technicians, a Marine Corps CSE technician, an equipment operator, training personnel, East and West Coast and Reserve Type Commanders, Naval Air Technical Data and Engineering Services Command (civilian equipment expert), and the in-service engineer. Under the strict guidance of an RCM facilitator, the Review Group carries out the RCM analysis.

Eight end items of CSE have been analyzed: three A/S32A-30A aircraft tow tractors, an A/M32C-17 mobile air conditioning unit, two mobile electric power plants (NC-10A/B/C and MMG-1A), and three hydraulic power supplies (T-5, T-7, and 55/E). RCM analyses have been performed with overwhelming positive results. The following two sections detail the results.

The economic savings identified via the RCM analyses are staggering.

  • On average, scheduled maintenance is reduced by 75 percent per year.
  • On average, consumable usage is decreased 88 percent per year.
  • The disposal of hazardous material (HAZMAT) is decreased 84 percent per year.

With reductions of 75 percent annually in scheduled maintenance, it is important to note the following. First, it has been established that CSE was over-maintained so the opportunity to significantly reduce maintenance exists. Second, such large reductions raised a question to the RCM Review Groups as to how much of the published maintenance was actually being performed in the Fleet. They reported that approximately 70 percent of the maintenance was performed, which reflects a real-world reduction in maintenance of approximately 50 percent.

Finally, note that there are no dollar values associated with the reduction of maintenance man-hours. There are two reasons for this. First, because only approximately 6000 units out of more than 700,000 pieces of CSE have been analyzed at this early stage of the RCM effort, considering a reduction in work force simply does not make sense. But most importantly, CSE maintenance activities are currently understaffed. RCM analyses offer a way to do business better because they relieve the burden of performing unnecessary maintenance and allow the Fleet to concentrate on what matters most.

It follows that if maintenance is reduced 75 percent on average, the quantity of consumables (filters, lubricant, rags, etc.) required would be lessened. Scheduled maintenance consumable usage per year is reduced by an average of 88 percent, Fleet-wide. The HAZMAT disposal of hazardous material is decreased 84 percent per year.

Maintenance before RCM
The drastic differences in the current maintenance plans and the plans established using RCM prompted the question “What is wrong with the old maintenance schedules?” to RCM Review Groups. The following factors were identified:

  • The maintenance plans were typically prepared by the equipment manufacturer or based heavily on the equipment manufacturer’s recommendations. The motive for such extensive maintenance plans may be challenged in that the manufacturer is also the vendor of consumable materials.
  • The equipment manufacturer generally did not understand how the equipment would be used, how severe the operating environment would be, or how often the equipment would be operated.
  • As a result, most maintenance plans are out of date. With the emergence of improved consumables (filters, lubricants, etc.), the periodicities of current maintenance tasks could be extended. However, a process to review such issues was not previously in place.
  • The maintenance plan process is static. Rarely are maintenance regimes reviewed once they have been established.
  • Many maintenance plans were developed when it was believed that “more is better.” It follows that CSE and RAST, in many cases, are over-maintained.
  • In some cases, maintenance schedules for new equipment were simply copied from existing schedules of the same type of equipment. For example, when a fleet of new tow tractors was procured, the maintenance schedule for the new model was prepared based on a model that is 20 years old.

RAST RCM analyses
RAST RCM Review Groups are comprised of East and West Coast RAST technicians, a depot overhaul technician, an aeronautical shipboard installation representative (ASIR) (civilian equipment expert), and the in-service engineer.

Maintenance requirement cards (MRCs) are currently being updated as a result of RCM analyses. However, preliminary results boast a 35 percent reduction in scheduled maintenance. Similar reductions in consumable materials and HAZMAT disposal are expected.

There are a number of nonquantifiable achievements from performing RCM analyses. As mentioned previously, the economic savings as a result of RCM analyses performed on CSE and RAST are impressive.

However, the most prodigious achievement of RCM is the relationship that has been fostered with the Fleet.

RCM is quickly bridging the gap between the Fleet, NAVAIR, and NAWCADLKE. RCM has established a direct line of communication between management and maintenance personnel. Participants function as a true team. Hesitation from the maintainer level to contact the equipment’s governing agency is quickly becoming extinct because the roles of all team members are now better understood and respected. A common goal has been established.

The Navy is making the move from conducting maintenance in a reactive mode to a proactive one. As more equipment is analyzed, funds previously spent on consumables and maintenance man-hours that have been eliminated through RCM may be redirected to perform corrective actions. Additionally, discussion of the depot rework for CSE revealed the notion that a substantial portion of units are in need of rework because the Fleet simply does not have adequate manpower and resources to address some issues, such as chipped paint, that don’t affect a unit’s ability to perform its primary function. Much of the Fleet’s time is consumed performing maintenance it instinctively knows is unnecessary but is a requirement. As a result, common failures that do not “down” equipment often get deferred to the point that, over time, the equipment degrades, which eventually leads to a depot rework that otherwise may have been avoided.

Several redesigns have been recommended that, when incorporated, improve equipment safety and increase the availability of the end item. For example, it was identified during the RCM analysis of the mobile air conditioning unit that if there is a leak of Freon in the pre-cooler or after-cooler, personnel working in the cooled spaces could be severely injured due to the contaminated environment.

The RCM team recommended the installation of a Freon monitor and this redesign is currently being considered. Further, due to the reduction in scheduled maintenance, units spend less time being maintained and are, therefore, available more. Additionally, fewer failures are induced as a result of unnecessary intrusive maintenance.

Also, if units are down for maintenance 50 percent less, it is logical to assume that equipment availability is increased. The details of this are currently being investigated.

During RCM analyses, deficiencies in technical publications are discovered and noted for update. In the case of an electrical schematic, the correction of an error may significantly reduce troubleshooting time.

The RCM process has been received with overwhelming positive support from the Fleet. It can be described as an ownership process. Buy-in to the new maintenance plans has been achieved for two reasons. First, equipment experts carry out the RCM analyses, and secondly, the Fleet knows that the revised maintenance schedules are technically justified.

Information obtained during the RCM analysis is recorded in a database. The information is legally defensible and serves as an audit trail for all decisions.

Especially in the case of RAST, performing RCM analyses not only updated the maintenance schedules, but the exercise of updating the MRCs revealed many steps for maintenance tasks that were unnecessary or outdated. As a result, the MRCs are clearer and succinct.

RCM offers a cogent, technically sound process through which a maintenance regime may be developed. During an interview with a RAST engineer, he commented that because of the way the new maintenance schedules were revised, he now has a higher confidence that maintenance planning is “done right.” He further noted that this is the way business should have been done 10 years ago.

Most of the problems that are noted during an RCM analysis are not new. In several cases, the Fleet has known about them for some time. However, RCM offers a structured process for information to be extracted from the Fleet so that proactive action may be taken.

Future plans
The troubleshooting guides for most end items of CSE need to be updated. The documented equipment discrepancies and corresponding symptoms are unrealistic and, in many cases, do not effectively aid the CSE technician in isolating equipment failures. As a result, excessive troubleshooting time is expended on equipment failures.

Answers to questions two, three, and four of the RCM process describe, in great detail, the equipment failure, the cause, the symptoms, and corresponding effects. For end items that have already been subject to RCM analysis, this information has been recorded in the RCM database. Using this data, a detailed troubleshooting guide can be created to assist CSE technicians in isolating equipment failures.

An updated troubleshooting guide will allow the CSE technician to quickly identify equipment malfunctions. Distinct benefits include:

  • Expedited troubleshooting time
  • Decreased equipment turnaround time
  • Decreased unscheduled maintenance man-hours
  • Increased equipment availability

CSE RCM analyses are Affordable Readiness in action. RCM makes it possible to focus on problem areas and address issues costing the Navy extraneous funds. Most importantly, RCM analyses allow positive impacts to be manifested throughout the Fleet, with the Fleet. This is a new way of thinking and has been lauded by senior enlisted personnel as exactly what the Fleet needs as the work force is downsized and maintenance funds and resources are reduced. MT


At the time of writing, Nancy Regan was the RCM Team Leader and a certified RCM2 Practitioner at the Naval Air Warfare Center, Aircraft Division, Lakehurst, NJ.


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