5
Reliability and Maintainability Issues with Low‐Volume, Custom, and Special‐Purpose Vehicles and Equipment

Edward L. Anderson

5.1 Introduction

There remain today many industries where reliability testing is not developed or used in the products they produce and deliver. In these industries, testing, if performed at all, consists of only functional, performance, or operational testing at the factory, followed by some degree of ad hoc product evolution through real‐world operational experience by the customer. This is especially true when dealing with manufacturers of low‐volume, unique, custom or special‐purpose vehicles and equipment. Testing that may be done is mostly functional performance testing. This author's experiences are primarily with custom automotive vehicles typically production‐line light‐duty vehicles modified for special vocational applications, medium‐ and heavy‐duty trucks, construction equipment, emergency response vehicles for fire, police, and EMT services, standby or emergency generators and fire pumps, and work or patrol boats. Figures 5.1 through 5.6 depict typical equipment of this type. In his career with the Port Authority this author has been the responsible engineer for the acquisition of over 5,000 such vehicles with procurements of vehicles and equipment costing over a half billion dollars.

Photograph of a typical airport snow and ice control equipment (author in the center).

Figure 5.1 Typical airport snow and ice control equipment.

Photograph of an emergency generator rooftop installation.

Figure 5.2 Emergency generator rooftop installation.

Photograph of an aircraft fueling cart (tow type).

Figure 5.3 Aircraft fueling cart (tow type).

Photograph of a typical airport runway de-icer vehicle.

Figure 5.4 Typical airport runway deicer vehicle.

Photograph of an elevating platform truck.

Figure 5.5 Elevating platform truck.

Photograph of an emergency fire pump.

Figure 5.6 Emergency fire pump.

Most of these units are of limited production and frequently have minimal or no true reliability testing. But these units do have some common elements. They are often mission‐critical assets necessitating a high degree of reliability and maintainability. They are complex units and require operator and maintainer proficiencies. They are expected to work over a long service life. Finally, they generally are expensive and difficult to replace.

Another factor is the risks associated with acquiring such units from a vendor that has poor reliability or maintainability can be very high—especially when there are serious consequences for not having unit(s) in service, there are legal liabilities for not having operational units, there are negative public relations implications, or similar consequences to the equipment owner or service provider. Consider the consequences to your organization should an ambulance, police, or fire response vehicle break down and fail to respond to a life‐safety incident. Unfortunately, too often, organizational procurement practices may not allow selection of any offering other than lowest price.

5.2 Characteristics of Low‐Volume, Custom, and Special‐Purpose Vehicles and Equipment

While there can be no question that the testing detailed in other chapters in this book provides the surest solution to providing customers with the reliability and maintainability desired in a product, and provides the best profitability to the manufacturer, it is also true that many products, especially in the truck and equipment fields, are of low production volume and have little or no field testing by the manufacturer. Where testing is done, it probably meets the minimum requirements of consensus standards such as stability testing for man lifts and Aircraft Rescue and Fire Fighting (ARFF) vehicles [1] or pumping performance tests for fire pumpers. These tests typically are performance standards for a single set of test conditions and do not include widely different temperature or environmental conditions, so they are not truly real‐world conditions as described in this book. (The user must also consider whether industry consensus standards are adequate or appropriate for their operational needs. If they are not, more stringent requirements may be contractually required.) Often, these units may be unique, and often the “manufacturer” is an assembler of varied commercially available components with little control over the design of these components. Rarely are these units produced on a true assembly line, but rather are assembled by skilled workers on a unit‐by‐unit basis. Usually, such equipment is also of significant dollar value, having a long expected service life. Often, they also provide a critical function supporting the end user's mission or business function.

Assuring reliability and maintainability in such situations is especially challenging, particularly to the customer who has few mechanisms to assure purchase of a quality product (often depending solely on the manufacturer's sales or marketing claims), and the results of receiving a poor product can be expensive or potentially disastrous: How will your organization be affected by an ambulance, or police emergency unit that breaks down during response, or a backup generator or fire pump that fails to start during a power failure? The costs, including monetary loss, image, and potential legal liabilities could be devastating. But the results to your business or organization can be as problematic with failures in more routine products, such as delivery trucks, plumbers, electricians, or other trade' mobile equipment.

Let us consider some of the attributes of such equipment, especially as related to the mobile equipment industry.

  • Long life/high cost/long lead time Equipment of this nature will typically have a long life (often greater than 10 years in service) and in many cases will become technologically obsolete rather than mechanically cost prohibitive as end of useful life approaches. Consider how technology has changed in the last 20 years, and it is easy to see that units that were state of the art then are lacking in many features we take for granted today: GPS, cell phones, backup, and dashboard cameras to name but a few. Emissions changes and fuel choices are very different today. In many situations, the acquisition process is complex, with the development of written specifications defining the intended functionality of the equipment, and detailing many specifics that are related to the operating needs, operating environment, regulatory concerns, environmental impacts, and other considerations. This, too, must be included in the acquisition lead time, and often entails a committee or work group to formalize these into needs and wants. The development of these requirements can easily add one to two more years to the acquisition process, bringing the total time from recognition of the need to acquire or replace a unit to 3–5 years.

    Unlike going to a store and buying an “off‐the‐shelf” product, or going to a car dealership and buying an automobile from inventory, acquisition of this equipment typically takes much longer, and the unit is produced to order. Typical lead times from placement of order to delivery of finished product can be over 2 years.

  • Strategies for assuring reliability and maintainability of low‐volume, custom and special‐purpose vehicles and equipment Although these units rarely have extensive or real‐world testing, there are factors that can be employed to minimize the risks of acquiring poorly performing units, and to reduce the risks of operating substandard equipment. By using the tactics and strategies described in the following it is possible to minimize the risk of acquiring substandard units.

5.2.1 Product Research

Before beginning the procurement of new units, extensive research needs to be performed, preferably by a professional with engineering or technical expertise, to gain knowledge of the experience with the present generation (or a needs analysis for units that have no prior experience), changes that have occurred in the industry since the last procurement, and most importantly a look into the future to see if the operational needs are expected to change over the life of the new equipment. Research should involve operational management to define operational needs, machine operators, maintenance providers, and new equipment vendors.

5.2.2 Vendor Strength

A common feature on much of this equipment is a small vendor community (typically less than 10 manufacturers, and frequently less than five manufacturers). A key concern is whether the vendor has a robust engineering commitment. Frequently, sales staff will have little technical abilities, or answers to hard or difficult queries as to systems design or operational concerns. Vendors with a strong corporate engineering culture are more likely to be committed problem‐solvers than organizations with weak engineering. (It is this author's observation that successful organizations become successful by offering new or unique products and are entrepreneurial by nature. But, unfortunately, many later morph into short‐term profit‐ driven institutions and engineering and innovation are avoided or discouraged.) Unfortunately, this is a factor that generally is difficult to quantify, and organizational procurement policies may not allow consideration of the engineering strength of the manufacturer even though this factor is among the most critical in acquiring specialized or custom equipment.

5.2.3 Select a Mature Product

As a product is used in real‐world service, problems become evident and solutions are developed. Even with the best efforts in engineering a new product or updated model, problems will be discovered without real‐world testing. It is almost a certainty that purchasing the 100th unit will result in better reliability than the first production unit. The reality is that the customer is the real‐world test track for this equipment. Quality vendors will learn from customer experiences and improve their products over time. Over time, it has been this author's experience (for vehicles as varied as police cars, snow blowers, airport rescue and fire fighting vehicles, and even new or updated model medium‐ and heavy‐duty truck chassis) that the problems and failures occurring in the first year or two of a newly introduced model or product will be significant. And as these are new and unanticipated problems, solutions are rarely quick or simple, and often result in retrofit or modification to all units in the order.

5.2.4 Develop a Strong Purchase Contract

Because of the high cost of virtually all this type equipment, a written agreement, contract, or purchase order is required. This written document can provide the customer with clearly defined rights that can help assure product reliability and maintainability, and clearly define what level of performance is expected from the manufacturer or supplier. Performance requirements, defined “mean time to failure” requirements, operational limitations or restrictions, redress for nonperformance, and numerous other details need to be clearly specified and agreed to by both parties in this written document. There should be little ambiguity and unaddressed items in this written document, for the protection of both parties. Assuring product reliability and maintainability starts with a clear understanding of what is the expectation by the user.

5.2.5 Establish a Symbiotic Relationship

As previously indicated, this equipment generally does not undergo real‐world testing. By the customer sharing their real‐world experiences with manufacturers who are interested in, and committed to, improving their product the result can be a mutually beneficial relationship. However, for this to work there is a need for good communications between the parties, and trust that the information sharing will be used for improving the product and not for attributing blame or fault. It may be prudent to codify this agreement to share information with limiting associated liabilities.

5.2.6 Utilize Consensus Standards

Much of this equipment does fall under industry‐accepted consensus standards, which, among other things, set minimum performance standards that manufacturers should meet or exceed. These should be the minimum standards acceptable, but this does not mean that the customer cannot set more stringent requirements. For example, ANSI Standard A92.2 for Vehicle‐Mounted Elevating and Rotating Aerial Devices [2] permits the lifting of a tire or outrigger under the definition of stability. But, in this author's experience with several agencies, stability has been defined as prohibiting any outrigger or tire lifting from the ground. Of course, when the customer requires different requirements than that called for in the consensus standard, the costs associated with new performance testing will almost certainly be an incremental cost to the unit. (It should also be noted that earlier in this author's career it was common for the engineer to take exception to industry consensus standards when in his professional judgement there were valid reasons for the exception; however, due primarily to the legal liabilities in the USA, deviating from consensus standards today will rarely be supported and is quite risky.) While consensus standards often include performance measures and/or functional testing, it should be noted that most of these requirements are to assure uniformity in performance measures. It establishes uniform functional testing methods and results. They are generally not designed to duplicate all real‐world operational conditions as needed for successful reliability testing. Figure 5.7 shows this author during “SAE ARP5539 Rotary Plow with Carrier Vehicle” performance testing. This functional testing provides a uniform method of measuring the ratings for speed and tons per hour of snow removal by high‐speed airport and highway snow blowers. It is also strongly recommended that organizations become participants in consensus standards committees. These groups generally have many manufacturers working on their standards, but need user volunteers to balance their committees and to be sure the developed standard meets the user's needs. Figure 5.8 illustrates consensus standards functional testing.

Photograph of an SAE ARP 5539 snow blower performance testing.

Figure 5.7 Author overseeing SAE ARP 5539 snow blower performance testing [3].

Photograph of an NFPA 414 ARFF tilt table testing.

Figure 5.8 National Fire Protection Association 414 ARFF tilt table testing [1].

5.2.7 User Groups/Professional Societies

User groups and professional societies are valuable resources for sharing information between people and organizations with similar interests, problems and solutions. The American Public Works Association (Kansas City, MO), ARFF Working Group (Grapevine, TX), National Association of Fleet Administrators (Quincy, MA), the National Fire Protection Association (Quincy, MA), and SAE International (Warrendale, PA) are a few of such organizations.

5.2.8 Prerequisites

Prerequisites are a tool that can be used to preclude vendors with little or no experience in producing the requested units. It provides assurance that the manufacturer (or in some cases the distributer) is experienced and knowledgeable on the product. Unfortunately, it can also exclude some vendors who may be offering a new or innovative product. Typical prerequisites would be a requirement to have manufactured a minimum number of similar or identical units in a specified time frame.

5.2.9 Extended Warranties

Extended warrantees are another tool to enhance the reliability of a unit. These can be applied to the entire unit, or to certain components. In medium‐ and heavy‐duty trucks, it is common to have separate warrantees for the engine and the transmission. Lifetime warrantees against chassis, body, or frame rail cracking, corrosion, or permanent deformation can also be used to provide assurances on unit reliability. Generally, extended warrantees must be agreed to by the manufacturer, and they can be costly.

5.2.10 Defect/Failure Definitions/Remedies

Contractually defining defects or failures, and their remedies, can be used to define the expectations of the customer for the reliability of the unit. These are common in some industries, but not in all. A typical clause used for transit bus procurements is as follows.

Defects/Failures

The following shall be the design objectives for maximum frequency of in‐service failures of the types defined, provided that preventive maintenance procedures specified by the Vendor are followed within the limits of practicability dictated by transit maintenance practice.

  1. Class I: Physical Safety—A failure which leads directly to passenger or operator injury or represents a severe potential crash situation, an example of which is the loss of vehicle brakes. Mean distance between failures shall be greater than 1,000,000 miles, or the actual life of the bus.
  2. Class II: Road Call—A failure which results in the interruption of service. An example of this is a vehicle breaking down during service. Mean distance between failures shall be greater than 20,000 miles.
  3. Class III: Bus Change—A failure which requires removal of the bus from service during its assignment but does not cause an interruption in revenue service. An example of this would be full loss of HVAC or interior lighting systems or engine fault reducing engine power to a limp‐in mode. Mean distance between failures shall be greater than 16,000 miles.
  4. Class IV: Bad Order—A failure which does not require removal of the bus from service during the assignment, but degrades the operation or use of the bus, causing the failure to be reported by the operator. An example of this would be an inoperative lamp, public address system, or partial failure of the security recording system. Mean distance between failures shall be greater than 10,000 miles.

It should be noted that defining defects and failures requires knowledge of reasonable failure intervals to be enforceable.

5.2.11 Pre‐Award and/or Preproduction Meetings

A key part of assuring the units will provide the required reliability and maintainability objectives can be the requirement to have pre‐award and/or pre‐production meetings. These meetings can be instrumental in assuring that all parties understand the needs and mission of the completed vehicle and the manufacturer's processes and deliverables. These meetings should involve all interested parties. While similar in nature, the pre‐award meeting generally does not include fully developed technical details on the product, but is more of an assurance that the manufacturer and client have the same understanding of the proposed contract and deliverables. The pre‐award meeting should not provide for negotiations or contract changes, but an assurance that what is being asked for will be provided. The preconstruction meeting is a more detailed meeting with full detailing of the technical aspects of the offering, and the proposed timeline for the deliverables. Minutes of both pre‐award and preproduction meetings should be published, disseninated to all involved parties, and become part of the project records.

5.2.12 Variation

As presented earlier, these units are rarely produced on a true assembly line. As a result, variations or inconsistencies in the assembly of the unit are common. Different workers may do things slightly differently, minor differences may occur in the delivery of parts to the workstation, or human errors occur, such as, “I thought I tightened those bolts just before quitting time yesterday”; or “it's a lot easier to route this wiring harness different than the drawing shows.” While most of these variations are benign and may go unknown through the product's life cycle, occasionally they can have serious results.

Photograph of a bus lost due to fire.

Figure 5.9 Bus lost due to fire.

Photograph of a diesel injector line hole caused by chafing.

Figure 5.10 Diesel injector line hole caused by chafing.

An actual example of this occurred when the wiring harness in the engine compartment of an order of a new transit bus was routed and supported with very slight differences—so slight it was difficult to see even after learning of the issue. Unfortunately, in the correct method the harness was supported to hold the harness an inch or two above the diesel engine's high‐pressure injector fuel line. In some buses, a clamp to hold the harness was in a slightly different position and the full weight of the harness rested on the injector line. Over time the protective cover on the wiring harness wore through the injector line, developing a hole which sprayed diesel fuel throughout the engine compartment. The atomized fuel found an ignition source and resulted in the rapid spread of a fire that destroyed the bus. Fortunately, the bus had no passengers onboard at the time of the incident. The bus was equipped with an automatic onboard fire suppression system which discharged, and the driver and nearby personnel attempted to suppress the fire using handheld extinguishers, but the bus was a total loss (Figure 5.9). It took the efforts of several expert fire investigators to determine the cause of the fire. Once the failed injector line was identified, an immediate inspection was ordered on all buses (approximately 60 units), and it was discovered that about 10% of them had visible wear at the same location on the same fuel injector line (Figure 5.10). This very minor difference in assembly resulted in the loss of a bus, but very fortunately no injuries. Had the bus had a full load of passengers, the result could have been catastrophic. Because of this incident and the investigation into its cause, a recall was initiated and all units of that make and model were inspected and remedied (Figure 5.11).

Photograph of wiring harnesses re-routed to clear injector line.

Figure 5.11 Wiring harnesses rerouted to clear injector line.

While other failures due to unintended variations in the manufacturing process are numerous, this has been the most dramatic and significant from a potential impact on human life and injury, costliness, and difficulty in determining the root cause.

5.2.13 Factory Inspections

Factory inspections are another tool that can be used to enhance maintainability and reliability of low‐volume manufactured products. Factory inspections are also a valuable tool for understanding the assembly of the unit for maintenance staff who may have to disassemble the equipment for repairs. And maintenance staff may have meaningful input into accessibility, lockout, labeling, or other insights to improve the unit's maintainability. Inspections can be done at various stages of manufacture, or even for different components. Dynamometer testing of engines, transmissions, pumps, generators, or other major components or systems may be appropriate for critical acquisitions. For large orders, it may be advisable to have an engineer in residence at the vendor's plant to maintain continuous overview of the assembly process.

5.2.14 Prototype Functional or Performance Testing

Consensus standards, or contractual requirements, may require first‐unit or prototype testing to demonstrate conformance with the requirements. It is prudent to have an engineer or similarly qualified person to witness this functional or performance testing. If the testing is to be witnessed and attested to by an outside party, it is recommended that the services of a professional engineer be retained, and that written documentation as to the successful testing be provided and kept in the unit's file. This ensures the integrity of the testing and provides assurance to the end user that a properly designed and constructed unit is being provided. It is also valuable evidence that due diligence was employed should there be litigation at some future date. Figure 5.12 shows performance testing of a heavy‐duty wrecker demonstrating its ability to make a “K” turn the narrow confines in a tunnel.

Photograph of a prototype wrecker turn-around functional testing.

Figure 5.12 This author witnessing prototype wrecker turn around functional testing.

5.2.15 Acceptance Testing

Vendors do not always do a thorough final inspection of products before delivery to the customer; and even when they do, infant failures and defects during the early stages of a product's life cycle are not uncommon. A thorough acceptance inspection, including checking all service fluid levels, and appropriate performance testing as soon as practical after delivery and before placing units in service is prudent. And, it can also minimize out‐of‐service instances that would be experienced by the operational unit had the unit been placed in service without this quality assurance. (Surprisingly the author has personally experienced production line units delivered with errors in such fundamental systems as the air brakes because of a parts mix‐up during assembly.) Figure 5.13 illustrates acceptance testing of an airport snow blower. As the delivery was not during snow, load testing and noise‐level measurements were performed by immersing the snow blower's head in water.

Photograph of a snow blower acceptance testing.

Figure 5.13 This author supervising snow blower in‐cab sound level acceptance testing.

5.2.16 “Lead the Fleet” Utilization

A “Lead the Fleet” program is a tactic employed primarily by the military, in aviation, and by some civilian fleet operators, to help identify failure modes and life expectancy. This tactic maximizes the utilization of a statistically significant sample size of new fleet units to help identify failure modes and reliability issues. A select few units are doing real‐world reliability testing for the other units in the production run. Although conceptually simple, to be effective such a program requires dedicated efforts on the part of all players. It requires identifying and using the “Lead the Fleet” units in the most severe operations, minimizing out‐of‐service (fast maintenance turnaround for both scheduled and unscheduled maintenance) for these units, and excellent data collection and analysis for the program to produce meaningful results.

5.2.17 Reserves

One of the most vexing issues for any operator of equipment, and one that is directly associated with reliability and life cycle, is what is the appropriate number of vehicles to accomplish the mission at the lowest cost. It is a problem that lacks a simple quantifiable solution. It is essentially a measure of cost and risk. How can you accurately quantify the loss due to one or more units being out of service and the probability of such an occurrence? For now, there is no answer to this question. This is one more topic that could be better answered through a more robust real‐world testing process. The factors needing consideration in determining the number of units required include:

  • How many units are needed to be in service to meet operational needs?
  • Does this consider cyclic demands—peaks and valleys?
  • How much down time is needed for scheduled maintenance?
  • Can scheduled maintenance be performed during nonpeak times?
  • All operations involve nonscheduled maintenance. What is a prudent estimate of nonscheduled maintenance for your organization, operation, and/or equipment? How much reserve is needed to accommodate nonscheduled maintenance?
  • Repairs due to accidents, damage, or abuse for specialized equipment is lengthy and expensive. The question is what is a prudent estimate of nonscheduled maintenance for your organization, operation, and/or equipment? How much reserve is needed to accommodate accidents, damage, or abuse?
  • Is there an ability to rent, lease, borrow, or some other mechanism to obtain a temporary replacement for an out‐of‐service unit? If available, are there operator training/compatibility issues in obtaining such a replacement?
  • Will having additional units available allow for an increase in service life due to reduced duty cycle or wear and tear on operational units?
  • What are the potential costs, to your organization and its operational capability should one or more units be out of service?
  • What is the probability of such an occurrence?
  • What is your organization's tolerance for risk?
  • Who will sign off on the risk/reward or cost/benefit analysis for this decision?

5.2.18 Problem Log

An important, but often overlooked, step is documenting problems and solutions. As this is long‐life equipment, it will be many years between replacement cycles. The personnel who will do the next replacement may be different due to staff changes, retirements, reorganizations, or other causes. And, the passage of time causes us to forget. A log of significant problems and solutions is a step to avoid repeating problems in the next equipment cycle. During the next replacement cycle, a careful review of the issues with the previous generation of the equipment is a powerful tool that will help to assure problems do not recur in the next generation. Unfortunately, this step is frequently overlooked or forgotten. Too often engineers are better at solving problems than in documenting them, so the narrative of what went wrong and how it was remedied is never documented and so is lost or forgotten.

5.2.19 Self‐Help

Reliability and maintainability of any industrial product entails not only the manufacturer, but to a large degree it also involves the user. Training, cleaning and maintenance practices, operational practices, data collection and analysis, and planning can significantly improve or diminish the reliability and maintainability issues for this type of equipment. The following list contains some things to consider to improve the uptime of products and equipment:

  • Include management, operator, and maintainer training when purchasing new units.
  • Obtain new training when staff changes, and refresher training for seasonal equipment.
  • If possible, schedule maintenance for off‐season or off‐hours to minimize impact on operations.
  • Have the manufacturer provide maintenance schedule recommendations and recommended parts (items and quantity) to be inventoried. And adjust items and quantities as appropriate for your uptime needs and operational conditions.
  • Combine required parts to perform scheduled maintenance tasks into kits containing all the necessary parts.
  • Label fluid service locations with the proper fluids for servicing and the appropriate quantities of fluid for servicing (including fuel tank and diesel exhaust fluid tank).
  • Rotate units to equalize use (unless using the previously described Lead the Fleet strategy).
  • If practical, assign units to specific operators and maintenance chiefs, including putting their names on the units. Pride is a powerful motivator in keeping a unit in prime condition, and it is an inexpensive way to recognize staff.
  • Collect use, repair, and parts data and use the data to develop meaningful information to improve maintainability and reliability (in‐service time).
  • When the units approach end of life, begin replacement activities early. End‐of‐life maintenance costs are very high, and timely replacement is the best way to avoid the increased out of service, repair costs, and reliability issues that result from late replacement.
  • Be creative! From first‐hand knowledge of the operational needs and requirements you may be able to develop other factors that can maximize unit maintainability and reliability.

References

  1. 1 National Fire Protection Association. (2012). NFPA 414, Standard for Aircraft Rescue and Fire‐Fighting Vehicles, 2012 edition. NFPA, Quincy, MA.
  2. 2 American National Standards Institute. (2009). ANSI/SIA A92.2 Vehicle Mounted Elevating and Rotating Aerial Devices. ANSI, New York, NY.
  3. 3 SAE International. (2013). SAE ARP5539, Rotary Plow with Carrier Vehicle. SAE International, Warrendale, PA.

Exercises

  1. 5.1 List some products that are generally not subjected to laboratory or test track reliability and maintainability testing.
  2. 5.2 Identify at least three characteristics of such equipment.
  3. 5.3 Provide three examples of products that entail a high risk to an organization should the equipment fail or be unavailable.
  4. 5.4 List five strategies or tactics that can help assure the maintainability/reliability of low‐ volume, custom, and special‐purpose vehicles and equipment.
  5. 5.5 Why are consensus standards tests not always true indicators of a product's reliability/maintainability?
  6. 5.6 Why should extended warranty and definitions of defects be included in the purchase of low‐volume, custom, and special‐purpose vehicles and equipment?
  7. 5.7 What are the differences between pre‐award and preconstruction meetings?
  8. 5.8 Discuss several different types of testing that might be appropriate in the procurement of low‐volume, custom, and special‐purpose vehicles and equipment.
  9. 5.9 When should acceptance testing be performed, and why is it important?
  10. 5.10 Explain “Lead the Fleet” as a tactic.
  11. 5.11 Discuss some of the criteria that need to be considered in determining the appropriate number of units to meet operational needs.
  12. 5.12 What is a problem log, and why is it important?
  13. 5.13 Discuss several tactics that can be employed to help improve maintainability and reliability of low‐volume, custom, and special‐purpose vehicles and equipment.
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