Logistics in the most common sense can be a complex network of many functions working together to meet a common goal. Logistics in the realm of system design and supportability is no different and requires scaling steps through each phase of the design. The procurement of goods, manufacturing, material handling, warehousing, storage, distribution, transportation, and maintenance are just a few of the most common elements a firm must coordinate in the design of a system. Before the end result of a design is executing its intended purpose, the measure of logistics and system support are exercised throughout the design phase. The reliability, maintainability, and availability outline one of the most important factors in the success of a system design and are considered vital requirements before moving forward with supportability, design and production.
Reliability, Maintainability, and Availability The success of a system is dependent on many things but none more important than its availability. The availability of a system is reliant on its reliability and maintenance requirements. As Blanchard (2004) explains, “The ultimate objective is to design and develop a system that will perform as intended, is available when required, and is cost-effective during its period of utilization” (p. 46). In order to meet this objective, availability of the system must be continually optimized to reach maxim production.
Reliability
Reliability determines maintenance requirements and affects availability of a system. As Blanchard (2004) defines, “Reliability can be defined simply as the probability that a system (or product) will perform in a satisfactory manner for a given period of time, or in the accomplishment of a mission, when used under specified operating conditions” (p. 46). In essence reliability equates to the dependability of a system or how often the system fails. Failure rates as they relate to system reliability are calculated by the rate at which failure will occur. Some system may determine failure rates in intervals of hours in service such as with generators, others may express failure rates in intervals of mileage in the case of rolling stock, and some systems may capture failure in the expression of units expended such as in the case of weapons. Regardless of the unit of measure in which failure rates are captured, it all equates to equipment down time and loss of production. In order to make the system operational again, maintenance is required. The more a system is down, the more maintenance is required. As Blanchard (2004) further explains, “The frequency of maintenance for a given item is highly dependent on the reliability of that item. In general, as the reliability of a system increases, the frequency of maintenance will decrease and, conversely, the frequency of maintenance will increase as system reliability is degraded” (p. 46). In addition to failure rates driving maintenance requirements, failure rates tend to be higher during the initial usage of the system and again towards the end of the systems life cycle. In regards to the initial use or break-in period, Speaks explains, “There is always the risk that, although the most up to date techniques are used in design and manufacture, early failures will occur” (Reliability and MTBF, n.d.). This failure is usually attributed to unforeseen errors and basically translates to working the kinks out. Once these concerns are addressed, the failure rate will decrease and the system will experience its normal life which will be different for each system type. Once the system has exhausted its normal life, a wear out period begins in which the system and system components begin to fail at a rate at which it become uneconomical to continue repairing the system and the system is retired. The below graph is provided to allow visualization of the failure rate through a systems life-cycle. Maintainability Maintainability refers to the degree and timelessness at which it takes to restore a system to an operations status. As Blanchard (2004) explains, Maintainability, defined in the broadest sense, can be measures in terms of combination of elapsed time, personnel labor-hour rates, maintenance frequencies, maintenance cost, and related logistics support factor. (p. 57).
Maintainability Factors As it sounds, elapsed time is concerned with the amount of time a system is in maintenance. Maintenance refers to both corrective and preventive. Corrective maintenance is unscheduled and used to restore a system to an operational condition after failure. As Blanchard (2004) explains of corrective maintenance, “Such activities may include troubleshooting, disassembly, repair, removal and replacement, reassembly, alignment and adjustment, checkout and so on” (p. 57). Preventive maintenance also referred to as schedule maintenance is intended to retain a system in an operational condition and extend the systems life cycle. Scheduled maintenance involves such functions as changing oil, lubing, calibrating, inspecting, cleaning, and changing filters. Regardless of the type of maintenance being performed, the process of maintenance is timely and costly. In the category of corrective maintenance, work is performed in phases. Once a failure occurs, the systems must be inducted into maintenance. This could be as easy as a technician coming to the location of the system or the system could require evacuation to a repair facility. Once the system is inducted, troubleshooting begins which may require the removal of components and the requisition of parts. This is followed by the active maintenance phase in which corrective maintenance is performed, reassembly, and quality assurance to ensure the system is operating as expected before being placed back into service. In this basic example of maintenance, time is consumed in terms of minutes, not days and notice the administrative requirements were not mentioned. The same concept holds true for preventive maintenance minus the troubleshooting. With preventive maintenance, a set of standards are established and the technician follows the set routine to ensure preventive measures are taken. The same concept can be applied to a privately owned vehicle. Oil and the oil filter are changed every three to five thousand miles. Tires are rotated, air filters are cleaned or changed, and fluids are capped off. Again, time is the factor with preventive maintenance as well as corrective maintenance. The next factor is concerned with labor hours. While maintenance elapsed time refers to time equipment is in maintenance, labor hours refer to the amount of time dedicated to performing maintenance. In the case of labor maintenance time, there is no quick fix for replacing a starter however in cases where more personnel resources can be applied to reduce the amount of time equipment is in maintenance, it may be beneficial. As Blanchard (2004) explains, “Maintainability is concerned with the ease and economy of the performance of maintenance. Thus, an objective is to obtain the proper balance of elapsed time, labor time, and personnel skills at a minimum maintenance cost” (p. 69). With a financial state of mind, additional resources to reduce maintenance down time may not always be the answer however situation will dictate. Maintenance frequency is a factor that is affected by reliability. Mean Time Between Maintenance (MTBM) is a major element of this factor. The Defense Acquisition University (DAU) defines MTBM as, “A measure of reliability that represents the average time between all maintenance actions, both corrective and preventive” (Mean Time, n.d.). In the realm of MTBM, such factors as induction of equipment, logistics delays, administrative delays, the actual maintenance and quality control are all factors that determine how long equipment will be inoperable. The procedures and policies established in the maintenance frequency factor are very important to ensuring equipment is in and out of the maintenance cycle as soon as possible to production continues. Lastly, cost is a major aspect of maintenance. Maintenance cost is a very important element of total life-cycle cost. Cost factors can be affected during the system design phase where intentions will be to keep maintenance cost to a minimum however there is no escaping maintenance cost. Blanchard (2004, p. 72) indexes cost related to maintenance during the design phase as outlined below:
• Cost per maintenance actions
• Maintenance cost per system operating hour
• Maintenance cost per month
• Maintenance cost per mission
• The ratio of maintenance cost to total life-cycle cost
Availability
Availability, the result of reliability and maintainability can have various meanings such being used to reference system readiness, or the probability a system can accomplish its intended mission. Blanchard (2004) explains, “In any event, the measure of availability should be related to the specific mission on the system; that is, an availability measure should be applied to a specific scenario or series of scenarios” (p. 72). Availability should not be made more complicated than it needs to be. In simple terms and related to a system functions it equates to how often a system is operable. As Gulati (2012) explains of availability, “ever organization wants to be pushing and pulling the levers controlling it, and not vice versa”. Reliability, maintainability and availability are key performance metrics that must be considered in the design of a system. When properly managed, these performance indicators can ensure continuous production and customer satisfaction.

References
Blanchard, B. (2004). Logistics engineering and management. Upper Saddle River, N.J: Pearson Prentice Hall.
Gulati, R. (2012, October 1). Does it pay to design for reliability and maintainability? . . Retrieved May 26, 2014, from http://www.apmadvisor.com/ archivearticle.asp?is=68&ord=3#.U4NOiNhOVMsSpeaks, S. (n.d.). Reliability and MTBF Overview. Retrieved May 14, 2014, from http://www.vicorpower.com/documents/quality/Rel_MTBF.pdf
Defense Acquisition Universtiy. (n.d.). . Retrieved May 26, 2014, from https://dap. dau.mil/glossary/pages/2234.aspx