System Operational Feasibility Great Deal of Time

System Operational Feasibility great deal of time and intellectual resources go into the conceptual design stage of a systems engineering process once a need is clearly defined by the end-user. However, this initial development step is a moot point if the product is not operationally feasible, which means, according to Benjamin Blanchard in his book Systems Engineering and Analysis, "that the system will perform as intended in an effective and efficient manner for as long as necessary."

In order for the systems engineer to determine operational feasibility, it is necessary to properly integrate the design-related specialties such as reliability, maintainability, human factors and supportability.

Reliability is one of the most important design elements, since it confirms or denies the long-term use of the product without major maintenance and repair. Unreliable systems do not meet the original project goals and lead to unnecessary expenditures of valuable resources. Simply stated, "reliability is the probability that a system or product will perform in a satisfactory manner for a given period of time when used under specified operating conditions." The four elements noted -- probability, performance in a satisfactory manner, time and specified operation conditions -- are highly significant when deciding on system or product reliability.

Probability can be defined as the quantitative expression representing a fraction or a percent specifying the number of times that one can expect an event to occur in a total number of trials. For example, if the probability of survival of a product for 150 hours is 80% (or 0.80), the user can expect that it will function correctly for at least 150 hours 80 out of 100 times.

The second factor or element, satisfactory performance, defines what specific criteria need to be established in order to consider the item to be satisfactory. The considerations include both qualitative and quantitative requirements. Time is very important, since it represents how long the product or system will be functioning at desired operational levels. Reliability is often designated in terms of mean time between failure (MTBF) or mean time to failure (MTTF).

Operating conditions include environment such as temperature and humidity, degree of vibration and amount of shock. These conditions are not only while the unit is operational, but also when it is resting in a nonuse or storage mode. Handling conditions, such as the heat of the truck that is transporting the product, can have a major impact on how well the system works.

The other all-important aspect of a product or system's operational feasibility is maintainability. This consists of the ease, accuracy, safety and economy in the performance of the maintenance functions. If a unit is difficult to repair, the costs of a process can get completely out of hand. While the item is not functioning, interrelated processes stop and labor is at a standstill. If a system works well when it is operational, but causes significant downtime, it is not functioning as expected.

Maintainability is inherent in the product design. It is the ability of an item to be maintained, whereas maintenance is the series of actions that must be taken to restore or retain the product in an effective operational manner. Maintainability can also be defined as a characteristic in design that can be expressed in terms of maintenance frequency factors, maintenance times (or elapsed times and labor hours) and maintenance cost.

It can also be defined as a design and installation aspect expressed as the probability that: an item will be retained in or restored to a specified condition within a given period of time; maintenance will not be required more than x times in a given period, when the system is operated in agreement with prescribed procedures; and the maintenance cost for a system will not exceed y dollars per designated period of time, when the system is operated and maintained as designated.