INTRODUCTION: SYSTEMS ENGINEERING ACROSS THE SYSTEM LIFE CYCLE Modern engineered systems arise in response to the needs of society or because of new opportunities offered by the advancement of technology, or both. The evolution of a particular new system, from the moment its need is recognized and a feasible technical approach identified, through its development and introduction into operational use, is a complex endeavor, which will be referred to as a development process of the system. This chapter is dedicated to describing the process of developing a basic system and how systems engineering is applied at each stage of this process. A typical core system development has the following characteristics: • It is a complex endeavor. • Satisfies an important user need. It usually takes several years to complete.• It is composed of many interconnected tasks.• It involves several disciplines.• It is usually performed by several organizations.• It has a specific program and budget.The development and introduction to the use of a complex system inherently requires increasingly larger resource commitments as it progresses from concept to engineering, manufacturing, and operational use. Furthermore, the introduction of new technologies inevitably involves risks, which must be identified and resolved as soon as possible. These factors require that system development be conducted in a phased manner, in which the success of each step is demonstrated and the basis for the next validated, before the decision to proceed to the next step is made. SYSTEM LIFE CYCLE The term "system life" is commonly used to refer to the gradual evolution of a new system from concept to development and... halfway through the document... to the operational phase includes the provision of a logistical support system and training programs for operators and maintenance personnel. This planning should have a lot of participation from systems engineering. There are always unexpected problems that arise after the system becomes operational that need to be recognized and included in logistics and training systems. Very often, the equipment needed for training and maintenance is itself an important component of the system to be provided. CONCLUSION A formal review at the end of each phase allows maximum management control. This approach creates impressive system documentation. Formal documentation ensures that system requirements can be traced back to stated business needs. It produces many intermediate products that can be examined to see if they meet user needs and comply with standards.