?Unmanned Aircraft Systems? (UAS) was an interesting buzz in aeronautics industry in 1970s; it is a raging storm now. Thanks to the bold and visionary approach of DRDO to technology capability building, India does not suffer from any serious ?technology lag? syndrome in the UAS domain today, even though imports have tended to dominate Indian military procurements in the last decade. There is every indication that this situation will change for the better in favour of Indian systems during the current decade. Major UAS design and development programmes are being taken up by DRDO [Aeronautical Development Establishment (ADE) and others]. Advanced technology development programmes relevant to futuristic concepts of UAVs ranging from UCAV to micro UAV have been taken up by research laboratories including the academia across the country. Indian UAV industry is clearly poised for take-off. It is therefore very timely that this technical compendium of information on design, analysis and testing of UAS is being brought out at this juncture. There is a great deal of information in the public domain on the usage and operational aspects of UAS in recent theatres of combat and civil applications. However, there is not much help available in public domain to someone who would like to view the operational UAV as a product of a system engineering process bringing out alternatives and trade-offs at each phase of the design, development, test and evaluation chain. The need for such a systems approach document on UAS was keenly felt during the technology growth phase of ADE in the last three decades ? especially for the purpose of training new entrants to this exciting technology domain and bringing them up to speed as quickly as possible. I am very happy to note that this publication authored by Shri J Jayaraman and sponsored by DRDO meets this felt need very handsomely. Manned aircraft design and manufacture is, by now, a highly mature process. The fiercely competitive nature of the market ensures very high degree of optimisation in every link of the chain ? from formulation of requirements through product definition, preliminary design, reviews, CAE, prototype integration, and flight testing. The highly interacting stages and complexity of the process demands a Systems Engineering approach to ensure that the broader goals are never lost sight off, even while attending to the minute details. UAVs, on the other hand, are often being built and operationalised using a more ad hoc approach. ?Available? propulsion, navigation and power supply units have been fitted into the best possible aerodynamic and structural configurations. It is unlikely that complex UAS programmes of the future will accept this approach without paying a heavy penalty in the market place. xii A top-down Systems Engineering process will become a technical necessity (might even be mandated) in major programmes. Jayaraman?s effort here addresses this need most competently, by emphasising the advantages of Systems Engineering and by providing detailed guidance through a practical UAV design example.