This book is the fourth edition of the ninth textbook in this series dealing with Introduction to Engineering Design.  Jim Dally, working with College House Enterprises and faculty members in the Clark School of Engineering, has prepared eight previous books in this series—a new one almost every academic year—for the first-year engineering students of the University of Maryland at College Park.  Several other Colleges of Engineering have adopted one or more of the books in this series to introduce design and engineering skills for their first or second year students.  The design, build and test of a hovercraft model, described in Book 9, is such an interesting and challenging project that this is the fifth year we have used it (eight previous semesters) with approximately 5,000 students.  The project is also assigned for the first year Introduction to Engineering Design at the University of Nevada @ Reno where it is in its sixth year.