This updated, second edition adds more reviews of modern four-winged aircraft belonging to convertiplanes, Medium Altitude Long Endurance UAVs, and solar planes. As in the first edition, different analytical, numerical, and experimental methods are discussed in detail. The book presents new sections on unsteady aerodynamic characteristics of tandem wings and specifics of their aerodynamic loading for stress analysis and structural design. Also, dependencies between key geometric parameters and aerodynamic characteristics were updated with new studies that helped to understand the physics more deeply and even reinterpret previous experimental results. Accordingly, practical recommendations in development and optimizing of tandem wing aircraft were updated to provide high endurance, wide range of flight velocities, stability, and controllability. This is an ideal book for graduate students, researchers, and engineers working in fields of aerodynamics and conceptual design of the aircraft especially UAVs and light piloted airplanes.