This is the latest edition - fully revised and updated - of the standard textbook on aerodynamic theory, as applied to model flight. Everything is explained in a concise and practical form for those enthusiasts who appreciate that a better understanding of model behaviour is the sure path to greater success and enjoyment, whether just for fun or in competition. The revisions for this new edition reflect the significant developments in model aircraft during the last few years, and include brand new data: - The chapter on aerofoils has been rewritten to take account of the vast amount of testing carried out recently in the USA by the University of Illinois. - A brand new chapter explains the latest research into the flight of birds and insects and how it is applied to small drones and model-sized surveillance aircraft. - Older wind tunnel test reports all replaced with the latest trials and measurements.