Abstract PREFACE TO THE FOURTH EDITION The wide use of the first three editions of the book, both by the general public and by schools and colleges, has indicated to the authors that their hope of meeting a definite need in aeronautical literature has been fulfilled. Like its predecessors, this edition is intended primarily for the reader who desires a sound knowledge of the basic principles and a broad view of the present development of the airplane and its power plant, without giving to the...