Page:Aerial Flight - Volume 2 - Aerodonetics - Frederick Lanchester - 1908.djvu/14

viii Chapter I. is an introductory account of the general principles concerned in the equilibrium and stability of an aerodone in flight, illustrated by actual examples, including an account of the author's earlier experiments.

Chapters II. and III. consist of an analytical investigation of the flight path on a basis restricted by a hypothesis excluding the influence of the size and moment of inertia of the aerodone, and assuming resistance to flight to be either absent or accounted for by an equal and opposite force of propulsion. This investigation culminates with the plotting of the flight path from the equation (as given in the frontispiece), and includes a discussion of certain special cases, notably that of the flight path or phugoid of small amplitude. This investigation is the foundation of the greater part of the subsequent work, where it is frequently referred to under the title of the Phugoid Theory; it constitutes the key to the quantitative study of longitudinal stability, and to the solution of many kindred problems in free flight.

Chapter IV. is devoted to the discussion of some of the more immediate and self-evident consequences of the Phugoid Theory, including the preliminary consideration of the influence of wind fluctuations both as isolated gusts and as possessing a definite periodicity.

Chapter V. deals with an important extension of the Phugoid Theory, by which account is taken of influences excluded by the initial hypothesis, i.e., resistance and moment of inertia. In this chapter the theory is brought to a point at which it becomes of very great value as bearing on the correct proportioning of an aerodone or aerodrome; the investigation culminates in an equation, the equation of stability, by which the conditions of the permanence of the flight path are clearly defined.

Chapter VI. is an account of the experimental verification of the previous work (Chapters II., III., and V.). This account comprises a brief résumé of observations by earlier writers as confirmatory of the Phugoid Theory, a series of experiments