66

Airplane Characteristics." by Frederick Bedell. Price $1.60 net. (Ithaca, N. Y.: Taylor and Co., 1918.)

The publication of this volume of only 74 pages of text may be explained by the following statement in the preface: "Any contribution to aviation, however small, needs to-day no justification." In fairness to the author it should be stated that in addition to the five chapters published, eight are in preparation. Under the circumstances, however, the price at which the book is retailed seems somewhat high.

The book is concerned solely with the theory of flight. Consideration of materials and power plant is rigidly excluded. The subject-matter is very well presented, each principle being discussed in a separate chapter. The five here published deal with Sustentation, Relations in Flight, Resistance, Lateral and Directional Stability. The following chapters are in preparation: Thrust, Power, Climbing, Gliding, Altitude, Single and Multiple Planes, Longitudinal Stability and Stability in General.

In is interesting to compare the first chapter of this book with the opening chapter of the "Aviator's Elementary Handbook" previously reviewed. In the latter the French system of measuring efficiency of a wing section by the percentage of drift to lift is used. Here, on the other hand, the more usual method of comparing wings by the quotient of lift drift is adopted. As explained in the text, this is more convenient than the French method, as the values of D/L approach infinity when L approaches zero. It is to be hoped that a common standard will be adopted after the war, as at present a good deal of unnecessary labor in conversion is required before the Eiffel, R. A. F., and U. S. A. wings can be intelligently compared.

In the second chapter the following important rule is given: "Velocity equals the square root of loading divided by square root of coefficient of

=

W
SK1

where V

lift." This may be expressed as follows: V = velocity, W = weight, S wing area and K1 = coefficient of lift. It is emphasized that the loading (weight per unit area of wing) affects V rather than the total weight or area, and that the only way of changing the speed of a machine or of getting different speeds in different machines is by changing the loading or the lift coefficient. Power has no direct effect on velocity, it merely determines whether the machine climbs, glides, or flies horizontally. Many text-books justly dwell on this simple rule. In Duchêne's "Flight Without Formula" it is the very first one given.

Chapter Three considers the question of Resistance, dividing it into two parts: Wing and Parasite. They are considered separately, as wing resistance (or drift) first decreases as velocity is increased, until a certain speed is reached after which it increases; whereas parasite resistance varies approximately directly as the square of the velocity. Charts are given showing the wing resistance with velocity for different conditions of weight and loading. In the section devoted to parasite resistance the importance of streamlining is discussed. It is stated that of the total parasite resistance of an aeroplane, one-third is contributed by the body, one-third by the wires and struts, and one-third by the tail and landing gear.

The last two chapters are given over to a discussion of Lateral and Directional Stability. The point is made that "wash-in" and "wash-out (progressive increase and decrease of incidence from body to wing tips) used on some British and German aeroplanes to correct for propeller torque tends to make the machine spin when diving with power off and should be avoided.

The book closes with several appendices, including a glossary of aviation terms approved by the National Advisory Committee for Aeronautics, and charts of thrust and power characteristics presumably to be used in conjunction with the chapters in preparation on these subjects.

J. J. I.

NOTICE TO MEMBERS

Attention is invited to extracts from the constitution on the opposite page as to the requirements in making applications for life, regular and associate membership.

191

Dear Sir:

The U. S. Naval Institute was established in 1873, having for its object the advancement of professional and scientific knowledge in the Navy. It is now in its forty-sixth year of existence, trusting as heretofore for its support to the officers and friends of the Navy. The members of the Board of Control cordially invite the co-operation and aid of their brother officers and others interested in the Navy, in furtherance of the aims of the Institute, by the contribution of papers and communications upon subjects of interest to the naval profession, as well as by personal support and influence. On the subject of membership the Constitution reads as follows:

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ARTICLE X

Sec. 2. One copy of the PROCEEDINGS, when published, shall be furnished to each regular and associate member (in return for dues paid), to each life member (in return for life membership fee paid), to honorary members, to each corresponding society of the Institute, and to such libraries and periodicals as may be determined upon by the Board of Control.

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