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24         U. S. AIR SERVICES        November, 1931

Review by
Bradley Jones
PRINCIPLES OF FLIGHT (by E.A. Stalker
--The Ronald Press)

THE sub-title of this book is "A College Text on Aeronautical Engineering" and the author states that the book is intended primarily for engineering students and for practicing engineers who wish to review some of the elements of modern theoretical developments. It is asserted that a knowledge of calculus will suffice and it is assumed that the reader has completed a course in elementary aerodynamics. 
    In writing any textbook for advanced students, an author is always confronted with the problem of how much knowledge he should assume that the reader has absorbed in his previous preliminary tutelage. In reading Principles of Flight, one is confronted on several occasions with statements which are used as bases for the development of the author's argument. The reader encountering these basic statements without any explanatory aids for the first time, will probably experience a guilty feeling that in his previous studies he has, in some way, missed some elementary concept with which every other aeronautical engineer is perfectly familiar. When he reads on however, he will find the cause of his puzzlement explained with meticulous detail several pages later. 
    In his chapters on airflow theory, it is to be doubted if all the mathematical manipulations can be followed by a reader lacking a background of more advanced mathematics than integral calculus. This does not necessarily detract from the value of his expositions unless one intends to check most rigorously each step in his deductions. Even a typo at calculus might perhaps fail to see the need of assuming infinite pressure on page 41. 
    While English people are alleged to speak the same language as Americans, their technical nomenclature is slightly at variance with ours. The author having an intensive and intimate acquaintance with English aeronautical literature can be pardoned for using the English term airscrew, the reader without effort will translate it to propeller, or with less elegance to "prop" More confusing is his use of "angle of incidence: in the English sense; I. e. meaning angle of attack. To an American reader, incidence angle has a different meaning. 
    In the first eleven chapters, the forces on an airfoil are treated from both the theoretical and experimental standpoint. A number of concepts of hydrodynamics, such as the stream function, the velocity potential, circulation, vortices, sources and sinks are explained in a clear manner. In addition a number of excellent figures from the reports of the British Aeronautical Research committee and our own N.A.C.A. have been introduced to illustrate certain important facts concerning airfoils which are unknown to most aeronautical engineers. In Chapter 12, the propeller (alias airscrew) and the autogiro are treated in a brief but clear manner.
     The rest of the book is devoted to the subjects of performance, controllability, static stability, dynamic stability, and spinning. The author has wisely inserted a chapter on classical dynamics as an introduction to the chapters on dynamic stability and spinning. In this part of the book also an extensive use has been made of figures and data from the reports of the N.A.C.A. and the British Aeronautical Research Committee to illustrate the subject matter of the text. 

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AIR NAVIGATION—By Lieut.-Comdr. P. V. H. Weems, U.S.N.—McGraw Hill Book Company—Price $5.

THIS book is a very complete treatise of Air Navigation in all its phases. In it the author has covered the entire field of the theory and practice of air navigation in a manner which is interesting as well as instructive. The volume is evidently intended for use as a textbook and it should bee an exceedingly valuable reference for all experienced aviators as well as a basic text for aviation students. 
    The chapters which are of major interest to the average pilot in connection with his routine day by day flying, are those dealing with the aircraft compass, the theory and practice of dead reckoning air navigation. The chapters on dead reckoning are alone worth the price of the book and the ground speed, drift and "off course" tables contained therein are sufficiently complete to fit almost any conceivable wind and flight conditions. 
    With the exception of long distacne over water flights the average pilot will have little opportunity or necessity for the use of celestial air navigation, but as Commander Weems points out, a full knowledge of all methods of air navigation is essential and the pilot who is thoroughly familiar with all phases of the subject increases his own capabilities to a surprising degree. 
     For the overseas flyer a study of celestial navigation as set forth in this book will supply him with the essential knowledge required for finding positions by means of the heavenly bodies. The use of pre-computed altitudes of celestial bodies will be a new thought to many aviators, but its utility as a means of checking one's position on a predetermined course will be apparent after brief consideration. The star altitude curves supply a very quick method of fixing one's position at night through the use of several well known navigational stars. These star curves have certain disadvantages which Commander Weems carefully points out. 
The inclusion of chapters dealing with theoretical and applied aerology is particularly meritorious and these chapters contain a great deal of valuable weather information. 
    While some of the reference information contained in this volume is already available from various other sources in a scattered form, the author has in this book placed all of the essentials between two covers, thereby saving the reader or the student much time and effort. The book is well worth its cost and any aviator, experienced or otherwise, will derive benefit form its use. 


ICARUS
(Andrée)

Dead in the glacial, polar north, 
He spread his wings again
Through all the dim, obscuring years
To thrill the hearts of men.

For long he lay there, cold and star, 
Casqued in a frosty white, 
But neither broken wings nor lives
Discredit . . . flight

Lefa Morse Eddy

volume is evidently intended for use as a textbook and it should be an exceedingly valuable reference for all experienced aviators as well as a basic text for aviation students.
The chapters which are of major interest to the average pilot in connection with his routine day by day flying, are those dealing with the aircraft compass, the theory and practice of dead reckoning are alone worth the price of the book and the ground speed, drift and "off course" tables contained therein are sufficiently complete to fit almost any conceivable wind and flight conditions. 
With the exception of long distance over water flights the average pilot will have little opportunity or necessity for the use of celestial air navigation, but as Commander Weems points out, a full knowledge of all methods of air navigation is essential and the pilot who is thoroughly familiar with all the phases of the subject increases his own capabilities to a surprising degree. 
For the overseas flyer a study of celestial navigation as set forth in this book will supply him with the essential knowledge required for finding positions by means of the heavenly bodies. The use of pre-computed altitudes of celestial bodies will be a new thought to many aviators, but its utility as a means of checking one's position on a predetermined course will be apparent after brief consideration. The star altitude curves supply a very quick method of fixing one's position at night through the use of several well known navigational stars. These star curves have certain disadvantages which Commander Weems carefully points out. 
The inclusion of chapters dealing with theoretical and applied aerology is particularly meritorious and these chapters contain a great deal of valuable weather information. 
While some of the reference information contained in this volume is already available from various other sources in a scattered form, the essentials between two covers, thereby saving the reader or the student much time and effort. The book is well worth its cost and any aviator, experienced or otherwise, will derive benefit form its use.