viii AUTHOR'S PREFACE 



In case any process given in Part II. is difficult to follow, 

 reference should be made to Part III., which consists of numerical 

 examples worked out at length. Doubt as to the validity of 

 any formula in Part II. can readily be dispersed by reference 

 to Part I., which contains the mathematical proofs. 



Students, however, would be better advised to study Part I. 

 very carefully, before using other sections, in order to obtain a 

 clear idea of the theory upon which the later work is based. 



The last chapter of the book contains complete performance 

 calculations for one machine ; this shows the application of the 

 methods better than do individual examples, and, moreover, gives 

 an idea of the amount of work usually involved in a complete 

 set of calculations. It also indicates the order in which these 

 calculations generally have to be taken in practice. 



As far as is feasible and reasonable the technical terms and 

 symbols laid down by the Royal Aeronautical Society in their 

 Glossary have been employed. An exception is the use of the 

 term "propeller" instead of " airscrew," following the lead of 

 Mr. H. C. Watts. Other exceptions are chiefly due to the fact 

 that the Glossary does not cover nearly all the ground of the 

 present book. 



Acknowledgments are due to Messrs. Harold Bolas, H. C. 

 Watts, and G. E. Petty for permission to make use of their work ; 

 as for the numerous test results, of which use has been made, 

 these form part of the great debt owed by the Aeronautical 

 Engineer to the National Physical Laboratory. The Author 

 also wishes to take this opportunity of tendering his grateful 

 thanks to Mr. G. E. Petty for the invaluable assistance he has 

 given by verifying the whole of the mathematical arid numerical 

 work. 



It is hoped that few errors exist in the book, but an indica- 

 tion of necessary corrections or suggestions for improvement in 

 any future edition would be welcomed. 



HARRIS BOOTH. 



LONDON, March, 1921. 



