WITHOUT POWER SB A K8 o 7" Loom is PILOT'S VIEW WHEN TAKING OFF AT ELMIRA FLIGHT WITHOUT POWER The Art of Gliding and Soaring By LEWIN B. BARRINGER Glider Specialist, Air Staff Headquarters of the Army Air Forces PITMAN PUBLISHING CORPORATION NEW YORK CHICAGO COPYRIGHT, 1940 BY PITMAN PUBLISHING CORPORATION All rights reserved. No part of tfiis book may be reproduced in any form without the written permission of the publisher. Revised Edition, 1942 Reprinted, Sept. 1942 Reprinted, Apr. 1943 ASSOCIATED COM TAN IKS SIR ISAAC PITMAN & SONS, LTD. Bath • London • Melbourne • Johannesburg • Singapore SIR ISAAC PITMAN & SONS (CANADA), LTD. 381-383 Church Street, Toronto Advisory Editor PROFESSOR ALEXANDER KI.EMIN DANIEL GUGGENHEIM SCHOOL OF AERONAIJIICS COLLEGE OF ENGINEERING, NEW YORK UNIVERSITY PRINTED IN Till', UNlll'.D SI A IKS OF AMERICA DEDICATED TO THE MEMORY OF Warren E. Eaton whose unselfish leadership did so much to promote gliding and soaring in the United States. FOREWORD During the two years after my first taste of motorlcss flying in 1930, I operated the Wings Gliding School near Philadelphia which trained over sixty students largely by methods that my associates and I had to devise due to lack of any adequate book or manual on the subject. Following my introduction to high performance soaring by my friend Richard du Pont in the summer of 1934, I frequently encountered conditions and had experiences in flight the correct explanation of which also could not be found in any book yet published. Many times during the two years as editor of Soaring and man­ ager of The Soaring Society of America I felt an increasing need for an up-to-date, authoritative book covering all phases of motor- less flying. Although several excellent books have been written, soaring technique and sailplane design have advanced so rapidly in recent years that these are now inadequate. An indication of this progress is the fact that while making several thousand flights at Wings Field some years ago we never suspected possibilities of soar­ ing over this field which is situated in level country. Now the mem­ bers of a soaring club are being taught not only how to win their "C" licenses but also how to go on to high performance soaring on thermal upcurrents in this same part of the country. From being restricted to a few isolated sites in the mountains, soaring can now be done from large fields situated nearly anywhere in the country. So it was that when approached to write this book I well knew the great need for such a work but also realized that to be truly authoritative certain chapters should be written by recognized ex­ perts in their particular fields. I wish to express my appreciation for the invaluable co-operation of my co-authors. H. Randers-Pehrson is a recognized authority in the historical field and a member of the staff of the Division of Aeronautics of the Library of Congress, Washington, D. C. Paul and Ernest Schweizer of Elmira, N. Y., are leading glider designers and builders who pioneered all-metal construction in this field. Karl O. Lange, an eminent meteor­ ologist connected with the Blue Hill Meteorological Observatory of Harvard University, is also a former soaring pilot, Contest vii viii FOREWORD Director for The Soaring Society of America and designer of one of the first successful radio-meteorgraphs. Charles O. Colvin is a well-known expert in the field of aircraft instruments. In expressing my thanks and gratitude to those who have assisted me I wish particularly to mention Milton Stoughton for his initial work on the aerodynamics of gliding flight; Fred C. Barnes, John Robinson, Gilbert Walters, Gustave Scheurer, and Amos Wood for their information on the soaring sites at Tejon Ranch, Torrey Pines Mesa, Altamount Pass, Schley Field, and Steptoe Butte, re­ spectively; Jay Buxton for help on technical details of launching methods used in California; A. Ivanoff, British "Silver C" pilot, for his suggestion that English data and statistics be included; The Soaring Society of America for permission to reprint certain passages published in Soaring; and all those who helped so much by supply­ ing photographs for illustrations. It is my sincere hope that this book may help to promote the soaring movement. LEWIN B. BARRINGER Llewellyn Park Orange, N. J. FOREWORD TO THE REVISED EDITION Increased public interest in motorless flight has exhausted the first edition of this book. In this revised edition we have eliminated three chapters: Soaring Sites, Clubs, and the Future of Gliding and Soaring. A new chapter on Transport Gliders has been added and a revised list of gliding clubs and schools is now in the Appendix. My gratitude and thanks are extended to August Raspet, physicist with the U. S. Geological Survey, for the valuable, new material on variometers, the explosive release and the aid to auto-pulley launch­ ing. The remaining chapters are largely unchanged except for a few additional items of value brought out by recent experience. All the information necessary for the student of motorless flight is in this edition. In the foreword to the first edition the hope was expressed that the book might help promote the soaring movement. I now express the more serious and important hope that this edition will help motorless flying to take its proper place in the national effort to make us supreme in the air for the defense of democracy. LEWIN B. BARRINGER Washington, D. C. CONTENTS PAGE FOREWORD ............... vii FOREWORD TO THE REVISED EDITION ........ viii CHAPTER I HISTORY OF MOTORLESS FLIGHT, by N. H. Randers- Pehrson ............. i II AERODYNAMICS, by Paul Schweizer, Assisted by Milton Stoughton and Ernest Schweizer ...... 15 III TYPES OF GLIDERS, by Lewin B. Barringer .... 33 IV DESIGN, CONSTRUCTION AND MAINTENANCE, by Paul and Ernest Schweizer ........... 40 V LAUNCHING METHODS, by Lewin B. Barringer ... 84 VI SOARING METEOROLOGY, by Karl O. Lange . ...in VII INSTRUMENTS, by Charles H. Colvin and August Raspet 145 VIII FLIGHT TRAINING, by Lewin B. Barringer . 164 IX SOARING TECHNIQUE, by Lewin B. Barringer . 175 X TRANSPORT GLIDERS, by Lewin B. Barringer . 196 APPENDIX. Gliding and Soaring Licenses—Records—Lists of "Silver C" and "Golden C" Pilots-Gliding Clubs and Schools in the United States—British Gliding Clubs . 201 BIBLIOGRAPHY ..............216 GLOSSARY ................ 217 INDEX ................ 219 ix CHAPTER I HISTORY OF MOTORLESS FLIGHT By N. H. Randers-Pehrson I HE EARLY HISTORY OF AVIATION is a history of failures and frustrations because, not realizing the possibilities of gliding and soaring, men tried to fly by muscular power and spent their time and ingenuity on futile wing-flapping devices. Later when this method had been discredited, practical progress was retarded by the false belief that an engine is indispensable for human flight. The foundation for scientific study of aviation was laid by Sir George Cayley who in the beginning of the nineteenth century made the first attempts to explain mathematically the principles of flight. He also experimented with glider models, and built a large machine which, although provided with some kind of propelling mechanism, was tried in gliding flight. When launched from a hill­ top without a pilot, it would sail with perfect balance to the plain below, and when a person ran with it against the wind, it would sometimes carry him a few yards. Probably Cayley had the knowl­ edge and ability to build and operate a man-carrying glider, but unfortunately he had his mind set upon the need for an engine and so missed the opportunity of becoming the father of motorless flight. He was followed by a number of gifted and enthusiastic workers, mostly in England and France, who made valuable theo­ retical contributions but achieved no practical results because they also were striving for power flight. Among the few who favored motorless flight was Captain Le Bris, a French sailor who used the albatross as a pattern for a glider. With this he was towed into the air like a kite in 1855, and again with a second Albatross in 1867, but mishaps and lack of funds brought the experiments to an end. Le Bris' glider had streamline form and a large aspect ratio; the angle of incidence of the wings could be varied in flight. There was also Louis Pierre Mouillard, a Frenchman who lived in Algeria and who spent all his spare time studying those masters of soaring flight, the great vultures. Mouillard described his observations in a book entitled L'Empire de I'Air, a work which furnished much inspiration to others, but his own attempts to make wings for glid­ ing were crude and ineffectual. 2 FLIGHT WITHOUT POWER Otto Lilienthal was the first man to learn the art of flight from the birds, to practice the art himself, and to give it to humanity. From boyhood he and his brother Gustav watched the birds, espe­ cially the storks, so abundant near their home in Pomerania. After years of study and aerodynamic experiments he produced the best treatise on the theory of flight that had yet appeared. The next step was to learn to fly. Lack of a suitable engine had been a stumbling block for other inventors, but Lilienthal concluded that an engine was not necessary or even desirable for pioneer flying. In 1891 he made his first glider of peeled willow rods covered with waxed fabric; it was shaped like a pair of broad bird's wings and had fixed horizontal and vertical tail surfaces. During the next five years he built several hang gliders, both monoplanes and biplanes. To oper­ ate these, the pilot stood in the middle of the apparatus, thrusting his arms through padded openings in the frame, so that the weight in flight rested on his elbows.