Document Type: Book (Technical Reference). Authority: Author Expertise. Purpose: Informational.

Scope: The third edition of a technical monograph written for an educated audience by G. Geoffrey Smith, M.B.E., editor of Flight magazine, the leading aeronautical journal in Great Britain.

From the Editors Note: "ORIGIN OF THIS BOOK It was early in 1941 that the author discussed with Lord Brabazon, then Minister of Aircraft Production, the desirability of reviewing the progress with turbine jet propulsion designs having regard to the fact that engineers of many countries were already carrying out experiments. technical book on the subject, but a great deal of technical material in the form of items had been gathered from various Continental and Scandinavian sources. From these it was evident that the future of the gas turbine was regarded as of considerable importance and promise. Lord Brabazon readily agreed and expressed the view that it would be a useful service to the British engineering world if the designs of this new form of prime mover were discussed but, of course, nothing was to be said of British experiments. The Chief Censor of the Ministry of Information also confirmed that patents publicly issued by the Patent Office could form the subject of reviews as patents of a secret nature are withheld from publication during wartime.

Actually the first public mention of an entirely new form of power unit was made by Lord Brabazon when, as the chief guest, he addressed the Institution of Automobile Engineers at their annual luncheon in June, 1941. Most of his hearers were mystified, not to say sceptical, as the reference was in cryptic terms. This timely hint of the coming of the gas turbine failed to make an impression, although a number of technical journals quoted the speech.

A series of articles by the present writer was commenced in " Flight" of August 28th, 1941, and the rest of the story has been related.

In previous editions, in accordance with the desires of the Minister of Aircraft Production, there could be no emphasis upon British activities-to the chagrin of my patriotic instincts. As a consequence, Continental and Swedish experimental work received undue prominence. In this third and enlarged edition, the fact that Whittle has led the way in the development of the small gas turbine, as Parsons did with the steam turbine, receives due recognition. This historical fact will stand for all time.

Turbine-compressor design is still in an early stage of its development. The potentialities of this lighter and simpler rotary form of prime mover are incalculable at this juncture. In the future, progress will be governed by the success of research by metallurgists in evolving new heat-resisting materials, by physicists, chemists, aerodynamic and thermodynamic specialists and, particularly, development engineers translating theory into practice. Improved heat exchangers and thrust augmentors offer the greatest scope for advancement. The English-speaking races of Britain and America have obtained a big start in this new field of engineering and future development will be assured by their joint enterprise.""

Contents: "EDITOR'S NOTE Aircraft design is progressing at a phenomenal rate. Speed, operational height, rate of climb and load-carrying capacity have all been improved beyond recognition in recent years. So far, engine and airscrew designers have been able to meet requirements, but always the demand is for more power in a single unit, reduced overall dimensions and lighter weight. Practical considerations limiting the size of individual engine cylinders and also the tip speed of airscrew blades can be circumvented by multiplying the number of cylinders and by increasing the number of relatively small airscrew blades by means of counter-rotating tandem designs, but these measures are liable to lead to undue complication. Aircraft propulsion by means of purely rotative units would seem to be both necessary and desirable as the next step. Gas turbine and rotary compressor combinations can be employed either to drive airscrews or to deliver a propulsive jet of air.

Aircraft propulsion by jet reaction is a fascinating and intriguing study. Present-day schemes are far removed from the simple projects of early experimenters, and jet-propelled aircraft have actually been flown without the aid of an airscrew. So much interest and discussion was aroused by articles which appeared in "Flight" from August, 1941, onwards that, as back numbers are unobtainable, a widespread demand is met by publishing the material in book form. These articles on propulsion projects are reprinted in their entirety, together with amendments and additions.

In collaboration with a technical assistant, F. C. Sheffield, whose expert and willing help is gratefully acknowledged, I have devoted much time to a search for information concerning the work that has been accomplished in this country, in Europe and in America. This is the first published work dealing with aircraft propulsion plants employing combustion gas turbines and rotary compressors. Examples of gas turbine units driving orthodox airscrews are included and steam turbines are briefly reviewed.

As far as possible the notes are couched in non-technical terms. At this juncture the survey cannot be completed, since engineering data and working results are not available for publication under wartime conditions. In the view of the author, combustion gas turbines hold great promise as a propulsive unit for aircraft of the future. By comparison with a supercharged four-stroke reciprocating engine, a turbine-compressor plant should materially reduce cost, weight, production time and complication.

ADDENDUM TO THIRD EDITION The foregoing appeared in the early editions of this book, published many months before the official announcement on January 7th, 1944, of the adoption of jet-propelled fighter aircraft by the British Royal Air Force and the U.S. Army Air Corps.

The world is indebted to Group Captain Frank Whittle, C.B.E., R.A.F., for the first practical solution of the problem of aircraft propulsion by thermal jet reaction utilising a gas turbine-compressor unit. His original patent was dated 1930. He spent eleven years developing and perfecting a scheme that had attracted but eluded engineers in many countries. Further important developments may be expected now that British and American technicians have become engaged in research work on the Whittle turbine-compressor unit. Some notes on Frank Whittle's career are included in this new and enlarged edition.

Additions have been made in the form of general observations, a description with original diagrams showing the working cycle of a turbine-compressor unit, new chapters, including "Turbine-Compressor Units," "Jet v. Air-screw" and "Boundary Layer Control," as well as broadcast talks on turbine-compressor motive units generally. Otherwise the chapters remain essentially as previously published, with sundry new designs and added comment, and indicate in unmistakable terms the writer's original confidence in the future prospects of this new form of prime mover."