AN important application of the science of Meteorology to Aviation is inconnection with the provision of accurate data for navigation This aspect of thesubject involves a knowledge of what may be termed “windstructure,” that is, the horizontal variation of wind with place andtime, and the variation with height within the atmospheric layer in which flyingnormally takes place

In discussing the variation of wind with height it is desirable first to assume astandard of reference The wind near the surface of the ground is of little usein this respect since it is subject to many local variations The most convenientstandard is the undisturbed wind in the lowest layer which is free fromfluctuations caused by the upward propagation of disturbances from the surfaceof the earth

The Chairman It is my pleasing duty to-night to introduce Captain Tymms, whom youall know very well I cannot think of anyone who is better qualified to read thispaper than Captain Tymms, as not only is he a practical aviator, but he is alsoa member of the Air Survey Committee, who are the recognised authority on airsurvey matters in the British Empire

We are also very fortunate in having another member of the Air Survey Committeepresent in the person of Captain McCaw, the Secretary

I have received letters from Colonel Edwards, Colonel Crosthwait and WingCommander Laws regretting their inability to be present to-night

I now have much pleasure in calling upon Captain Tymms to read his paper CaptTYMMS Flying for air photography is essentially a matter of navigation If“navi-gation,” by its root, means no more than the moving of aship, it has come to imply the moving of a ship with precision to the placedesired

The surest way of improving the design of aircraft structures appears to be by anextension of the “team spirit,” whereby the experience andknowledge of everyone engaged in the craft are pooled and focussed on anyproblem requiring solution

For instance, when a pilot flies a machine he discovers its good and bad points,and, knowingly or unknowingly, compares it instinctively with every othermachine he has flown On returning to earth he naturally communicates his opinionto others In the course of time his views reach the ears of the designer, who,also, naturally adapts the design to meet any criticism The ultimate result isthat the experience of every pilot, and not only of every pilot, but ofeverybody dealing with the aeroplane, is gradually pooled for the purpose ofimproving the design

It is to be noted that it is usually extremely difficult or impossible tointerpretate this experience mathematically, because there are too many unknownfactors operating

THE CHAIRMAN Mr Sidney Arthur Main, B Sc, is a distinguished engineer andscientist He takes a prominent part in the Research Laboratories of MessrsHadfields, Ltd, Sheffield With Sir Robert Hadfield he was joint author of thepaper on “Shock Tests and their Standardisation,” read before theInstitution of Civil Engineers in 1921, and for this paper that Institutionawarded him the “James Watt” Gold Medal

During recent years general interest in Heat-Resisting Steels has grownconsiderably, and there is a wide field for their application in aeronauticalengineering However, little has been published with regard to the more complexnoncorrodible and non-scaling steels, and it is a matter of satisfaction thatthis Institution has been able to secure a paper on the subject by such aneminent collaborator of Sir Robert Hadfield, as the present lecturer

I now have much pleasure in calling upon Mr Main to deliver his paper

IN introducing the lecturer, Dr Thurston said Professor Lea is a distinguishedengineer and professor of engineering, very well known both in aeronautics andin the world of general engineering He is a Whitworth Scholar, the first, or oneof the first Doctors of Science (Engineering) in the University of London, andthe author of many valuable researches During the war he was responsible formany researches of great value to the nation, not only in the design ofaeroplanes as a whole, but also in construction of metal parts and fittingsProfessor Lea’s activities have been so numerous that it is difficult togive a brief summary of his life work in a few sentences, but we may be sure ofthis—that the paper which he will give us to-night will add to hisalready great reputation, and at the same time be a most valuable contributionto our own Proceedings I now have pleasure in calling upon Professor Lea to readus his paper

I have attempted in the following paper to deal with the commercial aspect of airsurveying from my own personal experience. The technical side of the work I willnot attempt to go into fully, as there are others who are better able to dealwith that aspect than I am. As air surveying has been developed in this countryentirely by private enterprise unassisted by subsidies, it may be of interestbriefly to review its development to date.

Early Work.

One of the few benefits that we derived from the War was the development ofaerial photography to a stage where it could be of great value for explorationand mapping work in the Empire. The authorities responsible to the Governmentfor the development of civil aviation in this country and the Empire failed torealise this, and it was left to private enterprise to develop that side ofcivil aviation, the Authorities concentrating their efforts on the developmentof air transport.

IN introducing the Lecturer, Colonel Moore-Brabazon said that Mr von Baumhauerwas a distinguished aeronautical engineer and scientist in his own country, andthat the Institution felt very grateful to him for coming over for the specialpurpose of giving aeronautical people in England some information regarding hiswork and its results The Chairman then called upon Mr von Baumhauer to deliverhis paper

Mr A G VON BAUMHAUER We want progress in aviation because we are convinced thatefficient air traffic will give interesting and useful new possibilities

Wind channel tests have shown that wings can be made with a lift-drag ratio offar more than 20, and that streamline-bodies may have a resistance which at highspeed is so small for a body of the cross section of modern transport machinesthat the lift drag ratio of the whole could still be over 20(eg, at a speed of 160 m p h ) So it would seem quitesimple to build efficient aeroplanes

But it is not really so simple

IN approaching any problem in Aerodynamics the student, and the severely practical engineer, whose academic knowledge may be limited, are too frequently confronted with two difficulties The first of these is that though the literature on the subject is extensive, yet the information sought usually has to be collected from a number of sources and the second is that when found the information is frequently presented in such a manner as to be of little immediate practical value without a certain amount of simplification

The object of this paper is to collate and present in an immediately useful form the information contained in parts of the following publications