38 



NATURE 



[September 13, 191 7 



accurate comparison be obtained between model and 

 full-scale conditions. The matter is of importance, 

 and attention is being given, so far as existing cir- 

 cumstances permit, to the devising of suitable meas- 

 uring apparatus. 



Improved methods of supporting the models under 

 test in the channel have been devised for use in special 

 cases. The effect on the measured resistance of the 

 method of holding the model is often surprisingly 

 large, and without the necessary care and experience 

 in avoiding effects due to interference with the air- 

 flow, very large errors may result. The difficulty is, 

 of course, in leneral greatest in measurements on 

 forms of small head-resistance, e.g. aeroplane bodies 

 and airship envelopes. Earlier measurements on air- 

 ship models of stream-line shape were made to de- 

 termine the form of least resistance, and were, in 

 the main, comparative ; from the cause mentioned, 

 it is probable that little reliance can be placed on the 

 absolute values then obtained. With the new methods 

 of support the possible error has been greatly reduced, 

 and when full-scale values have been determined with 

 accuracy, the prediction of full-scale resistance from 

 the model experiments will be established on a satis- 

 factory basis. The new method of support is employed 

 also in tests of models of complete aeroplanes. 



Experimental Work in Aerodynamics. — It is not 

 proposed at present to enter in detail into the considera- 

 tion of questions on which experiment has been in 

 progress. Flyers and designers have, of course, given 

 close attention to matters in which improvement would 

 be of value, and this has led to the repetition and 

 re-examination, from a somewhat modified aspect, of 

 many earlier investigations. The experiments have 

 been of very varied character, and have included tests 

 of models of, probably, all types of aircraft at present 

 employed. A large part of the work has arisen from 

 specific inquiries proceeding from the service depart- 

 ments, but progress has been made with some investi- 

 gations of more general character. 



A number of experiments have been carried out 

 relative to the resistance of airship shapes, and further 

 observations on the distribution of pressure in such 

 cases have been made. 



The investigation into the stability of the aeroplane 

 has been continued. A number of special cases have 

 been examined, and results of importance have been 

 reached. The theory of airship stability has also 

 been investigated. 



Research into the nature of the flow of fluids round 

 obstacles has been continued. 



A number of investigations relating to airscrews 

 have been carried out with the view of increasing the 

 accuracy of prediction of performance, and thus 

 facilitating the design of airscrews for special pur- 

 poses. Tests on screws to be used as windmills for 

 the production of power have also been made. 



The work has included a complete series of tests on 

 more than one complete aeroplane model. The in- 

 formation thus derived is ot considerable importance 

 for practical purposes in aeroplane design. 



Strength of Construction. — A number of questions 

 relating to strength of construction have been inves- 

 tigated, and some general conclusions have been 

 reached tending to simplification of strength calcula- 

 tions. The basis to be adopted in design to secure 

 adequate strength in high-speed machines, with the 

 power of rapid manoeuvring essential in aerial fight- 

 ing, i^ a matter demanding the most careful con- 

 sideration. To secure the highest possible speed it 

 is necessary to keep down the weight to a minimum, 

 and the best compromise between these two opposed 

 conditions does not admit of precise determination. 

 This Question has received attention, and the manner 

 in which strength varies with increase of dimensions 

 NO. 2498, VOL. 100] 



has also been made the subject of investigation. 

 Cases in which vibration has been set up have been 

 examined, and calculations relating to the strength of 

 the body structure have been made. 



Engines. — A number of questions relating to engines 

 and engine design have been submitted by the Air 

 Board for consideration by the Engine Sub-Committee. 

 These have required very careful investigation, and 

 the sub-committee has been closely occupied since its 

 formation with the various problems which have 

 arisen. Experimental work has been carried out, by 

 request of the sub-committee, at the Royal Aircraft 

 Factory ; and the sub-committee has received much 

 assistance in the examination of special questions, 

 both from the Royal Aircraft Factory and from manu- 

 facturing firms the works of which have been visited. 



An extensive series of experiments on radiators 

 has been carried out at the National Physical Labora- 

 tory, and other investigations relative to the transfer 

 of heat from surfaces to fluids flowing over them 

 ate in progress. These have an immediate bearing 

 on the design of the cooling systems in aeroplane 

 engines. Experiments relating to the performance 

 and efTiciency of magnetos have also been made. 



Light .Alloys. — The use of light alloys in the con- 

 struction of aircraft and aircraft engines is becoming 

 of rapidly increasing importance, and improvements 

 in the production of light alloys will have great effect 

 on future development. The investigations relating 

 to light alloys which have been in progress for many 

 years at the National Physical Laboratory have been 

 continued, and results- of special interest have been 

 achieved during the past year. Suggestions have been 

 made to the Air Board by the committee which may, 

 it is hoped, help to secure the best conditions in manu- 

 facture for the development of such alloys. The 

 formation of the Light Alloys Sub-Committee will be of 

 great assistance in co-ordinating the work on light 

 alloys which is being done in various quarters, and 

 in collecting the information resulting from experi- 

 mentnl investigation and manufactuting experience. 

 Experimental work ha.^ been carried out for the sub- 

 committee at the Royal Aircraft Factory, the Uni- 

 versity of Birmingham, the National Physical 

 Laborafory, and elsewhere, and arrangements have 

 been made for placing the information obtained at the 

 disposal of manufacturers. 



Fabrics. Dopes, etc. — A number of special questions 

 have arisen for investigation in relation to airship 

 and aeroplane fabrics. A large amount of attention 

 has been given to materials for use as dopes, var- 

 nishes, etc., and the Laboratory has collaborated with 

 the Military Air Department in an investigation into 

 the behaviour of fabrics, dopes, and protective coatings 

 under the conditions of tropical exposure. The results 

 of exposure to ultra-violet radiation have been studied 

 in relation to the effect of sunlight, and conclusions 

 of importance have been reached. The committee is 

 indebted to Dr. Shakespear, of the University of 

 Birmingham, f^or information he has placed before 

 them as to the methods developed by him for deter- 

 mining the permeability of fabrics by hydrogen ; com- 

 parisons have been made with the results obtained 

 at the National Physical Laboratory. Methods of 

 determining the purity of hydrogen have been in- 

 vestigated. 



Investigations Relating io Seaplanes. — Tests on 

 models of seaplane floats in the William Froude 

 National Tank have been continued and extended. 

 The provision made last year for an increase in the 

 staff available for carrying out this work has enabled 

 more rapid advance to be made, and a number of 

 important questions have received attention The 

 methods employed have been improved and elaboratP'^\ 

 and new apparatus has been designed whereby addi- 



