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Aviation History
1917
1917 - 0763.PDF
JULY 26, 1917. ADVISORY COMMITTEE FOR AERONAUTICS. ANNUAL REPORT. THE following is the full text of the report of the Advisory Committee for Aeronautics for the year 1916-17, which was issued last Saturday :— The experimental investigations carried out under the control of the Advisory Committee for Aeronautics into the many problems affecting the development of aircraft have been continued and extended during the past year. Some additions to, and changes in, the personnel of the Committee have been made. Dr. Dugald Clerk was appointed a member in June, 1916. Mr. Henry Fowler became a member on taking up the post of Superintendent of the Royal Aircraft Factory. Commodore Murray F. Sueter has lately retired from membership, after serving for seven years, on receiving a new appointment, and has been succeeded by Commodore Godfrey Paine. General Pitcher, Controller of the Technical Department of the Air Board, has recently been nominated an additional member of the Committee. Owing to the growth of the work of the Committee in certain directions, Sub-Committees have been formed to advise in regard to special matters. An Internal Combustion Engine Sub-Committee has been appointed under the chair- manship of Dr. Dugald Clerk; Mr. Fowler is acting as chairman of a Light Alloys Sub-Committee. Other Sub- Committees have been constituted from time to time to investigate particular problems. Many changes and developments in the design and con- struction of aircraft have taken place as the result of the continued and varied experience gained from their use in warfare under modern conditions. An increasing number of special problems is thus constantly presented for investiga- tion, and these have very closely occupied throughout the year the attention of the staffs engaged in experimental work both at the National Physical Laboratory and at the Royal Aircraft Factory. In addition to aeordynamical research, much attention has been given to questions relating to engines, materials of construction, strength of construction and design, instruments and accessories, as well as to methods of attack from aircraft, and other matters. Equipment for Experimental Work at the National Physical Laboratory.—Reference was made in the report for last year to the additional equipment provided for experimental work. The wind channels now available comprise two 7-ft. channels, two 4-ft. and one 3-ft. The new 7-ft. channel was completed and brought into use early in the year 1916-17. No important departure has been made in its design from that of the earlier 7-ft. channel, but some minor modifications have been introduced which experience had indicated as tending to greater convenience in working. An air speed of 85 ft. per second can be reached in this channel with an expenditure of 160 h.p. It is doubtful whether further increase in size of channel or in speed of air current would advance existing knowledge to an extent sufficient to outweigh the greatly increased cost and other disadvantages involved. If it should prove necessary, for certain purposes, to conduct experiments on a larger scale and at higher speeds, it would appear, therefore, to be necessary to employ a method in which the model is moved through the air. As is well known, this procedure presents various difficulties, and the securing of even moderately accurate data in this manner is, at the best, extremely laborious. Probably the least troublesome way of applying this method is by installing measuring apparatus on the aeroplane itself, and it seems probable that only in this way can an accurate comparison be obtained between model and full-scale conditions. The matter is of importance, and attention is being given, so far as existing circumstances permit, to the devising of suitable measuring 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 general greatest in measurements on forms of small head resistance, e.g., aeroplane bodies and airship envelopes. Earlier measurements on airskip models of stream-line shape were made to determine 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 satisfactory 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 consideration of questions on which experiment has been in progress. Fliers 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 experi- ments 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 enquiries proceeding from the service departments, but pro- gress has been made with some investigations 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 investiga- tions relating to airscrews have been carried out, with a view to increasing the accuracy of prediction of performance, and thus facilitating the design of airscrews for special purposes. Tests on screws to be used as windmills for the production of power have also been made. The work has included a com- plete series of ,tests on more than nne complete aeroplane model. The information thus derived is of considerable importance for practical purposes in aeroplane design. Strength of Construction.—A number of questions relating to strength of construction have been investigated, and some general conclusions have been reached tending to simplifica- tion of strength calculations. The basis to be adopted in design to secure adequate strength in high speed machines, with the power of rapid manoeuvring essential in aerial fighting, is a matter demanding the most careful consideration. 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 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 manufacturing firms whose works have been visited. An extensive series of experiments on radiators has been carried out at the National Physical Laboratory, and other investigations relative to' the transfer of heat from surfaces to fluids flowing over them are in progress. These have an immediate bearing on the design of the cooling systems in aeroplane engines. Experiments relating to the performance and efficiency of magnetos have also been made. Light Alloys.—The use of light alloys in the construction 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 manufacture 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 experimental investigation and manufacturing experi- ence. Experimental work has been carried out for the Sub-Committee at the Royal Aircraft factory, the University
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