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Aviation History
1917
1917 - 0612.PDF
Equipment Officer under the Air Board with the rank of Lieutenant. His place on the stafl has been taken by Mr. Frazer. ^Equipment.—The new wind channels, 4 and 7 ft. in diameter respectively, which were reported to be almost complete at the close of the last annual period, have been in continuous use for almost the whole of the current year. In both it has been found possibly to obtain air speeds of 80 ft. per second with the more powerful motors installed, and the steadiness of the current is quite satisfactory when the supply is steady. In the early months difficulties were experienced from very sudden changes in the frequency of the supply voltage to the Laboratory, which caused much inconvenience. The steadi- ness has since been greatly improved by the supply com- pany, and the electrical plant rendered suitable for accurate work by careful attention to the voltage regulator installed in the generator room of the Division. In the evenings the control so obtained is sufficient to render unnecessary con- tinuous ..hand regulation of the air speed during an experi- ment. • The channels and balances of the new equipment were care- fully set up independently of results obtained in the older channels. The speed standard was, as before, the standard National Physical Laboratory anemometer calibrated on the whirling arm to the nearest o-i per cent, on velocity. After setting up in this way, a standard wing section was tested, and the results were found to agree with those in the earlier channels. The same accuracy of agreement was found in a comparison made by the Massachusetts Institute of Tech- nology and by the Royal Aircraft Factory, who followed National Physical Laboratory methods. The absolute accuracy of the methods appears to be established as of a high order. • New methods of test have been developed during the year in order to deal with new requests; the difficulty of the experiments called for is steadily increasing, and greater complexity in the models has made it important to consider new methods of holding, them, so as to get the necessary mechanical strength without undue aerodynamical effects, which may be large unless the utmost caution is ob- served. It is believed that the new methods have now been estab- lished beyond the experimental stage, and will form part of the accumulated experience of the Division. Experiments on Airship Models.—Much work on the resistance and stability of airships has been carried out during the year, both on the non-rigid and rigid types. The results when applied in practice have proved to be very valuable, having led to the economy of time which follows from the success of the first, attempt. Work on screens for the shielding of airships has .also received considerable attention. Tne structure of eddies is very complex, but methods have been devised whereby the necessary observations and records can be made. The more advanced results of the investigation are now becoming available and will shortly reach the stage at which a report can be made on the motion of the air in the neighbourhood of an airship shed and screen. Further investigations have been carried out oa the equili- brium of kite balloons in direct connection with their use on the full scale, and modifications have been indicated which are now commonly adopted. Experiments on Models of Aeroplane Wings.—The work on aerofoils has covered the usual field, which includes work on new sections, the effect of combinations of planes and, in particular during this year, the aerodynamic properties of triplanes. Deformations of wing form due to the sagging of the fabric have been reproduced on a model and the variation of wing characteristics dependent on such deformations has been determined. Experiments on complete Models of Aeroplanes and Sea- planes.—The results in the seven foot channels have proved that the increased scale and speeds made available do not lead to appreciably different results from those obtained in the smaller channels. The advantages of a larger section of channel are considerable in dealing with complete model aeroplanes as the mechanical accuracy of construction can be carried to further length. The number of tests on complete models has again been considerable, and recently two very accurate and complete models have been constructed, one at the National Physical Laboratory, and the other at the Royal Aircraft Factory, on JUNE 21, 1917. which work will continue for comparison with full scale observation of stability and performance. The results so obtained are also useful for the calculation of the motion of an aeroplane when manoeuvring or when looping, conditions in which the aerodynamical conditions react direetly on the stress problems connected with aero- nautics. General methods of dealing with the strengths of aeroplanes and propellers come up for consideration from time to time and where necessary the calculations are supple- mented by additional experiments directed towards the deter- mination of the forces acting. The conditions of flight are continually changing and are accompanied by fresh problems requiring solution. Test on Aeroplane Bodies.—The experiments under this head refer more particularly to the body as forming part of the whole aeroplane structure. The conditions of shape are fixed partly by aerodynamical considerations but on the whole more by the size of engine employed. The increase of resist- ance of the body due to the slip stream from the propeller is important, and for both pusher and tractor types has been made the subject of direct experiment. Stability.—In this section very little new ground has been broken, but the applications and detailed analysis have received much attention. Some work has been carried out on the stability of kites and kite balloons in addition to that on airships which, has already been referred to. Propellers.—A number of propellers have been tested during the year, mostly in a wind channel, but occasionally on the whirling arm. The subject of the airflow round a propeller has been investigated from the point of view of design, and the investigation has led to an addition to the theory of design' which is expected to ensure greater certainty in producing a propeller which is suitable for a special purpose. The work has given an explanation of a large part of the empirical design factors which have been used in the past. The theory in its new form has a direct bearing on the problem of the helicopter, and shows reason for large errors in applying the older methods of calculation to the problem of direct lift. Special Investigations.—During the year an analysis has been made of the performance of aeroplanes as measured by tests on the full scale. Tne conclusions reached are of very direct practical application, and it is hoped that they will lead to improved performance by directing attention to the salient features of importance in the design of a modern aeroplane. Calculations have been made of the trajectories of aerial bombs, and the experiments on radiators have been continued. Alloys Research.—To a large extent, the work on aluminium alloys, which has been carried on thrqughout the year with the greatest possible energy, has been devoted to the imme- diate practical requirements of aircraft construction- A very large amount of work has been carried out and a long list of reports on a number of points of first-rate importance has been submitted, in the first place to the Advisory Committee on Aeronautics and to the various Admiralty and Army authorities concerned with aircraft construction. More recently the Advisory Committee on Aeronautics has formed a Sub-Committee to deal with light alloys, and on this Sub- committee the Laboratory is represented by the Superin- tendent of this Department. The work 01 this Sub-Committee is already making itself felt in a considerable increase in the amount and urgency of the work required of the Department in connection with light alloys. At the same time it is gratify- ing to find that a considerable number of these results, thanks to the -activity of the Suls-Committee and the representatives of the Air Board upon it, are finding immediate translation into practice. The work of the Department in this connection may, therefore, reasonably claim to have assisted to a material extent in the development of the very marked improvements, particularly in aeronautical engines, which have been achieved during recent months. During the year there has also been a marked revival in connection with those aspects of work on light alloys which have been carried on under the auspices of the Alloys Research Committee of the Institution of Mechanical Engineers. Much of this work overlaps and interlocks with the work required for immediate aircraft purposes, but, thanks to the grants from the Alloys Research Committee of the Institution of Mechanical Engineers, and, through them, from the Indus- trial Research Department, it has been possible to investigate a number of matters of broad and fundamental interest in connection with the whole question of aluminium alloys and their future use and development. Boelcke's Vanquisher in New York, Capt. Boelcke, the crack German airman, has assumed charge A MESSAGE from New York states that Capt. Bonnell, of recruiting for the British aviation service. It is stated an American flying officer, who is credited with having killed that 843 men were enlisted in the first week. 6l2
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