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Aviation History
1922
1922 - 0423.PDF
JULY 27, 1922 a REPORT OF THE AERONAUTICAL RESEARCH COMMITTEE FOR THE YEAR 1921-22 THE Annual Report of the Aeronautical Research Committee for the year 1921-22 has just been published. As in previous years, the report gives a summary of the work of the past year, although it should not be confused with the technical reports known as Reports and Memoranda, which contain the technical details of the various experiments. The present report refers to the subjects that have been dealt with, but does not go into technical details. The Committee pay a warm tribute to the work done by those who lost their lives in '* R.38," notably Mr. Campbell, * Mr. Pannell and Mr. Duffield, all of whom had been closely connected with the work of the committee, and it is pointed out in the report that experiments were planned which, had they been allowed to take place, would have rendered obvious the danger of fast flight at low altitudes in " R.38." But even without these experiments, it is stated, it would still have been an important safeguard had the committee been put in a position to study the drawings and calculations relating to the design, and it is pointed out that the investi gations into the cause of the accident to " R.38 " have shown how much may be lost by not realising at an early stage that the committee were in a position to give, and had published, advice, since proved to be useful and correct. The Committee, therefore, naturally regret the decision to abandon research with airships, and they have urged the importance of carrying out a quite limited scheme of research with one of the existing ships before she is completely dismantled or otherwise disposed of. In view of these facts, it is not without interest to note that the report states that " The whole of the work supervised by the Aeronautical Research Committee costs about 1 per cent, of the vote for the Royal Air Force and Air Ministry. The money which would have come to this country had " R.38 " been a success would have maintained the research of the Committee in full activity for a period of five years. In another way, it may be stated that, should the work of the Committee lead to a reduction by one of the aeroplanes written off per year as a result of crashes, it would have earned the cost to the Air Ministry of the fees paid to its members." The report further states that in September last they were asked to consider a serious curtailment of the activities of the Aerodynamics Department of the N.P.L., but, as a result of urgent representations, arrangements have since been made for the department to be maintained. Aerodynamics Turning now to the more technical aspects of the report, which are contained in a supplement, the report states that the Aerodynamics Sub-Committee hairnet nine times during the past year, and has dealt with a large number of papers on full scale, and on wind channel experiments. It is stated that a series of international trials on model wings and model airships have been initiated. The models have been carefully constructed to conform to the many methods of test used in the different laboratories, and it is hoped that the results, when finally collected together, will be of material assistance in co-ordinating all wind channel experimental work. At present, as is well known, there is considerable differences in the results obtained in the wind channels of the different countries, and the utilisation of results is thereby hampered. Some time ago it was announced in this journal that in America work is progressing on the construction of a wind channel in which the air is compressed so as to obtain high velues of VL. It is gratifying to find it stated in the report that a channel on somewhat similar lines is contemplated for the N.P.L., although it appears that at present it is only intended to try out the scheme in a i-foot channel, which does not appear to us to be large enough for the purpose. Regarding the question of stability and control, two wind channels at the N.P.L. are now devoted almost exclusively to work on these problems, and it is to be hoped that methods may be discovered for maintaining the lateral control of aeroplanes near the stalling angle. At present this is, perhaps, one of the most serious difficulties, as the majority of machines cannot be landed at their minimum speed, owing to the controls becoming "sloppy" just when they are most needed. From the report, it appears that experi ments are being initiated with machines fitted with ordinary ailerons, with floating inter-plane ailerons, with large rudders, and with a special form of control which gives rise to a yawing moment of reverse sign to that given by ordinary ailerons. On the subject of aeroplane wings a great deal of work has been carried out, and it is interesting to note that the vortex theory of Prandtl and others at the Gottingen labora tory has received considerable attention, and that an analysis has been made at the N.P.L. to establish the soundness, in so far as monoplane aerofoils are concerned, of the Prandtl aerofoil theory. <£j Apart from the problems of control at low speeds, perhaps the subject which interests practical designers most is that of scale effect. For certain fairly normal wing sections the scale effect is not serious, and generally the full-size wing gives greater lift and a better L/D than indicated by model experiments. When it comes to high-lift wings, however, appreciable doubt still appears to exist, and it is interesting to see it stated in the report that for such wings the maximum lift coefficient of the full wing may actually be smaller than that of the model. Not only so, but the gain in maximum lift coefficient obtained by using a high-lift wing may be only about one-half of that indicated by model experiments. With reference to tail planes, the report states that recent experiments on an S.E.5A have shown that with this machine the loss in tail plane efficiency is caused: by wing interference, 5 per cent. ; fuselage, 15 to 20 per cent. ; and gap at the elevator hinge, 15 per cent. It would, therefore, appear that the effect of wing interference may be smaller than generally imagined, and that the shape of the fuselage and the gap between tail plane and elevator are of very considerable importance. Although it should be a relatively simple matter to remedy the latter, it would appear that it might be worth while to experiment with a slotted tail plane of the Handley Page type. If that should be found more effective than the ordinary tail plane and elevators it might be possible materially to reduce the size of tail which is now usually necessary. Internal Combustion Engines The report states that the Engine Sub-Committee have held seven meetings in the past year. Of the work under taken, reference may be made to the research work on detonation, in regard to which continuous progress has been made at the N.P.L. with the programme initiated by Sir Dugald Clerk. A thorough investigation has been made into the effect of turbulence in producing detonation in hydrogen air mixtures, and the research is now being extended to other fuels, including various forms of liquid fuel. General research is being devoted to the use of a number of fuels under varying conditions. The Air Ministry, it is stated, have initiated a considerable programme, part of which will be carried out at the R.A.E., and part by Messrs. Ricardo, Ltd., The experiments will include an investigation into the possibility of obtaining higher economy, the use of fuels in supercharger units, and the possibility of using gases, other than hydrogen, to accelerate the rate of com bustion. It is also hoped to carry out certain engine research work at Universities, and the report states that two Ricardo units for experiment are being supplied, one to Cambridge and one to the Armstrong College, Newcastle. The report , further states that work is proceeding at the R.A.E. on a variety of engines, including the use of heavy oils in Diesel type engines, but that this is not regarded as hopeful on account of the inherent heavy weight of this type of engine. The use of engines in which a stratified charge is employed, first suggested by Mr. Ricardo in a paper read before the Royal Aeronautical Society, and published in full in FLIGHT, gives promise of good fuel economy, and it is satisfactory to find that work on this problem is included in this year's programme. Owing to the great fuel economy which is rendered possible by the use of hydrogen added to ordinary fuel, it is regrettable to find it stated in the report that " owing to the discontinuance of the airship service it has been decided that, since the experiments have no immediate application to heavier-than-air craft, they should be dis continued." As stated in FLIGHT recently, these experiments are now being continued privately by Mr. Ricardo in connection with the Burney airship scheme. The Fire Prevention Sub-Committee, which has met eleven times during the past year, has, it is stated, directed its attention almost entirely to the investigation of fires occurring on crash. It is concluded that the chief danger arises from the contact of inflammable materials with hot parts of the engine, and that the worst offender in this respect is the hot exhaust pipe. The report states that the most promising line of development appears to be the use of separate exhaust 423
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