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Aviation History
1924
1924 - 0568.PDF
SEPTEMBER 11, 1924 REPORT OF THE AERONAUTICAL RESEARCH COMMITTEE, 1923-24 THE Annual Report of the Aeronautical Research Committee was issued recently, and is obtainable from H.M. Stationery Office, Imperial House, Kingsway, London, W.C.2, price 2s. 6d. net. As in previous years, the report contains a summary of the work done and progress made during the last twelve months, and in a short supplement to the report certain subjects are gone into rather more fully than in the report itself. Aerodynamics In the commencement of the report it is pointed out that owing to the wide field of inquiry it is essential to concen trate on certain lines of research. Thus in the case of aero dynamics the report states that " attention has been paid chiefly to the control and stability of aeroplanes to the part exclusion of other work : this concentration on the attempt to secure low speed control is justified by the continued occurrence of accidents in which spinning is a primary or secondary feature ; in the near future more attention will be paid to questions affecting performance, including the use of high lift and high speed wings." On this subject it is stated that " the general research on complete models at the N.P.L., aiming at the determination of their stability characteristics, has been continued through out the past year. The ordinarv range of experiments has been extended to include angles of incidence considerably above the stalling angle, with a vie.v to the investigation of control at low speeds. To obtain more directlv comparisons between the model and the aeroplane, a special investigator has been appointed, under the direction of Frof. B. M. Jones, to calculate the initial movements of an aeroplane under a variety of conditions. An interim report of the first three months' work on this subject is now under discussion. Tabu lations of data relating to the stability and control of different types of machines has also been undertaken for the Committee by the Airworthiness Department of the Air Ministry." Concerning the light aeroplane development the report says :—" The new and important development of the light aeroplane is welcomed by the Committee as providing a possible avenue for rapid and relatively inexpensive trial of new characteristics of certain types of control. In this con nection the Stability and Control Panel held a special meeting which the pilots of the various machines flown last October at Lympne were invited to attend. It became immediately evident that the pilots had had only a limited experience, frequently on but one type of light aeroplane, and it was. therefore, difficult to co-ordinate the experience gained. It is understood that in order to overcome this drawback five aeroplanes, selected by the Air Ministry from the successful types, have been ordered and allocated to the R.A.E. and Martlesham, for the accumulation of flying experience on them. It is of interest to note that pilots with their limited experience were generally of the opinion that light aeroplanes were much more comfortable for flying in indifferent weather than the ordinary higher-powered aeroplane." Airships. In view of the revival of an airship policy the following reference to airships is of interest:— " The Committee have on several occasions emphasised the importance of work on airships, and welcome the recent decision to return to the development of this type of aircraft. In their last annual report attention was drawn to the inadequacy of our present knowledge and the necessity, if design is to progress satisfactorily, for further full scale experiments on the aerodynamic forces which may be en countered and the structural problems involved. It is hoped that these experiments will be undertaken in connection with any large scale construction which is approved." Accidents. A considerable amount of space is devoted to the subject of the investigation and prevention of accidents, and the report states that : " The Committee note with pleasure that the Air Council agree with them in their 'view that the problem under con sideration can only be solved satisfactorily and finally by securing a higher standard of technical knowledge in all ranks of the Royal Air Force and particularly among squadron officers. They welcome the steps which have been taken by the organisation of courses at Cambridge and at the I mperial College with this object, and they desire to co-operate with the Ministry in every endeavour towards this end. But a general raising of the standard of technical knowledge must take time. Meanwhile accidents which, in the view of the Committee, are primarily due to the absence of this knowledge, continue to occur. Manv machines are destroyed, while in some instances lives are lost; the Committee have felt it to be within their province to urge any steps that might reduce such losses. It is impossible at once to secure the necessary knowledge in the case of all officers. They hope it will not be impossible to provide for highly-skilled persons to make a correct technical diagnosis of each power plant failure immediatelv it occurs, and to report it in a manner which will enable the Ministry to take measures to prevent recurrence. In cases of difficulty the Ministry will, it is hoped, place the Sub-Committee in direct contact with the original sources of information, with a view to special investigation. By means such as these, the technical maintenance would be improved at least up to the standard of the Civil Transport Aircraft, and the general standard of technical knowledge would be raised. The Committee trust that the steps now being taken may lead to this desired end. " Intimately connected with the same problem of prevention of accident is an investigation into the cause of incipient spinning in aeroplanes. Serious accidents in the majority of cases are due to one of three causes, some of which follow engine failure. The causes are (1) stall followed by nose dive, (2) stall followed by incipient spin, and (3) stall followed by a spin from which no recovery is made. The two latter are frequently present in designs of aeroplanes which show a particularly ready response to the movement of the controls. The peculiarities in design which lead to (3) arc not adequately known, and the subject presents features which will involve length - investigation. This investigation is now started in connection with two as yet unexplained accidents on different types of aeroplanes." Concerning the accident to the Bristol monoplane flown by the late Major Foot in the Grosvenor Cup race in June of 1923, the report of the Accidents Investigation Sub- Committee recalls that when the machine was approaching the village of Ottershaw, flying probably at over 120 m.p.h. and at a height of 800-1,000 ft., the port plane was seen to fold back. The pilot was killed instantly, and the wreckage was almost destroyed by fire. The following statement on the probable cause is of general interest, and is therefore given in full :— " While, owing to the destruction of the wreckage by fire, and to other causes, much evidence of significance may have been lost, an important clue to the cause of this accident was found in the form of a fatigue fracture in the port front landing wire fitting at the wing end. The other landing wire, the rear one, had broken by a manifestly tensile fracture ; all the flying wires were intact. Further, about 200 yards from the main wreckage, a piece, about 2 ft. long, of the bottom flange of the front port spar was found, indicating that the spar had broken in the air along the web to the root of the wing. " From the above and other evidence the Sub-Committee were led to the conclusion that the accident was due to breakage of the port wing under down load caused probably by a convection current in the air. The weather conditions on the occasion in question were such that vigorous convection currents were probable up to the height of about 2,000 ft., so that a change from an up current of, say, 5 ft./sec. to a down current of similar magnitude would not be improbable. Such a change, it was found, would at the small angle of incidence in question easily account for a down load which would explain the breakage in the special circumstances. " With relation to this monoplane accident, attention is drawn to the fact that in monoplanes of the braced type, as distinct from biplanes, it is frequently found that no provision is made for the duplication of the anti-lift wires upon which depends the strength of the wings under down load ; and in order effectively to carry out design to meet the conditions imposed by the presence of convection currents in the air it is necessary to have means of measuring the magnitude of these currents at various heights. Recommendations have been made that steps be taken to gain this information, and that the load factors necessary to give adequate pro vision against down load for machines of different types, should be investigated." 568
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