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Aviation History
1932
1932 - 0826.PDF
FLIGHT, AUGUST 19, 1932 and work was taken in hand at once to bring together representatives of the Mother Country and the Dominions. The task was none too easy, partly on account of the great distances which separate the Dominions from London, and partly because opera tional conditions in many of the Dominions are so very different from those at home. However, largely due to the energy and enthusiasm of the late Air Commodore F. Vesey Holt, who was at that time Director of Technical Development at the Air Ministry, a committee was formed, and technical representatives from the Dominions were summoned to London, where work was commenced. In the meantime, there had been flying accidents in which structural failure had occurred, and after most thorough investigations it was concluded that unusually violent air disturbances must have been the primary cause. Machines flying at fairly high speed and suddenly encountering rising and falling air currents of high velocity are subjected to stresses which may attain magnitudes which were not con templated when the present system of load factors was drawn up. In this connection it is of interest to record that experiments made on an aircraft fitted with special instruments such as accelerometers, etc., indicated that even in the British Isles it is possible to meet ascending or descending air currents of high velocity. Accelerometer readings showed that stresses as high as 3g or even a little more could be induced in steady flight. The Dominions, although, generally speaking, willing to accept the British system of airworthiness, might be more liable to troubles from gusts than we at home, and their representatives, not unnaturally, were a little doubtful concerning the entire adequacy of British load factors in certain cases. Canada in particular had been accustomed to having load factors as high as 8 or even 12 quoted by American firms, and although fully appreciating the very high quality of British workmanship, was inclined to press for an increase. In the early part of ihis year, under the title the Civil Airworthiness Committee, a permanent committee was formed, composed of representatives of the Government (i.e., the Air Ministry), the Society of British Aircraft Constructors, the insur ance companies, and the operational concerns, such as Imperial Airways, the flying clubs, etc. When the Ottawa conference was planned, and aviation included in the agenda, it became obvious that before the broader questions could be discussed there, that of an Empire system of airworthiness for civil aircraft would have to be settled, at least in principle. By dint of extremely hard work on the part of everyone concerned, the numerous problems were attacked and promising solutions found. Although we would not claim that complete agreement has been reached on matters of minute detail, the broad outlines of an Imperial system of airworthiness regu lations have been drafted. Details of the new airworthiness system have not been disclosed, but it is generally known in the air craft industry that we shall have to make up our minds to agree to higher load factors. Although it seems almost inevitable that these will necessarily result in some increase in structure weight, it is not thought that such increase will be really serious, and we presume that allowances will be made in other respects, which will help to make up for any loss in useful load which the higher factors may incur. For example, under the present system of granting certificates of airworthiness, more than one machine has been well up to the stipulated load factors, but has fallen somewhat short in the matter of height attained in a given run. When it is remembered that many an aircraft is, once it has left the con structor's works and is quite beyond his control, habitually overloaded during its regular operation, it is almost impossible that anomalies should not exist, and the present take-off regulations may need modification. Apart from a probable increase in load factors, it seems likely that a " gust " clause will be inserted in the new Imperial system of airworthiness regula tions. The Dominions are almost certain to press for this, and in our own interests it may well be advisable to agree to it. What exact figure will be used we do not know, but it seems likely that gusts of 25 ft. per sec. may have to be catered for, and probably with a load factor of 2 or so on top of that. This would appear to be a minimum, judging from the experiments in which loads of 3g or more indicate gusts of even greater strength than 25 ft. per sec. We have still some way to go before a new set of regulations can be made effective, but the subject is one of very great importance to the British aircraft industry, and although members of the S.B.A.C. and other interested bodies have, of course, full knowledge of the work that has been done, the dis cussions which have taken place and the arguments put forward, we have felt that the aviation-minded general public has known little or nothing of it. The effects of an Imperial system of airworthiness regu lations may be very far-reaching, and to such firms as do not cater particularly for the Dominions it is possible that the new system may impose certain unwelcome handicaps. It may, of course, be that individual firms will have the option of retaining the present regulations should they so wish. In the great majority of cases, however, we believe that a uniform system of airworthiness will, even if there is an occasional grumble, be to the general benefit of the industry. An increase in load factors looks at first sight like something of a hardship on the constructor, but, on the other hand, higher figures than ours have for years been quoted against British civil aircraft, and although one may treat them with a certain amount of mistrust as mere " paper figures," there is little doubt that they have had a certain effect. If, by a well-thought-out system of regulations, we can quote as high figures as the foreigner, the fact will not be without its value as a selling point.
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