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Aviation History
1940
1940 - 1854.PDF
SUPPLEMENT TO FLIGHT 28 THE AIRCRAFT ENGINEER JUNE 27, 1940 it is necessary to introduce the pitch angle, or more precisely the angle (<f> + y) in standard terminology (see figure), at the typical section, representative of the blade as a whole, which it is found satisfactory to take at 70 per cent, of the blade radius in accordance with the usual practice. , The actual working of the method is as follows. The torque Q, in terms of the brake-horse-power (P) and propeller revolutions per minute (N), is given by Q = 33,000 P -4- 2irN = 5,250 P/N (ft.-lb.) or 63,000 P/N (in.-lb.) The axis bending moment, Mo = Q -^ wsin (<f> + y) where n is the number of blades. This follows from a Simple resolution of the torque into its components. At any other section of the blade the bending moment M=/Mo where the value of the factor / is found to be as given in the following table, and in the figure. Fraction of blade radius from axis(»-/R) .. .. 0.2 0.3 0.4 0.5 0.6 0.7 ioS Factor/ .. .. .715 .572 .430 .300 .190 .105 .043 Apart from the horse-power and revolutions, the only data required for the application of the method is the value of the angle (<f> + y) at the typical section. This will usually be known, if this section has been analysed as a preliminary to aerodynamic analysis of the blade as a whole. Alternatively, if an estimate of the efficiency of the screw can be made for the given working conditions (pitch setting and advance constant, J = V/ND, -for a variable-pitch propeller) the value of (<£ -\-y) can be deduced, since the screw efficiency, • r, = J.-=- 7r(r/R)tan(* + y) = J 4-2.2 tan (<f, +y) on putting (r/R), the fractional radius at the typical section, equal to 0.7. Hence tan (<f> +y) = J -f- 2.2 r? and the value of the angle (<j> + y) and sin (<j> + y) follows. LOOKING FORWARD (CONCLUDED FROM PACE 56 6) ness and air navigation regulations of the constituent coun- tries could be reduced to a single code adhered to by all, and that the vast labour of research could be shared between them. Civil Survival in Wartime 1 have tried in this paper to define the goal to aim at, with little reference to the effect of war; I have given a peacetime plan. Until we reach that happy time I realise with sorrow that we must be content with a much more modest scheme. What should be our minimum pro- gramme? Primarily, I suggest, the preservation of our civil aviation in such a form that at the end of the war we can expand it rapidly. We should first decide upon the organisation best fitted to direct civil "aviation after the war. With some diffidence I submit this paper as pre- iiminary notes on which a detailed study might be based. Having decided upon the organisation, I suggest that it should be brought into being hr skeleton form so that the various branches may be instructed in their duties when the war ends. I would hope that the important duty of "keeping the airworthiness regulations up to date could be resumed and- the problems of civil safety studied again. A small staff should be adapting the results of military research to the solution of civil problems. We should aim at the main- tenance of our routes in Africa and the East, and at the re-establishment of the Atlantic route. Close consideration should be given to the establishment of the London- Bathurst-Port Natal route, the first leg of which, to Lisbon, has recently been inaugurated. Extensions of our civil activities in the Balkan countries would also appear advan- tageous. [Dr. Cox's lecture was written and delivered before some of the more recent events of the war.—ED.] We must plan for replacement of our existing airliners, and to have some up-to-date civil types at the end of the war. I suggest that we should work on : 1. A small airliner for the internal airways of Great Britain and similar lines in the Empire. 2. A larger airliner of 30,000 lb. for European routes. 3. A transatlantic craft suitable for adaptation to Empire routes, 4. The conversion of a fast bomber into a mail plane. The conversion of the first three to military types should also be immediately considered. The reduction of our military effort would be trivial, and the military effort is* not the only one we have to make. We must maintain our communications not only because t we shall want them after the war, but for the better prosecution of economic warfare and for the main- tenance of our commercial prestige. Interference with industrial man-power would be minimised by the conver- sion basis suggested. If we do not follow some such plan as this, we shall have again to buy foreign machines to keep our airlines alive. There is also a very difficult post-war problem which must be tackled. When the war ends the productive capacity of the Empire's aeroplane factories may be tens of thousands of aeroplanes per year ; at the end of the last war the figure was approximately 40,000. This order of magnitude is altogether different from that of the pos- sible civil production required. In 1938 in Great Britain fewer than 400 civil aeroplanes, mostly small ones, were built, -and at- the end of that year only about 1,400 air- worthy aeroplanes were on the register. Even the vastly greater American civil industry only produced 3,715 aero- planes, of which 3,122 were one- or two-seaters, in 1939. There can, therefore, be no hope of utilising more than a small fraction of our productive capacity after the war for civil work. : . , Summary I have tried in this paper to define the aims of British civil aviation and I have suggested, among other things, that: ' 1. We need to develop and extend our routes, using British aircraft only on them. 2. We should develop foreign markets. 3. Our operations require new and advanced' aircraft, including large fast transatlantic and fast mail aeroplanes. 4. There is a great deal of work to be done to improve safety. 5. Civil accident investigation should cover a wider field. 6. Design needs stimulation and encouragement. 7. The staff for civil research and development has a vast programme ahead and needs large augmentation, with a special establishment for civil technical investigations. 8. Engines specially designed for civil work are needed. 9. A special staff for economic studies should be estab- lished. 10. A closely knit organisation should control civil avia- tion, regarding it as an Imperial and not a national matter. As this programme cannot be pursued in full in war- time, I have suggested that: 1. We should plan our organisation and maintain it in skeleton form so that it can rapidly be expanded. 2. We should, within limits, extend our routes. 3. We should pursue a modest civil design and construc- tion programme. 4. The civil designs should be converted to military types and both versions constructed. 5. Military research should be studied in its applica- tion to civil problems. 6. Civil airworthiness regulations should be kept up to date. 7. The reduction after the war of the expanded industry to normal peacetime needs should be considered.
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