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Aviation History
1941
1941 - 2245.PDF
SEPTEMBER 25TH, 1941. FLIGHT 201 ICE FORMATION rain with an outside air temperature of about +8 deg. C. on "Cold Air" intake. Carburettor ice forms, and this can be detected by a reduction of boost pressure, or rather, by inability to obtain high boost pressures Inci- dentally, it should be remembered that at small throttle openings ice can form to a serious degree before it starts to reduce boost and therefore to become noticeable. If an exhaust gas analyser is fitted, it gives an early indica- tion of ice formation by showing a richening of mixture. The immediate action in this case is to change over to "Full Hot Air"—which, if the engine is still hot, will soon remove the ice. The second common example of ice formation in the pressure-injection carburettor is the case where the air- craft flies into snow, sleet or hail on "Hot Air" intake, with outside air temperatures between about —5 deg. C. and —20 deg. C. Under these conditions " Hot Air " gives a temperature rise of only about 10 deg. C. to 20 deg. C. plus melting the snow or ice. Thus water enters the car- burettor at a temperature within the — 1 deg. C to +16 deg. C. danger zone, and ice forms. The remedy is to go ever to "Cold Air." To remove the ice which has formed recourse can, if necessary, be made to backfiring (caused by the use of the cut-out and mixture controland/or by the ignition switches), but in cases where the engine is still functioning the ice-will soon disappear due to evapora- tion. In closing, let me repeat the rule: Run on "Cold Air" intake at all times except when in rain or moisture at outside air temperatures of — 1 deg'. C. to +16 deg. C, when " Hot Air " should be used. AMERICA IS BUILDING Aircraft Production Reached 1,854 During August : The Curve is Still Rising THE month of August showed a marked rise in theoutput of military and heavy commercial aircraft inthe United States, a total of 1,854 being constructed. This is 394 greater than the total for July, a very big increase. But judgment of the rate at which American production is increasing cannot be formed on a comparison of two months only, and it is necessary to look back some time. Average monthly production during ^939 of this same class (military and heavy commercial) was only 178, though, including all types of aircraft, the figure was 488 per month. But Lord Beaverbrook's statement in July, 1940, that he had made arrangements with U.S.A. "to put into immediate production aeroplanes for our account up to a total output of 3,000 per month " was evidence that we would, at some time, obtain great help from over the Atlantic. So under the stimulus of great urgency the monthly rate of 178 of 1939 had risen to the total of 799 military and heavy commercial aircraft for the month of December, 1940, a great increase for this first sixteen months of the war. But the monthly total has kept on rising since December of last year, and now has reached the impressive figure of 1,854. How this rise has taken place is shown in our graph, the average for the eight months of this year being 1-347- Naturally, the rate of rise has not been quite constant, and production was almost steady for the four months, April to July. Examination shows that the average rate of increase in the production rate is no per month; that is to saj', in each month no more aeroplanes were made than in the previous month. If this increase is maintained to the end of this year—and there is no reason why it should not be—the rate should then be 2,200 per month. For readers who are interested in watching the rise of ?500 2000 1 21500 o £1000 500 - Monthly totals of mili-tary and heavy com- mercial aircraft builtin U.S.A. this year. In ! 1939 the average wasonly 178 per month. - alii! ml iflflf 0 SJ I 1 JAN FEB MAR APR MAY JUN JUL AU6 SEP OCT NOV DECIS4-I American production, the graph has been prepared in such a way that they can add to it as the figures for the later months are released. If the rate of increase is maintained for still longer, a monthly rate of 3,000 will probably be reached about July 1942, but the arrangement was that we receive about half of this output, not the whole of it. Now, with Russia numbered among the Allies, a certain amount of American production must go to her, for this field of conflict is a most important one, and much of Germany's menace must ba met on Russian soil if she is to be defeated. JET PROPULSION (Continued from p. 192.) As shown in the diagrammatic illustration, the plant is contained in a shell A, having a forward intake and a rear propulsion nozzle, which forms the main air duct. The lower cycle is effected by an axial flow compressor B driven by an axial flow gas turbine C through step-down gearing D. For the higher cycle a compression-ignitione ngine E drives a centrifugal compressor F through gearing G. Of the single rotor, bilateral intake type described •D connection with a Whittle plant in the preceding article, this compressor draws air at the intermediate pressure from the interior of the main duct A and delivers into duct H leading to the nozzle scroll of the turbine C. By intake pipe J, engine charging air is drawn from duct H, and the engine exhaust by pipe K joins the air in duct H to form the working medium for turbine C. The effluent from the turbine is led through duct L to a rearwardly directed auxiliary propulsion nozzle. The possibility is suggested of enhancing the propulsive efficiency by deriving some or all of the air from the boundary layer at or over any part of the structure, and also by utilising the discharged gases to modify or improve aerodynamic effects. As in other schemes, further heat may be added before final expansion by the combustion of additional fuel. This, of course, would be provided to carry temporary overloads. (A further article on this subject will follow.)
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