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Aviation History
1951
1951 - 0207.PDF
FLIGHT, 1 February 1951 133 3635 30 H EIGHT 25 20 868i 1000 824- 782 738 695- >652- > :608 564- 521 478 434 391 i ran •••••UUUUH -15 -5 f +5 15 25 35 45 55 65 29 -13 8+5 23 41 59 77 95 113 131 149 AIR TEMPERATURE Deg C -55-54 Deg F-67-65 and T.A.S. Another "Flight" Conversion Table : Math Number to TA.S. at Given Temperature SO well ha^Tllu- fiitiphu of umiuAphGiic'Tactors pub-lished in the September 7th, 1950, issue of Flightbeen received that, in response to many requests, we have devised an addition to the range. This permits a true air speed to be derived from a Mach number at a given air temperature. Mach number is, of course, a direct function of tem- perature, and one of the drawbacks of the LC.A.N. scale is that it has a datum sea-level temperature of but 15 deg C/59 deg F. Whilst not exactly a common occurrence, a seaJevel ambient of 30 deg C (86 deg F) is occasionally experienced even in England, and in such conditions, the T.A.S. equivalent of a given Mach number departs markedly from I.C.A.N. data. In fact, as may be seen from the graph, a Mach number of 0.7 at I.CA.N. sea- level is a T.A.S. of 532 m.p.h., whereas, at a temperature of 30 deg C, the equivalent T.A.S. is 542 m.p.h. To take a further example, a fighter aircraft with a limiting Mach number of, say, 0.95, will be capable of a One air speed of 727 m.p.h. in the normal temperate climate of England—widi which the I.C.A.N. scale is in good agreement—but the same aircraft operating at, say, Karachi or Hong Kong, where the sea-level ambient might well be circa 55 deg C (131 deg F), gains in actual speed no less than 56 m.pJi., for at 55 deg C a Mach number of 0.95 equals 783 nxp.h.
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