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Aviation History
1924
1924 - 0093.PDF
FEBRUARY 14, 1924 Fig. 6 curves of AL max. ranging from 0 -5 to 0 -9 have been plotted, covering the range of maximum lift coefficients met with in ordinary aerofoils. The next step in the performance estimates outlined by Mr. Chadwick was to calculate, for the machine assumed, the various performance figures, using the curves just described, and then, on the results obtained, to proceed with general arrangement drawings of a machine to fulfil the conditions. This completed the first method. Mr. Chadwick then worked out the performance figures in detail according to the second method, explaining the procedure as he went along. Unfor tunately, we have not the space to follow the lecturer through the somewhat complicated calculations of this method, but it" may be said that the procedure indicated was the usual one, based upon the assumption that it is sufficiently accurate to assume that the total resistance of an aeroplane is equivalent to the sum of the resistances of its component parts. It is, of course, well known that this assumption is not strictly correct, but as the lecturer stated, apart from the third method—of having a complete scale model tested in a wind tunnel—it is the best that can be done with our present knowledge of the subject. As we have already stated, we hope the paper will be published in full by the Institution of Aeronautical Engineers, when it will, we believe, be available to non-members of the Institution. We shall inform our readers as soon as the complete paper has been issued. In the meantime we congratulate Mr. Chadwick on the com pletion of what must have been a very arduous task, and one involving a very great amount of work. Especially do we thank Mr. Chadwick for having placed at the disposal of all interested the results of his long experience in work of this kind, which has enabled him to get out figures of weight and resistance of numerous components and to plot curves of averages which, if used with discretion and common sense, should enable almost any draughtsman to produce aeroplane performance estimates of quite a good order of accuracy. apoo PERFORMANCE DATA CLIMB CHART. 1600 £00 BOO I 400 E5D00 THE3E CURVES APPLY TO NORMAL WAR SERVICE MACHINES. AND ALLOWANCE5 MOST BE MADE WHEM -gOOOO MACHINES HAVE ABNORMALLY LARGE BODtEi,. ABNORMAL WING SECTIONS. ETC. teooo 10,000 L 500O? PLANE LOADING X ENGINE LOADING! 1 , ( L_^ . Zl 60 eo too ISO 140 160 i6o aoo RATEOFCLIMB CHART [ FOR NORMAL MACHI! WITH COOP CARBUEATtoN o • zoo 600 looo i.-»oo i.eoo RATE OF CLIMB IN FEET PER MINUTE CLIMB CURVES FOR NORMAL. MACHINES WITH GOOD CARBURATION AT ALL HEICHTS 20 25 30 36 TIME: IN MINUTE8 • SPEED VARIATION CURVE. DATA REQUIRED " / ABSOLUTE CEIUNC IFROM CLIMB CURVES) 1 MAX SPEED LEVEL AT ANT ALTITUDE . in EXAMPLE MACHINE WITH ABSOLUTE CEILING Of le.OOOFI ANOl FROM HQ MAX <M»E£D AT 3EA-LE VEL OF OO M PH JCURVC WE OCT 32 LMSTAJ1CE FRACTION OF SJ ALTITUDE BELOW CEILIMG CEILING SPEEO EQUIVALENT SPEED «g SEA LEVEL IS.OOOFT I 317 MH.PH < 5,000 7,OOOFT I ZS5 JrjS%X0O-6SSMP.M "4 10.000 2.000 Pr I M3 f5iT»SO-16MPH 15000 iLiqooo ui 5,000 I 105 II 115 l-£ 125 1-3 135 14 1-45 FRACTION OF SPEED LEVEL AT ABSOLUTE CEiUNC LANDING SPEEDS RTR VARIOUS PLANE LOADINGS. p/*?-Q-Oq?37 3LUG6 PER CU FT. 5 6 7 8 9 IO II 12 SURFACE LOADING IN LBS/SQ.FT 13 14 AEROPLANE PERFORMANCE ESTIMATES : Fig. 1 giveslcurves for estimating the speed of a normal machine when the wing loading and power loading are known or assumed. From Fig. 2 it is possible to predict the rate of climb and ceiling when the " combined loading," i.e. wing loading multiplied by power loading, is known. Fig. 3 is a •« rate-of-climb-at-altitudes" chart for use when the rate of climb at sea level has been found; while Fig. 4 is a " time-to-altitude" chart. Fig. 5 gives the speed variation at various altitudes when the speed at ground level is known, and Fig. 6 enables the landing speed to be read off when the maximum lift coefficient of the wing section used and the wing loading are known. The figures relate to average machines, and for special types allowances must be made.
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