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Aviation History
1931
1931 - 0917.PDF
August 28, 1931 Supplement to FLIGHT EMGINlSECTION Edited by C. M. POULSEN August 28, 1931 CONTENTS Correction of Aeroplane Performance to Standard Atmosphere (Density Basis). By Clifford W. Tinson, F.R.Ae.S., M.I.Ae.E. .. 57 Forces on the Engine Mounting of a Spinning Aircraft. By D. Williams, B.Sc, A.M.I.Mcch.E. .. 59 Technical Literature .. . . . . . . .. .. .. . . 61 CORRECTION OF AEROPLANE PERFORMANCE TO STANDARD ATMOSPHERE (DENSITY BASIS). % CLIFFORD W. TINSON, F.R.Ae.S., M.I.Ae.E. (Concluded from page 55) CLIMB TIMES, NORMALLY ASPIRATED ENGINE. Taking the normally aspirated engine, and assuming in the first place that the reduction of rate of climb is regular throughout, the trial rate of climb line is drawn and the time to any chosen altitude A, is calculated from the formula : — T = 2-303 log where T = Time in min. to altitude A, ; C,= Rate of climb at altitude Alf ft./min.; C,= Rate of climb at ground level, ft./min. If Aj is the altitude at which Ci is the climbing rate, and A, is the altitude at which Ca is the climbing rate (ground level in this case), then reduction of climbing rate —- ft. per mm. per ft.A,-A. The absolute ceiling is given by H_ = A, + ^ ft. EXAMPLE. Climbing rate, ground level, C2 = 1,645 f.p.m. Climbing rate, at 17,000 ft., d = 440 f.p.m. Altitude chosen, A,, = 17,000 ft. Reduction in Climbing Rate— r_ 0,-Ci Ai — [A.t • From R. & M., No.il316. _ 1,645—440 ~~ 17,000 0 = 0-0709 ft. per min. per ft. Time to Altitude A,- 2-303 /1645\ = 0-0709 °8 \ 440 ) = 18-62 min. Ceiling, Absolute = 17,000+, 440^ 0709 = 23,200 ft. After adjusting the rate of climb time until the time to altitude chosen agrees with the climb time, check the times to some other altitudes of which one or more is near the ground, in order to ensure that the general inclination of the rate of climb line is correct. CLIMB TIMES, SUPERCHARGED ENGINE. In the case of the supercharged engine, commence by assuming that the rate of climb is represented by two straight lines joining at the supercharged limit as described above. The time to climb from zero height up to the super- charge limit will be:— *(C,+ C,) where T, = Time to altitude As in min.; A, = Altitude of supercharge limit, ft.; Ca = Rate of climb at ground level, ft./min.; C« = Rate of climb at altitude of supercharge limit, ft. per min. Above the altitude As, the times to be added to T, will be: — 2-303 , /I where T, = Time to climb from altitude A, to altitude A,, in min. ; 862a
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