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Aviation History
1935
1935 - 0247.PDF
JANUARY 31, 1935- THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT 1260 so the maximum gross revenue per flight will be earned rhen the weight of revenue load -+- fuel divided by twice the fuel consumption per mile, say, is numerically eaual to the distance flown. Let us substitute this value for L in the first equation. KW2 K#W2 R R = "ZX 4.r <\x* which expresses the maximum gross revenue which can be earned by any aeroplane on any one flight on the basis given. The effect of fuel consumption will be noticed. The importance, commercially, of reducing the drag to a minimum is a matter which seems to have been first realised by the Americans, and is the principal lesson to be learnt from such machines as the Douglas. This aero plane is probably not an ideal type for use on our Empire Air Routes, whatever may be the case ior the transconti nental route for which it was designed, but it does represent a very definite and successful attempt to reduce the drag of an aeroplane to a minimum as far as our present know ledge will allow, and this is an example which we should copy whatever the proposed speed may be of the aeroplanes we intend to use on our own routes. SOME USEFUL NOMOGRAMS By NORMAN SYKES, B.Sc, A.F.R.Ae.S. THE nomogram is a very handy instrument for con necting a number of variables. By now its use is becoming fairly general, but there are still those who prefer the slide rule for every fresh problem. Some times, however, the slide rule has been mislaid, or the fundamental formula has been forgotten, and reference must then be made to a text book before the work can proceed. In such cases the nomogram is extremely handy, and it is thought that the following four will find ready application in many drawing offices. They have been prepared by Mr. Sykes in the course of his work in the Technical Department of A. V. Roe & Co., Ltd., where they have been found very useful. It is likely that most readers will be quite familiar with the use of a nomogram, but for the benefit of any who may be in doubt, the simplest is that connecting wing loading, lift coefficient and airspeed. The fundamental formula is, of course, L (Lift) = W (Weight) = 0.002378 po-k,. SY*. where p is the density of the air, o- the relative density at height, kL the lift coefficient, S the wing area in sq. ft., and OJ Ib/sq Fr 40j 30- 20- 18 16 15 • 14 • 13 • 12 • II j 10 • 9 • 8 7 • 6 • 5 - 4 • 3 2 -J • • V# m.p.h. kL T-280 -, - . -260 -240 -220 -200 - 180 -160 -140 -120 -lOO ' 30 • 80 - 70 60 - - 50 * -40 -50 ' -25 ' -20 - 18 • 16 L 14 J M0 - II •12 - 13 -14 - 15 . - 20 - 22 24 •26 •28 - 30 -40 -50 -•60 -•70 •80 -SO -10 - II -1-2 1-3 1-4 1-5 <-2-0 Nomogram connecting indicated air speed, wing loading and «u The formula is: V\/o = i^\/^j\/'h.. At sea level soel?'0 T* therefore VV° is true air speed. Best climbing speed and most economic cruising speed occur at ki = 0.33 approx. Sp Feet- ^ m.p.h. Ref: 4000-r 3000:- 2000 1500 + 1000 900 800 700 600 500- 400-- 300-- 200 150 + 100 90- 80-- 70-- 60- 50 + 40-1- 100- - 90- 80-: 70- GO 50-- 40-: 30-- 25-- 20 line (Vs-Vu))m.p.h. Sm feeC T40 -HO --15 -20 --25 5.7 ••40 -•50 Connect inner and outer pairs via their intersection with fief: line -50 --60 -70 -80 --90 -100 150 200 300 •^400 500 600 700 800 SCO 1000 1500 --2000 •^-3000 --4000 is where Sw is take-off run in wind Nomogram for wind correction of take-off run. The formula Sw _ /Vs -Vw\ I.85, s0 - \ vs ; of speed Vw m.p.h. S0 = take-off run in still air, and Vs — take-off speed in m.p.h.
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