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Aviation History
1912
1912 - 0814.PDF
RICH f Manriot I Hanriot 2 BleViotTan. ... Bleiiot Soc. ... Avro ... Bristol Mon. 14 Bristol Mon. 15 British Dep. 21 M. Farman ... Fr. Dep. Cody ITI *. 82 79 82 6s 87 in 123 80 46 74 65 E,. 73 81 72 tt 69 81 — 75 58 79 69 et. 70 77 77 68 '*3 78 — 64 68 86 110 E* 99 105 90 90 77 96 96 75 103 89 No. 15. Gliding angle unknown. « = anticipated efficiency calculated from X. £1 = efficiency actually at tained, calculated from TV max. : HP. «( = efficiency on a fuel basis, from TV max. : P + 0, which assumes 1 pint of petrol and oil per hour= 1 h.p. Ej=efficiency if the climb ing power is still in re serve at the maximum flight speed, i.e., TV max. + H.p. : HP. multiplying the gliding By how much the resis- actually obtained, as demonstrated by resistance by the maximum flight speed. tance at maximum speed exceeds the resistance at gliding speed is unknown, but it is certainly not less than that resistance, consequently Ei is an understatement rather than otherwise of the true value. The final column E2 is obtained by adding the power available for climbing, on the assumption that it is still available when the machine is flying its fastest. The object of E2 is to present a figure of merit for combined speed and climbing. In the column e, the efficiency is placed on a uel basis, instead of on an actual power basis, in order to put a premium on economy of fuel and oil consumption, as there is such a wide difference in this respect among aeroplane engines. Where machines like the Bristol, Hanriot and Dep. may be regarded as the standard of overall power efficiency, the economy of the Green engine places the Avro above all the others on a fuel basis, and the Cody with its 120 h.p. Austro-Daimler makes a very good second. In this estimate, oil has been added to petrol, on the assumption that they are of equal importance, and for the sake of convenience in reckoning, one pint of fuel plus oil per hour is assumed to be equivalent to one h.p. It is instructive to observe that the biplanes as a class are not as efficient in their overall design as the monoplanes as a class. It may be remembered that, when first discussing the factor X, I suggested that the limiting value for biplanes might be different from the limiting value for monoplanes. The equivalent question now is whether it is safe to design for as high an efficiency in a biplane as in a monoplane. In a monoplane it is apparently reasonable to anticipate 80 per cent, efficiency or perhaps 82 per cent. In a biplane it looks as if 70 per cent, is about the limit. Among the monoplanes, it is interesting to observe how the Avro has anticipated lightly too much, which was diagnosed last week as being due to SEPTEMBER 7, 1912. having an engine that was not quite powerful enough. The Bristol monoplanes, which were also over designed, primarily need a reduction in dead weight, for reasons also explained last week. _ Among the biplanes, the Farman designs for a very low efficiency which it easily exceeds, but the Cody in designing for 65 per cent, efficiency plays up to it just as the best monoplanes do to their own higher value, and the result has been a performance which for all round excellence has been unexcelled. Adding fuel and oil together, the cost of operation ranges from a little over i%d. a mile (Avroj to just over t,d. a mile, the Cody costing only a little over z\d. a mile. Now these are very remarkable figures. It has probably not occurred to many people that the cost ot operating an aeroplane under this head is anything like so low. Moreover, let us for a moment assume that the aeroplane is on an equality with the motor car in the matter of safety and convenience. What else is there that stands as a charge against the aeroplane that does not equally stand as a charge against the car ? The garage and the hangar cancel one another, for example. The natural depreciation of fittings and fabric is, let us say, comparable with that taking place in eoachwork and uphols'ery. The aeroplane has tyres, but what are they ? Certainly not to be compared in their cost of upkeep, I hope, with those on a motor car. For its extravagance in going virtually up hill all the way, the aeroplane gives the user the compensation of no tyre bill ! it is something, indeed, to be thankful for, and in truth, it just makes all the differ ence in the outlook of the aeroplane from the point of view of utility. True, the engine on an aeroplane is hard worked, but it is not sub ject to sudden acceleration, and aho there is not transmission gear to speak of, nor are there any brakes. There is no reason why the cost price of an aeroplane should not be comparable with the cost price of the car, and with the main outstanding charge of operations already down to l$d., it will be a wonderful thing if the aeroplane does not find an uncommonly useful niche in the world later on. And, remember the speed ; certainly the wind has to be reckoned with, but then the wind may be blowing either way. A machine that will already take you between 60 and 70 miles an hour for no more than it costs to travel first class by rail is not to be ignored in a community where time means money. In the last column of the table, an attempt has been made to equalise the basis of comparison by introducing the factor of speed. The figures given are the cost per mile per hour for a journey of 100 miles at the fastes speed of the machine. Thu«, the Avro travels 100 miles at 62 miles an hour at the rate of 2J3'. per mile per hour. The Hanriot does the same journey at 75 miles an hour at a cost of 4$d. per mile per hour. The Maurice Farman at 55 miles an hour costs 5££ per mile per hour and the big Cody travels for about T,\d. per mile per hour at 72 miles per hour, a very remarkable performance. RANGE OF ACTION. Hanriot I ... Hanriot 2 ... Bieriot Tan. Bleriot Soc. Avro Bristol Mon. 14 Bristol Mon. 15 British Dep. 21 M. Farman Fr. Dep. ... Cody P. O. miles, miles. 408 400 36t 305 252 345 343 421 320 276 315 336 406 295 340 840 3*8 420 590 266 379 740 O + P. •98 I '12 •97 i-35 2-42 •95 i-oo 1-84 •96 1*2 2'2 P=distance in miles that can be covered on one charge of petrol. 0=ditto for oil. P+0=reIative dis tance that the fuel lasts as compared with the oil. In an aeroplane it is essential that one should have a wide range action, and particularly will this be necessary in military, and more especially in naval, operations. The machines in the trials have a range of about 250 miles (Bleriot) to 420 (Bristol), but from a casual glance at the figures one would say that the modern aeroplane under the trial conditions is good for 300 miles at least. A little point in design that is worthy of closer attention on the part of manufacturers is the fact that the oil consumption would in. some cases cause the supply to run out before the petrol tank | was empty. It is obvious that the relative capacities of the tanks on a mileage basis should give a surplus of oil. In the Cody and the Avro, the machines could do an outward and a return journey by merely filling up with fuel at the turning point, but this double range is of less importance on these machines that use ordinary lubricant than in the case of the machines fitted with Gnome engines, where the necessity of using caslor oil makes it all the more- imperative to carry an adequate supply. The ratio of oil to petrol is shown in the last column. One of the Bristol monoplanes which secured a third prize of £500 in the Military Trials. 814
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