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Aviation History
1912
1912 - 0797.PDF
AUGUST 31, 1912. r/pGHTi MACHINE AS A WHOLE. EL Overall. Speed : power effi ciency p -TV E'-HP Hanriot 2 \ Bristol 14 J Fr. Dep. ... Hanriot 1 \ Bleriot Soc. j Bleriot Tan. Avro Cody M. Farman,,. N.B.—For Overall. Speed : fuel effi ciency TV e i- USEFUL WEIGHT CARRIED ONLY = 350 LBS. ON EACH MACHINE. With climb added. Ea=E1 + H%. V HP" Speed : power effi ciency 7S 77 70 68 Hanriot 2 ... Fr. Dep. ... Hanriot 1 ... Bristol Bleriot Soc. ^ BWriotTan. J Cody Avro M. Farman ... 350 lbs. 105 103 99 96 oo 89 77 75 Bleriot Tan.. Bleriot Soc.. Hanriot I Hanriot 2 Bristol Avro Fr. Dep. ., M. Farman., Cody % 102 100 F- % Avro ... 123 Codv ... no Fr. Dep. ... 86 Bristol 14 \ Bleriot Soc. / 72 BleViotTan. \ ... 69 Hanriot 2 J .. 69 Hanriot 1 ... 58 M. Farman... the purposes of approximation, climbing. For the purposes of approximation, 350 lbs. is regarded as = W+G for all machines "4 So 76 60 Speed V : fuel effi ciency V+-OIH HP SpMd + climb : power. V+01H F Speed + climb Avro Bleriot Tan.. Bleriot Soc.. Cody Fr. Dep. . Bristol 14 . Hanriot 1 . M. Farman. Hanriot 2 166 108 106 96 93 91 9° §0 •S.N Bleriot Tan. Bleriot Soc.. Hanriot 1 Hanriot 2 Bristol 14 Fr. Dep. ., M. Farman .. Cody % 106 102 98 08 97 go 79 63 BWriot Soc.. BWriotTan.. Cody Kr. Dep. Hanriot I . Bristol 14 . M. Farman. Hanriot 2 . fuel. % 113 109 100 97 94 93 9a 92 for = 1 h. iooft./min. ascent is regarded as=l h.p. .•. '0lH = h.p. credited to machine and also that 350 lbs. at 1 m.p.h. p. ,-. V = h.p. credited to machine for transporting useful load in horizontal flight. Maurice Farman.—This machine belongs so very much to a class of its own, because of its low value of X = 78, that it is almost impossible to compare it with any of the other machines. The low value of X results solely from its exceedingly low loading on the wings, and not from a low load per horse-power, which has the second highest value of the machines that have flown, the Avro being the highest. In a word, therefore, the Maurice Farman biplane, if it were a motor car, would be described as under-geared. The effect of this on a flying machine is to give it an extraordinary capacity for flying safely at slow speeds, and it seems to be manoeuvrable under any conditions. At its natural gliding speed, which is 38 m.p.h., it has a good gliding angle, and heads the list in this respect, but the effort required to force up the speed to the maximum of 55-2 is not attended with economical results for the machine as a whole when regarded from an overall power efficiency. There is a considerable improvement in the figure, however, when the useful weight carried and the rate of climbing and the fuel are reckoned as the basis in addition to the maximum speed. As there seems to me to be no particular reason why there should be any feature in the detail design of the Farman which should particularly be to its dis advantage, the results mentioned must be attributed to excessively low loading resulting from the very large sail area. In so far as the abilities that attend this peculiarity in design are virtues on their account, therefore, the machine must be removed from comparison with others where the loading is about twice as much and considered on the basis of slow speed safely by itself. « = 46 per cent. Considerable interest attaches to the smaller table containing the figures under the columns X and e. The argumention which these values are based will be found beneath the big table on p. 796. The point is that I regard X as a function of the flight speed that must be attained in order to satisfy the conditions established by the design, the constant of the function being o-5. Thus, x, which is X-»-2, becomes the anticipated flight speed, whence may be deduced, by multiplying by the weight, the horse-power (h.p.) required. By equating this to the available engine power (HP.), the data in column * is obtained, showing the efficiency anticipated, which it is interesting to compare with the efficiency E, actually obtained. The Hanriots, the French Deperdussin and the Bleriot sociable approximate to the anticipated values proper to the design, i.e., x and v (flight speed) are almost identical. Extreme cases that are at variance with this equality, are the Maurice Farman and the Cody, the former of which has surplus power sufficient to increase the speed proper to the design by 40 per cent. It is interesting to note in this case that the actual gliding speed of the machine is almost identical with x. Cody's similarly shows reserve power for 10 per cent, gain on the speed proper to the design. On the other hand, by this reckoning, the Bristol monoplanes ought to fly at about 100 m.p.h. in order to per form under conditions corresponding to those governing the Hanriots and the French Deperdussin and the Bleriot sociable. In a word, they have been designed for too high an efficiency, as is shown in the column e. Although the Farman and the Cody succeed in converting their reserve power into speed, the actual efficiency of the machines does not increase in the same ratio ; thus, the Farman, which designs for 46 per cent, efficiency, obtains 58 per cent., whereas Hanriot 2 obtains 81, having designed for 79. Bristol monoplane 14, similarly obtains 81 per cent., but by designing for 111 per cent, is handicapped automatically in the matter of reserve power appropriate for the con ditions of a 75 m.p.h. flight speed, also its speed is only 72 m.p.h. The AVTO, it will be noticed, is designed for 87 per cent, efficiency, which is just about 7 per cent, more than the best available these days. Thus, as suggested elsewhere, it is slightly more horsepower that is required on this machine. 797 TABLE t. V Hanriot 1 Hanriot 2 Bleriot Tan. ... Bleriot Soc. Avro Bristol Mon. 14 Bristol Mon. 15 M. Farman Fr. Dep. Cody 76-5 75-5 735 59-o 72-0 I02'0 III'O 39 "o 69-0 65-5 75-2 75-4 bi-i 5»-9 59'9 70-5 72- 5 SV2 69-1 72-4 98-5 lOO'O 830 ioo'o 82-0 69*0 65-2 i40-o IOO'O IIO'O h.p. 6S S3 49 p ( <>~ 33 57 78 HP. Bo 80 IK, (»(> 65 75 75 72 .So 120 82 7"' Br <M 87 III 12 46 72 6J i? 73-5 73J 81 58 79 x = X •+• 2 = speed required to satisfy conditions of design, h.p. = power required to satisfy conditions of design. «= efficiency required to satisfy conditions of design. V = speed actually obtained. HP. = power actually available. Ei = efficiency actually demonstrated. It now remains to mention the machines that have not yet been tested, which is somewhat complicated by the fact that the exact weights in flying order are unknown. In most cases the machines have been weighed empty, however, and by adding about 700 lbs. to each I have inserted the probable weight in flight to the nearest round number. Machines not yet Tested. HP. A. lbs. 1.436 i,5'9 1.57i 1,671 w. W,. W, \. 26*2 20-0 28-8 230 21'8 25"0 W = weight in flight. W,= weight per h.p. W5 = loading. that catches the eye in the 2,100 2,200 2,300 2,300 2,400 1,500 o 35 7 75 75 25 157 147 164 132 125 156 eye the Coventry 10 ... 80 350 Coventry II ... 110 300 Bristol Bi. t2 ... 80 387 Flanders .. 100 400 Martin- Handasyde 110 310 Handley Page ... 60 240 — HP. = actual horse-power. A -area sq. ft. w = weight empty. Bristol Biplanes.—The first thing table is the extremely high value for X = 164 against the Bristol biplane No. 12. Here, the weight per horse-power is proportionately higher than the load on the wings, so that it is the weight of the machine that needs to be reduced in order to bring the working value of X more nearly within the range of modern machines. Unfortunately, the number of biplanes flying successfully in the present trials is so limited that the data for this class will be scarce, but, having regard to the monoplane values, where X » 150 already begins to be high, it is reasonable to say that biplanes ought to be designed below this value if they are to be successful under the trial conditions. It is designed for an efficiency c = 105 per cent. Coventry Ordnance.—Both these biplanes have a very high value of X, but in this case, as distinct from the Bristol, the tendency, at any rate on the machine No. n, has been to overload the wings. If the Chenu engine gives 110 h.p., the weight per h.p. of No. n is quite moderate, so that the evidence points towards the desirability of increased sail area, apart from lightening the machine as a whole. The Gnome-engined biplane is carrying a heavier load per h.p., but one that is quite reasonable in biplanes as a class. No 10 is designed for efficiency « = 88 per cent. ; No. 11 * = 65 per cent. Flanders.—The engine for which this machine has so patiently been kept waiting, having stripped a timing-wheel during its trial run, left no option but to withdraw from the competition ; but if the
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