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Aviation History
1916
1916 - 0616.PDF
f/DCHTl the gliding angle from the dotted curve, while the curved line is used to intersect the h.p. on slide No. 2. As the wind resistance of the machine is an important factor in the calculations, it is necessary to know the resistance of the aeroplane under consideration. As this is not always known, a table is given in the book of instructions accompanying every instrument, in which are given the detrimental head resistances of a number of various types, ranging from an equivalent normal area of 6 sq. ft. for a small fast monoplane to 20 sq. ft. for a twin-engined battleplane. These figures are, of course, only approximately correct, but for first estimates the error involved is probably not of serious moment. That they are not and cannot be absolutely accurate will be realised when it is remembered that no allowance is made for variation of resistance of items in the slip stream according to the amount of slip given by the particular propeller, used. In the tables of head resist ance is not included the resistance of the supporting surfaces, and in order to obtain what the inventors of the instrument call the "efficiency of construction," desig nated on the base of the calculator by the letter E, it is necessary to divide the area of the main planes by the number of square feet of detrimental head resistance. If, for instance, the area of the main planes is 400 sq. ft., and the detrimental head resistance is 10 sq. ft., the efficiency of construction E is 400 -f- 10 = 40. A list of some of the characteristics that may be calcu- iated by means of the " Triple-Slide " will give an idea of the usefulness of this instrument. The speed at any angle of incidence, the landing speed, the climbing speed per minute, the maximum attainable altitude, and the speed at this altitude, the economical speed, minimum and maximum speed, minimum horse-power, greatest possible flying weight and useful load, gliding angle, &c. A numerical example of one of the calculations that can be made by means of the " Triple-Slide," although not explaining the complete manipulation of the instru ment, will give a good idea of the simplicity of the operation. Let us suppose that we have a machine weighing 2,000 lbs. "all on," with an area of 400 sq. ft., JULY 20, 1016. and an engine developing 100 b.h.p. The wing section is the R.A.F. 6, and the machine is a vertical biplane. In the book of instructions the detrimental area is given as 10 sq. ft., which may be considered sufficiently accurate. Taking the propeller efficiency as 75 per cent., which is a fair average, we obtain 75 as the pro peller horse-power. The "Efficiency of Construction" = E = A/DH = 400/10 = 40. On slide 1 we connect the arrow with E40. On slide 2 connect W2000 with A400. On slide 3 connect W2000 with A400. Turn the indicator until it intersects HP on slide 2 at 75. It is found that the indicator intersects the full line wing curve on slide 1 at L80. On slide 3 L80 is connected with V78'6, which is the maximum speed. The highest value of L on the full line wing curve is found to be 255. On slide 3 we find L255 connected with V"44'2, which is the minimum speed. The speed range is, therefore, 44*2 to 786 m.p.h. If it is desired to find the gliding angle of the same machine as above, all the slides are kept in the same position, and the indicator is turned tangent to the dotted line wing curve. The indicator" will then be found to intersect (4), the base of the instrument, at 1/7. The gliding angle is, therefore, 1 in 7. With each instrument is furnished a set of standard wing curves complete for calculations of monoplane, vertical biplane and staggered biplane, comprising the following sections: Eiffel No. 32 (Lanier Lawrance), Eiffel No. 35 (Commandant Dorand), Eiffel No. 38 (Coanda), R.A.F. 6, Farman, and Curtiss Wright. Extra slides can be furnished at a dollar each, if they are of sections tested at a laboratory, or designers who are using their own section will be furnished with a laboratory test of same and a slide, for $55, provided they supply a model of their section measuring 3 ins. by 18 ins. The price of the " Triple-Slide " aeroplane calculator with a standard set of wing curves is stated to be $15 (about jQz) for the first fifty purchasers, and after that $25. We understand that arrangements are being made for an agent in England, and that the instrument will be on the market here very shortly. ® ® ® ® AIRCRAFT WORK AT THE FRONT. OFFICIAL INFORMATION. British. General Headquarters, July llth, 12.48p.m. " In continuation of my report on the aerial combats of Sunday, one of our aeroplanes was shot down by a direct hit from an anti aircraft gun, and three other machines have not returned to our lines." 8.30 p.m. " Apart from a number of guns hidden in houses buried by dtbris and the like, we have in the course of these operations brought in 26 field guns, I naval gun, 1 anti-aircraft gun, and a heavy howitzer, while the number of German prisoners captured exceeds 7,500." July 12th, I.32/.W. " Several combats took place in the air on the 10th, as a result of which we destroyed one German machine, while one of our own machines was brought down by the enemy's gunfire." General Headquarters, July 13M, 2p.m. " Despite the unfavourable weather, our aeroplanes have been constantly at work. Hostile machines were active, but all their attacks on our aeroplanes operating over the German lines were driven off. One of our aeroplanes is missing." War Office, fuly 13M. "Mesopotamia—Tigris Line.—On the evening of the nth the enemy's artillery and aircraft were both engaged in an ineffectual bombardment of our trenches. No material damage was done. On 12th the temperature was 117 deg." French. Paris, July 12th. Evening. " In the region of the Somme our aeroplanes fought 14 actions yesterday. Four enemy machines, badly hit by our machine guns, were foraed to dive suddenly. One of our pilots brought his machine, which was on fire, back to our lines and landed without accident. " Our bombardment squadrons were active last night. Two hundred and twenty bombs were dropped on various stations, where great excitement was observed, particularly the stations of Ham, La Fere, and Chaulnes." Paris, July 14th. Evening. " In reprisal for the bombardment by the enemy on the open town of Luneville on the night of June 24th one of our airmen, fly ing at a height of 1, 500 ft., last night dropped several heavy bombs on the town of Mulheim (east bank of the Rhine)." • Paris, July i6ti. Afternoon. " In the region of the Somme our aeroplanes displayed great activity. Four German machines attacked by ours over the enemy lines were brought down. Two others, badly hit, were obliged to descend. " In the region of Verdun one of our aeroplanes set fire to a captive balloon. " During the night of the 15th one of our air squadrons bom barded the stations at Hombleux and Roisel, and a heavy battery near the latter. During the same night another squadron dropped numerous bombs on the stations of Abbecourt, Tergnier and Chauray." 614
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