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Aviation History
1914
1914 - 0887.PDF
AUGUST 21, 1914. whilst a couple more engines had to be left in the cellar of an hotel in France, presumably disguised under the cloak of some Chateau vintage. XXX At the Caudron School an excellent selection of biplanes is at the disposal of pupils. The little Caudron monoplane in which Ewen crossed the Channel has been erected and fitted with a 35 h.p. Anzani engine. This should prove a very serviceable unit for pupils who are out to obtain experience on a monoplane in addition to training on the biplanes. XXX In one of the top sheds I found Beatty bending busily over a Wright wing that was being re-covered. What with the brace of 2-seater Wright biplanes, the little single seater 50 Gnome-Wright and the Handley-Page monoplane, pupils joining this school have an oppor tunity of gaining some varied experience. XXX The little Martinsyde scouting biplane to which reference was made some time ago is now nearing com pletion, and is expected to be out in about a week's time. Her appearance gives great promise of some fine per formances, for although she is the first of her type to be turned out by the Martinsyde firm, their experience with other models has furnished them with valuable information which has been successfully applied in the design of this their latest product. XXX Mr. W. L. Brock, whose great performances in the Aerial Derby, the London-Manchester-London and the London-Paris-London races stamped him as in the very front rank of crosscountry pilots, has now returned to his native land, the United States, where I hear he has been given an important Government commission. ® ® (/OGHT] During his several visits to these shores he has made many friends, and although he will be greatly missed over here, it is gratifying to hear that his achievements have been recognised in the high quarters of " home waters." Mrs. Jas. V. Martin, who, it will be recalled, learnt to fly—as Miss Lilian Irvine—at Hendon, before marrying her instructor, and going with him to the States, has been distinguishing herself on a Benoist flying boat recently. On the 23rd ult. she flew with a passenger from Cedar Point, Sandusky, O., to Cleveland, a distance of 74 miles, in 60 mins. As briefly recorded in " Eddies " last week, the Scout ing biplane P.B. IX constructed at the supermarine works of Mr. Pemberton-Billing, Southampton, was ready for flight on Tuesday of last week. On Wednesday (just over a week after beginning the actual construction), the seven day 'bus, as the machine has been nicknamed, was taken out to a small field in the vicinity, and Mr. V. Mahl, the well-known Sopwith pilot, climbed into the seat. The propeller was swung round when the engine started immediately. After a very short 4run along the ground Mr. Mahl took the machine up and commenced a steeply - banked left - hand turn, ascending all the while. The rate of climbing seemed to be in the neigh bourhood of 500 ft. per min. and the speed about 75 m.p.h. After carrying out all sorts of evolutions Mr. Mahl landed again at a speed of just over 30 m.p.h. Altogether he was very pleased with the 'bus and her little ways—her steadiness he found exceptionally good and he was immediately at his ease in flying her—which spells another fine achievement for Mr. Pemberton- Billing, to whom congratulations. " ^EOLUS." ® ® THE TURNING CIRCLE OF AN AEROPLANE. WHEN a mass travels on a circular path, centrifugal force tends to make it move off at a tangent. Its circular path is maintained only so long as there is a centripetal force to oppose the centrifugal force ; and this centripetal force is provided in an aeroplane by banking the machine at the turn so as to tilt the wing pressure towards the centre of the turning circlet When thus tilted, the wind pressure on the wings provides a centripetal force acting towards the centre of the turning circle as well as a vertical force supporting the machine in flight. But, if the total pressure on the wings is no greater than it was when the machine was flying on a straight level path, the vertical lifting force when the machine is banked will be inadequate entirely to prevent the gradual descent of the machine. In short, it will no longer be equal to the weight of the machine. It is fundamental, therefore, that either the aeroplane must descend while turning, or else be in a position to increase the power output from its engine, so as to fly faster or at a coarser angle, in order to augment its wing pressure sufficiently to maintain the complete support of the machine as well as the centripetal force required for turning. If the aeroplane is banked to 45°, and has sufficient reserve power to keep on the same level while turning, then there is a centripetal force equal to the weight of the machine. The centrifugal force is, by first principles, equal to the centripetal force, and, therefore, also equal to the weight of the machine. Wz'2 The fundamental formula for centrifugal force is F = ——, where F = force, W = weight, v — linear velocity, g= gravity, and r= radius. For the case in question we can find the radius of the turning circle by writing F = = W; whence r= . The interesting point about the solution to this problem, which in general is applicable to any other angle of bank, is that the radius corresponding to a given degree of banking increases as the square of the speed. Of a series of aeroplanes all banked to the same amount, the slowest machine will thus turn in the shortest radius. 887 " Flight " Copyright. Diagrams illustrating the forces that steer an aeroplane when it is banked. It is here assumed that the machine has sufficient reserve power to continue its turn on the same level. In the above example, if the machine is flying at 68 miles an hour—or, roughly, too ft. a second—the radius for a 450 bank is about 315 ft. The diagram on the right shows the wing pressures required fcr various excessive banks that are required to maintain a machine on a constant level while turning. It will be observed that the radius of the turning circle is only dependent on the wing loading in so far as that function is expressed in the flight speed. Inasmuch as the centripetal force for any banked turn executed without increase of wing pressure (and, therefore, on a descending spiral) may be written F = Wsin0, where $ is the angle of bank from the vertical and W is the weight in flight, the radius for any such turn becomes r= —;—' .rsin 0
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