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Aviation History
1930
UNTITLED0 - 1279.PDF
1-LlGHT, NOVEMBER 7, 1930 THE SPARTAN "ARROW" A New Two-Seater with Good Climb WHEN, some years ago, Mr. O. E. Simmonds establishedhis own aircraft firm, he did so on the strength of avery ingenious scheme whereby was attained a degree of interchangeability never before attempted. By thisscheme, use ".was made of wings of symmetrical aerofoil section, which made it possible to use one spare wing in anyof four positions : Top right-hand, bottom right-hand, top left-hand "and bottom left-hand plane of a biplane. Struts,bracing wires and fittings were so designed that they could be attached to either side of the wing, and the same system ofinterchangeability was extended to ailerons, elevator flaps and rudder. For example, a portion of the elevator flapwas identical with the horn-balanced rudder. Similarly, in the undercarriage the right-hand half could be turned aroundand'used 'on the left-hand side and vice versa. One spare wing bracing wire could be used in any position in the wing structure. The reduction in the number of spare parts which a clubor a private owner needed to stock was. therefore, very con- siderable, and it might have been thought that such asystem would have a strong appeal. While this was un- doubtedly so, the fact that the whole scheme was basedupon the use of a symmetrical aerofoil section has, in practice, proved to be something of an obstacle to complete success.Certain machines using symmetrical wing sections have been found to be rather vicious in a stall, flicking into a spinas soon as the stalling angle is reached. It is by no means certain that this is anunavoidable feature of the symmetrical section wing,but a good deal of prejudice undoubtedly grew up, andas a result, there were many who looked with suspicionon a machine with such a wing section. The fitting ofHandley Page automatic slots would cure any tendency amachine might have to go into a spin, but some pur-chasers prefer aircraft with- out slots, and it is for suchas these that Spartan Air- craft, Ltd., have producedthe new version of their machine, the " Arrow." Apart from the fact thatin the Spartan " Arrow " a non-symmetrical wing sectionof greater lift has been adopted, the performance hasbeen further improved by increasing the wing span andthus reducing the induced drag at low speeds. Thecombination has resulted in a considerable improvementin take-off and climb, both of vrhich are very good in the Arrow," as will be seenfrom the fact that, at aero- batic gross weight, and withthe " Gipsy II " engine, the take-off run is only 60—80yards, while the initial rate AN UNDERNEATH VIEW : flying at Hamble. of climb is 830 ft./min. Even when the machine is loadedup to its somewhat remarkable " normal " gross weight of 1,750 lb., the take-off is only 100—130 yards, while the initialrate of climb is 700 ft./min. It might have been thought that the use of a non-sym-metrical wing section would preclude the features of inter- changeability, which the earlier Spartan machines possessed,but actually the majority of interchangeable parts have been retained in the " Arrow," although in a slightly modifiedform. To those who knew Mr. Simmonds when he first started manufacture, this will not come as a surprise, andthe writer of these notes recollects that when discussing the subject some years ago with Mr. Simmonds the possibilitywas mentioned of using one spare wing, not of symmetrical section, in any of the four positions in a biplane. Thus, thearrangement adopted in the " Arrow " is not, as it were, an afterthought on the part of Mr. Simmonds. On the contrary,it was foreseen several years ago, and is, we believe we are right in saying, a part of the original patent. As far as the wings are concerned, the system adopted inthe Spartan " Arrow " consists in slightly modifying the shape of a well-known aerofoil section in such a manner thatthe rear portion, from the rear spar to the trailing edge, is symmetrical, and in using a wing tip which forms a detach-able unit, so that it can be placed at either end of the rect- angular portion of the wing. By this means the spare" or " key " wing can be used ineither of the four positions on the biplane. To do so it isnot, of course, "turned up- side-down," as was the sparewing of the earlier Spartans, but the end which is nearestto the fuselage or top centre- section on one side of themachine becomes the outer end when the spare wing isused on the other side. The complication is just a littlegreater, but as the detachable wing tip is a small lightstructure costing, fi g u r a - tively, a few shillings, thisis no great drawback. That the interchangeability is notobtained in the " Arrow " at the expense of a great increasein structure weight seems to be proved by the fact thatthe tare weight is, with the " Gipsy II " engine, 965 lb.,while the maximum per- missible gross weight for the" Normal " category of the Certificate of Airworthinessis 1,750 1b. This gives a ratio of gross to tare weight of1-814, which seems to point to very efficient structuraldesign. General Description The Spartan " Arrow " is, inits general design, a normal 1207 B 2 The Spartan "Arrow " (FLIGHT Photo.),
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