M.Goodall, A.Tagg British Aircraft before the Great War (Schiffer)

Журнал Flight

Flight, June 10, 1911.

THE SHORT BIPLANE, 1911 TYPE.

   CONSIDERING their position as pioneers of aeroplane construction in England, and the reputation that they have established for thoroughly reliable if particularly British workmanship, it is a matter of course that any production of Short Brothers should be regarded with special interest. The machine at present under review, which is the latest output of the Sheppey factory, reflects modern prejudice in favour of the Farman type biplane, a prejudice that is well founded, for шt is after all not surprising that pilots should prefer to fly those machines which have proved most successful. Moreover, it is often by taking a successful type as a basis in design that there is most scope for originality in detail development, and it is in this respect that Short Brothers' work has always been notable, in their earlier machines no less than in this. As a matter of fact, too, the general design of this machine differs considerably from the real Farman so soon as its construction is looked into with more than superficial interest. Even the casual observer, for instance, will notice some difference in the appearance of the tail, which includes a monoplane lifting member fitted with a trailing elevator attachment and a large divided rudder half of which is above and half below the horizontal plane.
   Particular attention may also be directed to the trussing of the tail outrigger, which is especially well stayed laterally by diagonal ties leading to the rear transverse boom of the main planes. The same system of trussing is applied to the elevator outrigger, which member is of the accepted triangular frame type. The elevator itself is a cambered monoplane, and is operated on the Farman system from a universally pivoted lever that is mounted vertically and centrally in front of the pilot. From this lever wires also pass laterally to the hinged balancing planes that trail behind the extremities of the upper main planes. A glance at the front view of the machine shows how these balancers are of exceptionally long span, and consequently have a relatively high aspect ratio.
   It will also be observed from this front view of the machine that it belongs to the extended upper plane or "military" type, the upper plane having a span 14 ft. in excess of the lower plane, and the overhanging extremities being supported by slanting stays attached to the extremities of the lower main spars. Altogether the machine is a neat and well thought out example of rather a large type of flyer, and by no means the least interesting or important of its features is the elaborate system of bracing that characterises the design. Two points of special importance in this connection are the struts in the gap of the panels on either side of the main central panel, and the fore and aft struts in the chord of both upper and lower main planes. The former struts join the points of intersection of the diagonal tie wires with the rear spar of the lower main plane, and their purpose is to add stiffness by resisting the bending that is apt to take place at this point when the machine lands. The nature of the stress induced is illustrated by one of the accompanying sketches, which shows how the principal mass represented by the engine and pilot tends to make the spar sag in the centre, while the same result tends to take place at the extremities, due to the mere weight of the planes. As a result a sinuous deflection is set up in the spar, which tends to bend up in those panels immediately adjacent the main central panel. The presence of vertical struts in this position thus tends to stiffen the entire spar by resisting deflection at the point where the tendency to bend is most pronounced. Similarly a V-frame trussed diagonally is introduced immediately beneath the centre of both main spars. The purpose of the fore and aft struts in the chord of the main planes is to provide a framework that is independent of the ribs or fabric of which the planes proper are constructed. In the Short biplane the ribs and fabric might be stripped off the machine, and the box-girder construction would still remain as a skeleton to which the planes might be refitted. This system of construction enables lighter rib sections to be used throughout, and in some respects gives greater latitude for the design of the planes as independent supporting members than can be considered apart from any subsidiary purpose they may play in the construction of the machine.
   Another interesting constructional detail of the same order is the axle of the under-carriage of this machine. It will be observed that the axle it stiffened by vertical struts adjacent to the wheels, which struts are tied together by a horizontal wire and are trussed down to the axle extremities by diagonal wires. The undercarriage itself belongs to the Farman type, inasmuch as it is a wheel and skid combination joined by rubber springs, the use of radius-wires and the arrangement of the radius-rods, as shown in one of the accompanying sketches, however, really puts the Short under-carriage quite in a class by itself.
   Some minor constructional details are shown in another accompanying sketch, which illustrates several of the special joints employed. Short Brothers have always had a marked preference for the use of manganese steel fittings, and the illustration in question shows a variety of ways in which this material is employed. Especially interesting are the U bolts and slotted ferrules, by means of which the struts are attached to the booms with a minimum reduction in the material of either. A detail that is sure to attract attention in our photograph is the use of straight ribs at the extremities of the main planes. Elsewhere the planes are cambered as usual.