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Aviation History
1919
1919 - 1594.PDF
DECEMBER II, 1919 AIRCRAFT UNDERCARRIAGES' BY JOHN D. NORTH, F.R.AE.S., F.R.MET.SOC. THE undercarriage is described in the Society's Glossary as " That part of the aircraft beneath the body intended for its support on land or water and to absorb shock on alighting." 1*. It is my intention to confine my remarks in this paper to undercarriages designed to support aircraft on land, that is to say, colloquially, " landing gears." The reasons for this limitation are obvious ; it is scarcely possible to compare even in a general manner the undercarriage problem of the land machine and the seaplane, and in the latter case the already wide subject has to be extended to consider float design. The historical development of the undercarriage shows well- defined phases reflecting the performances and functions of the complete aircraft. In the early Wright machines, which were provided with a launching gear, the problem of alight ing only required to be considered. The light weight and slow landing speed of the aeroplane demanded but slight shock absorbing capacity and long skids only were fitted to bridge inequalities in the ground. iK ff Contemporaneously in France and in this country attempts were being made to fly without launching gears. As the amount of time spent in taxi-ing, or " rolling " as it used to be called, represented a very large proportion of the total " flying" time, the undercarriages were designed to meet these conditions. The outstanding feature was the extensive use of swivelling forks carrying the wheels, the erratic course of the machine in its frantic efforts to rise requiring a liberal measure of tracking. As these machines frequently suffered disaster, being upset by running into ditches and so forth, the idea of combining the wheel and skid was materialised n the Henri Farman undercarriage. This had very long skids, each provided with two wheels mounted on a common axle and sprung to the skid with rubber. This system was * Paper read before the Royal Aeronautical Society, at the Royal Society Arts, John Street, Adelphi, on Wednesday, December 10, i9ro. extensively adopted, but as the performance of machines im proved the skid gradually became shorter and shorter till in the well-known and almost universal " Vee " type under carriage it disappeared altogether. At the same time the arrangements of springs and radius rods provided in the original Farman also died out. It is perhaps interesting to recall that the " Vee " undercarriage was extensively con demned on its appearance as highly dangerous. Fig. 1 shows diagrammatically the process of development culminating in the " Vee " type undercarriage. By a similar process of development the wide-track Farman chassis developed into the typical undercarriage of the twin engined machine exemplified by the Vickers Vimy and the Handley Page, while in a different form it appears with two wheels only in the B.A.T. and the Boulton and Paul Bourges (see Fig. 2). The most notable departures from these types originated in the Breguet Oleo gear, which is shown developing into the R.E.7 and F.E.2C. Oleo gears. The undercarriage of the Avro tuition machine may be traced to the early single wheel R.E.P. (Fig. 3). I hasten to add that I do not suggest that all designs sub sequent to the original type were plagiarisms, but rather that they represent natural lines of development. Of the final types found in general use there is no doubt that the " Vee " holds the field by sheer weight of numbers, and the reason for this is not far to seek. The development of aircraft has been almost exclusively military for the last five years and, in considering the safety and utility of an aeroplane, danger from enemy action was an important item. By cutting down the resistance of the undercarriage to a minimum a definite improvement in performance was obtained and the consequent added security in action more than compensated for any increased difficulty or danger in landing. FI6.1 TT WRIGHT riAyRuis, fARMAN V0151N BX.£- e=M£~S9t3 BLERSOT 1909 r*«r*»WrH tllO B.E.JX 1596
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