Undercarriage Types.
The type of landing gear in use to-day does not vary in principle to any great extent, the differences usually occurring in the choice of material, the system being that usually known as the Vee type, from the fact that viewed in side elevation, the struts form a V. While this type has much to commend it from the points of low head resistance and great strength for weight, there are other systems, some of which have been tried-out, while others still exist, incorporating features designed for some specific purpose. Of these the Farman type is an example of a landing gear designed for the requirements of school work, consisting of two long ash skids, which, extended from the rear end of the nacelle, being gradually bent upwards to carry the front elevator. This was the arrangement on the “Longhorn” machine, but on the “Shorthorn,” produced at
Fig. 86.—Side view of Farman landing gear.
a later date, the skids, as shown by [Fig. 86], terminated in short bends. Each skid carried a pair of rolling wheels, attached to a short axle, this being bound to the skids by rubber bands. The wheel base being almost 9 ft., this type gave excellent results. In the case of big machines, where it is desired to keep the load on the tail skid as light as possible, three wheels are sometimes used, two main rolling wheels and a light pilot wheel in the front. This enables the main rolling wheels to be placed under the centre of gravity, the pilot wheel preventing the consequent tendency to pitch forward when rolling. A further development of this system dispenses with the tail skid, two main wheels being placed under the centre of gravity, and two smaller wheels a little forward of
Fig. 87.—Side view of four-wheeled landing gear.
the propeller, as in [Fig. 87]. The skids were sometimes continued back behind the rear struts, and saw-kerfed to increase the resiliency. The base of support was formed by the rear wheels and the ends of the skids, the machine being pulled on to the front wheels by the thrust of the propeller. The short wheel base is bad for rolling on bumpy ground, and frequent skid replacements are necessary with this system. A similar type with no tail skid has the wheels disposed forward of the C.G., while a single central skid, connected to the fuselage by
Fig. 88.—Side view of Nieuport undercarriage.
a series of V struts, replaced the double skids, as in [Fig. 88]. This type was used on the original Nieuport monoplane, and with minor modifications on the Avro 80 h.p. Gnome tractor biplane. Its chief advantage is low head resistance, but unfortunately with this system a narrow wheel base, with the attendant defects, is inevitable. A very distinctive system was that favoured by Bleriot, and used with minor alterations on all the Bleriot monoplanes. This is shown, diagrammatically, in side elevation, by [Fig. 89], and was unusual in that the wheels were arranged to swivel, this being an attempt to counteract the side strains set up when landing in a side wind. Although in the hands of some of our most famous exhibition pilots this has functioned excellently, it is complicated and somewhat heavy.
Fig. 89.—Bleriot undercarriage.