Steel Tube.
Steel, in the form of tubing of various sections, enters largely into aeroplane construction, and may be said to contribute largely to the efficiency of the structure. It is now being used for the different items of the undercarriage, for struts in the fuselage, interplane struts, and in many cases control surfaces, such as the ailerons, elevators, and rudder, are being built of this material entirely. In the early days of aviation steel tubing attained some considerable popularity, many machines being built almost entirely of tubing; but difficulties in its manipulation, and the fact that very often the methods of attachment reduced its strength considerably, gradually led to the general employment of wood. The great advances lately made in the production of a high-grade nickel-chrome steel, with a high ultimate tensile stress, are responsible for its present increasing use.