A cable is a group of wires or a group of strands of wires twisted together into a strong wire rope. The wires or strands may be twisted in various ways. The relationship of the direction of twist of each strand to each other and to the cable as a whole is called the opposite to the twist of the strands around the center strand or core, the cable will not stretch (or set) as much as one in which they are all twisted in the same direction. This direction of twist (in opposite direction) is most commonly adopted, and it is called a regular or an ordinary lay. Cables may have a right regular lay or a left regular lay. If the strands are twisted in the direction of twist around the center strand or core, the lay is called a lang lay. There is a right and left lang lay. The only other twist arrangement-twisting the strands alternately right and left, then twisting them all either to the right or to the left about the coreis called a reverse lay. Most aircraft cables have a right regular lay.

When aircraft cables are manufactured, each strand is first formed to the spiral or helical shape to fit the position it is to occupy in the finished cable. The process of such forming is called preforming, and cables made by such a process are said to be preformed. The process of preforming is adopted to ensure flexibility in the finished cable and to relieve bending and twisting stresses in the strands as they are woven into the cable. It also keeps the strands from spreading when the cable is cut. All aircraft cables are internally lubricated during construction.

Aircraft control cables are fabricated either from flexible, preformed carbon steel wire or from flexible, preformed, corrosion-resistant steel wire. The small corrosion-resistant steel cables are made of steel containing not less than 17 percent chromium and 8 percent nickel, while the larger ones (those of the 5/16-, 3/8-, and 7/16-inch diameters) are made of steel that, in addition to the amounts of chromium and nickel just mentioned, also contains not less than 1.75 percent molybdenum. 

Cables may be designated 7 x 7, 7 x 19, or 6 x 19 according to their construction. A 7 x 7 cable consists of six strands of seven wires each, laid around a center strand of seven wires. A 7 x 19 cable consists of six strands of 19 wires, laid around a 19-wire central strand, A 6 x 19 IWRC cable consists of six strands of 19 wires each, laid around an independent wire rope center.

The size of cable is given in terms of diameter measurement. A 1/8-inch cable or a 5/16-inch cable means that the cable measures 1/8 inch or 5/16 inch in diameter, as shown in figure 2-32. Note that the cable diameter is that of the smallest circle that would enclose the entire cross section of the cable. Aircraft

Figure 2-32.-Cable cross section.

control cables vary in diameters, ranging from 1/16 of an inch to 3/8 of an inch.

Cable ends may be equipped with several different types of fittings such as terminals, thimbles, bushings, and shackles. Terminal fittings are generally of the swaged type. (The swaging process is described in detail in chapter 9 of this manual.) Terminal fittings are available with threaded ends, fork ends, eye ends, and single-shank and double-shank ball ends. 

Threaded-end, fork-end, and eye-end terminals are used to connect the cable to turnbuckles, bell cranks, and other linkage in the system. The ball terminals are used for attaching cable to quadrants and special connections where space is limited. The

Figure 2-33.Types of cable terminal fittings. 

single-shank ball end is usually used on the ends of cables, and the double-shank ball end may be used at either the ends or in the center of a cable run. Figure 2-33 shows the various types of terminal fittings. 

Thimble, bushing, and shackle fittings may be used in place of some types of terminal fittings when facilities and supplies are limited and immediate replacement of the cable is necessary. Figure 2-34 shows these fittings.