containing not less than 17 percent chromium and 8
CABLES
percent nickel, while the larger ones (those of the 5/16-,
A cable is a group of wires or a group of strands of
3/8-, and 7/16-inch diameters) are made of steel that, in
wires twisted together into a strong wire rope. The
addition to the amounts of chromium and nickel just
wires or strands may be twisted in various ways. The
mentioned, also contains not less than 1.75 percent
relationship of the direction of twist of each strand to
molybdenum.
each other and to the cable as a whole is called the lay.
Cables may be designated 7 7, 7 19, or 6 19
The lay of the cable is an important factor in its
according to their construction. A 7 7 cable consists
strength. If the strands are twisted in a direction
of six strands of seven wires each, laid around a center
opposite to the twist of the strands around the center
strand of seven wires. A 7 19 cable consists of six
strand or core, the cable will not stretch (or set) as much
strands of 19 wires, laid around a 19-wire central
as one in which they are all twisted in the same
strand. A 6 19 IWRC cable consists of six strands of
direction. This direction of twist (in opposite direction)
19 wires each, laid around an independent wire rope
is most commonly adopted, and it is called a regular or
center.
an ordinary lay. Cables may have a right regular lay or a
The size of cable is given in terms of diameter
left regular lay. If the strands are twisted in the direction
measurement. A 1/8-inch cable or a 5/16-inch cable
of twist around the center strand or core, the lay is
means that the cable measures 1/8 inch or 5/16 inch in
called a lang lay. There is a right and left lang lay. The
diameter, as shown in figure 3-32. Note that the cable
only other twist arrangement--twisting the strands
diameter is that of the smallest circle that would enclose
alternately right and left, and then twisting them all
the entire cross section of the cable. Aircraft control
either to the right or to the left about the core--is called
cables vary in diameters, ranging from 1/16 of an inch
a reverse lay. Most aircraft cables have a right regular
to 3/8 of an inch.
lay.
When aircraft cables are manufactured, each strand
Fittings
is first formed to the spiral or helical shape to fit the
position it is to occupy in the finished cable. The
Cable ends may be equipped with several different
process of such forming is called preforming, and
types of fittings such as terminals, thimbles, bushings,
cables made by such a process are said to be preformed.
and shackles. Terminal fittings are generally of the
The process of preforming is adopted to ensure
swaged type. Terminal fittings are available with
flexibility in the finished cable and to relieve bending
threaded ends, fork ends, eye ends, and single-shank
and twisting stresses in the strands as they are woven
and double-shank ball ends.
into the cable. It also keeps the strands from spreading
Threaded-end, fork-end, and eye-end terminals are
when the cable is cut. All aircraft cables are internally
used to connect the cable to turnbuckles, bell cranks,
lubricated during construction.
and other linkage in the system. The ball terminals are
Aircraft control cables are fabricated either from
used for attaching cable to quadrants and special
flexible, preformed carbon steel wire or from flexible,
connections where space is limited. The single-shank
preformed, corrosion-resistant steel wire. The small
ball end is usually used on the ends of cables, and the
corrosion-resistant steel cables are made of steel
double-shank ball end may be used at either the ends or
Figure 3-32.--Cable cross section.
3-19
