set at 7 inches. New purchase cables will stretch very
rapidly during the first few arrestments. The initial
7-inch dimension between the crosshead and the stop
allows for this structural stretch, which causes a
progressive narrowing of the gap distance between the
crosshead and crosshead stop. After the purchase cable
has been stretched and reaches the minimum allowable
clearance of 1 inch between the crosshead and
crosshead stop, a 6-inch dimension is used thereafter.
When
it
becomes
necessary
to
rereeve
a
single-reeved engine, both purchase cables must be
replaced. Reeving only one purchase cable on a
single-reeved engine result in unequal length of the two
cables, because of the initial stretch of the new cable.
An offcenter deck pendant is an indication of one cable
stretching more than the other. This condition could
cause one of the purchase cable terminals to rest in the
deck sheave. To correct this condition, you will have to
crop the longer cable and repour the terminal.
During arrestment operations, torque builds up in
the purchase cables. Failure to remove this torque
results in accelerated wear and bird-caging of the
cables, with vastly increased susceptibility to failure.
Compliance
to
detorquing
methods
at
specified
intervals is mandatory. Newly installed purchase cables
should be detorqued after the initial 50 landings (no
more than 60) and every 200 landings thereafter.
WARNING
Keep hands free of spinning parts when
releasing torque from cables.
Purchase cable torque can be removed in the
following ways. During flight operations, disconnect
one side of the crossdeck pendant at the completion of
an arrestment and partially retract the engine. This
allows the cables to untwist. If time allows, blow the
engine down to 200 psi and pull the engine out to its full
stroke; disconnect one side of the crossdeck pendant;
and retract the engine slowly to approximately 20 feet
out of battery.
If torque buildup is greater than normal, it is
recommended that the crossdeck pendant be discon-
nected from both topside terminals to allow a more
efficient detorque of the cable system.
Preparing Cable and Terminal for Pouring
When working around an arresting gear engine,
make sure the arresting engine retracting system is
depressurized before performing any of the following
steps involving the handling of the wire rope.
Preparing Wire Rope
When it is necessary to cut the wire rope, place two
seizings of approximately 15 or 20 turns of soft steel
seizing wire on the cable, approximately 1 inch apart.
(See fig. 3-47, view A.) Cut the cable between the two
seizings.
Remove the seizing from the cut end of the cable
and, with the use of a marlinespike, unlay three strands
of the cable. Using a pocketknife, cut and remove the
hemp center a distance equal to the length of the
terminal plus 1 inch. (See view B of fig. 3-47.) Re-lay
the strands of the cable.
Make a seizing a distance equal to the length of the
terminal plus 1 inch. The seizing should be made with
the use of a serving tool and be 15 or 20 turns of soft
steel seizing wire. (See fig. 3-47, view C.) Place two
wraps of seizing wire immediately above the large
seizing, as shown in view D.
Loop
and
tighten
one
or
two
turns
of
0.047-inch-diameter copper wire on the end of all
strands, as shown in view D. Using a marlinespike and
tubing, unlay and straighten the strands of the cable to
the top of the seizing. Pull the strands in toward the
center to ensure a good distribution when the individual
wires of each strand are straightened. (See view D of
fig. 3-47.) After all the strands are straightened, remove
the two turns of seizing previously placed at the top of
the large seizing. Do NOT remove the large seizing;
this seizing remains in place until pouring procedures
are completed.
Do NOT use pliers to straighten the wires; pliers
may damage or weaken the wires.
3-47
