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
dimension is used thereafter.
NOTE
stop,
a 7-inch
These dimensions are applicable to the
Mod 2 arresting engine.
The Mod 3
clearances are different. Mod 3 clearances
are as follows: On newly reeved engines a
7-inch clearance is set up between the
crosshead and crosshead stop. After the
new cable stretches to the minimum
allowable distance between the crosshead
and the crosshead stop, crop and repour a
new terminal and set the crosshead a
distance of 6 inches from the crosshead stop.
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 results 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 internals 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.
NOTE
If torque buildup is greater than normal,
it is recommended that the crossdeck
pendant be disconnected from both topside
terminals to allow a more efficient detorque
of the cable system.
As shown in figure 3-45, stored torque is
removed at the anchored end of the purchase cable
by removing the quick-release pin from the coupling
lock lever and striking the lock lever with a hammer.
This allows the purchase cable to spin and release
the torque.
Figure 3-45.—Releasing torque from cables.
3-50
