when bottomed out, will be as high as 20,000 psi. In the
purpose. The spring is located within a recess of the
static condition, the oil trapped within the spring
hook shank, and the keyed end presses against the
assembly is under a return preload pressure of 350
centering cam. On installation, shim the spring until the
pounds, which is created by the reassembly of the close
thickness of the spacer and shims is approximately
tolerance parts that confine the liquid.
0.125 inch. Install the spring in the shank, and then
secure the shank to the drag link. Check the hook point
The tolerances of parts within the liquid spring and
for excessive side play. If side play exceeds 0.24 inch,
the necessity to subject certain parts to approximately
add more shims to the spring. The total thickness of
-110F for varying lengths of time during the
shims must not exceed 0.185 inch. Any time shim
disassembly and assembly process make it impractical
thickness exceeds 0.150 inch, move the hook laterally
for it to be overhauled at the lower levels of main-
several times in each direction to make sure that the
tenance.
hook can move 40 degrees left and right without
bottoming out the liquid spring.
Damper Cylinder
While liquids are normally thought of as
The representative arresting gear assembly
incompressible, the action of the liquid spring is based
employs a vertical damper cylinder and two horizontal
on the slight compressibility of liquids. Figure 15-6
dampers to dampen hook motion caused by deck
illustrates the disassembled spring assembly. Most of
impact forces. See figure 15-7. Two centering spring
the internal parts are classified as nonrepairable, and
assemblies maintain the hook in the center position.
damage will require replacement of the parts at the
depot level of maintenance.
With the arresting hook lowered, the centering
springs are adjusted in the following manner:
The spring assembly contains 19 cubic centimeters
of oil, MIL-S-21568. The oil is confined within the
1. Center the hook assembly.
piston cylinder assembly, and any side movement of the
2. Adjust the rod ends of both centering springs
arresting hook shank must be against the com-
to reach the attaching pivot holes. Threads must be
pressibility of the oil. The maximum travel or
visible through the rod end inspection hole. See figure
compressibility of the overall liquid spring assembly is
15-8.
0.68 inch. The operating pressure within the assembly,
1. Cap
5. Seal cap
9. Piston
13. Valve slide
2. Roller, boss cap
6. Stud
10. Seal, piston
14. Seal, cylinder
3. Roller, tire cap
7. Seal, stud and piston
11. Pin, dowel, valve
15. Cylinder
4. Seal cap
8. Seal, stud
12. Valve stop
Figure 15-6.--Liquid spring shock assembly.
15-8
