Figure 12-10.–Nose gear shock strut.
Figure 12-9.–Landing gear shock strut (metering tube type).
On some types of shock struts now in service, a
metering tube replaces the metering pin, but shock strut
operation is the same. An example of this type of shock
strut is shown in figure 12-9.
Some shock struts are equipped with a dampening
or snubbing device, which consists of a recoil valve on
the piston or recoil tube. The purpose of the snubbing
device is to reduce the rebound during the extension
stroke and to prevent a too rapid extension of the shock
strut, which would result in a sharp impact at the end of
the stroke.
The majority of shock struts are equipped with an
axle that is attached to the lower cylinder to provide for
tire and wheel installation. Shock struts not equipped
with axles have provisions on the end of the lower
cylinder for ready installation of the axle assembly.
Suitable connections are also provided on all shock
struts to permit attachment to the aircraft.
A fitting, which consists of a fluid filler inlet and a
high-pressure air valve, is located near the upper end of
each shock strut to provide a means of filling the strut
with hydraulic fluid and inflating it with air or
nitrogen.
A packing gland designed to seal the sliding joint
between the upper and lower telescoping cylinders is
installed in the open end of the outer cylinder. A packing
gland wiper ring is also installed in a groove in the lower
bearing or gland nut on most shock struts to keep the
sliding surface of the piston or inner cylinder free from
dirt, mud, ice, and snow. Entry of foreign matter into the
packing gland will result in leaks. The majority of shock
struts are equipped with torque arms attached to the
upper and lower cylinders to maintain correct alignment
of the wheel.
Nose gear shock struts are provided with an upper
centering cam that is attached to the upper cylinder and
a mating lower centering cam that is attached to the
lower cylinder. See figure 12-10. These cams serve to
line up the wheel and axle assembly in the straight-ahead
position when the shock strut is fully extended. This
prevents the nosewheel from being cocked to one side
when the nose gear is retracted, preventing possible
structural damage to the aircraft. These mating cams
12-9
