Re-install the air valve assembly, using
a new O-ring packing. Torque the air valve assembly to
the values recommended in the applicable maintenance
Install the air valve core.
Inflate the strut, using a high-pressure
source of dry air or nitrogen.
Bottled gas should not be used to
inflate shock struts. On some shock
struts the correct amount of inflation
is determined by using a high-
pressure air gauge. On others it is
determined by measuring the amount
of extension (in inches) between two
given points on the strut. The proper
procedure can usually be found on
the instruction plate attached to the
shock strut. Shock struts should
always be inflated slowly to avoid
excessive heating and over inflation.
Tighten the swivel hex nut, using the
torque values specified in the applicable maintenance
Remove the high-pressure air line
chuck and Install the valve cap Tighten the valve cap
Shock Strut Bleeding. If the fluid level of a
shock strut has become extremely low, or if for any
other reason air is trapped in the strut cylinder, it may be
necessary to bleed the strut during the servicing
operation. Bleeding is usually performed with the
aircraft placed on jacks. In this position the shock struts
can be extended and compressed during the filling
operation, thus expelling all the entrapped air. The
following is a typical bleeding procedure:
(1) Construct a bleed hose containing a fitting
suitable for making an airtight connection to the shock
strut filler opening. The base should be long enough to
reach from the shock strut filler opening to the ground
when the aircraft is on jacks.
(2) Jack the aircraft until all shock struts are
(3) Release the air pressure in the strut to be
(4) Remove the air valve assembly.
Fill the strut to the level of the filler port
with an approved type hydraulic fluid.
(6) Attach the bleed hose to the filler port and
insert the free end of the hose into a container of clean
hydraulic fluid, making sure that this end of the hose is
below the surface of the hydraulic fluid.
(7) Place an exerciser jack or other suitable
single-base jack under the shock strut jacking point.
Compress and extend the strut fully by raising and
lowering the jack until the flow of air bubbles from the
strut has completely stopped. Compress the strut slowly
and allow it to extend by its own weight.
(8) Remove the exerciser jack, and then lower
and remove all other jacks.
(9) Remove the bleed hose from the shock
(10) Install the air valve and inflate the strut.
General Maintenance of Shock Struts. All
maintenance personnel should study all technical
manuals which pertain directly to the shock strut in
question, or aircraft maintenance publications which
have a portion of the Instructions devoted to the
particular shock strut in question. General maintenance
for pneumatic, rubber block, and spring steel shock
struts is described in the following paragraphs.
procedures for maintenance of pneumatic type shock
(a) Clean the exposed part of the piston
tube using the following procedures.
Cleaning of piston tubes reduces
excessive wear and possible failure
of shock strut packing rings.
Remove ice, mud, dust, or
sand, then wipe using a clean cloth saturated with
hydraulic fluid MIL-H-5606.
When extreme Ice, dust, mud
or sand conditions are encountered, wipe piston tubes
before and after each flight.
freezing temperatures, piston tube can be cleaned more