strut fully (by raising and lowering the jack) until the
If the strut's chamber is overpressurized, the
flow of air bubbles from the strut has completely
additional pressure will tend to keep the strut
stopped.
pressurized after takeoff. On those aircraft that use
shrink mechanisms, the shrink mechanisms may be
NOTE: Compress the strut slowly and allow it to
overloaded or stall the strut actuator as the gear retracts.
extend by its own weight.
If the gear retracts in the wing without shrinking, due to
8. Remove the exerciser jack, and then lower and
the failure of the shrink mechanism, damage to both the
remove all other jacks.
wing and landing gear may result.
9. Remove the bleed hose from the shock strut.
10. Tighten the air valve swivel hex nut to a
recommended torque of 50 to 70 inch-pounds.
10. Install the air filler valve and inflate the strut.
11. Remove the high-pressure air-line chuck and
Inspection
install the valve cap fingertight.
Because some aircraft struts require special
Shock struts should be inspected regularly for
servicing procedures, the General Information and
leakage of fluid and for proper extension. Exposed
Servicing section of the applicable MIM should always
portions of the strut pistons should be cleaned in the
be checked before servicing the shock struts of any
same manner as actuating cylinder pistons during
aircraft.
preflight and postflight inspections. Exposed pistons
should be inspected closely for scoring and corrosion.
Bleeding
Excessive leakage of fluid can usually be stopped by
deflating the strut and tightening the packing gland nut.
If the fluid level of a shock strut has become
If leakage still persists after tightening the packing
extremely low or, if for any other reason, air is trapped
gland nut and reinflating the strut, the strut must be
in the strut cylinder, it may be necessary to bleed the
disassembled and the packings replaced.
strut during the servicing operation. Bleeding is per-
The tools shown in figure 13-17 are typical of the
formed with the aircraft placed on jacks. In this posi-
tools used during disassembly and assembly of landing
tion, the shock struts can be extended and compressed
gear shock struts. Normally, each tool is designed for,
during the filling operation, expelling all of the en-
and should be used only on, one type of installation.
trapped air. As mentioned earlier, certain aircraft must
When using wrenches, you must take care to maintain
be placed on jacks for routine servicing of the shock
the lugs of the wrenches in their respective positions.
struts. The following is a typical bleeding procedure.
Slippage of the wrench, when under torquing
1. Construct a bleed hose that contains a fitting
conditions, may cause damage to aircraft parts, the tool,
suitable for making an airtight connection to the shock
or even injury to personnel. NEVER place extension
strut filler opening. The hose should be long enough to
handles of any type on these tools to increase the
reach from the shock strut filler opening to the deck
applied force.
when the aircraft is on jacks.
2. Jack the entire aircraft until all shock struts are
fully extended.
3. Release the air or nitrogen pressure in the strut
to be bled, as previously described in this chapter.
4. Remove the air filler valve assembly.
5. Fill the strut to the level of the filler port with
hydraulic fluid.
6. Attach the bleed hose to the filler port, and
insert the opposite end of the hose into a quantity of
clean hydraulic fluid.
7. Place an exerciser jack or other suitable
single-base jack under the shock strut jacking point.
See view C of figure 13-15. Compress and extend the
Figure 13-17.--Landing gear shock strut tools.
13-17
