struts. The amount a strut is inflated depends upon the
5. When the strut is fully compressed, the air
specific aircraft strut being serviced. One manufacturer
valve assembly may be removed by breaking the safety
may use a strut inflation chart, such as the one shown in
wire and turning the 3/4-inch body nut counter-
view D of figure 13-15. The strut is measured as
clockwise.
indicated at dimension "A." This measurement, in
6. Use the type of hydraulic fluid specified on the
inches, is then located on the bottom of the inflation
shock strut inspection plate to fill the strut to the level of
chart. For example, locate the measurement of 1.75
the air valve opening. Figure 13-16 shows the
inches on the chart. From this point, vertically trace an
instruction plate found on one type of aircraft main
imaginary line until it intersects the curved line. At this
landing gear strut. Improper oil level in the strut
point of intersection, horizontally trace a second
chamber will decrease the shock absorbing capabilities
imaginary line to the left edge of the chart. The figure
of the strut and could cause the strut to bottom out
indicated at this point (550 psi) is the required pressure
during landing. This would damage the strut and/or
for that particular extension of the strut.
wing structure.
All aircraft struts are not measured from the same
NOTE: The instruction plate may be found on the
points. View E of figure 13-15 shows another location
strut or on the wheel door near the strut.
where strut extension is measured. The proper
7. Reinstall the air valve assembly, using a new
procedure to use will always be found on the instruction
O-ring packing. Torque the air valve body hex nut from
plate attached to the shock strut. If these instructions
100 inch-pounds to 110 inch-pounds, as shown in view
are not legible, consult the applicable MIM.
B of figure 13-15.
If the strut's chamber is underpressurized, the strut
8. Lockwire the air valve assembly to the strut,
may not overcome normal O-ring friction during
using the holes provided in the body nut.
extension on takeoff. This condition could prevent the
strut from fully extending, thus the torque scissors limit
9. I n f l a t e t h e s t r u t , u s i n g a r e g u l a t e d
switch would not actuate to close the electrical circuit
high-pressure source of nitrogen or dry air. Under no
to retract the gear. It would also cause the strut to
circumstances should any type of bottle gas other than
bottom during taxiing and landing operations.
nitrogen or compressed air be used to inflate shock
Figure 13-16.--Landing gear strut servicing instruction plate.
13-16
