FAA Advisory Circular 43.13-1B
Acceptable Methods, Techniques, and Practices
Aircraft Inspection and Repair
AC 43.13-1B | 9. Aircraft Systems and Components | 1. Inspection and Maintenance of Landing Gear | 9-4. Fixed-gear Inspection
AC 43.13-1B CHG 1
9/27/01
nual inspection of the fixed gear, the aircraft
should be jacked up to relieve the aircraft
weight. The gear struts and wheels should be
checked for abnormal play and corrected.
a. Old aircraft landing gear that em-
ploys a rubber shock (bungee) cord for shock
absorption must be inspected for age, fraying
of the braided sheath, narrowing (necking) of
the cord, and wear at points of contact with the
structure and stretch. If the age of the shock
cord is near 5 years or more, it is advisable to
replace it with a new cord. A cord that shows
other defects should be replaced, regardless of
age.
b. The cord is color-coded to indicate
when it was manufactured and to determine
the life of the shock cord. According to
MIL-C-5651A, the color code for the year of
manufacture is repeated in cycles of 5 years.
Table 9-1 shows the color of the code thread
for each year and quarter year.
TABLE 9-1. Bungee cord color codes.
YEARS ENDING
WITH
0 or 5
1 or 6
2 or 7
3 or 8
4 or 9
COLOR
Black
Green
Red
Blue
Yellow
QUARTER
1st
2nd
3rd
4th
1st
COLOR
Red
Blue
Green
Yellow
Red
c. The color coding is composed of
threads interwoven in the cotton sheath that
holds the strands of rubber cord together. Two
spiral threads are used for the year coding and
one thread is used for the quarter of the year
sheath, e.g. yellow and blue would indicate
that the cord was manufactured in 1994 during
April, May, or June.
d. Shock struts of the spring-oleo type
should be examined for leakage, smoothness
of operation, looseness between the moving
parts, and play at the attaching points. The
extension of the struts should be checked to
make sure that the springs are not worn or bro-
ken. The piston section of the strut should be
free of nicks, cuts, and rust.
e. Air-oil struts should undergo an in-
spection similar to that recommended for
spring-oleo struts. In addition, the extension
of the strut should be checked to see that it
conforms to the distance specified by the
manufacturer. If an air-oil strut “bottoms”—
that is, it is collapsed—the gas charge and
hydraulic fluid has been lost from the air
chamber. This is probably due to a loose or
defective air valve or to defective O-ring seals.
CAUTION: Before an air-oil strut is
removed or disassembled, the air
valve should be opened to make sure
that all air pressure is removed. Se-
vere injury and/or damage can occur
as the result of disassembling a strut
when even a small amount of air pres-
sure is still in the air chamber.
f. The method for checking the fluid
level of an air-oil strut is given in the manu-
facturer’s maintenance manual. An alternate
means of servicing an oil strut is to jack up the
aircraft, remove the strut’s valve cap, release
the air charge in the strut by depressing the
valve core, remove the strut’s valve core, at-
tach a clean two-foot rubber or plastic hose to
the threaded portion that houses the valve core,
and secure with a hose clamp. Put the other
end of the hose into a clean two quart con-
tainer filled with the correct hydraulic fluid for
the strut. Cover the container with a clean rag
to prevent spillage. Now, slowly raise the
gear/strut assembly either manually or with
another jack under the strut. This will drive
the remaining air out of the strut into the con-
tainer of hydraulic fluid. Once the gear is fully
retracted, slowly lower the gear. The hydraulic
fluid in the can will be sucked into the strut.
Repeat this procedure until you cannot hear
any more air bubbles in the container when the
wheel strut is fully retracted. With the strut
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