type, cure date, and stock number. Under no
tubes. Identify the procedures for the inspec-
circumstances should inner tubes be hung over nails or
tion of aircraft tire tubes.
The purpose of the inner tube is to hold the air in the
tire. Tubes are identified by the type and size of the tire
in which they are to be used.
Inner tubes should be inspected and classified as
serviceable or nonserviceable. Usually, leaks due to
punctures, breaks in the tire, and cuts can be detected by
Tubes are designated for the tires in which they are
the eye. Small leaks may require a soapy water check.
to be used. For example, a type I tube is designed for
Complete submersion in water is the best way to locate
use in a type I tire. The size of the tube is the size of the
small leaks. If the tube is too large to be submerged,
tire in which it is designed to fit.
spread soapy water over the entire surface and examine
Inner tubes required to operate at 100 psi or higher
it carefully for air bubbles. The valve stem and valve
inflation pressures are usually reinforced with a ply of
base should be swished around to break any temporary
nylon cord fabric around the inside circumference. The
seals. The tube should be checked for bent or broken
reinforcement extends a minimum of one-half inch
valve stems and stems with damaged threads.
beyond that portion of the tube that contacts the rim.
Type III and type VII inner tubes have radial vent
ridges molded on the surface, as shown in figure 7-29.
Inner tubes should be classified as serviceable if
These vent ridges relieve air trapped between the
they are found to be free of leaks and other defects
casings and the inner tube during inflation.
when they are inflated with the minimum amount of
nitrogen required to round out the tube and water
Inner tube valves are designed to fit specific wheel
rims. However, when you are servicing the tire, a
special valve-bending configuration or extension to
provide access to the valve stem may be required.
Nonserviceable tubes may be repairable or
nonrepairable. Nonserviceable tubes with the following
defects should be classified as repairable:
Tubes should be stored under the same conditions
as new tires. New tubes should be stored in their
· Bent, chafed, or damaged metal valve threads
original containers. Used tubes should be partially
· Replaceable leaking valve cores
inflated (to avoid creasing), dusted with talc (to prevent
sticking), and stored in the same manner as tires. Each
Nonserviceable tubes with the following defects
tube should be plainly marked to identify contents, size,
should be classified as nonrepairable:
· Any tear, cut, or puncture that completely
penetrates the tube
· Fabric-reinforced tubes with blisters greater
than one-half inch in diameter in the reinforced
· Chafed or pinched areas caused by beads or tire
· Valve stems pulled out of fabric-base tubes
· Folds or creases
· No balance marker
Figure 7-29.--Inner tube vent ridges.