toe-in. The wheel alignment should be corrected to
avoid further wear and mechanical problems.
BALANCE.—Correct balance of the tire, tube,
and wheel assembly is important. A heavy spot on an
aircraft tire causes that spot to always hit the ground
first upon landing. This results in excessive wear at
the one spot and an early failure at that part of the tire.
A severe case of imbalance may cause excessive
vibration during takeoff and landing. This makes
handling of the aircraft difficult.
Nylon Flat Spotting
If the aircraft stands in one place under a heavy
static load for several days, local stretching may cause
an out-of-round condition with a resultant thumping
during takeoff and landing.
Dual Installations
On dual-wheel installations, tires should be
matched according to the dimensions indicated in
table 11-1. Tires vary somewhat in size between
manufacturers and can vary a great deal after being
used. When two tires are not matched, the larger one
supports most or all of the load. Since one tire is not
designed to carry this increase in load,
result.
AIRCRAFT TUBES
a failure may
Learning Objective: Identify the procedures
for the selection, storage, and inspection 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.
IDENTIFICATION
Tubes are designated for the tires in which they
are to be used. For example, a type I tube is designed
for use in a type I tire. The size of the tube is the size
of the tire in which it is designed to fit.
Inner tubes required to operate at 100 psi or
higher inflation pressures are usually reinforced with
a ply of nylon cord fabric around the inside
circumference. The reinforcement extends a
minimum of one-half inch beyond that portion of the
tube that contacts the rim.
Table 11-1.—Tolerances for Diameters of Paired Tires in Dual
Installations
Tire outside
Maximum
diameter
difference in outside
diameters
Less then 18 inches
1/8 inch
18 to 24 inches
1/4 inch
25 to 32 inches
5/16 inch
33 to 40 inches
3/8 inch
41 to 48 inches
7/16 inch
49 to 55 inches
1/2 inch
56 to 65 inches
9/16 inch
More than 65 inches
5/8 inch
Type III and type VII inner tubes have radial vent
ridges molded on the surface, as shown in figure
11-29. These vent ridges relieve air trapped between
the casings and the inner tube during inflation.
Inner tube valves are designed to fit specific
wheel rims.
However, special valve-bending
configurations or extensions to provide access to the
valve stem when you are servicing the tire may be
required.
TUBE STORAGE
Tubes should be stored under the same conditions
as new tires. New tubes should be stored in their
original containers.
Used tubes should be partially
inflated (to avoid creasing), dusted with talc (to
prevent sticking), and stored in the same manner as
tires. Each tube should be plainly marked to identify
contents, size, type, cure date, and stock number.
Under no circumstances should inner tubes be hung
over nails or hooks.
INSPECTION
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 the eye. Small leaks may require a soapy water
check. Complete submersion in water is the best way
11-28
