TM 9-2330-294-14
Figure 1-3. Air suspension system.
(2) Service brakes. The service brakes are
applied when air pressure is routed to the two air
chambers on each wheel. The service brakes are
normally activated by a sequence of manual and
automatic operations. When the towing vehicle
operator applies the brake treadle in the cab, an air
pressure signal is transmitted through the
semitrailer service air line to the emergency relay
valves. The emergency relay valves then operate
automatically to route reservoir air through the
service brake air supply lines to the air chambers to
(1) General. When the semitrailer brake
apply the brakes. The service brakes will also apply
system is connected to the towing vehicle air brake
automatically if the semitrailer breaks away from the
system, the towing vehicle air brake system controls
towing vehicle, if a severe leak occurs in the
the brakes on both vehicles. The system will hold the
emergency air line, or when the towing vehicle
semitrailer loaded with rated payload on a 30-percent
parking brake is set. When the service brakes are
grade with the towing vehicle and semitrailer brakes
applied as a result of a severe leak or uncoupling
applied. The self-adjusting, internal-expanding
from the towing vehicle, the brakes can be released
brakes are of a dual-actuating, wedge-type brake
by pushing the service brake release knob on the
shoe design. Each wheel has two identical brake
schematic representation of the brake air system
lines and components.
(3) Fail-safe brake unit. Each axle end is
Change 2