Towing vehicle Operator manual
The trailer is designed for use in a wide range of conditions. The paragraphs in this work package
provide the data and procedures to be used by the Operator when operating the trailer under emergency
conditions. Items covered include loss in air pressure and nuclear, biological, and chemical (NBC)
LOSS IN AIR PRESSURE
When the trailer is attached to a towing vehicle, the vehicle air supply is opened to the trailer, creating a
single air system. If a leak occurs, the towing vehicle air system will attempt to compensate for the loss.
If the leak is greater than the system's ability to compensate, the towing vehicle alarm will sound. If the
leak is in the trailer and air pressure drops to 55 - 65 psi, (379-448 kPa) the towing vehicle air brake
protection valve will start to close, isolating the trailer and protecting the towing vehicle air supply. The
trailer will continue to lose air until the spring brakes activate.
While Coupled to Towing Vehicle
Check brake air pressure gages if indicator(s) and/or an audible alarm sounds on the towing vehicle
indicating low air pressure.
Trailer axle service brakes will not operate if towing vehicle brake air pressure
gage reads below 75 psi (517 kPa). Trailer braking will be provided by spring
brakes for a limited time. Allow greater stopping distance. Discontinue
trailering operation as soon as possible. Failure to comply may result in
serious injury or death to personnel.
Do not attempt to tow the trailer with spring brakes caged except to move the trailer out
of the traveled portion of the highway. Failure to comply may result in damage to
If air pressure reads below 75 psi (517 kPa):
Leave additional distance between vehicles.
Apply brake pedal earlier than usual when slowing towing vehicle and trailer.