CDL Combination & Air brake Test
Questions and Answers
"Off-tracking" occurs when you go around a corner and... - ANSWER-The rear wheels
follow a different path than the front wheels
A kingpin is.... - ANSWER-A pin which locks the trailer to the tractor on the fifth wheel
After you supply air to the trailer, make sure the air lines are not crossed and the trailer
brakes are working. This is done by: - ANSWER-Applying and releasing the trailer
brakes and listening for brake sounds.
Air lines on a combination vehicle are often colored to keep them from getting mixed up.
The emergency line is ____; the service line is ____. - ANSWER-Red, Blue
before you back under a trailer, make sure the... - ANSWER-trailers brakes are locked
Before you begin coupling.... - ANSWER-Check your path for Hazards
How should you test the tractor semi trailer connection for security? - ANSWER-Pull
gently forward in low gear against the locked trailer brakes, then look at it carefully.
If one of the glad hands on your blue air line is missing a seal... - ANSWER-You might
end up with a service line air leak.
If the service air line comes apart while you are driving a combination vehicle but the
emergency line stays together, what will happen right away? - ANSWER-Nothing is
likely to happen until you try to apply the brakes. (Correct Answer)
If you cross connect the two air lines the following will result... - ANSWER-You will not
have air going to the trailer brakes
If you cross your air lines on a new trailer with spring brakes... - ANSWER-you won't be
able to release the trailer brakes
if you start a trailer skid you should. - ANSWER-Release the brakes to get traction back
In normal driving, some drivers use the hand valve before applying the brake pedal to
prevent a jackknife. Which of these statements is true? - ANSWER-Dont do it
In order to inspect the coupling you should... - ANSWER-use a Flashlight
In order to supply air to the trailer, you must first... - ANSWER-Push in the tractor
protection valve
, Large combination vehicles take longer to stop... - ANSWER-When they are empty
Semi trailers made before 1975 that are equipped with air brakes: - ANSWER-Often do
not have spring brakes. (Your Answer)
The air leakage rate for a combination vehicle (engine off, brakes off) should be no
more than ____ psi per minute. - ANSWER-3
The air leakage rate for a combination vehicle (engine off, brakes on) should not be
more than ____ psi per minute. - ANSWER-4
The device which connects the service and emergency air lines from the truck to the
trailer is called... - ANSWER-Glad Hands
The driver crosses the air lines when hooking up to an old trailer. What will happen? -
ANSWER-If the trailer has no spring brakes, you can drive away, but you will not have
trailer brakes.
The earliest way to notice a trailer skid is... - ANSWER-By seeing it in your mirrors
The fifth wheel locking lever is not locked after the jaws close around the kingpin. This
means that: - ANSWER-The coupling is not right and should be fixed before driving the
vehicle.
The fifth wheel should be checked to see if... - ANSWER-There is any damage or
missing parts
It is properly greased
The jaws are open
The front trailer supports are up and the trailer is resting on the tractor. Make sure: -
ANSWER-There is enough clearance between the tractor frame and the landing gear.
There is enough clearance between the tops of the tractor tires and the nose of the
trailer.
the hand valve should be used: - ANSWER-To test the trailer brakes.
The safety catch for the fifth wheel locking lever must be ____ for a coupling to be
complete. - ANSWER-Over the locking level
The service air line is controlled by.. - ANSWER-The pressure applied to the line by the
foot brake or the trailer hand brake
The relay valve which connects the trailer air tanks to the trailer air brakes
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