Questions and Answers
A tractor with a(n) ________ trailer requires the shortest amount of stopping distance.
fully loaded
The air leakage rate for a combination vehicle (engine off, brakes on) should not be more than _____ psi per minute.
4
What could happen if you do not do the final air brake check for air leaks before driving?
you could lose your brakes while driving
Which part of the kingpin should the locking jaws close around?
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Glad hands are used to connect the....
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Trucks roll over more easily when fully loaded and are ...
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In general, the higher your truck's center of gravity, the...
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You are driving a combination vehicle when the trailer breaks away, pulling apart both air lines. You would expect the trailer brakes to come on and...
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When you drive a set of doubles, which shut-off valve must be closed in the last trailer?
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The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means that...
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What gear should the tractor engine be in after you uncouple the trailer and are inspecting the trailer?
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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...
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If the brakes did not release when you pushed the trailer air supply valve, you should...
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You have a major leak in the service line, and you apply the brakes. Service air pressure will escape and cause the...
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You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you should...
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When should you use the hand valve to park a combination vehicle?
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The front trailer supports are up, and the trailer is resting on the tractor. Make sure that...
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Study Notes
Stopping Distance
- A fully loaded trailer requires the shortest stopping distance compared to empty or lightly loaded trailers.
Air Leakage Rate
- The acceptable air leakage rate for a combination vehicle (engine off, brakes on) should not exceed 4 psi per minute.
Importance of Final Air Brake Check
- Skipping the final air brake check can lead to a potential loss of brakes while driving.
Kingpin Locking
- The locking jaws should securely close around the shank of the kingpin.
Glad Hands Function
- Glad hands are crucial for connecting the service and emergency air lines from the truck to the trailer.
Rollover Risk
- Fully loaded trucks are ten times more likely to roll over in a crash compared to empty rigs.
Center of Gravity
- A higher center of gravity increases the likelihood of a truck turning over during maneuvers.
Trailer Breakaway Scenario
- If the trailer breaks away, the tractor protection valve will close, preventing air pressure loss in the tractor.
Shut-off Valve in Doubles
- The shut-off valve that must be closed in the last trailer of a doubles setup is the back section.
Fifth Wheel Locking Lever
- If the fifth wheel locking lever is not locked after the jaws close, it indicates that the coupling is incorrect and needs to be addressed before proceeding.
Gear Position after Uncoupling
- After uncoupling the trailer and during inspection, the tractor engine should be in neutral.
Trailer Brake Testing
- Testing trailer brakes involves applying and releasing them while listening for audible brake sounds to ensure proper operation.
Addressing Brake Release Issues
- If trailer brakes do not release, check the air line connections rather than crossing the air lines.
Major Leak in Service Line
- A major leak in the service line will trigger the trailer emergency brakes to engage when brakes are applied.
Uncoupling Procedure
- When uncoupling a trailer, after shutting off the trailer air supply, it is important to back up gently to relieve pressure on the fifth wheel locking jaws.
Hand Valve Usage
- The hand valve should never be used to park a combination vehicle.
Clearance Checks
- Ensuring adequate clearance between the tractor frame and landing gear is critical when the front trailer supports are lifted and the trailer rests on the tractor.
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Description
Test your knowledge on combination vehicles with this CDL practice test. The quiz covers essential topics such as stopping distances and air leakage rates, crucial for drivers operating combination vehicles. Perfect for anyone preparing for their CDL exam.