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NC CDL Combination Vehicles
Questions with expert curated
solutions ( GUARANTEED SUCCESS )
You are coupling a semi-trailer to your tractor but have not yet backed under, the trailer is at the right height when: - answer It will be raised slightly when the tractor is backed under it. You should not back a tractor under a trailer until the whole air system is: - answer At normal pressure. Which part of the kingpin should the locking jaws close around? - answer The shank. When you get ready to back under the semi-trailer you should line up: - answer Directly in front of the trailer. 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. When should you use the hand valve to park a combination vehicle? - answer Never.
You supply air to the trailer tanks by: - answer Pushing in the trailer air supply valve. Why should you be sure that the fifth wheel plate is greased as required? - answer To prevent steering problems. 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. There are two things that a driver can do to prevent a rollover. They are: (1) Keep the cargo as close to the ground as possible; and (2): - answer Go slowly around turns. Before you back under a trailer, make sure the: - answer Trailer brakes are locked. 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.
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. You are coupling a tractor to a semi-trailer and have backed up but are not under it. What should you hook up before backing under the semi- trailer? - answer The emergency and service air lines. 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 Which of these statements is true? - answer "Bobtail" tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight. After connecting the air lines, but before backing under the trailer, you should: - answer Supply air to the trailer system, then pull out the air supply knob. The hand valve should be used: - answer To test the trailer brakes.
The air leakage rate for a combination vehicle (engine off, brakes off) should be no more than ___ PSI per minute. - answer 3 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. 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: - answer The tractor protection valve to close. Semi-trailers made before 1975 that are equipped with air brakes: - answer Often do not have spring brakes. Almost half of all truck driver deaths are the result of: - answer Rollovers. What statement best explains "crack the whip effect"? - answer When you make a quick lane change or sudden movement with your steering wheel, the rear trailer tends to swing out. The force of the rear trailer becomes amplified, causing it to roll over (rearward amplification). Which type of truck-trailer combination has the best chance of the "crack the whip" rollover? - answer A tractor pulling 3 trailers.
Glad hands are used to connect the: - answer Service and emergency air lines from the truck to the trailer. A driver crosses the air lines when hooking up to an old trailer. What will happen? - answer If the trailer has no spring brakes, you could drive away but you wouldn't have trailer brakes. The hand valve should be used: - answer To test the trailer brakes. When driving a set of doubles it is necessary to close which shut-off valve in the last trailer? - answer Back. Your emergency air line breaks or gets pulled apart while you are driving. The loss of pressure will cause the: - answer Emergency trailer brakes to come on. How much space should be between upper and lower fifth wheel after coupling? - answer None. If the brakes are not released when you pushed the trailer air supply valve you should: - answer Check air line connection.
You have pushed the trailer air supply valve. You shouldn't back a tractor under a trailer until the whole air system is: - answer At normal pressure. You are coupling a tractor to a semi-trailer. You have connected the air lines. Before backing under the trailer you should: - answer Supply air to the trailer system, then pull out the air supply knob. After you have coupled the trailer you should have to raise the landing gear by using: - answer Low gear. When connecting the glad hands press the two seals with the coupler together at what degree to each other? - answer 90 degrees. The iron 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 gears. When you are uncoupling a loaded trailer lower the landing gear until it: - answer Makes firm contact with the ground. When coupling, the proper position of the fifth wheel is: - answer Tilted down toward the end of the tractor.
The tractor protection valve will close and the trailer emergency brakes will come on when there is a major leak in the ____ brake line. - answer Emergency. To unlock the fifth wheel, pull the release handle to the _____ position. - answer Open. Off-tracking or cheating causes which of these to follow the wider pass while making a turn? - answer Triple towing a 45-feet trailer. To stop a trailer skid you should: - answer Release the brakes. When should you use the hand valve to park a combination vehicle? - answer Never. When checking the trailer emergency brakes, the tractor protection control valve should be place in the ________ position. - answer Emergency. What gear should the tractor be in after you uncouple from the trailer and are inspecting the trailer supports? - answer Neutral.
You are uncoupling a trailer. After you shut off the trailer air supply and lock the trailer brakes, you should: - answer Back up gently to ease pressure on the fifth wheel locking jaws. Combination vehicles are usually heavier, longer, and require more driving skill than single commercial vehicles. - answer True. More than half of truck driver deaths in crashes are the result of rollovers. Trucks turn over easier when fully loaded and are: - answer Ten times more likely to roll over in a crash than empty rigs. When you turn suddenly while pulling doubles, which trailer is most likely to turn over? - answer The rear trailer is twice as likely to turn over as the tractor. Why should you not use the trailer hand brake to straighten out a jackknifing trailer? - answer Because the brakes on the trailer wheels caused the skid in the first place. What is a tractor jackknife? - answer When you lock up the driver tires on the tractor and the tractor spins out sideways as the trailer continues to push forward. You should swing wide to the left before starting a 90 degree turn to the right? - answer No
When a vehicle is carrying a load at night which extends four feet or more beyond the rear of the body, there must be _____ at the extreme end of the load. - answer 2 red lights. How long does it take a typical tractor-trailer to clear a single track? A double track? - answer It takes 14 seconds to clear a single track, and more than 15 seconds to clear a double track. You have pushed in the trailer supply valve. You should not move the tractor until the whole air system is: - answer At normal pressure. The best way to tell if your trailer has started to skid is to: - answer See it in your mirrors. Which of these vehicles off-track the most. - answer 5-axle tractor towing a 52-foot trailer. A tractor with a(n) ____ trailer requires the shortest amount of stopping distance. - answer Fully loaded. A trailer is most likely to jackknife when it is: - answer Empty.
If you have coupled with a semi-trailer, where should the front trailer supports be before driving away? - answer Fully raised with the crank handle secured in its bracket. 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 coupled unit. You want to inspect the trailer supports. You should place the tractor transmission in which gear after you have uncoupled the trailer? - answer Neutral. When should you use chocks to park a trailer not equipped with spring brakes? - answer Always.
