Combination Vehicles Flashcards
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Questions and Answers

You supply air to the trailer tanks by:

Pushing in the trailer air supply valve.

Loss of air pressure in the emergency line causes:

The trailers emergency brakes to come on.

A tractor with a (n)_____ trailer requires the shortest amount of stopping distance.

fully loaded

Bobtail tractors can take longer to stop than a combination vehicle loaded to the maximum gross weight.

<p>True</p> Signup and view all the answers

After connecting the air lines but before backing under the trailer, you should:

<p>supply air to the trailer, then pull out the trailer air supply valve.</p> Signup and view all the answers

What should you hook up before backing under a trailer?

<p>The emergency and service air lines.</p> Signup and view all the answers

The trailer is at the right height when:

<p>the trailer is raised slightly when the tractor is backed under it.</p> Signup and view all the answers

Why should you connect the air lines to a dummy coupler when they are not in use?

<p>It will keep dirt and water out of the lines.</p> Signup and view all the answers

The air leakage rate for a combination vehicle with the engine off and the brakes off should be less than_____ per minute.

<p>3 psi</p> Signup and view all the answers

Air and electric lines from the tractor to the trailer should be:

<p>secured properly with enough slack for turns.</p> Signup and view all the answers

Air brake equipped trailers made before 1975 often do not have spring brakes.

<p>True</p> Signup and view all the answers

If you cannot make a right turn without swinging into another lane, you should:

<p>turn wide as you complete the turn.</p> Signup and view all the answers

The tractor protection valve will close and the trailer emergency brakes will come on when there is a major leak in what air line?

<p>emergency</p> Signup and view all the answers

Off tracking or 'cheating' causes which of these to follow the widest path while making a turn?

<p>3 axle tractor towing a 45 foot trailer.</p> Signup and view all the answers

If your vehicle gets stuck on a railroad crossing, you should:

<p>get out of the vehicle and away from the tracks.</p> Signup and view all the answers

Where are the shut-off valves located on some trailers that must be closed when driving a set of double trailers?

<p>At the back of trailers used to tow other trailers.</p> Signup and view all the answers

Before you back under a trailer, make sure of what?

<p>Trailer brakes are locked.</p> Signup and view all the answers

To unlock the fifth wheel, you pull the handle to what position?

<p>to open.</p> Signup and view all the answers

If the service line comes apart but the emergency line stays together, what will happen right away?

<p>Nothing is likely to happen until you try to apply the brakes.</p> Signup and view all the answers

When backing a tractor under a trailer, you should:

<p>always use the lowest reverse gear.</p> Signup and view all the answers

After you have coupled the trailer, you should begin raising the landing gear using what gear?

<p>low gear.</p> Signup and view all the answers

You will know the trailer you are using has ABS by:

<p>a yellow malfunction lamp on the left side.</p> Signup and view all the answers

If you cross the air lines while coupling to an old trailer what will happen?

<p>If the trailer has no spring brakes, you could drive away but you would not have trailer brakes.</p> Signup and view all the answers

When should you get out of your vehicle when you are backing a trailer?

<p>When you are unsure of your path of travel.</p> Signup and view all the answers

When you are uncoupling a loaded trailer, you should lower the landing gear until it:

<p>makes firm contact with the ground, then turn it a few extra cranks in low gear.</p> Signup and view all the answers

How much space should be between the upper and lower fifth wheel after coupling?

<p>none.</p> Signup and view all the answers

The front trailer supports are up and the trailer is resting on the tractor. Make sure:

<p>there is enough clearance between the frame and the landing gear.</p> Signup and view all the answers

Why should you be sure that the fifth wheel is greased as required?

<p>To prevent steering problems.</p> Signup and view all the answers

After you lock the kingpin into the fifth wheel, you check the connection by:

<p>Pulling the tractor ahead gently with the trailer brakes locked.</p> Signup and view all the answers

After you supply air to the trailer, make sure the lines are not crossed and the brakes are working. This is done by:

<p>applying and releasing the trailer brakes and listening for sounds.</p> Signup and view all the answers

To be safe while driving, you should leave at least 1 second for every_____feet of vehicle length as following distance.

<p>10</p> Signup and view all the answers

Two things you can do to prevent rolling over are keep the cargo as low to the ground as possible, and:

<p>go slow around turns.</p> Signup and view all the answers

You have a major leak in the service line and you put on the brakes. Service air pressure will escape and if it goes low enough will cause the:

<p>trailer emergency brakes to come on.</p> Signup and view all the answers

When uncoupling a trailer, after you have locked the trailer brakes, you should:

<p>back up gently to ease pressure on the fifth wheel jaws.</p> Signup and view all the answers

You need to use chocks to park a trailer that does not have spring brakes.

<p>False</p> Signup and view all the answers

The fifth wheel locking lever is not locked after the jaws close around the kingpin. This means:

<p>the coupling is not right and should be fixed before driving.</p> Signup and view all the answers

When you get ready to back under a trailer, you should line up:

<p>directly in front of the trailer.</p> Signup and view all the answers

After you have coupled to a trailer, the tractor protection valve should be placed in the position:

<p>normal.</p> Signup and view all the answers

How should you test the trailer connection for security?

<p>pull gently forward with the trailer brakes locked, then look at it carefully.</p> Signup and view all the answers

The trailer air supply valve should automatically close when air pressure falls to what range?

<p>20-45 psi.</p> Signup and view all the answers

What part of the kingpin should the jaws be locked around?

<p>shank.</p> Signup and view all the answers

The higher your center of gravity of your truck, the easier it is to turn over.

<p>True</p> Signup and view all the answers

When checking that the trailer is securely coupled to the tractor, the landing gear should be:

<p>slightly raised.</p> Signup and view all the answers

If you must back your trailer on a curved path, you should position your vehicle so you can back:

<p>driver's side.</p> Signup and view all the answers

If your ABS is not working on your trailer, you should:

<p>drive normally, but get the system serviced soon.</p> Signup and view all the answers

Compared to a straight truck or bus, there are_____ things to inspect on a combination vehicle.

<p>more.</p> Signup and view all the answers

Air lines are often colored. Match the lines to their respective colors:

<p>emergency line = red service line = blue</p> Signup and view all the answers

To stop a trailer skid you should?

<p>release the service brakes.</p> Signup and view all the answers

What gear should the transmission be in after you have uncoupled and are inspecting the trailer supports?

<p>neutral.</p> Signup and view all the answers

You have coupled to a trailer. Where should the landing gear be before driving away?

<p>fully raised with the crank handle secure in the bracket.</p> Signup and view all the answers

The hand valve should be used:

<p>to test the trailer brakes.</p> Signup and view all the answers

The air leakage rate for a combination vehicle with the engine off and the brakes on should be less than_____ per minute.

<p>4 psi.</p> Signup and view all the answers

Your emergency line breaks or gets pulled apart while driving. The loss of pressure will cause the:

<p>emergency trailer brakes to come on.</p> Signup and view all the answers

You have pushed in the trailer air supply valve. You should not move the vehicle until the whole system is:

<p>at normal pressure.</p> Signup and view all the answers

You should use the hand valve to park a combination vehicle.

<p>False</p> Signup and view all the answers

The best way to tell that your trailer has started to skid is to:

<p>see it in your mirrors.</p> Signup and view all the answers

A trailer is most likely to jackknife when it is:

<p>empty.</p> Signup and view all the answers

Study Notes

Air Supply and Braking Systems

  • Air to the trailer tanks is supplied by pushing in the trailer air supply valve.
  • Loss of air pressure in the emergency line engages the trailer's emergency brakes.
  • Air leakage should be less than 3 psi per minute with the engine off and brakes off, and less than 4 psi with the engine off and brakes on.
  • The tractor protection valve closes during a major leak in the emergency air line, activating trailer emergency brakes.

Coupling and Uncoupling Procedures

  • A fully loaded tractor-trailer combination requires the shortest stopping distance.
  • "Bobtail" tractors take longer to stop than fully loaded combination vehicles.
  • Ensure trailer brakes are locked before backing under the trailer.
  • Prior to coupling, the emergency and service air lines should be hooked up while not yet under the trailer.
  • After coupling, raise the landing gear using low gear until firmly in contact with the ground.

Trailer Visibility and Handling

  • Off-tracking or "cheating" refers to a wide path taken by a 3 axle tractor towing a 45-foot trailer during turns.
  • When turning right, if the vehicle could swing into another lane, make a wider turn to avoid conflict.
  • Use chocks to park trailers without spring brakes to prevent movement.

Safety and Maintenance Checks

  • Check the fifth wheel is greased adequately to avoid steering difficulties.
  • Verify the trailer is securely attached by gently pulling forward while trailer brakes are locked.
  • The fifth wheel locking lever must be properly locked around the kingpin to ensure secure coupling.
  • Look for a yellow malfunction lamp on the left side to confirm if the trailer has ABS.

Emergency and Performance Protocols

  • If unable to make a right turn without encroaching into another lane, opt for a wider turn arc.
  • In case of vehicle being stuck on railroad tracks, exit immediately and move away from the tracks for safety.
  • The transmission should be in neutral when inspecting trailer supports after uncoupling.
  • Anticipate an empty trailer is more likely to jackknife during sharp turns.

Other Important Facts

  • Release the service brakes to stop a trailer skid and avoid engaging the hand valve for parking.
  • When backing, align directly in front of the trailer for better control.
  • Secure air and electric lines properly while allowing enough slack for turns.
  • Ensure clearances are maintained between the trailer frame and landing gear when lifted.

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Description

Test your knowledge of combination vehicles with these flashcards. Each card focuses on crucial concepts such as air supply, emergency brakes, and stopping distances. Perfect for anyone preparing for a commercial driver's license.

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