CDL Combination Flashcards

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Questions and Answers

Glad hands are used to connect the?

Service and emergency air lines from the tractor to the trailer

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

To prevent steering problems

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

Supply air to the trailer system, then pull out the supply knob

A tractor trailer vehicle combination is most likely to roll over in a turn when the configuration includes?

Triple 28 foot trailers Signup and view all the answers

The trailer air supply control valve should automatically close when the air pressure falls to between what PSI?

20 and 45 Signup and view all the answers

When coupling, the proper position of the fifth wheel is?

Tilted down towards the end of the tractor Signup and view all the answers

Which part of the king pin should the locking jaws close around?

The shank Signup and view all the answers

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

Slightly raised Signup and view all the answers

A trailer is most likely to jackknife when it is?

Empty Signup and view all the answers

The spring doesn't release when you push the trailer air supply control valve; you should?

Check the air line connections Signup and view all the answers

Loss of air pressure in the emergency lines causes?

The trailer emergency brakes to come on Signup and view all the answers

When you get ready to back under a semi-trailer, you should line up?

Directly in front of the trailer Signup and view all the answers

The best way to tell if your trailer has started to skid is to?

See it in your mirrors Signup and view all the answers

Why should you lock the tractor glad hands to each other or to the dummy couplers when you are not towing a trailer?

It will keep dirt and water out of the air lines Signup and view all the answers

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

Open Signup and view all the answers

When should you use the hand valve to park a combination vehicle?

Never Signup and view all the answers

A driver crosses the air lines when hooking up to an old trailer; what will happen?

If the trailer has no spring brakes, you could drive away but would have no trailer brakes Signup and view all the answers

You supply air to the trailer trucks by?

Pushing in the trailer air supply valve Signup and view all the answers

The front trailer supports are up and the trailer is resting on the tractor; make sure?

Connecting to the service line glad hand Signup and view all the answers

The safety latch for the fifth wheel locking lever must be and for a coupling to be correct?

Over the locking lever Signup and view all the answers

You are hooking a tractor to a semi-trailer and have backed up but are not under it; what should you do before backing under the trailer?

Hook up the emergency and service air lines Signup and view all the answers

After pushing in the trailer supply valve, you should not move the tractor until air system is?

At normal pressure Signup and view all the answers

There are two things that a driver can do to prevent a rollover; they are one keep the cargo as close to the ground as possible and what else?

Reduce your speed before entering curves or turns Signup and view all the answers

With the engine off, and the brakes released and your foot on the brake pedal, a combination vehicle air brake system should not leak more than how many PSI in one minute?

4 PSI Signup and view all the answers

If the fifth wheel locking lever is not locked after the jaws close around the king pin?

The coupling is not correct and should be corrected before driving the coupled unit Signup and view all the answers

After coupling a semi-trailer you should crank the front trailer supports how high?

Fully raised with the handle in its bracket (cradle) Signup and view all the answers

Air brake equipped trailers made before 1975?

Usually do not have spring brakes Signup and view all the answers

During normal driving, some drivers use the trolly (hand valve) before the brake to prevent trailer skids. This should be done.

False Signup and view all the answers

You are hooking up to a tractor and semi-trailer and have connected both air lines; before backing under the trailer what should you do?

Supply air to the trailer system then pull out the supply knob to lock the trailer brakes Signup and view all the answers

If the service line disconnects while you are driving, what will happen right away?

Nothing is likely to happen until you try to use your brakes Signup and view all the answers

After hooking up you should check the fifth wheel connection by?

Pulling the tractor ahead gently with the trailer brakes locked Signup and view all the answers

When hooking a tractor to a trailer, you will know the trailer is at the correct height when the?

The coupling device of the trailer is just below the middle of the tractor fifth wheel Signup and view all the answers

You are driving a combination vehicle when the tractor breaks away and pulls apart the air lines; you would expect the trailer brakes to apply and?

The tractor brakes to keep working properly Signup and view all the answers

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

None Signup and view all the answers

At what angle do you connect your glad hand connections to the trailer?

90 degrees Signup and view all the answers

The hand valve should be used?

To test the trailer brakes Signup and view all the answers

What is off tracking?

When the rear wheels follow a different path than the front Signup and view all the answers

What is the purpose of the service lines?

To carry air to the trailer service brakes Signup and view all the answers

In coupling, when is the trailer height correct?

When the trailer will be lifted slightly when the tractor connects Signup and view all the answers

Which of these statements about backing a vehicle is true?

You should avoid backing whenever possible Signup and view all the answers

According to accident reports, the vehicle trucks and buses most often collide with is?

The one in front of them Signup and view all the answers

Which of these is a good thing to do when steering to avoid a crash?

Don't turn any more than needed to clear what is in your way Signup and view all the answers

For your safety when setting out reflective triangle, you should?

Hold the triangle between yourself and oncoming traffic Signup and view all the answers

You are dropping a trailer and the release arm won't release properly because the locking jaws have too much pressure on them; what should you do?

Gently back up the tractor and set your tractor brakes Signup and view all the answers

If you are dropping a fully loaded trailer, how do you lower the landing gear?

After landing gear makes firm contact with the ground, turn crank in low gear a few extra turns Signup and view all the answers

After unhooking tractor from trailer, pull tractor forward how far?

Pull tractor forward until back tires are even with the front of the trailer Signup and view all the answers

After the tractor is pulled to the proper distance in front of the trailer, how do you secure the tractor?

Engage the parking brakes with the transmission in neutral Signup and view all the answers

When inspecting the trailer supports, you should check for?

Ground support and damage Signup and view all the answers

If your trailer doesn't have spring brakes, how should you secure it?

Use chalk blocks Signup and view all the answers

What color are the trailer service and emergency air lines?

Blue and red Signup and view all the answers

Study Notes

Glad Hands and Air Lines

Glad hands connect service and emergency air lines from the tractor to the trailer.
Trailer service air lines are colored blue; emergency air lines are red.

Fifth Wheel Maintenance

Grease the fifth wheel plate to avoid steering issues.
The proper fifth wheel position is tilted down toward the tractor's end.

Air System Procedures

Supply air to the trailer system before backing under the trailer, then pull the supply knob.
The trailer air supply control valve closes automatically when air pressure drops between 20 and 45 PSI.
Avoid using the hand valve for parking; it should only be used to test trailer brakes.

Coupling and Coupling Safety

Coupling is correct when the safety latch for the fifth wheel locking lever is over the lever.
Before backing under a trailer, connect emergency and service air lines.
The coupling device should be just below the middle of the tractor's fifth wheel to indicate proper trailer height.

Trailer Stability and Braking

Triple 28-foot trailers are prone to rollovers, especially in turns.
A trailer is likely to jackknife when it is empty.
Loss of air pressure in emergency lines activates trailer brakes.

Driver Awareness and Safety

Check fifth wheel connections by gently pulling the tractor ahead with the trailer brakes applied.
Drivers should always see the trailer in mirrors to detect skidding.
In the event of air line disconnection while driving, trailer brakes will engage only if the trailer has spring brakes.

Parking and Uncoupling a Trailer

After unhooking from a trailer, pull the tractor forward until the rear tires align with the front of the trailer.
When lowering landing gear on a fully loaded trailer, turn the crank a few extra turns after firm ground contact.

Safety Precautions

Hold reflective triangles in a manner that positions you safely away from oncoming traffic.
If the release arm won't disengage due to pressure on locking jaws, gently back up and set the tractor's brakes.

General Knowledge and Best Practices

Maintain no gap between upper and lower fifth wheel plates during coupling.
Off-tracking occurs when rear wheels follow a different path than the front.
Turning should be minimal while steering to avoid collisions.

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Description

Test your knowledge on key terms and procedures related to combination vehicles in CDL training. From connecting air lines to maintaining the fifth wheel, these flashcards cover essential concepts for aspiring truck drivers. Perfect for preparing for your commercial driver's license exam!