ELDT - Entry Level Driver Training Coupling and Uncoupling Questions and Answers 2 — Questions and Answers

Question 1: When coupling a tractor to a trailer, what should you check before backing under the trailer?

That the trailer brakes are released
That the trailer landing gear is fully raised
That the kingpin is not bent or broken (Correct answer)
That the trailer doors are closed

Correct answer: That the kingpin is not bent or broken

A bent or broken kingpin will not lock properly in the fifth wheel, creating an extremely dangerous situation where the trailer could separate from the tractor.

The kingpin is the critical connection point between the trailer and the fifth wheel on the tractor. Before backing under the trailer, drivers must visually inspect the kingpin to ensure it is straight, undamaged, and free of debris. A damaged kingpin may appear to lock but could fail under load, causing trailer separation. FMCSA regulations require this check as part of the coupling procedure.

Question 2: After coupling, how do you test that the fifth wheel is securely locked?

Apply the trailer brakes and pull forward gently (Correct answer)
Rock the trailer side to side
Check the air line connections
Drive at highway speed for one mile

Correct answer: Apply the trailer brakes and pull forward gently

The tug test involves applying the trailer brakes and gently pulling forward in low gear to verify the fifth wheel jaws are locked around the kingpin.

The tug test is the standard method for verifying a secure coupling. With the trailer brakes applied (either via the trailer hand valve or by having the air supply disconnected), the driver puts the tractor in low gear and gently pulls forward. If the fifth wheel is properly locked, the tractor should not be able to pull away from the trailer. This test must be performed every time a trailer is coupled.

Question 3: What is the correct height for the trailer when coupling?

The trailer should be slightly higher than the fifth wheel
The trailer should be at the same height as the fifth wheel
The trailer should be slightly lower than the fifth wheel (Correct answer)
The height does not matter during coupling

Correct answer: The trailer should be slightly lower than the fifth wheel

The trailer nose should be slightly lower than the fifth wheel so that it is raised by the fifth wheel during coupling, ensuring the kingpin engages properly.

When coupling, the trailer should be positioned so its apron (nose) is slightly lower than the center of the fifth wheel. This slight downward angle allows the fifth wheel to lift the trailer as the tractor backs under it, guiding the kingpin into the fifth wheel throat and locking mechanism. If the trailer is too high, the tractor may strike the trailer nose; if too low, the kingpin may not engage properly.

Question 4: During uncoupling, when should you lower the landing gear?

After disconnecting the air lines
After pulling the fifth wheel release handle
Before disconnecting the air lines and pulling the release handle (Correct answer)
After the tractor has pulled away

Correct answer: Before disconnecting the air lines and pulling the release handle

Landing gear must be lowered before disconnecting anything to support the trailer's weight and prevent it from tipping or falling when separated from the tractor.

Lowering the landing gear is one of the first steps in uncoupling. The landing gear supports the front weight of the trailer once the tractor pulls away. If the landing gear is not lowered before uncoupling, the trailer nose could drop to the ground, potentially damaging the trailer, landing gear mechanism, and air/electrical connections. The gear should be cranked down until it contacts the ground with slight pressure against the trailer.

Question 5: What should you do if the fifth wheel release handle is hard to pull during uncoupling?

Use a longer lever for more force
Back up slightly to relieve pressure on the kingpin (Correct answer)
Disconnect the air lines first
Have another driver help pull the handle

Correct answer: Back up slightly to relieve pressure on the kingpin

Backing up slightly shifts the weight off the locking jaws, relieving pressure on the kingpin and making the release handle easier to operate.

When a fifth wheel release handle is difficult to pull, it is usually because there is too much horizontal pressure on the locking jaws from the kingpin. This happens when the tractor and trailer are not perfectly aligned or when the tractor has pulled slightly forward. By backing up a few inches, the driver repositions the kingpin to relieve this pressure, allowing the release mechanism to operate freely. Forcing the handle with tools can damage the release mechanism.

Question 6: What is the purpose of the glad hands in the coupling process?

They connect the electrical system between tractor and trailer
They connect the air lines between tractor and trailer (Correct answer)
They secure the landing gear in the raised position
They lock the fifth wheel jaws

Correct answer: They connect the air lines between tractor and trailer

Glad hands are the coupling devices used to connect the air brake hoses between the tractor and trailer, allowing the tractor to supply air pressure to the trailer braking system.

Glad hands (also called palm couplings) are the standardized connectors that join the air brake lines between the tractor and trailer. There are typically two sets: one for the service (foot brake) line and one for the emergency (supply) line. They are color-coded - blue for service and red for emergency. Proper connection of glad hands is essential for brake operation. Drivers must ensure the seals are in good condition and the connections are secure to prevent air leaks.

ELDT - Entry Level Driver Training Coupling and Uncoupling Questions and Answers 2

When coupling a tractor to a trailer, what should you check before backing under the trailer?