Coupling and Uncoupling Flashcards

Before backing under a trailer, where should the fifth wheel plate be positioned relative to the trailer's apron?

Answer: Slightly lower than the trailer apron

The fifth wheel should be low enough that the tractor lifts the trailer slightly as you back under it, ensuring the kingpin engages properly.

What is the correct height for the trailer before backing the tractor under it?

Answer: So the trailer is raised slightly when the tractor backs under

The trailer should be at a height where the tractor raises it slightly when backing under, guaranteeing solid kingpin contact.

When testing the coupling by pulling forward gently against the locked kingpin, this is called a:

Answer: Tug test

The tug test involves gently pulling the tractor forward against the locked fifth wheel to confirm the kingpin is secured.

Which color glad hand or line typically supplies the emergency (supply) air to the trailer?

Answer: Red

The red line/glad hand is the emergency supply line that charges the trailer air tanks and controls the spring brakes.

What should you do with the tractor parking brake before crawling under to inspect the coupling?

Answer: Apply it and chock the wheels if needed

Always apply the parking brakes before going under the vehicle to prevent it from rolling and crushing you.

After coupling, how much space should there be between the tractor frame and the bottom of the trailer?

Answer: No space at all

There should be no space between the fifth wheel and the trailer apron, as a gap means the coupling may be resting on the kingpin only.

Where should the kingpin sit in relation to the fifth wheel locking jaws when properly coupled?

Answer: Locked inside the closed jaws

A proper coupling has the kingpin fully seated and the locking jaws closed around it, which you verify by inspection.