Coupling and Uncoupling Trailers Flashcards

The yellow (service) airline on a truck-trailer combination is used for:

Answer: Controlling the service (foot) brakes on the trailer

The yellow service line transmits braking signals from the driver's foot brake to the trailer's service braking system during normal driving.

If you discover a cracked or damaged kingpin during a pre-coupling inspection, you should:

Answer: Not couple the trailer until the kingpin has been repaired or replaced

A damaged kingpin could fail under load and cause the trailer to detach from the tractor, creating an extreme danger to all road users.

What is the risk if the fifth wheel height is too high when coupling?

Answer: The kingpin may not lock fully into the fifth wheel jaws

If the fifth wheel is too high, the kingpin will ride up on the edge of the fifth wheel plate rather than dropping into the jaw, resulting in an insecure or failed coupling.

After uncoupling a trailer, before driving the tractor unit away, you should check:

Answer: That the trailer is stable and the fifth wheel jaws are clear of all obstructions

Confirming the trailer is stable and the fifth wheel is fully clear prevents damage to the coupling and ensures the tractor can drive away safely.

What does 'bobtail' mean in the context of truck driving?

Answer: Driving a tractor unit without a trailer attached

A 'bobtail' tractor is a tractor unit being driven without a trailer; this condition affects braking distance and handling due to the different weight distribution.

Why is it essential to ensure the landing legs are fully lowered and secure before releasing the fifth wheel during uncoupling?

Answer: To support the trailer's weight and prevent the nose from crashing to the ground

Without the landing legs bearing the trailer's weight, releasing the fifth wheel would cause the front of the trailer to drop violently, risking injury and damage.

Which of the following is a legal requirement before a truck and trailer combination departs on an Irish public road?

Answer: The coupling must be inspected and confirmed secure by the driver

Under Irish road traffic legislation and driver CPC requirements, the driver is responsible for ensuring the vehicle is roadworthy, including confirming the coupling is secure before every journey.