DTT HGV Coupling and Uncoupling Trailers

Question 1

Before reversing a tractor unit under a semi-trailer for coupling, the fifth wheel should be:

Accepted Answer

Clean, greased and in the unlocked (open) position

Answer

The fifth wheel must be greased and in the open/unlocked position so the kingpin can enter and the jaws can close around it during coupling.

Question 2

The kingpin on a semi-trailer connects with which part of the tractor unit?

Accepted Answer

The fifth wheel coupling plate

Answer

The kingpin is the steel pin on the underside of the trailer that locks into the jaws of the fifth wheel coupling plate on the tractor unit.

Question 3

After coupling a trailer, how should you test that the coupling is secure?

Accepted Answer

Attempt to move forward with the trailer parking brake applied

Answer

Moving forward against the applied trailer parking brake confirms the fifth wheel jaws are properly locked around the kingpin without risking movement.

Question 4

When uncoupling a semi-trailer, which sequence of steps is correct?

Accepted Answer

Apply trailer brake, lower landing gear, disconnect airlines, release fifth wheel, drive away

Answer

The trailer brakes must be applied and landing gear lowered to support the trailer's weight before the airlines are disconnected and the fifth wheel is released.

Question 5

After connecting the airlines to a trailer, what should you do before departure?

Accepted Answer

Allow air pressure to build and check for air leaks

Answer

Air pressure must reach the correct level and the system must be checked for leaks to ensure the trailer's braking system will function safely.

Irish DTT Truck/Bus Practice Test

Irish DTT Truck/Bus Practice Test

DTT HGV Coupling and Uncoupling Trailers