Semi Trailer Coupling Quiz

What should you ensure before backing under a trailer?

• The trailer brakes are locked.

• The air supply knob is pulled out.

• The emergency air lines are hooked up.

• The trailer lights are on.

Answer explanation

Before backing under a trailer, ensure the trailer brakes are locked to prevent it from rolling. This is crucial for safety, as it secures the trailer in place while you connect it.

What should you do before backing under the trailer when coupling a tractor to a semi trailer?

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

• Disconnect the airlines.

• Lower the trailer.

• Increase the speed.

Answer explanation

Before backing under the trailer, you should supply air to the trailer system and then pull out the air supply knob. This ensures the trailer's brakes are released, allowing for safe coupling.

What should be done if the fifth wheel locking lever is not locked after the jaws close around the kingpin?

• Drive the coupled unit immediately

• Ignore the issue

• Fix the coupling before driving

• Remove the kingpin

Answer explanation

If the fifth wheel locking lever is not locked after the jaws close around the kingpin, it is crucial to fix the coupling before driving. Driving with an unsecured coupling can lead to serious safety hazards.

What should be the space between the upper and lower fifth wheel after coupling?

• A small gap

• A large gap

• No space

• A flexible space

Answer explanation

The correct answer is 'No space' because after coupling, the upper and lower fifth wheel should be tightly connected to ensure stability and safety during towing. Any gap could lead to instability.

What must be ensured when the iron trailer supports are up and the trailer is resting on the tractor?

• The trailer is locked

• The brakes are engaged

• There is enough clearance between the tractor frame and the landing gear for turning

• The lights are functioning

Answer explanation

When the iron trailer supports are up, ensuring enough clearance between the tractor frame and the landing gear is crucial for safe turning. This prevents potential collisions and ensures smooth maneuverability.

How should the landing gear be positioned when checking if the tractor is securely coupled to the trailer?

• Fully lowered

• Slightly raised

• Fully raised

• Not touching the ground

Answer explanation

The landing gear should be slightly raised to ensure it is not bearing weight, allowing for a proper check of the coupling between the tractor and trailer. This position indicates that the trailer is securely attached.

What should you do if the brakes are not released after pushing in the trailer air supply valve?

• Check the brake pads

• Check the air line connections

• Check the tire pressure

• Check the fuel level

Answer explanation

If the brakes are not released after pushing the trailer air supply valve, checking the air line connections is crucial. A faulty or disconnected air line can prevent proper brake function, unlike the other options listed.

What happens to the tractor protection valve when a trailer breaks away from a combination vehicle?

• It closes

• It opens

• It remains neutral

• It locks

Answer explanation

When a trailer breaks away, the tractor protection valve closes to prevent air from escaping the braking system, ensuring the tractor can still stop safely. This is why the correct answer is 'It closes'.

What should you expect to happen to the trailer brakes if the trailer breaks away from a combination vehicle?

• They come on

• They release

• They remain off

• They malfunction

Answer explanation

If a trailer breaks away from a combination vehicle, the trailer brakes are designed to engage automatically to prevent further movement. Therefore, you should expect that they come on.

What happens when there is a major leak in the emergency brake line?

• The tractor protection valve will open and the trailer emergency brakes will release.

• The tractor protection valve will close and the trailer emergency brakes will come on.

• The tractor protection valve will close and the trailer emergency brakes will release.

• The tractor protection valve will open and the trailer emergency brakes will come on.

Answer explanation

When there is a major leak in the emergency brake line, the tractor protection valve will close, which activates the trailer emergency brakes to ensure safety by preventing the trailer from rolling.