Combination Vehicle Operations Flashcards

What does a 'glad hand' connection do on a combination vehicle?

Answer: Connects the air lines between the tractor and trailer

Glad hands are the air line connectors that join the tractor's service and emergency brake lines to the trailer.

Why is it important to check that the sliding fifth wheel is locked in position before driving?

Answer: An unlocked fifth wheel can slide and shift the load, affecting steering and braking

If the fifth wheel slides unexpectedly, weight distribution changes dramatically, causing dangerous handling and possible loss of control.

When making a right turn with a long combination vehicle, why should you swing wide to the left first?

Answer: To give the rear trailer enough room to complete the turn without riding up on the curb

Long combination vehicles off-track severely, so swinging wide before turning gives the rear axles the turning radius they need to avoid the curb.

What is the function of the emergency (supply) air line in a combination vehicle?

Answer: It charges the trailer air tanks and triggers emergency brakes if it ruptures

The emergency line keeps the trailer spring brakes released when pressurized; if it breaks or disconnects, the spring brakes automatically apply.

How far should the landing gear be cranked down when uncoupling a trailer on a firm, level surface?

Answer: Until it just contacts the ground and the weight is transferred off the fifth wheel

The landing gear should bear the trailer's weight before uncoupling so the trailer is stable and the fifth wheel can be released safely.

What causes 'crack-the-whip' effect in doubles or triples?

Answer: Each rear unit amplifies the side-to-side motion from the unit ahead of it

Each successive trailer magnifies the lateral movement of the trailer ahead, creating a dangerous whipping action at the rear.

What is the purpose of the converter dolly used in double/triple trailer combinations?

Answer: It connects a second or third trailer by converting the lead trailer's rear into a towing hitch

A converter dolly is a set of axles with a fifth wheel that attaches to the rear of the lead trailer, allowing it to tow an additional trailer.