CLP Combination Vehicle Operations 3 — Questions and Answers
Question 1: What does a 'glad hand' connection do on a combination vehicle?
- Connects the air lines between the tractor and trailer (Correct answer)
- Secures the landing gear to the trailer frame
- Locks the fifth wheel to the kingpin
- Connects the electrical lines for trailer lights
Correct 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.
Question 2: Why is it important to check that the sliding fifth wheel is locked in position before driving?
- An unlocked fifth wheel can slide and shift the load, affecting steering and braking (Correct answer)
- An unlocked fifth wheel will cause the trailer brakes to fail
- An unlocked fifth wheel prevents proper air line connection
- An unlocked fifth wheel will sound the low-air warning alarm
Correct 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.
Question 3: When making a right turn with a long combination vehicle, why should you swing wide to the left first?
- To give the rear trailer enough room to complete the turn without riding up on the curb (Correct answer)
- To allow other drivers to see your turn signal better
- To reduce the braking distance needed after the turn
- To prevent the fifth wheel from binding during the turn
Correct 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.
Question 4: What is the function of the emergency (supply) air line in a combination vehicle?
- It charges the trailer air tanks and triggers emergency brakes if it ruptures (Correct answer)
- It supplies air only to the trailer service brakes during normal braking
- It connects the tractor parking brakes to the trailer
- It provides air to the landing gear lift cylinder
Correct 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.
Question 5: How far should the landing gear be cranked down when uncoupling a trailer on a firm, level surface?
- Until it just contacts the ground and the weight is transferred off the fifth wheel (Correct answer)
- Until the landing gear fully extends to its maximum length
- Only a few turns just to stabilize the trailer
- Landing gear position does not matter if the kingpin is locked
Correct 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.
Question 6: What causes 'crack-the-whip' effect in doubles or triples?
- Each rear unit amplifies the side-to-side motion from the unit ahead of it (Correct answer)
- Air pressure surges from the rear trailer back to the tractor
- The weight of each trailer pulls the preceding trailer to one side
- Electrical signal interference between trailer ABS modules
Correct 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.
Question 7: What is the purpose of the converter dolly used in double/triple trailer combinations?
- It connects a second or third trailer by converting the lead trailer's rear into a towing hitch (Correct answer)
- It converts air pressure from service to emergency line
- It adds extra braking capacity to the lead trailer only
- It converts a flatbed trailer into an enclosed trailer configuration
Correct 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.
CLP Combination Vehicle Operations 3
What does a 'glad hand' connection do on a combination vehicle?