CDL Combination Vehicles TestCoupling and UncouplingEasy
A driver is preparing to couple a tractor to a trailer. After backing the tractor until the fifth wheel touches the trailer, what is the next critical step before raising the landing gear?
- AAdjust the trailer height using the trailer's air suspension.
- BEnsure the kingpin is properly locked into the fifth wheel.
- CConnect the glad hands and electrical cable.
- DInspect the trailer's brake lines for leaks.
Show answer & explanationAnswer & explanation
Correct answer: B. Ensure the kingpin is properly locked into the fifth wheel.
Before raising the landing gear, it's crucial to confirm that the kingpin is securely locked in the fifth wheel. Failure to do so can result in the trailer separating from the tractor, leading to a dangerous situation.
Why the other options are wrong
- A. Adjusting trailer height happens before backing under, or as part of raising/lowering, but not as the direct next step after contact and before locking verification.
- C. Connecting air and electrical lines is done later in the coupling process, after the mechanical connection is secure.
- D. Brake line inspection is part of the pre-trip, and also after connecting lines, but not the immediate next step after initial fifth wheel contact.
Kingpin Lock Verification
The process of visually and physically confirming that the trailer's kingpin is securely engaged and locked within the fifth wheel jaws of the tractor.
- Crucial safety step during coupling.
- Prevents trailer separation.
- Involves a visual check of the locking jaws.
Memory trick: Lock the kingpin, verify with a tug, then connect everything up.