CDL Combination Vehicles TestCoupling and UncouplingEasy
When uncoupling a combination vehicle, after disconnecting the air and electrical lines, what is the next step to ensure the trailer is stable before pulling the tractor away?
- ACrank the landing gear to firmly support the trailer.
- BLower the fifth wheel assembly.
- CPerform a final visual check around the trailer.
- DRelease the tractor's parking brakes.
Show answer & explanationAnswer & explanation
Correct answer: A. Crank the landing gear to firmly support the trailer.
Before disconnecting air and electrical lines, the landing gear must be cranked down to firmly support the trailer's weight. This ensures stability once the tractor is removed.
Why the other options are wrong
- B. Lowering the fifth wheel assembly is typically done after landing gear is supporting the trailer and air/electrical lines are disconnected.
- C. A final visual check is done at the end of the uncoupling process.
- D. Releasing tractor parking brakes is done after the trailer is completely stable and disconnected, just before pulling away.
Landing Gear Deployment (Uncoupling)
During uncoupling, the landing gear must be fully cranked down to firmly support the trailer's weight before disconnecting air/electrical lines and moving the tractor.
- Ensures trailer stability.
- Prevents trailer nose drop.
- Critical safety step.
Memory trick: Gear down, then lines out, no trailer doubt.