Nebraska CDL Combination Vehicles flashcards
Nebraska CDL Combination Vehicles · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Fifth wheel jaws
- The locking mechanism that grips the trailer kingpin. After coupling, verify the jaws are closed around the kingpin and the release handle is in the locked position.
- Kingpin
- The pin mounted under the trailer nose that locks into the fifth wheel jaws. It must be fully seated and visible in the jaw opening after coupling.
- Emergency air line
- The red air line that supplies air to the trailer and applies the trailer brakes if the line separates. Connect it before the blue service line.
- Service air line
- The blue air line that carries brake application pressure from the tractor to the trailer. Connect it after the red emergency line.
- Tractor protection valve
- A valve that closes automatically if the trailer air lines separate, trapping tractor air and applying the trailer brakes. Test by closing the red knob.
- Trailer hand valve
- A control on the tractor that applies only the trailer brakes. Use it to test that the trailer brakes hold while the tractor is stationary.
- Landing gear
- The retractable legs under the trailer nose that support it when uncoupled. Fully raise them before moving and lower them before uncoupling.
- Off-tracking
- The tendency of the trailer's rear wheels to follow a shorter path than the tractor's front wheels in a turn. Longer wheelbases increase off-tracking.
- Swing-out
- The outward movement of the trailer's rear end during a turn. Longer trailers swing out more, so allow extra clearance on the inside of turns.
- Coupling test
- After coupling, pull the tractor forward gently with the trailer brakes applied to confirm the fifth wheel is locked and will not release.
- Uncoupling sequence
- Park level, set trailer parking brake, lower landing gear, disconnect air lines, release fifth wheel, then pull tractor forward slowly while watching the trailer.
- Trailer air pressure build
- After connecting air lines, the trailer air pressure should build to at least 100 psi. Listen for leaks at the couplings and check the gauge.
- Red knob test
- Close the trailer air supply valve (red knob) to simulate a line separation. The trailer brakes should apply and stay applied, confirming the protection valve works.
- Fifth wheel inspection
- Check that the fifth wheel is greased, the jaws are open before coupling, and the mounting bolts are secure. A damaged fifth wheel can cause trailer separation.
- Kingpin visibility check
- After coupling, look under the trailer to confirm the kingpin is visible inside the closed fifth wheel jaws. If not, the coupling is not secure.
- Trailer brake test
- Charge the trailer air system, release the parking brake, then apply the trailer hand valve. The trailer brakes should engage and hold the trailer.
- Air line leakage check
- With the engine off and brakes released, listen for air leaks at the couplings. A steady leak means a bad seal or loose connection.
- Landing gear ground support
- When uncoupled, the landing gear must support the trailer nose without sinking. Use pads on soft ground and ensure the gear is fully lowered before releasing the fifth wheel.
- Trailer parking brake
- A spring-applied brake that holds the trailer when parked. Set it before uncoupling and confirm it releases before driving.
- Tractor parking brake
- The tractor's spring brakes. Set them during coupling and uncoupling to prevent the tractor from rolling while you work.
- Wheelbase and off-tracking
- The distance between the tractor's front and rear axles affects off-tracking. A longer wheelbase causes the trailer to track farther inside the turn.
- Trailer length and swing-out
- Longer trailers have greater rear swing-out in turns. Check mirrors and allow extra room on the inside of the turn to avoid hitting objects.
- Coupling alignment
- Before backing under the trailer, align the tractor's fifth wheel with the trailer kingpin. Use mirrors and go slowly to avoid damaging the kingpin.
- Backing under trailer
- Back the tractor slowly until the fifth wheel contacts the trailer. The trailer should be pushed slightly forward, and you should hear the jaws lock.
- Fifth wheel release handle
- The lever that opens the fifth wheel jaws. After coupling, it should be in the locked position; pull it to verify the jaws are closed around the kingpin.
- Trailer air supply valve
- The red knob in the cab that controls air to the trailer. Pulling it out (closing) applies the trailer brakes and tests the protection valve.
- Glad hands
- The coupling fittings on the ends of the air lines. They must be clean and securely locked; a poor connection causes air leaks and brake failure.
- Trailer brake Release check
- After charging the system, push in the red knob and confirm the trailer brakes release. The trailer should roll freely when the tractor moves.
- Fifth wheel grease
- Lubrication on the fifth wheel plate reduces friction and wear. A dry fifth wheel can cause steering difficulty and damage to the kingpin.
- Trailer height adjustment
- Before coupling, adjust the trailer landing gear so the trailer height matches the tractor's fifth wheel. A mismatch can damage the kingpin or fifth wheel.
- Tug test
- After coupling, pull the tractor forward gently with the trailer brakes applied. If the fifth wheel is locked, the tractor will not pull free.
- Trailer air line order
- Connect the emergency (red) line first, then the service (blue) line. Disconnect in reverse order: blue first, then red, to avoid brake drag.