FL CDL Combination flashcards
FL CDL Combination · 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. Jaws must close fully around the kingpin shank with the release handle locked and the safety latch engaged over the handle.
- Kingpin
- The vertical steel pin mounted under the trailer nose that the fifth wheel jaws lock onto. It transmits pulling and braking forces from tractor to trailer.
- Tug test
- A coupling check in which you pull gently forward against set trailer brakes. If the trailer moves or the tractor is pulled backward, the coupling is not locked.
- Safety latch
- A small latch that holds the fifth wheel release handle in the locked position. It must be over the handle before the vehicle is moved.
- Landing gear
- Retractable legs supporting a parked trailer. They must be fully raised and the crank secured before travel to avoid striking the ground or a crossing.
- Trailer air supply knob
- The red dash valve that charges the trailer air system. It pops out automatically when trailer pressure falls below about 45 psi, applying the trailer spring brakes.
- Tractor protection valve
- A valve that closes on a breakaway or major air leak, sealing the tractor's air supply so tractor brakes still work while the trailer emergency line vents.
- Emergency air line
- The line that supplies trailer air and signals a breakaway. If it separates, the trailer spring brakes apply automatically. Connect it before the service line.
- Service air line
- The line that carries the driver's brake application signal to the trailer relay valve. It is connected after the emergency line and checked for kinks and crossed lines.
- Glad hands
- Couplers joining tractor and trailer air lines. They must be locked, sealed, and matched by color (blue emergency, red service) so the lines are not crossed.
- Pintle hook
- A hook-and-eye coupling used for heavy trailers. The latch must close over the drawbar eye and be secured with a safety pin before moving.
- Safety chains
- Chains that keep a towed vehicle attached if the primary coupling fails. They must be crossed under the drawbar and attached to the towing vehicle frame.
- Converter dolly
- A coupling device with its own axle and fifth wheel that connects a second trailer to a tractor-trailer combination, forming a double or triple.
- Rearward amplification
- The tendency of the last trailer in a multi-trailer combination to swing wider than the tractor during lane changes or turns, increasing rollover risk.
- Off-tracking
- The difference between the path of the front wheels and the rear wheels in a turn. Longer combinations and multiple trailers increase off-tracking, so turns must be wider.
- Jackknife
- A loss of control in which the tractor and trailer fold at an angle. Causes include locked wheels, low landing gear catching ground, and excessive speed on slippery surfaces.
- Trailer spring brakes
- Air-released, spring-applied parking brakes on the trailer. They set automatically when trailer air pressure is lost or the emergency line separates.
- Parking brake test
- With the combination coupled and air charged, apply the parking brake and try to pull forward gently; the combination must not move if the brakes hold.
- Air leak check
- With brakes applied and engine off, watch the air gauge. Loss greater than 3 psi per minute on a single vehicle or 4 psi on a combination indicates a leak.
- Low air warning
- A buzzer and light that activate before pressure drops below about 60 psi, warning the driver to stop safely before spring brakes apply automatically.
- Spring brake pop-out
- The automatic application of trailer spring brakes when trailer air pressure drops below roughly 45 psi, signaled by the red knob popping out.
- Trailer hand valve
- A dash valve that applies only the trailer brakes. It is used to test trailer brake operation and to straighten a skid, but not for normal stopping.
- Coupling inspection
- A visual check after coupling: jaws closed around the kingpin, no gap, release handle locked, safety latch engaged, air lines secure, and landing gear raised.
- Pre-trip air build
- The compressor should build pressure from about 85 to 100 psi within 45 seconds at normal idle, showing the air system is charging properly.
- Governor cut-out
- The pressure at which the compressor stops pumping, typically around 120 to 125 psi. Pressure above this range may indicate a faulty governor.
- Slack adjuster check
- With brakes released, pull the slack adjuster by hand; movement of more than about one inch at the push rod indicates excessive brake adjustment.
- Breakaway protection
- A system that seals the tractor air supply and vents the trailer emergency line if the combination separates, applying the trailer brakes automatically.
- Double trailer coupling
- The dolly is backed under the second trailer's nose, the fifth wheel jaws lock the kingpin, air lines are connected, and the dolly's spring brakes are released.
- Trailer height check
- Before backing under a trailer, confirm the fifth wheel height matches the kingpin so the trailer is lifted, not struck, and the landing gear clears the ground.
- Release handle position
- The fifth wheel release handle must be pushed fully in and locked before travel. A handle left out allows the jaws to open and the trailer to separate.
- Mirror check on turns
- Watch the trailer wheels in the mirrors through the turn to confirm they clear curbs and objects, since the rear wheels track inside the tractor's path.
- Combination stopping distance
- A loaded combination needs much more distance to stop than a car. Maintain a following distance of at least one second per ten feet of vehicle length.