IN CDL Combination flashcards
IN CDL Combination · Build recall with a focused review session.
33 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Fifth wheel pull test
- After coupling, set the trailer brakes and gently pull the tractor forward against them. If the trailer does not move, the jaws are locked around the kingpin.
- Kingpin
- The vertical pin mounted under the trailer that locks into the fifth wheel jaws. It carries the trailer's pulling load and must be fully seated and greased.
- Landing gear
- The retractable legs under the front of the trailer. They must be fully raised and the crank secured before the combination vehicle is driven.
- Emergency air line
- The supply line that charges the trailer air tanks. It is connected first and disconnected last so the trailer brakes stay set if lines separate.
- Service air line
- The line that carries the driver's brake application to the trailer. It is connected last and disconnected first during coupling and uncoupling.
- Tractor protection valve
- A valve that closes the tractor air supply if the trailer separates, keeping tractor air pressure available and setting the trailer spring brakes.
- Coupling sequence
- Inspect the fifth wheel and kingpin, back under squarely, lock the jaws, tug test, set the tractor brake, connect lines, raise landing gear, then check trailer brakes.
- Off-tracking
- The tendency of a trailer's rear wheels to follow a shorter path than the front wheels. It is why combination vehicles need extra room in turns.
- Right-turn swing
- Swing wide to the left before turning right without entering the opposing lane, then watch both mirrors because the trailer cuts the corner.
- Following distance rule
- Allow at least one second per 10 feet of vehicle length below 40 mph, plus one extra second above that speed, to leave room to stop.
- Controlled braking
- On a long downgrade, choose a low gear so the engine and retarder hold speed, and use short brake applications instead of continuous pressure that overheats drums.
- Backing a trailer
- Steer the trailer by turning the wheel opposite the desired trailer direction. Use a spotter and stop at once if the trailer begins to jackknife.
- Blind spots on a combination
- The area directly behind the trailer and alongside it is not visible from the cab. Check flat and convex mirrors before every lane change.
- Air pressure build-up check
- With the engine at fast idle, pressure should rise from 85 to 100 psi within 45 seconds in a dual system. Slower build-up means a leak or weak compressor.
- Static leak test
- With the engine off and the system charged, release the parking brake and watch the gauge. A drop over 4 psi in one minute on a combination vehicle means a leak.
- Applied leak test
- With the engine off, hold the brake pedal fully applied for one minute. A pressure drop of more than 4 psi on a combination vehicle signals a leak.
- Low-air warning
- The buzzer and warning light must come on before pressure falls below 60 psi, and spring brakes should apply automatically in the 20 to 45 psi range.
- Governor cut-out pressure
- The compressor normally stops pumping around 120 to 125 psi and restarts around 100 psi. Pressures outside these ranges indicate a governor or compressor fault.
- Slack adjuster free play
- With the brakes released, pull the slack adjuster by hand. More than about one inch of free play at the pushrod means the brakes need adjustment.
- Parking brake test
- With the spring brakes applied, try to move the vehicle in a low gear. It must not move, which confirms the spring brakes can hold the load.
- Drive-wheel skid
- Release the accelerator and steer in the direction the vehicle should go. Do not brake until the wheels regain traction.
- Steer-wheel skid
- Release the brakes so the front wheels roll again, then steer toward the intended path. Braking during a front-wheel skid makes it worse.
- Trailer skid
- Release the brakes and accelerate slightly to pull the trailer straight. Braking harder will worsen a trailer swing.
- ABS on combination vehicles
- Anti-lock brakes prevent wheel lock-up and help retain steering control, but they do not shorten stopping distance on every surface. Brake firmly and steer.
- Brake fade
- Overheated drums and shoes lose stopping power, and the pedal may feel soft. Downshift and let the brakes cool instead of pumping them harder.
- Hydroplaning
- Water lifts the tires off the pavement and steering and braking are lost. Ease off the accelerator and avoid hard braking until the tires regain contact.
- Rear jackknife
- The trailer folds toward the tractor, usually because the trailer brakes locked on a slippery surface. Release the brakes and steer with the slide to recover.
- Front jackknife
- The tractor's steer axle locks and the tractor swings toward the trailer. Release the brakes to let the front wheels roll and regain steering.
- Jackknife prevention
- Brake early and gently on slippery roads, keep tractor and trailer braking balanced, and avoid hard steering while braking hard.
- Emergency stop procedure
- Brake firmly with both hands on the wheel and keep the vehicle straight. Steer only after speed drops, because swerving at speed risks a rollover.
- Tire blowout handling
- Hold the wheel firmly, keep the vehicle straight, and ease off the accelerator. Brake gently once control is regained, especially after a steer-tire blowout.
- Runaway truck ramp
- A gravel escape ramp for vehicles that lose brakes on a downgrade. Aim for it early, enter straight, and expect the soft bed to stop the vehicle.
- Off-road recovery
- Slow before leaving the pavement, keep two wheels on the shoulder if possible, and return to the road at a shallow angle after checking for traffic.