AK CDL Combination study guide
AK CDL Combination · Work through your exam, one topic at a time.
The Alaska CDL Combination Vehicles knowledge test is the endorsement-area written exam a driver must pass to operate a tractor-trailer or other articulated vehicle under a Commercial Driver's License. It is aimed at drivers who already hold or are working toward a Class A or Class B CDL and want the combination-vehicle endorsement added to their record, which is required before a driver can legally operate most tractor-trailer configurations and before taking the combination-vehicle skills test. The AK CDL Combination study guide has 7 sections and about 1,903 words.
01Combination Vehicle Basics and Trailer Hookup
A combination vehicle is a tractor pulling a trailer, and the candidate must understand the parts that make the pair work as one unit: the fifth wheel (the horseshoe-shaped coupling plate on the tractor), the kingpin (the pin under the trailer that locks into the fifth wheel), the landing gear (trailer support legs), the air lines (service and emergency/supply), the electrical cord, the glad hands that connect the air lines, and the trailer's spring brakes. Know that the service line carries air to apply the trailer brakes, while the emergency (supply) line charges the trailer tanks and triggers emergency braking if it separates.
301 words, about 2 min02Pre-Trip Inspection of Combination Vehicles
A pre-trip inspection of a combination vehicle covers the tractor, the trailer, and the coupling between them. Candidates should know the walk-around sequence and the specific items: coupling system (fifth wheel jaws locked around the kingpin, no gap between the tractor and trailer, safety latch engaged, release handle in), air lines and electrical cord (connected, not chafed, supported so they don't drag), landing gear (fully raised, no missing parts, crank secured), trailer frame and body, doors and ties, mud flaps, lights and reflectors, tires and wheels (tread depth, sidewall condition, lug nuts, rust streaks), brake chambers and slack adjusters, and the rear impact guard.
278 words, about 1 min03Coupling and Uncoupling
Coupling and uncoupling are step-by-step procedures where order matters, and exam questions test whether you know the sequence and the safety checks. When coupling: inspect the fifth wheel and kingpin, back under the trailer squarely, listen for the click of the jaws locking, do a tug test, visually check the jaws around the kingpin, connect the air lines and electrical cord, raise the landing gear, and check the trailer lights.
306 words, about 2 min04Inspection and Air Brake Checks
Air brake checks on a combination vehicle confirm that the tractor and trailer brake systems work together. Candidates must know the standard tests: the static leak test (build pressure, shut off the engine, and watch for pressure loss), the applied leak test (hold the brake pedal and watch the gauge), the low-air warning test (the warning must come on before pressure drops too low), the spring brake test (with low air, the parking brake should apply), and the tractor protection valve check.
253 words, about 1 min05Driving Combination Vehicles: Turns, Braking, and Skids
Driving a combination vehicle requires planning because the unit is long, heavy, and slow to respond. In turns, the trailer off-tracks toward the inside of the turn, so you must swing wide and watch the trailer's rear wheels in the mirrors.
273 words, about 1 min06Trailer Sway, Off-Tracking, and Rearward Amplification
This domain covers the dynamics that make combination vehicles behave differently from single units. Off-tracking is the difference between the path of the tractor's rear wheels and the trailer's rear wheels; the trailer cuts the corner, and the effect increases with trailer length and sharpness of the turn.
247 words, about 1 min07Special Conditions and Safety Procedures
Special conditions test judgment: rain, snow, ice, fog, high wind, steep grades, and railroad crossings. In poor visibility, slow down and increase following distance; in high wind, be ready for the trailer to be pushed and reduce speed.
245 words, about 1 min