Texas CDL -Combination Test Graded A+ 2023

In coupling, just before the tractor is coupled with the trailer you should: - ANSWER-connect the emergency and service air lines. In coupling, you should not move the tractor after it is coupled until you push in the air supply knob and: - ANSWER-wait until the air pressure is normal. What happens immediately if the service air line comes apart while driving, but the emergency line is okay? - ANSWER-Nothing is likely to happen until you press the brakes. In coupling, before you back under the trailer, how do you lock the trailer brakes? - ANSWER-Pull out the yellow air supply knob. For the coupling to be complete, the safety catch for the fifth wheel locking lever must be: - ANSWER-over the locking gear. What is the air leakage rate for a combination vehicle with the engine and brakes off? - ANSWER-Less than 3 PSI per minute. What is the maximum air leakage rate for a combination vehicle with the engine off and the brakes on? - ANSWER-4 PSI per minute. A driver crosses the air lines when hooking up to an old trailer. What will happen? - ANSWER-If the trailer has no spring brakes, he or she could drive away but wouldn't have trailer brakes. To unlock the fifth wheel, pull the release handle to the: - ANSWER-open position. When driving a set of doubles, it is necessary to close the: - ANSWER-back shut-off valve in the last trailer. You are coupling a semitrailer to your tractor but have not yet backed under. The trailer is at the right height when: - ANSWER-it will be raised slightly when the tractor is backed under it. Air and electric lines from the tractor to the trailer should be: - ANSWER-secured, but with enough slack for turns. When uncoupling a trailer, after you have shut off the trailer air supply and locked the trailer brakes, you should: - ANSWER-back up gently to ease pressure on the fifth wheel locking jaws. Glad hands are used for connecting the: - ANSWER-service and emergency air lines from the vehicle to the trailer. You should not back a tractor under a trailer until the whole air system is: - ANSWER-at normal pressure. If the spring brakes don't release when you push the trailer air supply control, you should: - ANSWER-check the air line connections. You are coupling a tractor to a semitrailer and have backed up but are not under it. What should you hook up before backing under? - ANSWER-The emergency and service air lines. In general, the higher the "center of gravity" of your truck the: - ANSWER-easier it is to turn over. After you supply air to the trailer, make sure the air lines are not crossed and the trailer brakes are working. This is done by: - ANSWER-applying and releasing the trailer brakes and listening for brake sounds. You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the: - ANSWER-trailer emergency brakes to come on. To prevent a rollover, keep the cargo as close to the ground as possible, and: - ANSWER-Go slow around curves. Why are "bobtail" tractors harder to stop than some loaded combination vehicles? - ANSWER-The vehicle is relatively light. To stop a jackknife of a combination vehicle: - ANSWER-Do not use the trailer hand brake. What is offtracking? - ANSWER-When the rear wheels follow a different path than the front wheels. When should you use the trailer hand valve? - ANSWER-In combination with the foot brake. What is the purpose of the tractor protection valve? - ANSWER-It keeps air in the tractor if the trailer breaks away or develops a bad leak. When will the tractor protection valve close automatically? - ANSWER-When the air pressure is low (20 - 45 PSI) What is the purpose of the trailer air supply? - ANSWER-To supply the trailer with air. What is the purpose of the service air line? - ANSWER-To carry air to the trailer brakes.