MVA CDL Combination Vehicles Study Guide
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Keep cargo as close to the ground as possible; Drive slowly around turns.
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What two things are important to prevent rollover?
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The rear trailer is twice as likely to turn over.
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When you turn suddenly while pulling doubles, which trailer is most likely to turn over?
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Because the brakes on the trailer wheels caused the skid in the first place.
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Why should you not use the trailer hand brake to straighten out a jackknifing trailer?
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When a vehicle goes around a corner and the rear wheels follow a different path than the front wheels.
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What is off-tracking?
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To the drivers side so you can see
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When you back a trailer, you should position your vehicle so you can back in a curved path ____________________.
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Low slung units (lowboy, car carrier, moving van, possum-belly livestock trailer); Single-axle tractor pulling a long trailer with its landing gear set to accommodate a tandem-axle tractor.
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What type of trailers can get stuck on railroad-highway crossings?
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Because of the danger of making the trailer skid.
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Why should you not use the trailer hand valve while driving?
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You push it in to supply the trailer brakes with air, and pull it out to shut off the air supply to put the trailer emergency brakes on.
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Describe what the trailer air supply control does.
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(Also called the control line or signal line) Carries air, which is controlled by the foot brake or trailer hand brake. Depending on how hard you press the foot brake or hand valve, the pressure in the service line will similarly change.
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Describe what the service line is for.
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It supplies air to the trailer air tanks; controls the emergency brakes on combination vehicles.
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What is the emergency air-line for?
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The brakes only hold as long as there is air in the air tank, eventually the air will leak away and there will be no brakes.
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Why should you use chocks when parking a trailer without spring brakes?
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The back of trailers.
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Where are shut-off valves?
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It may not couple correctly.
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What might happen if the trailer is too high when you try to couple?
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There should be no space between the upper and lower fifth wheel.
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After coupling, how much space should be between the upper and lower fifth wheel?
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Look into the back of the fifth wheel
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You should ____________________ to see if it is locked onto the kingpin.
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All the way up
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To drive, raise the landing gear _____________________.
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Trailers will have yellow ABS malfunction lamps on the left side, either on front or rear corner.
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How do you know if your trailer is equipped with antilock brakes?
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At the rear of the rig, Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged, close the shut-off; Open the service line valve to check that service pressure goes through all the trailers.
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How can you test that air flows to all trailers?
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With the air-brake system charged, turn off engine, pump brake pedal to fan out air, the trailer air supply control (aka tractor protection valve) should pop out when the air pressure falls between 20-45 psi
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How can you test the tractor protection valve?
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Charge the trailer air brake system and check the trailer moves freely, pull trailer air supply control, pull gently on the trailer with the tractor to check that the trailer emergency brakes are on
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How can you test the trailer emergency brakes?
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Check for normal air pressure, release parking brakes, move the vehicle, apply trailer brakes with the hand control, you should feel the brakes come on showing the service brakes are working
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How can you test the trailer service brakes?
