CDL Combination Vehicles øvingsprøve

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Alle 15 spørsmål i oversikt

Vil du heller lese før du spiller? Alle spørsmålene i smakebiten står listet under. Svar og forklaringer er skjult til du åpner dem.

1. 1. Which pair of habits does the most to keep a loaded combination vehicle from rolling over?

   • A. Load the heaviest cargo on top and brake hard just before each curve
   • B. Push the load toward one side wall so it cannot shift, and keep your speed up through ramps
   • C. Keep the cargo as close to the ground as possible, and drive slowly around turns
   • D. Run the trailer a little overloaded so it settles lower on its springs
   Vis svar og forklaring

   Svar: C. Keep the cargo as close to the ground as possible, and drive slowly around turns

   Stacking cargo high raises the center of gravity, and a higher center of gravity tips more easily, which is why a fully loaded rig is far more likely to roll in a crash than an empty one. Keeping the load low and slowing down for corners, ramps and off ramps are the two things a driver controls directly. Centering the load matters too, because a load pushed to one side makes the trailer lean and starts the roll for you.

2. 2. You are making a tight right turn and cannot finish it without using part of the next lane. What does off-tracking tell you to do?

   • A. Swing wide to the left before you start the turn, so the trailer has room
   • B. Start the turn close to the curb and swing wide as you complete it, keeping the rear near the curb
   • C. Turn from the left lane every time, because the trailer wheels track outside the tractor wheels
   • D. Nothing, since off-tracking only affects backing
   Vis svar og forklaring

   Svar: B. Start the turn close to the curb and swing wide as you complete it, keeping the rear near the curb

   Going around a corner, the rear wheels follow a tighter path than the front wheels, and the rear wheels of the trailer cut in the most. So you have to steer the front end wide enough that the rear does not climb the curb. Swinging left first invites a following driver to think you are turning left and slip up your right side, which is where your trailer is about to be. Turning wide at the end instead, with the rear kept close to the curb, blocks that gap.

3. 3. Rearward amplification, the crack the whip effect, is greatest in which of these?

   • A. A bobtail tractor with no trailer
   • B. A three axle tractor pulling one short semitrailer
   • C. A five axle tractor semitrailer with a 45 foot trailer
   • D. The last trailer of a set of triples
   Vis svar og forklaring

   Svar: D. The last trailer of a set of triples

   In a quick lane change, each trailer swings harder than the unit ahead of it, so the more trailers you add, the more the back one whips. The CDL manual charts this: a five axle tractor semitrailer sits near the bottom of the scale and triples sit at the top, roughly three and a half times as easy to roll at the last trailer. That is why you steer gently and smoothly, look far enough ahead to avoid sudden lane changes, and slow down before a turn rather than during it.

4. 4. You brake hard on a wet ramp and see in your mirror that the trailer is starting to swing out. What is the first thing you do?

   • A. Release the brakes so the trailer wheels can roll and get traction back
   • B. Press the brake pedal harder to pull the trailer back in line
   • C. Apply the trailer hand valve to straighten the rig out
   • D. Set the parking brake and steer toward the shoulder
   Vis svar og forklaring

   Svar: A. Release the brakes so the trailer wheels can roll and get traction back

   A trailer jackknife starts when the trailer wheels lock up and slide, which happens most easily when the trailer is empty or lightly loaded. Locked wheels cannot steer or track, so the fix is to stop braking and let them roll again. Once they grip, the trailer follows the tractor and straightens itself out. Checking your mirrors every time you brake hard is what buys you the time to catch it, because once the trailer leaves your lane it is very hard to save.

5. 5. What is the trailer hand valve, also called the trolley valve or Johnson bar, actually for?

   • A. Holding the rig on a grade instead of using the parking brakes
   • B. Straightening the rig out when the trailer begins to swing
   • C. Testing the trailer brakes, and nothing else
   • D. Releasing the trailer spring brakes before you pull away
   Vis svar og forklaring

   Svar: C. Testing the trailer brakes, and nothing else

   The hand valve applies the trailer brakes only, which is exactly the condition that starts a trailer skid, so it has no place in normal driving. The foot brake sends air to every brake on the rig, tractor and trailer together, and is far less likely to jackknife you. It is also wrong for parking, because on a trailer without spring brakes the air can leak away overnight and release the brakes, so use the parking brakes and chock the wheels.

6. 6. You crawl under with a flashlight after coupling and see a gap between the upper and lower fifth wheel. What does that mean?

   • A. The coupling is wrong, and the kingpin may be sitting on top of the closed jaws
   • B. It is normal, because the plate needs clearance for grease
   • C. The trailer is loaded too heavy and is lifting the plate slightly
   • D. Nothing, as long as the tug test already passed
   Vis svar og forklaring

   Svar: A. The coupling is wrong, and the kingpin may be sitting on top of the closed jaws

   There should be no visible space at all between the upper and lower fifth wheel. A gap usually means the jaws closed before the kingpin dropped in, so the pin is resting on top of them instead of being captured, and the trailer can come loose very easily. This is one of the reasons you shut the engine off, take the key with you and look with a light rather than trusting the tug test alone. If the coupling is not right, do not drive it, get it fixed.

7. 7. When you look into the back of the fifth wheel, the locking jaws should be closed around which part of the kingpin?

   • A. The head
   • B. The shank
   • C. The base plate
   • D. The trailer apron
   Vis svar og forklaring

   Svar: B. The shank

   The kingpin has a base, a narrower shank and a wider head at the bottom. The jaws are meant to wrap the shank, so the head sits below them and cannot pull up through. Jaws closed around the head look locked from a distance but hold almost nothing. While you are under there, also confirm the locking lever is in the lock position and the safety latch is seated over it, since on some fifth wheels that catch has to be placed by hand.

8. 8. You couple to a modern trailer with spring brakes and accidentally cross the air lines. What happens?

   • A. The trailer brakes drag but the rig still rolls normally
   • B. Nothing changes, because both lines carry the same air
   • C. The marker lights fail while the brakes keep working
   • D. Supply air goes to the service line, the trailer tanks never charge, and the spring brakes will not release
   Vis svar og forklaring

   Svar: D. Supply air goes to the service line, the trailer tanks never charge, and the spring brakes will not release

   Air meant to fill the trailer tanks gets sent down the service line instead, so there is never enough pressure to push the spring brakes off. If you push the trailer air supply control and the spring brakes stay set, check your glad hand connections first. The dangerous version is an older trailer with no spring brakes and a drained tank: crossed lines there let you drive away with no trailer brakes at all, which is why you shut the engine off and listen for the trailer brakes applying and releasing before you move.

9. 9. A trailer breaks away and tears the emergency line apart. What happens next?

   • A. The tractor loses its air too, and the driver is left with no brakes
   • B. The tractor protection valve closes to keep air in the tractor, and the trailer emergency brakes come on
   • C. Only the trailer lights go out, because the emergency line is electrical
   • D. The service line keeps the trailer brakes released until the trailer tank drains
   Vis svar og forklaring

   Svar: B. The tractor protection valve closes to keep air in the tractor, and the trailer emergency brakes come on

   The emergency line does two jobs: it charges the trailer air tanks and it holds the trailer emergency brakes off. Lose pressure in it and those brakes apply on their own. At the tractor end, the tractor protection valve shuts so the tractor keeps the air it needs for its own brakes, and the red eight sided trailer air supply knob pops out. That valve closes by itself once pressure falls into the range the manufacturer specifies, usually somewhere between 20 and 45 psi.

10. 10. Before you back the tractor under the trailer, which of these must already be done?

    Velg alle som passer.

    • A. The trailer wheels are chocked, or the trailer spring brakes are set
    • B. The tractor is lined up directly in front of the trailer, not at an angle
    • C. The trailer is set low enough that the tractor lifts it slightly as it backs under
    • D. The landing gear is fully raised and the crank handle is secured
    • E. The electrical cord is plugged into the trailer and the safety catch is fastened
    Vis svar og forklaring

    Svar: A. The trailer wheels are chocked, or the trailer spring brakes are set, B. The tractor is lined up directly in front of the trailer, not at an angle, C. The trailer is set low enough that the tractor lifts it slightly as it backs under

    Chocking or setting the trailer brakes keeps the trailer from walking away as the tractor pushes into it. Backing under at an angle can shove the trailer sideways and snap the landing gear, so line up straight and check both sides in your mirrors. Trailer height matters in both directions: too low and you hit the trailer nose, too high and the pin will not seat. The electrical cord goes on after you have crawled under and inspected the coupling, and the landing gear comes up last of all.

11. 11. Which walkaround checks are added because the vehicle is a combination, and are not part of a straight truck inspection?

    Velg alle som passer.

    • A. The lower fifth wheel is mounted securely, greased, with no visible space against the upper plate
    • B. The air and electrical lines are connected, undamaged, and secured with enough slack for turns
    • C. The landing gear is fully raised and undamaged, with the crank handle in place and secured
    • D. The windshield wipers are secure and the blades are not torn
    • E. The steering wheel has no more than the allowed amount of free play
    Vis svar og forklaring

    Svar: A. The lower fifth wheel is mounted securely, greased, with no visible space against the upper plate, B. The air and electrical lines are connected, undamaged, and secured with enough slack for turns, C. The landing gear is fully raised and undamaged, with the crank handle in place and secured

    You still run the same seven step inspection, plus a set of items that only exist once there is a trailer behind you: the coupling system, the lines that cross to the trailer, and the landing gear. On a sliding fifth wheel you also confirm every locking pin is present and locked, and that the fifth wheel is not so far forward that the tractor frame will strike the landing gear in a sharp turn. Wipers and steering play belong to the ordinary inspection you already do on any vehicle.

12. 12. You are dropping a loaded trailer. Which of these are the correct actions?

    Velg alle som passer.

    • A. Shut off the trailer air supply to lock the trailer brakes, back up gently against the kingpin, then set the parking brake while the tractor is still pushing
    • B. After the landing gear makes firm contact with the ground, crank a few extra turns in low gear to take some weight off the fifth wheel
    • C. Pull forward only until the fifth wheel clears, leaving the tractor frame under the trailer, then get out and check the supports
    • D. Pull the release handle and drive straight out in one move, since the landing gear will catch the trailer
    • E. Leave the air lines connected so the trailer keeps its brakes applied after you drive away
    Vis svar og forklaring

    Svar: A. Shut off the trailer air supply to lock the trailer brakes, back up gently against the kingpin, then set the parking brake while the tractor is still pushing, B. After the landing gear makes firm contact with the ground, crank a few extra turns in low gear to take some weight off the fifth wheel, C. Pull forward only until the fifth wheel clears, leaving the tractor frame under the trailer, then get out and check the supports

    Backing gently against the kingpin takes the load off the locking jaws so the release handle will move, and setting the parking brake holds it there. On a loaded trailer, a few extra cranks lift a little weight off the fifth wheel, which makes the jaws easier to open now and easier to couple next time, though you never lift the trailer off the plate. Stopping with the tractor frame still under the trailer means that if the landing gear sinks or collapses, the trailer lands on your frame instead of the ground.

13. 13. Complete the sentence.

    On a rig pulling more than one trailer, the shut-off valves in the service and supply lines must be _____ at the rear of the last trailer and _____ on all the others.

    Alternativer for luke 1: open, closed, removed

    Alternativer for luke 2: open, closed, capped

    Vis svar og forklaring

    Svar: closed, open

    Those valves exist so the lines can be sealed off when nothing is being towed behind that trailer. Leave the last one open and air escapes out the back, so nothing downstream of the leak builds pressure. Leave a middle one closed and the trailers behind it never get air at all. You check this by opening the valve at the rear of the last trailer and listening for air, which proves the whole system is charged all the way back.

14. 14. Complete the sentence.

    To check that the coupling caught, raise the landing gear slightly off the ground, keep the trailer brakes locked, and _____.

    Alternativer for luke 1: pull the tractor gently forward, rock the tractor back and forth in reverse, release the parking brake and let the rig roll backward, apply full throttle against the trailer

    Vis svar og forklaring

    Svar: pull the tractor gently forward

    A gentle tug against locked trailer brakes is the quickest proof that the jaws actually captured the kingpin rather than sliding past it. Keep it gentle, because a hard pull against a bad coupling is how a trailer ends up on the ground. Passing the tug is not the end of it either. You still put the transmission in neutral, set the parking brakes, shut the engine off, take the key with you and inspect the coupling by eye before anything else.

15. 15. Complete the sentence.

    The service line, which carries the air your foot brake meters out to the trailer, is usually color coded _____, while the emergency line, which fills the trailer air tanks and holds the emergency brakes off, is usually color coded _____.

    Alternativer for luke 1: blue, red, green, yellow

    Alternativer for luke 2: blue, red, black

    Vis svar og forklaring

    Svar: blue, red

    The service line is also called the control line or signal line, and the pressure in it rises and falls with how hard you press the pedal, which is what tells the relay valves how much brake to apply. The emergency line is also called the supply line, and it does the two jobs above at once. Colors are a helpful habit and not a guarantee, so read the metal tags stamped service and emergency when they are fitted, and clean the rubber seals before you couple the glad hands.

Dette står på combination vehicles-prøven

Combination vehicles-prøven er en av de skriftlige kunnskapsprøvene du tar hos delstatens førerkortkontor, og alle som søker Class A tar den. Den er atskilt fra general knowledge-prøven, atskilt fra air brakes-prøven og atskilt fra endorsementet doubles and triples, så de fleste Class A-søkere ender opp med minst tre skriftlige prøver før de i det hele tatt rører en lastebil. Delstatene skriver sine egne spørsmålssett fra den samme modellmanualen for CDL, så antall spørsmål, tidsgrensen, gebyret og hvor snart du kan ta ny prøve etter stryk varierer alt sammen fra delstat til delstat. Grensen for bestått varierer ikke på samme måte. Føderale regler krever at du svarer riktig på minst 80 prosent av spørsmålene på hver kunnskapsprøve, så en delstat som gir deg 20 spørsmål lar deg bomme på fire, og en delstat som gir deg 50 lar deg bomme på ti.

Innholdet kommer fra Section 6 i delstatens CDL-manual, og det deler seg i fem deler. Driving combination vehicles safely dekker veltefare og tyngdepunkt, myk styring og pisksnert-effekten, tidlig bremsing, lave hengere som setter seg fast på hevede planoverganger, hengerskrens, det å svinge vidt på grunn av sporing i sving, og rygging med henger. Combination vehicle air brakes dekker håndventilen for hengerbremsen, tractor protection valve, betjeningen for trailer air supply, service- og nødledningen, glad hands, som er koplingshodene der luftslangene på bil og henger møtes, lufttankene på hengeren og stengeventilene. Blokkeringsfrie bremser får en kort egen del, mest om hva ABS ikke gjør for deg. Så kommer de nummererte stegene for tilkopling og frakopling, og de ekstra punktene som legges til en runde rundt kjøretøyet når du har en henger bak deg.

Stegene for tilkopling og frakopling fortjener den største delen av lesetiden din, fordi de dukker opp to ganger. De blir spurt om på denne skriftlige prøven, og senere må du finne, ta på og navngi koplingsdelene høyt under kontrollrunden i skills test. To andre ting er verdt å få på plass tidlig. Last ned din egen delstats manual i stedet for en generisk PDF, for delstaten din skriver spørsmålene sine fra den utgaven den selv publiserer, og ordlyden vil stemme. Og sjekk hvor du står med entry level driver training. Siden februar 2022 har føderale regler krevd opplæring hos en tilbyder på det føderale registeret før du kan ta skills test for et første Class A-førerkort, og det er et eget steg atskilt fra alle kunnskapsprøvene.

Slik bruker du smakebiten, og slik leser du Section 6

Disse 15 spørsmålene lener seg på forståelsen bak reglene framfor på ordene. De spør hvorfor en henger velter før trekkvogna gjør det, hvorfor du slipper opp bremsen i en hengerskrens i stedet for å legge på mer, hva som faktisk skjer når glad hands blir byttet om, og hvilken rekkefølge koplingsstegene går i. Det er den delen den skriftlige prøven belønner, og det er også den delen som holder deg oppreist i en våt avkjøringsrampe om natten. Spørsmålene blander formatene en kunnskapsprøve bruker, også velg alle som passer og fyll inn luken, for å plukke tre riktige svar ut av fem er en hardere og ærligere test på hva du kan enn å plukke ett av fire.

Ta den i én økt uten notater, og les så forklaringen til hvert spørsmål, også de du fikk riktig. Behandle et galt svar som et tema og ikke som ett enkelt faktum. Bommet du på spørsmålet om ombyttede luftledninger og spørsmålet om tractor protection valve, gå tilbake og repeter hele underkapittelet om luftledninger under ett, for serviceledningen og nødledningen gir bare mening som et par. Det samme gjelder velt og rearward amplification, som er to blikk på ett problem, siden både en høy last og en pisksnertende henger ender med kassa på siden. Ingenting her blir vurdert eller lagret noe sted, så det koster deg ingenting å ta den kald og finne ut hva du ennå ikke kan.

For koplingsstegene holder det ikke å lese. Skriv de seksten tilkoplingsstegene og de ti frakoplingsstegene ned fra hukommelsen, i rekkefølge, til du klarer det uten å se, og si dem så høyt mens du går rundt et ekte vogntog hvis du har tilgang til ett. Rekkefølgen bærer sikkerhetslogikken, og logikken er det som får rekkefølgen til å sitte. Du legger klosser under hjulene før du plasserer trekkvogna, du låser hengerbremsene før du rygger under, du kryper under med en lykt og sjekker låsekjevene før du plugger i strømkabelen, og du sveiver opp støttebeina helt til slutt. Får du rekkefølgen riktig, svarer en god del av enkeltspørsmålene seg selv.

Slik bygger StudyPDF fullengdes øvingsprøver fra ditt eget CDL-materiale

Femten spørsmål kan vise deg hvor du er svak. De gjør deg ikke klar alene, og en generell spørsmålsbank sklir bort fra ordlyden din egen delstatsmanual bruker, og det er den ordlyden prøven din er skrevet fra. Når du først vet hvilke områder som er svake, er det du trenger videre mengde på akkurat de områdene, hentet fra sidene du faktisk fikk utdelt.

StudyPDF jobber fra ditt materiale i stedet. Du laster opp delstatens CDL-manual, Section 6-heftet fra skolen din eller notatene læreren din ga deg, og Bo, studieagenten, bygger fullengdes øvingsprøver fra akkurat de sidene. Hvert spørsmål er forankret i ditt materiale, og hver forklaring viser hvor svaret kommer fra, så du kan bla rett til kilden når noe ser rart ut. Du kan lage nye prøver så ofte du vil, spisse dem mot ett område som tilkopling og frakopling eller luftledningene, og følge med på hvilke temaer du stadig bommer på.

Du trenger ikke laste opp noe for å komme i gang. Har du ingen fil for hånden, kan du oppgi et tema i stedet, for eksempel tilkopling av trekkvogn og semihenger, tractor protection valve eller det å unngå hengerskrens, så skriver Bo en øvingsprøve fra det. Det hjelper når du venter på et hefte fra skolen, eller leser fra en manual du bare har på papir. Gratis å komme i gang.