Combination Test 2

1. Before you back under a trailer, make sure the:
Air brakes are off.
Tractor protection valve is normal.
Trailer brakes are locked.

2. If the service air line comes apart while you are driving a combination vehicle but the emergency line stays together, what will happen right away?
Nothing is likely to happen until you try to apply the brakes.
The trailer's air tank will exhaust through the open line.
The emergency tractor brakes will come on.

3. The air leakage rate for a combination vehicle (engine off, brakes on) should not Be more than ____ psi per minute.

4. In normal driving, some drivers use the hand valve before applying the brake pedal to prevent a jackknife. Which of these statements is true?
It results in less skidding than using the brake pedal alone.
It should not be done.
It is the best way to brake and keep the truck in a straight line.

5. The driver crosses the air lines when hooking up to an old trailer. What will happen?
If the trailer has no spring brakes, you can drive away, but you will not have trailer brakes.
The brake pedal will work the trailer spring brakes instead of the air brakes.
The hand valve will apply the tractor brakes instead of the trailer brakes.

6. Why should you lock the tractor glad hands (or dummy couplers) to each other when you are not towing a trailer?
The connected brake circuit becomes a back up air tank.
If you did not, you could never build system pressure.
It will keep dirt and water out of the lines.

7. The safety catch for the fifth wheel locking lever must be ____ for a coupling to be complete.
Under the locking lever
Over the locking lever
Through the locking lever

8. The front trailer supports are up and the trailer is resting on the tractor. Make sure:
There is enough clearance between the tractor frame and the landing gear.
There is enough clearance between the tops of the tractor tires and the nose of the trailer.
Both a and b are correct.

9. You have a major leak in the service line and you put on the brakes. Service air pressure will escape and cause the:
Trailer tank pressure to be lost.
Trailer emergency brakes to come on.
Tractor spring brakes to lock on.

10. When backing under a tractor under a trailer you should expect:
Trailer will be lifted slightly when the tractor backs under it.
End of the kingpin is even with the top of the fifth wheel.
Trailer landing gear is fully extended.