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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the North Carolina CDL knowledge test. The NC CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the North Carolina CDL Manual. Take this NC CDL practice test now to prepare for the actual air brakes test!
1. In a vehicle with a dual air brake system:
one system supplies air to the trailer.
each system has its own air tanks.
both systems typically operate the regular brakes on the rear axle.
All of the above.
2. When driving on slippery roads, you should NOT:
try to anticipate stops early.
go slowly.
use the engine brake.
watch far enough ahead to keep a steady speed.
3. Your vehicle has hydraulic brakes. When you press the brake pedal while driving and the pedal goes to the floor, remember that:
the parking brake should never used to slow the vehicle.
pumping the brake pedal may generate enough hydraulic pressure to stop the vehicle.
shifting into neutral may help slow the vehicle.
All of the above.
4. If the safety relief valve in the air brake system releases air:
the valve is fully operational.
something is wrong.
this will supply more power to the drive wheels.
this will supply more power to the brakes.
5. Radial and bias-ply tires:
should be used together only when driving in packed snow.
should not be used together.
should be used together.
should be used together only during bad weather.
6. ABS malfunction lamps are located:
on the driver'door.
on the instrument panel.
under the hood.
None of the above.
7. When the air pressure is built up to governor cutoff, the air leakage rate for combination vehicles with the engine off and the foot brake fully applied should be less than_____ in one minute.
5 psi
2 psi
4 psi
3 psi
8. To prevent drowsiness you should:
get adequate sleep before a trip.
avoid exercise to save more energy.
schedule trips for the middle of the night.
never drive with a passenger.
9. Perception Distance + Reaction Distance + Brake Lag Distance + Braking Distance = ?
Partial Stopping Distance
Total Stopping Distance
Total Air Pressure
Stopping Distance - (minus) Brake Fade Distance
10. After supplying air to the trailer brake system, you should check the brake system for crossed air lines by:
checking the air brake system pressure gauge for signs of major air loss.
shutting the engine off so you can hear the brakes.
applying and releasing the trailer brakes and listening for the sound of trailer brakes.
All of the above.
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NC CDL Air Brakes Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
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