Instructions

Air Brakes

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice.. Read More

This endorsement is required for driving a vehicle with air brakes. To receive this endorsement, applicants must pass a written test. The test consists of 25 multiple choice questions. Each question has two, three or four possible answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Minnesota Commercial Driver’s Manual. Questions come from the chapters covering: Air Brakes and Combination Vehicles. The Air Brakes endorsement may be used with the Class A, B or C CDL.

Number of Question 25

Passing Score 20

19. In a vehicle with dual parking control valves, a separate air tank can be used:

To make the air brakes work more effectively.

To temporarily release the spring brakes.

To charge the brakes on the rear trailer.

In a vehicle with dual parking control valves, there is a separate air tank that can be used to temporarily release the spring brakes if they have been activated due to low air pressure. Pushing in the proper control will release the spring brakes for a short period of time, allowing the driver to move the vehicle in an emergency.

20. When connecting a converter dolly to a second or third trailer, the trailer height should be:

Slightly higher than the center of the fifth wheel.

Level with the center of the fifth wheel.

Slightly lower than the center of the fifth wheel.

Next to the center of the fifth wheel.

When connecting a converter dolly to a second or third trailer, the trailer height should be correct. It should be slightly lower than the center of the fifth wheel.

21. Air tanks usually hold enough compressed air:

For one stop before needing to be refilled.

For several stops before needing to be refilled.

For a day’s worth of braking.

For an unlimited number of stops.

In an air braking system, the air storage tanks can usually hold enough compressed air for the brakes to be used several times.

22. During an applied leakage test, the maximum leakage rate for a double combination vehicle is:

10 psi in a minute.

8 psi in a minute.

6 psi in a minute.

4 psi in a minute.

It is important to know the maximum air loss rate that is safe for your specific vehicle. A double combination vehicle should have a leakage rate no higher than 4 psi in a minute during an applied leakage test.

23. The air entering air storage tanks may contain:

Water and compressor oil.

Frost.

Gravel.

Antifreeze.

The air that enters air storage tanks in an air brake system usually contains a certain amount of water and compressor oil. Because accumulations of these materials can damage the braking system, tanks are equipped with drains to allow their removal.

24. What does an air compressor do in an air brake system?

It pumps air into the air storage tanks.

It fills the tires.

It moves air to the back of the truck.

In an air brake system, the air compressor pumps air into the air storage tanks. The air compressor is controlled by the air compressor governor.

25. How should you test the low pressure warning signal?

Engage and disable the parking brake.

Rapidly press and release the brake pedal.

Open the rear shut-off valves.

Uncouple and recouple all glad hands.

It is essential that your low pressure warning light functions properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.

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