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 three or four answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the State of Delaware Commercial Driver License Manual. Questions come from the chapter covering: Air Brakes. The Air Brakes endorsement may be used with the Class A, B or C CDL.

Number of Question 25

Passing Score 20

19. A one-way check valve:

Drains the water and compressor oil from the air tanks.

Prevents air from escaping if the air compressor has a leak.

Activates the emergency brakes when there is a leak.

Holds the spring brakes in position until they are used.

A one-way check valve is required to be between an air compressor and the first main reservoir. This valve prevents air from escaping the system if the air compressor develops a leak.

20. Friction in an S-cam brake is caused when the brake shoes and linings:

Press against the outside of the brake drum.

Press against the inside of the brake drum.

Push against each other.

Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.

21. A ____ allows a driver to gradually apply spring brakes.

Modulating control valve

Trailer air supply control

Relay valve

A modulating control valve allows a driver to gradually apply spring brakes. In equipped vehicles, the valve is controlled by a lever located on the dashboard.

22. What can happen if the air pressure gets too low in an air brake system?

The brakes may squeak.

The brakes may not work.

The brakes may be sluggish.

The brakes will be very sensitive.

Pressing and releasing the brake pedal unnecessarily can let air out faster than the compressor can replace it, reducing the available air pressure. If the air pressure in an air brake system gets too low, the brakes will no longer work.

23. Why do you need to drain air tanks regularly?

Because the air gets old and needs to be replaced

Because compressed air contains some water which must be drained from the tanks

To allow for a change in air pressure

To remove bad air from the tanks

Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Tanks must be drained regularly to remove this build-up.

24. When the brake pedal is pushed down, air brakes work:

Immediately.

After a short delay.

After about a minute.

Only if it is warm outside.

Because air takes time to flow through the air lines to the brakes, air brakes cannot begin working instantly. There is often a brake lag of at least one-half of a second between the moment the brake pedal is pressed and the moment the brakes begin to work.

25. On a truck with air brakes, the braking system’s air compressor:

Pumps air into the air storage tanks.

Fills the tires.

Moves air to the back of the truck.

Cleans the brakes.

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.

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