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 Commercial Driver Guide. 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

13. Applying the brake pedal causes air pressure to activate an electric switch and:

Turn off the brake lights.

Turn on the low pressure warning light.

Turn on the brake lights.

Turn off the low pressure warning light.

In a vehicle with air brakes, the brake lights are activated when the brake pedal is pushed and air pressure moves an electric switch. With the application of air pressure, the switch will then turn on the brake lights.

14. What is often found in compressed air?

Water

Cardboard

Brake fluid

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.

15. Spring brakes come on:

When too much air pressure is lost.

When a control on the dashboard is activated.

When the tires have minimal tread depth.

When the brakes are noisy.

Spring brakes come on automatically when air pressure drops to an unsafe psi level. Instead of waiting for the spring brakes to automatically activate, you should safely exit the road as soon as you notice the low pressure warning signal and bring your vehicle to a stop while you are still able to control the brakes.

16. To use the stab braking method, you should:

Apply the brakes completely until the wheels lock up, release the brakes until the wheels start rolling, then repeat the process.

Apply the brakes about halfway, but allow the wheels to keep rolling.

Apply the brakes completely until the wheels lock up and the vehicle stops.

Apply the emergency brake until the vehicle starts to slow.

The stab braking method for emergency stops involves fully applying the brakes until they lock up. The brakes are then released until the wheels start rolling, and then the process is repeated.

17. The air pressure in a dual air brake system should build from 85 to 100 psi within:

Two minutes.

15 seconds.

10 minutes.

45 seconds.

When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.

18. To stop in a vehicle that uses air brakes, the driver should:

Pull the air brake lever.

Engage the brake lever.

Push the brake pedal down.

Pull the brake pedal up.

To make a normal stop in a vehicle with air brakes, push the brake pedal down. The harder the pedal is pressed, the more air pressure is released.

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