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 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 North Carolina 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
Passing Score
13. All air tanks must include:
Explanation
Air brake system tanks must contain drain valves. These valves are used to drain accumulated oil and water from the tanks and may be either manually or automatically operated.
14. Why should you regularly drain the air tanks?
Explanation
Compressed air usually contains a certain amount of moisture and compressor oil, which can build up in the air storage tanks and damage the brake system. The tanks should be drained to clean out these accumulations. On a tank with a manual drain valve, draining should be performed at the end of each day of driving.
15. In a vehicle with dual air brakes, a leak in one system ____ the second system.
Explanation
A dual air brake system is made up of two separate air brake systems. If there is an air leak in one system, it may not affect the other.
16. If the spring brakes are on, you should:
Explanation
Do not use the brake pedal when the spring brakes are on. This could damage the brakes by subjecting them to the combined forces of springs and air pressure.
17. On a truck with air brakes, the braking system’s air compressor:
Explanation
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.
18. What should happen before the air pressure in an air brake system tank falls below 55 psi?
Explanation
