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 answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Virginia 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. What does the air compressor governor do?
Explanation
In an air brake system, the air compressor governor controls when the air compressor pumps air into the storage tanks. It stops pumping if the pressure in the tanks becomes too high, and begins pumping if the pressure becomes too low.
14. If the safety relief valve in an air brake system is releasing air:
Explanation
The safety relief valve in an air brake system releases air if necessary to prevent pressure in the system from becoming too high. If the valve starts releasing air, there is something wrong. Have a mechanic fix the problem.
15. During an applied leakage test, the maximum leakage rate for a triple combination vehicle is ____ in a minute.
Explanation
It is important to know the maximum air loss rate that is safe for your specific vehicle. A triple combination should have a leakage rate no higher than 6 psi in a minute during an applied leakage test.
16. Why do large vehicles use air brakes?
Explanation
If used and maintained properly, air brakes are a safe and effective way to stop large, heavy vehicles.
17. When parked on a flat surface, you should:
Explanation
When parking on a level surface, you should use wheel chocks. If the vehicle is not equipped with spring brakes, this is essential to prevent the trailer from moving.
18. Air tank drains are used to remove ____ from the braking system.
Explanation
