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 answer choices. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Alaska 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. An air compressor governor controls:

Explanation
In an air brake system, the air compressor governor controls when the air compressor pumps air into the air storage tanks.

14. Which of the following is not part of a vehicle’s air brake system?

Explanation
Components of an air brake system include an air compressor, an air compressor governor, air storage tanks, air tank drains, an alcohol evaporator, a safety valve, a brake pedal, foundation brakes, supply pressure gauges, an application pressure gauge, a low air pressure warning signal, a stop light switch, a front brake limiting valve (on some older vehicles), spring brakes, and parking brake controls.

15. In a dual air brake system, if one air system is very low on pressure:

Explanation
In a dual air brake system, either the front or rear brakes will not be fully operable if one of the air systems gets too low on pressure. If the air pressure in either tank gets too low while you are driving, you should exit the road and park as soon as possible.

16. What helps prevent wheel lockup when braking?

Explanation
The purpose of an Anti-Lock Braking System (ABS) is to prevent wheel lockup while brakes are being applied.

17. What kind of brakes do most newer heavy-duty trucks use?

Explanation
Most newer heavy-duty vehicles use dual air brake systems. A dual air brake system has two separate air brake systems which use a single set of brake controls.

18. The leakage rate for a triple combination vehicle with air brakes should be no more than ____ in one minute during a static leakage test.

Explanation
When performing a static leakage test on a triple combination vehicle with air brakes, the leakage rate should be no more than 5 psi in one minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.
DMV Writen Test