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 Maryland 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. If one air system in a dual air brake system is very low on pressure:

None of the brakes will work at all.

Either the front or rear brakes will not be operating fully.

There will be no noticeable affect.

Lights on the outside of the tractor will flash.

In a dual air brake system, if one of the air systems gets very low on pressure, either the front or rear brakes will not be operating fully. You should bring your vehicle to a safe stop and have the air system repaired.

14. An air compressor governor will stop the compressor from pumping air once the air tanks have an air pressure level of:

125 psi.

100 psi.

150 psi.

80 psi.

An air compressor governor will stop the compressor from pumping air once the air tanks are at an air pressure level of 125 psi. This air pressure level is referred to as the "cut-out" level.

15. When you need to stop in an emergency, you should:

Lock the wheels and skid to a stop.

Stop in a way that keeps your vehicle in a straight line.

Stop in a way that turns your vehicle.

Expect your vehicle to slow down more quickly than usual.

If you need to make an emergency stop, you can use either the controlled braking method or the stab braking method. It's important to brake in a way that keeps your vehicle traveling in a straight line while still allowing you to turn, if necessary.

16. During a static leakage test, what is the maximum leakage rate that is safe for a double combination vehicle?

3 psi in one minute.

6 psi in one minute.

8 psi in one minute.

When performing a static leakage test on a double combination vehicle with air brakes, the leakage rate should be no more than 3 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.

17. 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.

18. Brake fade is a result of:

Exposure to sunlight.

Exposure to moisture.

Excessive use.

Not using the brakes enough.

If brakes are used too much, they will overheat and become less effective. This is referred to as brake fade.

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