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

19. An alcohol evaporator is especially important:

In cold weather.

In hot weather.

In dry weather.

Some air brake systems contain an alcohol evaporator. This evaporator introduces alcohol into the system to help prevent ice from forming in cold weather.

20. Vehicles with dual air brake systems:

Maintain full-capacity air pressure in the braking systems even when the vehicle is not running.

Maintain some air pressure in the braking systems when the vehicle is not running.

Must be run to build enough air pressure to brakes to operate properly.

Do not need time to build air pressure before a trip.

Before driving a vehicle with a dual air brake system, you must allow the air compressor time to build up at least 100 psi of air pressure in both the primary and secondary systems.

21. If the safety relief valve in the air brake system releases air:

The compressor needs more air.

The air pressure has become too high.

The brakes are fully operational.

An air brake system has a safety relief valve, which releases air from the tanks if the pressure gets too high. If the valve must operate, something in the system is wrong and should be addressed by a mechanic.

22. When leaving your vehicle unattended:

The parking brake must be always be used.

The parking brake should never be used.

Windows in the cab should be lowered.

Always apply the parking brake when leaving your vehicle unattended.

23. When stopping in an emergency situation, you should:

Veer your trailer to the right and stop.

Stop in a straight line.

Veer your trailer to the left and stop.

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 in a straight line but will still allow you to turn if necessary.

24. The application pressure gauge:

Shows how much air pressure is being applied to the brakes.

Shows the temperature of air being used in the braking system.

Shows the pressure of the air coming from the compressor.

Shows the number of times the brakes have been used.

In an air brake system, the application pressure gauge shows how much air pressure is being applied to the brakes. Not all vehicles with an air brake system have this gauge.

25. Friction in an S-cam brake is caused when the brake shoes and linings:

Press against the outside of the brake drum.

Press against the inside of the brake drum.

Push against each other.

Friction inside a brake drum is caused when the brake shoes and linings push against the inside of the drum. The friction in the drums will slow and stop the vehicle.

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