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. To pass, the applicant must answer at least 20 questions correctly. Test questions come from the Michigan 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
19. A ____ allows a driver to gradually apply spring brakes.
Explanation
A modulating control valve allows a driver to gradually apply spring brakes. In equipped vehicles, the valve is controlled by a lever located on the dashboard.
20. 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.
21. When the spring brakes are on, you should never:
Explanation
Never push down the brake pedal while the spring brakes are activated. The combined force of springs and air pressure could damage the brakes.
22. 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.
23. A wig wag is:
Explanation
Vehicles with air brakes are required to be equipped with a low pressure warning device. A wig wag is a type of low air pressure warning device. This device drops a mechanical arm into the driver's view if the pressure in the tanks drops to a level between 55 and 75 psi.
24. 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.
25. What is often found in compressed air?
Explanation
