Denison High School

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The air brakes endorsement applies to applicants who wish to drive a vehicle with air brakes in Class A, B, or C CDL. To drive a vehicle with air brakes, you must pass the air brake component of the Iowa CDL knowledge test. The IA CDL air brakes test consists of 25 questions, and you'll need at least 20 correct answers to pass (80%). The test covers the information found in the air brakes section of the Iowa CDL Manual. Take this IA CDL practice test now to prepare for the actual air brakes test!
1. To operate a vehicle equipped with air brakes, you must pass the air brakes knowledge test. Why?
All trucks have air brakes.
If you don't pass the air brakes test, you will be restricted to driving vehicles without air brakes.
If you don't pass the air brakes test, you can't get a CDL.
2. The application pressure gauge:
protects the tank and the rest of the system from too much pressure.
shows how much air pressure is being applied to the brakes.
tells you how much pressure is in the air tanks.
3. The one-way check valve:
supplies air to the trailer air tanks.
keeps your wheels from locking up when you brake hard.
keeps air from going out if the air compressor develops a leak.
4. Which of the following is TRUE about dual air brake systems?
Each brake system has its own air tanks, hoses and lines.
most heavy-duty vehicles use dual air brake systems.
All of the above.
5. When you push the brake pedal down, air brakes work:
after a short delay.
after about 15 seconds.
6. At passive railroad crossings, even if there are active railroad signals that indicate the tracks are clear, you must _________  to be sure it is safe to proceed.
stop, look, and listen
listen, look and stop
go, stop and listen
7. With air brake vehicles, you should use the parking brakes:
as little as possible.
whenever you leave the vehicle unattended.
only during the vehicle inspection test.
8. Typically an air system is fully-charged at:
75 psi
25 psi
125 psi
9. Slack adjusters:
regulate the distance that the air brake has to travel to apply friction to the wheel.
regulate the distance between the rear wheels.
should move more than one inch where the push rods attach to them.
10. An alcohol evaporator is important during:
hot weather.
cold weather.
dry weather.
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IA CDL Air Brakes Test

Number of questions: 25
Correct answers to pass:20
Passing score:80%
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